,this file was produced from page images at the ,internet ,archive4 ,transcriber's ,note ,this book was transcribed from scans of the original found at the ,internet ,archive4 ,tables are represented as images4 ,the index of the original book has been removed1 but the catalog of books from the publisher has been included4 ,there was no book cover image in the scans so ,i created one4 ,illustration3 ,frontispiece4 99,plate ,i4 ,electrical ,conventions499 ,,wireless ,,telegraph ,,construction ,,for ,,amateurs ,,by ,,alfred ,,powell ,,morgan ,,editor ,,mechanical ,,and ,,electrical ,,department ,,of ,,the ,,boys' ,,magazine ,,author ,,of ,,wireless ,,telegraphy ,,and ,,telephony ,,with #afg ,,illustrations 99,third ,edition1 ,revised and ,enlarged99 ,,with ,a ,,complete ,,description ,,of ,,the ,,new ,,wireless ,,law ,,new ,,york3 ,d4 ,,van ,,nostrand ,,company #be ,,park ,,place #aiad ,copyright1 #aiaj1 #aiac1 by ,d4 ,,van ,,nostrand ,,company ,stanhope ,press ,f4 ,h4 ,,gilson ,,company ,,boston4 ,u4,s4,a4 ,,preface4 ,in this work1 the author has endeavored to present a book embracing practical information for those who may wish to build for private or experimental use a set of wireless instruments which are more than toys but yet not so expensive as the commercial apparatus4 ,many books have been published on the subject of wireless telegraphy1 but in them the interests of the novice have been rather neglected and in order to build an outfit he has been forced to rely upon a series of disconnected articles published in the amateur periodicals4 ,it is the object of this book to show the construction of simple1 efficient instruments by means of clear drawings1 and to give enough elementary theory and practical hints to enable the experimenter to build a size and type in keeping with his needs and resources4 ,the tiresome how to make style has been avoided as far as possible4 ,history and all unimportant details are omitted to give in their place a concise explanation of the parts played by the different instruments and the influence of developing their various factors4 ,a small lathe and a set of taps and dies are necessary to produce apparatus having a good appearance1 but a little ingenuity displayed in adapting screws and parts of old electrical instruments oftentimes at hand will make these tools unnecessary4 ,ordinary precaution and plenty of time should be used in the work4 ,it is obvious that if a large coil is to be made1 it is well to insure its successful completion by painstaking care and the use of proper materials4 ,neither is it wise to strain an instrument through becoming impatient and using it before it is properly completed and adjusted4 ,wherever possible instructions have been given regarding the adjustment of the apparatus1 but it is only by actual practice that the operator will acquaint himself with the most efficient manipulation4 ,extracts from articles contributed by the ,author to ,popular ,electricity have been used in the chapters on ,spark ,gaps1 ,oscillation ,detectors and ,telephone ,receivers1 through the courtesy of the editor1 ,mr4 ,h4 ,w4 ,young4 ,in conclusion1 the writer wishes to express his thanks to the ,united ,wireless ,telegraph ,company for views of their apparatus and to the other firms who have loaned electrotypes and supplied information4 ,to those who have assisted in the preparation of the book1 more especially to ,mr4 ,safford ,adams1 for numerous suggestions and criticisms1 the ,author desires to express his full acknowledgments4 ,,alfred ,,powell ,,morgan4 ,,upper ,,montclair1 ,n4,j4 ,june1 #aiaj4 ,,preface ,,to ,,the ,,third ,,edition4 ,the success of the previous editions of this book has made a new and third one necessary4 ,there have not been any startling changes or new discoveries made in the field of wireless telegraphy since the first edition was published1 but the art has undergone a number of small changes and improvements which have increased the efficiency and selectivity of the apparatus4 ,since then a federal law restricting and controlling wireless telegraphy has been passed4 ,its effect has been to place wireless telegraphy upon a more certain basis1 and to give a recognized standing to the amateur experimenter4 ,this new law has been included in this edition in the form of an appendix4 ,the amateur will do well to read it carefully4 ,compliance with its regulations will prove beneficial rather than a hindrance4 ,a fully illustrated chapter explaining exactly how to comply with the law and how to build the apparatus required has been added4 ,complete descriptions of several new types of detectors are also included4 ,all old matter has been thoroughly revised and several illustrations replaced by ones more up-to-date and of direct interest4 ,,alfred ,p4 ,,morgan4 ,,upper ,,montclair1 ,n4,j4 ,may1 #aiac4 ,,preface4 4444444444444444444444444444444444444444 444444444444444444 ,,preface ,,to ,,the ,,third ,,edition4 4444444444444444444444444444444444444 ,,chapter ,i4 ,,introductory4 4444444444444444444444444444444444444444 44 ,the ,transmission and ,reception of ,electric ,waves4 444444444444444 ,,chapter ,,ii4 ,,the ,,apparatus4 4444444444444444444444444444444444444444 ,,chapter ,,iii4 ,,aerials ,,and ,,earth ,,connections4 44444444444444444444444 ,,chapter ,,iv4 ,,induction ,,coils4 44444444444444444444444444444444444444 ,,chapter ,v4 ,,interrupters4 4444444444444444444444444444444444444444 44 ,,chapter ,,vi4 ,,transformers4 4444444444444444444444444444444444444444 4 ,construction of a #b-,k4,w4 ,transformer4 444444444444444444444444444 ,,chapter ,,vii4 ,,oscillation ,,condensers ,,and ,,leyden ,,jars4 44444444444444 ,,chapter ,,viii4 ,,spark ,,gaps ,,or ,,oscillators4 44444444444444444444444444 ,,chapter ,,ix4 ,,transmitting ,,helixes4 444444444444444444444444444444444 ,,chapter ,x4 ,,keys4 4444444444444444444444444444444444444444 4444444444 ,,chapter ,,xi4 ,,aerial ,,switches ,,and ,,anchor ,,gaps4 4444444444444444444444 ,,chapter ,,xii4 ,,hot ,,wire ,,ammeter4 444444444444444444444444444444444444 ,,chapter ,,xiii4 ,,oscillation ,,detectors4 444444444444444444444444444444 ,,universal ,,detector4 4444444444444444444444444444444444444444 444 ,,electrolytic ,,detectors4 4444444444444444444444444444444444444444 4 ,,tantalum ,,detector4 4444444444444444444444444444444444444444 444444 ,,crystal ,,detectors4 4444444444444444444444444444444444444444 444444 ,,lead ,,peroxide ,,detector4 4444444444444444444444444444444444444444 4 ,,the ,,marconi ,,magnetic ,,detector4 4444444444444444444444444444444444 ,,chapter ,,xiv4 ,,tuning ,,coils ,,and ,,transformers4 44444444444444444444444 ,,chapter ,,xv4 ,,receiving ,,condensers4 444444444444444444444444444444444 ,,chapter ,,xvi4 ,,telephone ,,receivers ,,and ,,headbands4 4444444444444444444 ,,chapter ,,xvii4 ,,operation4 4444444444444444444444444444444444444444 44 ,,electrical ,,terms ,,and ,,definitions4 4444444444444444444444444444444 ,,chapter ,,xviii4 ,,the ,,amateur ,,and ,,the ,,wireless ,,law4 ,,what ,,it ,,is2 ,,how ,,to ,,comply2 ,,how ,,to ,,secure ,a ,,license4 4444444444444444444444444444444444 ,,apparatus ,,required ,,in ,,many ,,instances ,,in ,,order ,,to ,,comply ,,with ,,the ,,wireless ,,law4 4444444444444444444444444444444444444444 44444444444 ,receiving ,apparatus4 4444444444444444444444444444444444444444 4444 ,frontispiece4 99,plate ,i4 ,electrical ,conventions499 4444444444444444 ,fig #a4 ,hertz ,oscillator and ,resonator4 4444444444444444444444444444 ,fig4 #b4 ,hydraulic ,oscillator4 4444444444444444444444444444444444444 ,fig4 #c4 ,hydraulic ,transmitter and ,receptor4 444444444444444444444 ,fig4 #d4 ,simple ,wireless ,telegraph ,transmitter and ,receptor4 4444444 ,fig4 #e4 ,electric ,waves and ,lines of ,strain4 44444444444444444444444 ,fig4 #f4 ,resonance ,tube4 4444444444444444444444444444444444444444 444 ,fig4 #g4 ,lag and ,lead4 4444444444444444444444444444444444444444 44444 ,fig4 #h4 ,tuned ,hydraulic ,transmitter and ,receptor4 44444444444444444 ,fig4 #i4 ,tuned ,wireless ,telegraph ,transmitter and ,receptor 444444444 ,fig4 #aj4 ,long-distance ,receiving ,set4 44444444444444444444444444444 ,fig4 #aa4 ,murdock ,receiving ,set4 44444444444444444444444444444444444 ,fig4 #ab4 ,clapp-,eastham ,receiving ,set4 44444444444444444444444444444 ,fig4 #ac4 ,prague ,receiving ,set4 444444444444444444444444444444444444 ,fig4 #ad4 ,receiving ,set4 4444444444444444444444444444444444444444 444 ,fig4 #ae4 ,receiving ,set4 4444444444444444444444444444444444444444 444 ,fig4 #af4 ,murdock ,transmitting and ,receiving ,set4 444444444444444444 ,fig4 #ag4 ,united ,wireless ,portable ,outfit4 4444444444444444444444444 99,plate ,,ii4 ,aerial ,systems499 444444444444444444444444444444444444444 ,fig4 #ah4 ,electrose ,insulators4 444444444444444444444444444444444444 ,fig4 #ai4 ,guy ,insulator4 4444444444444444444444444444444444444444 444 ,fig4 #bj4 ,insulating ,tube4 4444444444444444444444444444444444444444 4 ,fig4 #ba4 ,high-tension ,cable and ,insulator4 444444444444444444444444 ,fig4 #bb4 ,flat-top ,t ,aerial4 444444444444444444444444444444444444444 ,fig4 #bc4 ,ground ,clamp4 4444444444444444444444444444444444444444 4444 ,fig4 #bd4 ,switch for ,lightning ,protection4 4444444444444444444444444 ,fig4 #be4 ,diagram of an ,induction ,coil4 4444444444444444444444444444 ,fig4 #bf4 ,induction ,coil ,core4 4444444444444444444444444444444444444 ,fig4 #bg4 ,theoretical and practical form of secondary4 4444444444444 ,fig4 #bh4 ,layer ,winding for ,small ,coils4 444444444444444444444444444 ,fig4 #bi4 ,section ,winder4 4444444444444444444444444444444444444444 44 ,fig4 #cj4 ,impregnator for ,silk ,covered ,wire4 44444444444444444444444 ,fig4 #ca4 ,methods of ,connecting the ,secondary ,sections4 444444444444 ,fig4 #cb4 ,coil ,case4 4444444444444444444444444444444444444444 4444444 ,fig4 #cc4 ,simple ,interrupter4 44444444444444444444444444444444444444 ,fig4 #cd4 ,independent ,interrupter4 444444444444444444444444444444444 ,fig4 #ce4 ,details of ,magnets4 44444444444444444444444444444444444444 ,fig4 #cf4 ,details of ,moving ,parts4 444444444444444444444444444444444 ,fig4 #cg4 ,details of ,standard and ,screws4 44444444444444444444444444 ,fig4 #ch4 ,diagram of ,connections for an ,independent ,interrupter4 444 ,fig4 #ci4 ,construction of a ,paper ,condenser4 44444444444444444444444 ,fig4 #dj4 ,wenhelt and ,simon ,electrolytic ,interrupters4 4444444444444 ,fig4 #da4 ,construction of ,electrolytic ,interrupters4 444444444444444 ,fig4 #db4 ,details of ,electrolytic ,interrupters4 44444444444444444444 ,fig4 #dc4 ,electrolytic ,interrupter4 44444444444444444444444444444444 ,fig4 #dd4 ,assembly and ,dimensions of ,core4 4444444444444444444444444 ,fig4 #de4 ,fiber ,head and ,separator4 44444444444444444444444444444444 ,fig4 #df4 ,section ,form4 4444444444444444444444444444444444444444 4444 ,fig4 #dg4 ,methods of ,connecting ,sections4 44444444444444444444444444 ,fig4 #dh4 ,assembly of ,leg4 4444444444444444444444444444444444444444 4 ,fig4 #di4 ,transformer with ,one ,secondary removed4 444444444444444444 ,fig4 #ej4 ,wiring ,diagram4 4444444444444444444444444444444444444444 44 ,fig4 #ea4 ,clapp-,eastham #a_/d-,k4,w4 ,transformer4 4444444444444444444444 ,fig4 #eb4 ,united ,wireless ,motor-,generator set for supplying ,alternating ,current to the ,transformer4 444444444444444444444444444 ,fig4 #ec4 ,simple ,condenser4 4444444444444444444444444444444444444444 ,fig4 #ed4 ,leyden ,jar4 4444444444444444444444444444444444444444 444444 ,fig4 #ee4 ,aerial ,switch4 4444444444444444444444444444444444444444 4 ,fig4 #ef4 ,amco ,oscillation ,condenser4 444444444444444444444444444444 ,fig4 #eg4 ,clapp-,eastham ,oscillation ,condenser4 444444444444444444444 ,fig4 #eh4 ,methods of ,varying ,capacity4 44444444444444444444444444444 ,fig4 #ei4 ,spark ,gaps4 4444444444444444444444444444444444444444 444444 ,fig4 #fj4 ,spark ,gap4 4444444444444444444444444444444444444444 4444444 ,fig4 #fa4 ,closely ,coupled ,helix4 44444444444444444444444444444444444 99,plate ,,iii4 ,transmitting ,circuits499 4444444444444444444444444444444 ,fig4 #fb4 ,prague ,transmitting ,helix4 4444444444444444444444444444444 ,fig4 #fc4 ,closely ,coupled ,tuning ,circuit4 44444444444444444444444444 ,fig4 #fd4 ,loosely ,coupled ,transmitting ,helix and ,contact ,clip4 44444 ,fig4 #fe4 ,loosely ,coupled ,transmitting ,circuit4 44444444444444444444 ,fig4 #ff4 ,united ,wireless ,helix1 ,spark ,gap and ,condenser4 4444444444 ,fig4 #fg4 ,morse ,key fitted with ,extension ,lever4 4444444444444444444 ,fig4 #fh4 ,wireless ,key4 4444444444444444444444444444444444444444 4444 ,fig4 #fi4 ,united ,wireless ,type ,key4 444444444444444444444444444444 ,fig4 #gj4 ,connections for ,aerial ,switch4 444444444444444444444444444 ,fig4 #ga4 ,aerial ,switches4 4444444444444444444444444444444444444444 4 ,fig4 #gb4 ,detail of ,contacts4 44444444444444444444444444444444444444 ,fig4 #gc4 ,details of ,switch ,parts4 444444444444444444444444444444444 ,fig4 #gd4 ,method of ,fastening ,knife4 4444444444444444444444444444444 ,fig4 #ge4 ,t ,aerial ,switch4 444444444444444444444444444444444444444 ,fig4 #gf4 ,united ,wireless ,lightning ,switch4 4444444444444444444444 ,fig4 #gg4 ,shoemaker ,tuning ,coil and ,aerial ,switch4 44444444444444444 ,fig4 #gh4 ,united ,wireless ,anchor ,gaps4 444444444444444444444444444 ,fig4 #gi4 ,anchor ,gap4 4444444444444444444444444444444444444444 444444 ,fig4 #hj4 ,simple ,hot ,wire ,meter4 44444444444444444444444444444444444 ,fig4 #ha4 ,meter with ,case ,removed4 444444444444444444444444444444444 ,fig4 #hb4 ,glass ,compensating ,strip4 44444444444444444444444444444444 ,fig4 #hc4 ,details of ,hot ,wire ,supports4 44444444444444444444444444 ,fig4 #hd4 ,details of ,movement4 4444444444444444444444444444444444444 ,fig4 #he4 ,complete ,movement4 444444444444444444444444444444444444444 ,fig4 #hf4 ,side ,view of ,hot ,wire and ,movement4 4444444444444444444444 ,fig4 #hg4 ,united ,wireless ,hot ,wire ,ammeter4 444444444444444444444444 ,fig4 #hh4 ,universal ,detector4 44444444444444444444444444444444444444 ,fig4 #hi4 ,details of ,universal ,detector4 444444444444444444444444444 ,fig4 #ij4 ,parts of ,universal ,detector4 44444444444444444444444444444 ,fig4 #ia4 ,bare ,point ,electrolytic ,detector4 444444444444444444444444 ,fig4 #ib4 ,effect of ,exposing too much ,wire4 444444444444444444444444 ,fig4 #ic4 ,electrolytic ,detector ,circuits4 44444444444444444444444444 ,fig4 #id4 ,electrolytic ,detector4 44444444444444444444444444444444444 ,fig4 #ie4 ,forming ,glass ,point4 44444444444444444444444444444444444 ,fig4 #if4 ,shoemaker ,detector4 44444444444444444444444444444444444444 ,fig4 #ig4 ,shoemaker ,detector ,circuits4 44444444444444444444444444444 ,fig4 #ih4 ,lamp ,detector4 4444444444444444444444444444444444444444 444 ,fig4 #ii4 ,simple ,electrolytic ,detector4 4444444444444444444444444444 ,fig4 #ajj4 ,electrolytic ,detector4 4444444444444444444444444444444444 ,fig4 #aja4 ,details of ,electrolytic ,detector4 44444444444444444444444 ,fig4 #ajb4 ,increasing the ,sensitiveness of an ,electrolytic ,detector4 ,fig4 #ajc4 ,tantalum ,detector4 44444444444444444444444444444444444444 ,fig4 #ajd4 ,united ,wireless ,carborundum ,detector 7horizontal type74 4 ,fig4 #aje4 ,united ,wireless ,carborundum ,detector 7vertical type74 444 ,fig4 #ajf4 ,clapp-,eastham ,ferron ,detector4 44444444444444444444444444 ,fig4 #ajg4 ,silicon ,crystal in ,cup4 444444444444444444444444444444444 ,fig4 #ajh4 ,silicon ,detector ,circuits4 444444444444444444444444444444 ,fig4 #aji4 ,perikon ,detector ,elements4 444444444444444444444444444444 ,fig4 #aaj4 ,perikon ,detector4 444444444444444444444444444444444444444 ,fig4 #aaa4 ,peroxide of ,lead ,detector4 444444444444444444444444444444 ,fig4 #aab4 ,marconi ,magnetic ,detector4 444444444444444444444444444444 ,fig4 #aac4 ,details of ,transformer4 444444444444444444444444444444444 ,fig4 #aad4 ,method of ,joining ,ends of ,band4 4444444444444444444444444 ,fig4 #aae4 ,pulley4 4444444444444444444444444444444444444444 444444444 ,fig4 #aaf4 ,pulley ,bearings4 4444444444444444444444444444444444444444 ,fig4 #aag4 ,circuit of ,magnetic ,detector4 444444444444444444444444444 ,fig4 #aah4 ,fleming ,oscillation ,valve4 444444444444444444444444444444 ,fig4 #aai4 ,flame ,audion4 4444444444444444444444444444444444444444 444 ,fig4 #abj4 ,circuit of ,flame ,audion4 44444444444444444444444444444444 ,fig4 #aba4 ,double-slide ,tuning ,coil4 4444444444444444444444444444444 ,fig4 #abb4 ,sliders4 4444444444444444444444444444444444444444 44444444 ,fig4 #abc4 ,double-slide ,tuning ,coil ,circuits4 4444444444444444444444 99,plate ,,iv4 ,receiving ,circuits4 7,straightaway ,aerial4799 444444444444 ,fig4 #abd4 ,murdock ,double-slide ,tuning ,coil4 44444444444444444444444 ,fig4 #abe4 ,united ,wireless ,receiving ,set4 44444444444444444444444444 ,fig4 #abf4 ,united ,wireless ,portable ,receiving ,set4 44444444444444444 ,fig4 #abg4 ,oscillation ,transformer4 44444444444444444444444444444444 ,fig4 #abh4 ,united ,wireless ,receiving ,transformer4 444444444444444444 ,fig4 #abi4 ,details of ,receiving ,transformer4 44444444444444444444444 ,fig4 #acj4 ,slider for ,loose ,coupler4 4444444444444444444444444444444 ,fig4 #aca4 ,loosely ,coupled ,tuning ,circuits4 444444444444444444444444 ,fig4 #acb4 ,combination ,loosely and ,closely ,coupled ,tuner4 4444444444 ,fig4 #acc4 ,clapp-,eastham ,loose ,coupler4 4444444444444444444444444444 ,fig4 #acd4 ,a ,highly ,efficient ,form of ,loose ,coupler4 444444444444444 ,fig4 #ace4 ,potentiometer4 4444444444444444444444444444444444444444 44 ,fig4 #acf4 ,amco ,potentiometer4 4444444444444444444444444444444444444 99,plate ,v4 ,receiving ,circuits499 444444444444444444444444444444444444 ,fig4 #acg4 ,tuning ,circuit with and without an ,adjustable ,condenser4 4 ,fig4 #ach4 ,tubular ,condenser4 44444444444444444444444444444444444444 ,fig4 #aci4 ,variable ,condenser4 4444444444444444444444444444444444444 ,fig4 #adj4 ,details of ,variable ,condenser4 44444444444444444444444444 ,fig4 #ada4 ,sliding ,plate ,variable ,condenser4 44444444444444444444444 ,fig4 #adb4 ,types of ,permanent ,magnets4 44444444444444444444444444444 ,fig4 #adc4 ,grinding ,tool4 4444444444444444444444444444444444444444 44 ,fig4 #add4 ,parts of a ,holtzer ,cabot ,receiver4 4444444444444444444444 ,fig4 #ade4 ,holtzer ,cabot ,head ,set4 444444444444444444444444444444444 ,fig4 #adf4 ,adjustable ,head ,band4 44444444444444444444444444444444444 ,fig4 #adg4 ,marconi ,station at ,siasconset1 ,mass4 44444444444444444444 99,plate ,,vi4 ,de,forest and ,marconi ,systems499 4444444444444444444444444 ,fig4 #adh4 ,experimental ,amateur ,station of ,w4 ,haddon1 ,brooklyn1 ,n4 ,y4 ,fig4 #adi4 ,complete ,receiving ,outfit ,consisting of ,receiving ,transformer1 ,detector1 ,fixed ,condenser1 ,loading ,coil1 ,two ,variable ,condensers1 ,potentiometer1 ,battery1 ,switches1 etc4 4444444444444444 ,fig4 #aej4 ,receiving ,outfit ,consisting of ,receiving ,transformer1 ,fixed ,condenser and ,detector4 4444444444444444444444444444444444444 ,fig4 #aea4 ,amco ,oscillation ,helix4 444444444444444444444444444444444 ,fig4 #aeb4 ,details of ,oscillation ,helix ,construction4 44444444444444 ,fig4 #aec4 ,quenched ,gap4 4444444444444444444444444444444444444444 444 ,fig4 #aed4 ,quenched ,gap4 4444444444444444444444444444444444444444 444 ,fig4 #aee4 ,details of ,disk and ,ring4 4444444444444444444444444444444 ,fig4 #aef4 ,explanatory ,drawing of ,quenched ,gap4 44444444444444444444 ,fig4 #aeg4 ,amco ,rotary ,gap4 4444444444444444444444444444444444444444 ,fig4 #aeh4 ,details of ,revolving ,parts of ,rotary ,gap4 444444444444444 ,fig4 #aei4 ,details of ,rotary ,gap4 4444444444444444444444444444444444 ,fig4 #afj4 ,methods of ,preventing ,kick ,back4 4444444444444444444444 ,fig4 #afa4 ,variometer4 4444444444444444444444444444444444444444 44444 ,fig4 #afb4 ,silicon ,detector4 444444444444444444444444444444444444444 ,fig4 #afc4 ,pyron ,detector4 4444444444444444444444444444444444444444 4 ,fig4 #afd4 ,galena ,detector4 4444444444444444444444444444444444444444 ,fig4 #afe4 ,audion4 4444444444444444444444444444444444444444 444444444 ,fig4 #aff4 ,audion ,circuit4 4444444444444444444444444444444444444444 4 ,fig4 #afg4 ,rotary ,variable ,condenser4 444444444444444444444444444444 ,,chapter ,i4 ,,introductory4 ,being desirous of keeping this book as far as possible within the limits prescribed by the title1 it is not possible to go deeply into the theory of the propagation of electric waves1 but at the same time it is not deemed advisable to plunge suddenly into the construction of wireless apparatus without giving some explanation of the underlying principles4 ,if the reader desires information upon this subject he is referred to ,fleming's ,electric ,wave ,telegraphy or the same author's ,elementary ,manual of ,radio-telegraphy and ,radio-telephony4 ,the explanations given in this chapter do not involve any actual theory of the transmission and reception of electric waves4 ,they are merely intended to show the train of actions which take place and may be observed in a physical sense4 ,with this purpose in view1 several references have been made to simple hydraulic apparatus and an analogy drawn to render the explanation clearer4 ,the ,transmission and ,reception of ,electric ,waves4 ,wireless telegraphy by means of electromagnetic waves may be divided into four distinct operations1 namely3 #a4 ,the generation of electrical oscillations4 #b4 ,the transformation of electrical oscillations into electrical waves4 #c4 ,the transformation of electrical waves into electrical oscillations4 #d4 ,the detection of the electrical oscillations4 ,the first two operations comprise those taking place at the transmitter1 while the last two1 which are the converse of the first1 are in evidence only when receiving4 ,illustration3 ,fig #a4 ,hertz ,oscillator and ,resonator4 ,fig4 #a illustrates the original ,hertz oscillator and resonator1 which is the simplest form a wireless installation may take4 ,t represents the transmitting apparatus and ,r the receptor4 ,at the transmitting station a telegraph key is placed in series with a battery and an induction coil4 ,two large metal plates1 t and t'1 are connected to the opposite sides of the spark gap1 which in turn is connected to the secondary of the induction coil4 ,when the key is pressed the electrical circuit is completed and the voltage of the battery is raised sufficiently by the induction coil to charge the metal plates t and t'4 ,the key serves to break the current into periods corresponding to the dots and dashes of the telegraph code4 ,when the high voltage of the induction coil is impressed upon the plates they become charged1 and being of opposite polarity1 when at a maximum the energy rushes across the gap and produces a disruptive spark4 ,each discharge1 although appearing like a single spark passing in one direction1 is in reality made up of a large number of rapid oscillations or surgings4 ,the first passage of current serves to more than discharge the plates and they become charged in the opposite direction4 ,a reverse discharge then occurs which also oversteps itself1 and thus the oscillations go on1 but gradually become weaker and weaker until they die completely or are damped out4 ,the heated air of the spark gap becomes a conductor during the passage of the spark1 and the oscillations are enabled to surge back and forth at the rate of #ae1jjj to #a1jjj1jjj per second1 although the actual discharge may take only a fraction of a second4 ,illustration3 ,fig4 #b4 ,hydraulic ,oscillator4 ,the generation of electrical oscillations may perhaps be made more clear by reference to the hydraulic apparatus illustrated in ,fig4 #b4 ,t and ,t' are communicating tubes divided by an elastic membrane ,m4 ,the tubes may be likened to the metal plates t and t' or the arms of the oscillator4 ,the membrane may be likened to the layer of air between the knobs which separates the opposite arms of the oscillator4 ,p is a pump connected to the two tubes ,t and ,t'1 and the broken lines in the apparatus represent water4 ,the pump corresponds to the induction coil in ,fig4 #a1 and the water to the secondary currents of the induction coil4 ,when the pump is set in operation1 the water is drawn from the tube ,t and injected into ,t'4 ,the pump valves prevent it from flowing back4 ,when the level becomes very high in ,t'1 the great pressure distends the membrane in the direction shown by the dotted line until finally it bursts and the water is allowed to flow with a rush into the tube ,t4 ,but the inertia of the water causes it to rise higher in the tube than its final position of equilibrium1 while in returning and endeavoring to seek its level its inertia carries it below this position4 ,thus the water oscillates back and forth until finally it comes to rest4 ,similarly the difference of potential of the oscillator arms is not immediately equalized upon the breaking down of the air gap1 and the apparatus becomes the seat of extremely rapid electrical oscillations1 as explained above4 ,all space is supposed to be filled with a highly attenuated1 invisible and weightless medium called ether4 ,when the electrical oscillations surge back and forth through the arms of the oscillator1 portions of the energy are thrown off from the apparatus and travel in enlarging circles like the ripples on a pond4 ,these consist of lines of dielectric stress or electrostatic flux which pass through the ether and constitute electromagnetic waves4 ,the receptor or resonator ,r1 ,fig4 #a1 consists of a circle of wire having in it a small spark gap capable of minute adjustment4 ,two metal plates r and r' are sometimes attached to the opposite sides of the spark gap4 ,when the key is pressed at the transmitting station and waves are sent out through the ether1 they strike the resonator and set up therein electrical oscillations which pass across the gap in the shape of sparks4 ,illustration3 ,fig4 #c4 ,hydraulic ,transmitter and ,receptor4 ,to make the explanation clearer1 let us consider ,fig4 #c in which two floats or blocks of wood are represented as resting on the surface of a tank or pool of water4 ,one float1 ,a1 is connected by a rope and pulley so that by jerking the rope the float may be made to oscillate and cause little ripples or waves to pass outwards in a gradually enlarging circle4 ,when the waves reach the float1 ,b1 they cause it to rise and fall with each wave or to oscillate and reproduce the movements of the float1 ,a4 ,likewise the oscillations set up by a wireless transmitter are sent out into space to be caught and duplicated at the receiving station4 ,of course this analogy to the propagation and reception of electric waves is not the same as the true electrical actions1 but is merely a graphical1 representation4 ,illustration3 ,fig4 #d4 ,simple ,wireless ,telegraph ,transmitter and ,receptor4 ,the wireless telegraph outfit illustrated in ,fig4 #a would not serve for more than short distances of a few feet1 and so a somewhat similar but more efficient apparatus is employed in practice4 ,fig4 #d shows such a system in its simplest form4 ,in this case the secondary or high potential leads of the induction coil are connected1 one to an earth and the other to an aerial or antenna composed of a number of bare copper wires insulated and suspended from a mast4 ,all electrically charged bodies are surrounded by an electrostatic field of force1 the nature of which in theory is a state of strain4 ,the action of an induction coil connected as in ,fig4 #d is to charge the upper part of the aerial above the spark gap1 say with negative electricity and establish a field of force in its vicinity varying in area from a few feet to several miles4 ,when the charge reaches a certain potential it is sufficient to puncture the layer of air in the gap and a spark takes place1 setting up electrical oscillations4 ,illustration3 ,fig4 #e4 ,electric ,waves and ,lines of ,strain4 ,previous to the rupture of the spark gap1 lines of electric strain or force stretch from the aerial to the earth on all sides as in the center of ,fig4 #e4 ,a line of force may be defined as a curve drawn in the electric field so that the direction of the curve is the same as that of the electric intensity at that point4 ,the aerial and the earth act like the two metal plates in ,fig4 #a or like the opposite plates of a condenser4 ,as soon as the air gap is punctured it becomes conductive and the aerial charge rushes down into the earth4 ,with the discharge1 the strain in the electrostatic field is released and the aerial charge rushes down into the earth1 but in so relaxing produces a new current and builds up a strain around the antenna opposite in direction to the first4 ,this process repeats itself very rapidly and electrical oscillations are thus set up in the antenna4 ,every oscillation changes the direction of the magnetic flux or dielectric strain and causes the imaginary lines which originally stretched from the aerial to the earth to be displaced and the ends terminating at the aerial to run down it and form semi-loops or inverted ,u's standing with their ends on the earth in a circular ripple around the aerial and moving away from it with the speed of light4 ,in ,fig4 #e three oscillations are supposed to have taken place4 ,the shortest distance between two adjacent points at which the electric strain is at a maximum in the same direction and period of time is the wave length emitted by the aerial4 ,the separate standing groups of dielectric strain moving away from the antenna are electromagnetic waves4 ,in the figure1 the adjacent groups are separated by half a wave length4 ,these waves are emitted at right angles to the transmitting aerial1 whence they pass through the ether to the other station4 ,when they reach the receiving aerial they set up electrical oscillations therein which are too weak to be perceptible in the shape of sparks as in the original ,hertz oscillator and resonator because of the great distance separating the stations1 so they are made to flow through a detector1 which in ,fig4 #d is represented as being a crystal of a mineral called silicon4 ,when the high frequency currents strike the silicon1 they set up a weak pulsating direct current4 ,this action is due to a peculiar rectifying property of the mineral4 ,the direct current flows through the telephone receiver and produces an audible sound4 ,if the aerial and ground were connected directly to the terminals of the telephone receiver1 without the silicon1 the oscillations would not pass because of the impeding or choking action of the electro-magnets in the telephone receivers4 99,tuning499--,it is sometimes desirable that messages should be made selective or secretive4 ,it is obvious that if there were several large stations in the same neighborhood they could not all operate at the same time unless some means of preventing the stations from receiving more than one message at a time were possible4 ,this is the object in view of the so-called tuning of wireless telegraphy4 ,it also accomplishes a second purpose which is perhaps considered more important than the first4 ,the length of the aerial may be too great or too short for the amount of energy and the length of the waves which it emits or receives4 ,when this is the case1 the oscillations are quickly damped out and do not generate very powerful waves or produce strong signals at the receiving station and thus by properly adjusting the circuit all undesirable messages may be cut out as well as the signaling range greatly increased4 ,every electrical circuit has a definite period or electrical length1 determined by its inductance and capacity4 ,a circuit emits waves of only one length for given values of inductance and capacity1 and must also be of a certain length before it will respond to waves sent out by another transmitter4 ,the careful adjustment of a circuit to emit or receive a given wave constitutes tuning4 ,illustration3 ,fig4 #f4 ,resonance ,tube4 ,this may be made more clear by the comparison of an electrical circuit with a column of air4 ,fig4 #f represents a cross section of a glass tube1 ,t1 lying in a horizontal position and containing a cork1 ,c1 which can be slid to various positions4 ,by adjusting the cork we are able to obtain various depths of air in the tube from its open end1 ,m1 to the cork1 ,c4 ,when a vibrating tuning fork1 ,f1 is held opposite the open mouth and the cork slid back and forth it is found that the sound of the tuning fork is greatly increased in volume at a certain position of the cork4 ,if the cork is then removed from this position the sound decreases in intensity4 ,when the cork is in such a position that the sound of the fork is reenforced1 we have secured resonance4 ,when in this condition and the prong of the vibrating fork is moving toward the open mouth of the tube a condensed pulse of air travels down the tube and back again1 having been reflected at the cork and reaching ,m just as the prong of the fork begins its excursion away from the open mouth of the tube4 ,when the prong of the fork is moving away from ,m a rarefied pulse of air moves from ,m to ,c and back again by the time the prong is ready to begin its next vibration4 ,when the tube is not in resonance1 the successive condensations and rarefactions passing up and down the air column interfere with one another and decrease instead of increase the sound of the tuning fork4 ,if we substitute the sound waves emitted by the tuning fork for high frequency oscillations and the air column for the electrical circuit we may readily see that by adjusting its length1 resonance can be produced4 ,if the length of the air column is measured it will be found that the reenforcing of the sound of the fork reaches a maximum when the depth of the air column is one-fourth of the sound wave length given by the fork4 ,likewise resonance is produced in wireless telegraphy when the length of the circuit is approximately one-fourth the length of the waves4 ,vice versa1 the wave emitted from an ordinary closed circuit transmitter is approximately four times the length of the aerial wire4 ,for example1 an aerial #be meters long will emit waves having a length in the neighborhood of #ajj meters4 ,as stated above1 tuning is accomplished and resonance or syntony established by varying the inductance and capacity of the circuit4 ,the capacity of a circuit may be defined as its relative ability to retain an electrical charge1 while inductance is the property of an electric circuit by virtue of which lines of force are developed around it4 ,capacity and inductance are opposite or reactive in their effects upon a circuit4 ,if the value of one is decreased the influence of the other in increased4 ,fig4 #g and the following explanation will serve to illustrate this4 ,illustration3 ,fig4 #g4 ,lag and ,lead4 ,alternating currents do not always keep step with the voltage impulses of a circuit4 ,if there is inductance in the circuit1 the current will lag behind the voltage1 and if there is capacity1 the impulses of the current will lead4 ,fig4 #g ,a illustrates the lag produced by inductance and ,b the lead produced by capacity4 ,in ,a the impulses of the current1 represented by the full line1 occur a little later than those of the volts as represented by the dotted line4 ,in ,b the effect is just the opposite and the current leads4 ,these reactive effects of inductance and capacity are very pronounced with the high frequency currents of wireless telegraphy1 and1 as stated before1 are the factors which determine the period of the circuit4 ,illustration3 ,fig4 #h4 ,tuned ,hydraulic ,transmitter and ,receptor4 ,tuning is represented graphically in ,fig4 #h4 ,the two floats ,a and ,b are not only resting on the surface of a pool of water as in ,fig4 #c but are also suspended from the springs ,s and ,s'4 ,the springs will have1 like a pendulum1 a definite time of rising and falling1 or period of oscillation1 depending upon their length4 ,if we strike the float ,a the spring will cause the float to rise and fall at a definite rate and send out a little wave or ripple with every oscillation4 ,if the springs ,s and ,s' are of the same length1 the float ,b will be caused to oscillate with every wave sent out by ,a1 for1 the periods of the springs being equal1 ,b will be permitted to rise with a wave and fall again just in time to be raised by the next oncoming ripple4 ,on the other hand1 if the springs are of different lengths1 ,b may only rise slightly and in falling meet an oncoming wave which will cause it to rise before it has reached its lowest point and so dampen or weaken its oscillations that they either do not become very strong or are entirely obliterated4 ,thus several floats having different periods of oscillation might be sending out ripples in the same pool1 and the float ,b could be made to respond to any of them by adjusting the length of the spring4 ,we may also see in this illustration the part that tuning plays in causing the apparatus to emit or receive more powerful impulses4 ,when the rope in the untuned apparatus illustrated in ,fig4 #c is jerked1 the block ,a oscillates only once or twice before a new jerk is required to keep it in motion4 ,in ,fig4 #h it is quite the contrary1 for when an impulse has been given to the float ,a it will oscillate much longer than the untuned float before it requires to be set in motion again4 ,likewise the float ,b in ,fig4 #h will oscillate longer and more powerfully than the float ,b in ,fig4 #c1 when once it has been set in motion4 ,illustration3 ,fig4 #i4 ,tuned ,wireless ,telegraph ,transmitter and ,receptor ,fig4 #i shows a diagram of a simple wireless telegraph system employing an inductance and capacity for tuning the circuits4 ,when the induction coil is in operation it charges a condenser4 ,the condenser discharges through the sending helix and across the spark gap4 ,the sending helix is merely a spiral coil of wire of large diameter1 and constitutes the greater part of the inductance in the circuit4 ,two movable contacts1 ,a and ,b1 make connections with the helix4 ,the spark gap1 condenser and lower portion of the helix up to the movable contact ,a are known as the closed circuit4 ,by shifting ,a1 more or less inductance may be included in the closed circuit until resonance is secured4 ,the aerial1 the inductance from the contact ,b down1 the condenser and the ground compose the open circuit4 ,by varying the contact ,b more or less inductance may be included in the open circuit and its period altered until the oscillatory currents of both circuits flow in the same period of time4 ,the closed and open portions of the transmitting helix form an auto transformer1 and the voltages of the open circuit are raised above those of the closed circuit4 ,the tuned receptor shown in ,fig4 #i is the simplest form possible and is known as the single slide system4 ,the tuning coil or helix is much longer in proportion to its diameter than the sending helix1 and is made of finer wire1 since it does not carry such heavy currents4 ,when the contact is slid up or down on the tuning coil1 the inductance of the circuit is varied4 ,since the oscillating currents in the receiving aerial have the same frequency as those in the radiating aerial1 the receptor must have the same relative values of inductance and capacity4 ,this condition is obtained by varying the slider until the signals in the telephone receivers are the loudest4 ,in practice more than one sliding contact is used1 and these together with adjustable condensers make the circuit more complicated4 ,these devices are necessary because oscillations may be forced on a receptor by a near-by transmitter unless other precautions than the single slider are taken4 ,such circuits are illustrated in ,plates ,,iv and ,v4 ,with them it is possible to obtain a considerable degree of selectivity and tune out an undesirable message4 ,,chapter ,,ii4 ,,the ,,apparatus4 ,it is generally the receiving apparatus which first attracts the attention of the amateur operator1 and so it will be considered first here4 ,an efficient receiving set consists of some form of ,detector1 ,tuning ,coil1 ,telephone ,receivers1 and ,condenser4 ,other accessories such as adjustable condensers1 potentiometer1 battery and testing buzzer improve the outfit and make it more complete4 ,the choice of the type of instruments must be left entirely to the person who is constructing them4 ,his resources will determine whether he is to use #a1jjj ohm telephone receivers built especially for wireless work or ordinary ones having a resistance of only #ge ohms4 ,it is therefore best to read carefully the chapters devoted to the different pieces of receiving apparatus and select the type of detector1 tuning coil1 etc41 which it is desirable to use before commencing the construction of any4 ,for beginners1 ,i would recommend an outfit consisting of a silicon detector1 a double slide tuning coil1 a condenser of fixed capacity and #ge-ohm telephone receivers4 ,such an outfit with a #ej-;foot aerial will receive messages about #aej miles4 ,if #a1jjj ohm telephone receivers are used1 messages may be read up to #djj miles4 ,much depends upon the location of the station and the ability of the operator4 ,a more elaborate and efficient set consists of an electrolytic or ,perikon detector1 a transforming tuner1 two adjustable condensers1 a potentiometer and a pair of #a1jjj ohm telephone receivers4 ,this outfit and a #ge-;foot aerial could be made to receive #ejj to #a1jjj miles by a careful operator4 ,several cuts of wireless apparatus built for private installation are shown both in this chapter and further through the book1 to give an idea of how the better instruments of this type are constructed and finished4 ,illustration3 ,fig4 #aj4 ,long-distance ,receiving ,set4 ,fig4 #aj illustrates a selective receiving set built by the ,long ,distance ,wireless ,company4 ,the set is mounted on a mahogany base and the instruments are finished in polished hard rubber and lacquered brass4 ,they comprise a detector stand so arranged that any of the sensitive minerals used in wireless work may be used4 ,the tuning coil is of the double slide type4 ,the condenser is sealed up in a square lacquered brass tube fitted with hard rubber ends and binding posts4 ,the arrangement and construction of the outfit may be readily understood from the cut4 ,illustration3 ,fig4 #aa4 ,murdock ,receiving ,set4 ,fig4 #aa illustrates a receiving set manufactured by the ,wm4 ,j4 ,murdock ,company4 ,the tuning coil is fitted with hard rubber composition ends and is wound on a special core which is not affected by temperature changes4 ,the detector is of the crystal type and is of rather unique construction1 since the small fixed condenser is mounted in the base of the detector itself4 ,the ,clapp-,eastham set in ,fig4 #ab employs a receiving transformer which makes great selectivity possible4 ,the detector is mounted at the left-hand side of the outfit4 ,a very sensitive mineral called ,ferron is used in the detector4 ,the fixed condenser is enclosed in a brass tube fitted with hard rubber ends and is located on the front of the base1 directly in the center4 ,a variable condenser of the rotary type is placed at the right-hand corner4 ,illustration3 ,fig4 #ab4 ,clapp-,eastham ,receiving ,set4 ,the ,prague ,electric ,company manufacture the apparatus shown in ,fig4 #ac4 ,the cabinet is mahogany and is fitted with a hard rubber cover4 ,a fixed condenser and a double slide tuning coil are mounted within the cabinet4 ,the sliders of the tuning coil project through two long slots in the cabinet4 ,a universal detector mounted on top of the cabinet is so designed that any material may be experimented with or tested4 ,illustration3 ,fig4 #ac4 ,prague ,receiving ,set4 ,fig4 #ad shows a receiving set built up from apparatus described in this book4 ,the cabinet is #ab x #af inches and #d inches deep4 ,the wood should be #a_/b inch thick1 and in order to present a good appearance is preferably of mahogany4 ,as mahogany is sometimes very hard to procure and expensive1 some may find red birch an excellent substitute4 ,when stained with a mahogany stain it presents a fine appearance4 ,illustration3 ,fig4 #ad4 ,receiving ,set4 ,varnishing and polishing are wasted time when applied to the average amateur's instruments in view of the rough handling and scratching which they receive4 ,the best plan is to stain the wood with an oil stain and give it a wax finish4 ,an oil stain contains no varnish but is merely coloring matter and oil4 ,a good coat should be applied with a wide brush and the surplus stain immediately wiped off by rubbing the whole surface with a piece of cheesecloth4 ,as soon as the stain is thoroughly dry the wood is waxed4 ,cut up some beeswax into fine shreds and place it in a jar4 ,pour some turpentine over the beeswax and let the mixture stand for five or six hours1 giving it an occasional stir4 ,allow it to stand further if necessary until the wax melts and then add enough turpentine to give the mixture a consistency similar to that of thick cream4 ,apply the preparation to the wood with a rag1 and then rub with a piece of clean cheesecloth until the finish is hard and dry4 ,waxing produces a gloss which is not so bright as a ,french polish but yet is more durable and not so easily scratched or marred4 ,a double slide tuning coil made as described in ,chapter ,,xiv is mounted on top of the cabinet in the rear4 ,a universal detector is mounted in the center1 directly in front of the tuning coil4 ,a tubular condenser of fixed capacity is placed on the left-hand side of the detector1 and a potentiometer on the opposite side4 ,a double point switch placed directly in front of the detector enables the potentiometer to be brought into play when a battery is used4 ,four binding posts are mounted on the front of the cabinet4 ,the ground and aerial are connected to the left-hand pair and the telephone receivers to those on the right hand4 ,the wiring diagram is shown also in ,fig4 #ad4 ,by placing the switch ,a on contact #a1 the potentiometer is brought into use4 ,when on contact #b1 the potentiometer is cut out4 ,the switch ,b must be opened when the detector is not in use so as not to run down the battery4 ,illustration3 ,fig4 #ae4 ,receiving ,set4 ,fig4 #ae shows a receiving set somewhat similar to that shown in ,fig4 #ad but more elaborate and efficient4 ,the cabinet in this case measures #ad x #bb inches and is #f inches deep4 ,a loosely coupled or transforming tuning coil is used in place of the closely coupled double slide type4 ,two variable condensers are mounted on either side of the tuning coil4 ,the detector and potentiometer occupy the space directly in front of the tuning coil1 while a fixed condenser is placed at their right4 ,the two switches for breaking the battery circuit and disconnecting the potentiometer are in front of the detector4 ,the aerial1 ground and telephone receiver leads are connected to binding posts mounted on the front of the cabinet4 ,the batteries1 in both cases1 are placed inside the cabinet4 ,the details and construction of all the separate instruments will be found in the respective chapters as denoted by the titles4 99,transmitting ,range499--,a simple transmitting outfit capable of sending about two miles consists of the necessary batteries1 a one-inch spark induction coil1 a small zinc spark gap and a key4 ,the connections of such a transmitting outfit are shown in ,fig4 #d4 ,if the same coil is used with a transmitting helix and a condenser1 the range may be increased from #c to #e miles4 ,a #a #a_/b-;inch spark induction coil using a condenser and a transmitting helix will send about #aj miles1 and a #c-;inch coil under the same conditions about #bj miles4 ,a #d and a #f inch coil will transmit about #cj and #dj miles respectively4 ,illustration3 ,fig4 #af4 ,murdock ,transmitting and ,receiving ,set4 ,the one quarter kilowatt transformer with a helix and four two-quart leyden jars or an equivalent condenser will transmit at least #ej miles with a suitable aerial4 ,used as a one half kilowatt transformer with a helix and eight two-quart leyden jars1 it will send about #ajj miles4 ,of course1 as in the case of the receiving outfits1 these distances are approximate and depend upon the location of the station1 the nature of the ground over which the messages are transmitted1 the kind of receptor used at the receiving station and the efficiency of the operator himself4 ,fig4 #af illustrates a complete ,murdock transmitting and receiving set4 ,the transmitting outfit consists of a #ae-watt induction coil giving about a one-inch spark1 a sending helix1 oscillation condenser1 a key and a double pole double throw switch for changing the antenna and ground from the transmitting to the receiving instruments or vice versa4 ,the spark gap is mounted on top of the coil4 ,the receiving outfit is the same as that illustrated in ,fig4 #aa4 99,a complete wireless station99--outside of the aerial consists primarily of a source of electrical energy1 a transformer or induction coil for charging the oscillation condenser1 an oscillation condenser1 a transmitting helix1 a key for breaking the primary current1 a spark gap1 an aerial switch1 a hot wire ammeter for tuning the transmitting circuits1 a detector1 a receiving tuner1 auxiliary tuning apparatus such as fixed and variable condensers1 a potentiometer and battery1 and a pair of telephone receivers with a headband4 ,other apparatus such as switches1 insulators1 anchor gaps1 testing buzzers1 reactance coils1 grounding switches1 etc41 have been described in various places throughout the book and their use suggested whenever it is of any advantage4 ,the choice of transmitting instruments1 as with the receiving apparatus1 is left entirely with the experimenter so that he may suit his ideas and means4 ,wherever possible the range and power of the instruments have been given and suggestions made as to the other apparatus which should be used in connection with them so that the completed outfit will bear some sense of proportion4 ,illustration3 ,fig4 #ag4 ,united ,wireless ,portable ,outfit4 ,fig4 #ag illustrates the portable wireless telegraph set manufactured by the ,united ,wireless ,telegraph ,company for army service and exploring expeditions or isolated camps4 ,the aerial and the mast can be unloaded1 erected1 and all parts be ready for operation in fifteen minutes4 ,the mast is made of interchangeable wooden sections4 ,the current for the transmitter is furnished by a portable storage battery4 ,the whole outfit is capable of furnishing efficient service for distances of #be to #cj miles4 ,,chapter ,,iii4 ,,aerials ,,and ,,earth ,,connections4 ,the aerial or antenna ordinarily consists of a number of wires elevated in the air to emit or intercept the ,hertzian waves4 ,in fitting up a wireless station the location and erection of an aerial are of prime importance1 and the successful reception and transmission of wireless messages will depend largely upon its condition4 ,a few years ago the wireless antenna consisted of a metal plate high in the air and having a wire suspended from it1 but to-day usually exists in one of the forms illustrated in ,plate ,,ii4 ,the higher an aerial is placed above the surface of the earth1 the wider will be its electrostatic field1 and consequently more powerful electrical waves will be developed4 ,but after a height of #ahj-bjj feet is attained1 the engineering difficulties and the expenses increase so rapidly that few stations exceed it4 ,other things being equal1 the increased range in transmitting varies as the square of the height of the radiating wires4 ,for example1 a #be-;foot aerial capable of transmitting one mile theoretically will send waves #af miles if made #ajj feet high4 ,the actual ratio is often greater1 but much is dependent upon the many meteorological conditions4 ,after the limit in a vertical direction has been reached1 the only remaining possibilities are to increase the surface and spread out horizontally4 ,the flat top aerials are used on shipboard or wherever it is an advantage to suspend the wires between two masts4 ,they are especially recommended for amateur use1 since they need not be so high as the other aerials1 to be efficient4 ,the flat top aerials are directive1 that is1 they receive or radiate waves better in certain directions4 ,the bent or inverted ,l type is one of these and exhibits a preference for waves coming from a direction opposite to that in which its free end points4 ,this directive action of an inverted ,l antenna may be somewhat lessened if the leads are taken off at the center and it is made a ,t aerial4 ,this is the most common form of flat top aerial in use on ships4 ,the inverted ,u type is not used extensively because the two opposite leads or rat-tails make a centrally located operating room necessary4 ,the loop aerial is used by the ,united ,wireless ,company1 in both their ship and land stations4 ,this type of aerial is well adapted to long waves and close tuning4 ,the ,lodge-,muirhead capacity aerial does not make use of a ground and is rarely seen in this country4 ,lately the ,united ,states ,signal ,corps have applied it to their balloons where an earth connection would be impossible4 ,the upper part of the balloon is covered with a network of wires which serves as the upper aerial1 and a second system of wires is suspended below the balloon to take the place of the ground4 ,by this means they have had little difficulty in establishing successful communication between the balloons and the earth4 ,the pyramid aerial is the type used by ,marconi in long-distance ultra-powerful stations1 but is debarred from extensive installation on account of the large cost of erection4 ,the cage and grid aerials are of the vertical type and are excellent where a high support to elevate them can be secured4 ,they are at present used principally by the ,massie and ,stone ,companies4 ,illustration3 99,plate ,,ii4 ,aerial ,systems499 ,the desirable feature of an aerial is a quantity known as its electrostatic capacity and is measured by the charge required to raise its potential one unit4 ,an increase in capacity enables more energy to be accumulated in the antenna1 and consequently greater radiation results4 ,the capacity of an aerial may be increased by adding wires1 but must not be carried too far or the transmitting apparatus will not be able to raise its potential sufficiently4 ,owing to an effect caused by mutual induction between the wires1 the lines of strain are not distributed symmetrically1 and the capacity will not vary directly but rather approximately as the square root of the number of wires4 ,in order to decrease this action and use the surface most efficiently1 the wires should not be placed nearer than one-fiftieth of their length and preferably farther apart4 ,the materials used for the insulation and suspension of an aerial must be reliable1 so that in event of bad weather the station will not lose energy or be put out of working order because the aerial blew down4 ,porcelain cleats or a string of porcelain insulating knobs make inexpensive insulators4 ,the standard insulator for wireless telegraph work is the ,electrose insulator4 ,these are made of a molded composition1 and have iron rings set firmly in the ends so that they can withstand a very heavy strain4 ,hard rubber is undesirable for an aerial insulator because it becomes carbonized and covered with a conducting layer4 ,illustration3 ,fig4 #ah4 ,electrose ,insulators4 ,high frequency currents permeate copper wire only about one three-hundredth of an inch1 and so1 in order to increase the surface and decrease the resistance1 it is best to make the aerial of stranded wire4 ,a phosphor bronze wire for this purpose which is very flexible but still does not sag or stretch1 is composed of #g strands of ,no4 #bj ,b4 ,s4 gauge4 ,such a wire #aej feet long suspended vertically and insulated from the earth will have a capacity of from #j4jjjc to #j4jjjd of a microfarad4 ,the aerial must receive very particular attention if the station is one kilowatt or over in power4 ,in that case stranded wire is necessary4 ,the insulation of the aerial must be as thorough as possible1 and proximity to large conductors such as smokestacks1 telephone lines1 etc41 avoided4 ,rope stays and guys are advisable in order to prevent dissipation of energy4 ,if wire stays must be used they should be divided up at frequent intervals by insulators4 ,fig4 #ai illustrates a guy insulator used by the ,united ,wireless ,telegraph ,company4 ,it is made of two strips of well paraffined wood separated by two porcelain knob insulators4 ,illustration3 ,fig4 #ai4 ,guy ,insulator4 ,copper wire is the most desirable for an aerial4 ,iron wire must never be used unless it is very heavily galvanized1 and even then it is not to be recommended4 ,aluminum wire is undesirable except for kite sustained aerials4 ,when used on an aerial and exposed to smoke and other fumes it becomes quickly coated with a layer of oxide4 ,all connections made in aluminum wire must be soldered4 ,this necessity may be better understood when it is explained that electro-magnets on dynamos1 etc41 are sometimes wound with bare aluminum wire and that the natural coating of oxide on the wire is sufficient insulation to separate the turns4 ,illustration3 ,fig4 #bj4 ,insulating ,tube4 ,where the aerial enters the building in which the instruments are located it must be very carefully insulated4 ,the simplest method is to bore a hole through the wall and push a porcelain tube through it4 ,the rat-tail or leading-in wire is then passed through and the interstices between it and the tube poured full of melted paraffin4 ,the best method is to bore a hole in the window pane and pass the wire through a hard rubber insulating tube4 ,fig4 #bj shows such a tube4 ,it is three-quarters of an inch in outside diameter and has an internal bore of three-eighths of an inch4 ,the tube is threaded throughout its entire length4 ,two hard rubber flanges inch thick and #b inches in diameter are threaded to screw on the tube4 ,the tube is inserted in the hole in the window pane and the flanges screwed on either side4 ,if a soft rubber washer is placed between the hard rubber flanges and the pane there will be less likelihood of cracking the glass4 ,the leading-in wire is then passed through the tube4 ,the hole in the window pane may be bored by using a copper tube having an external diameter equal to that of the required hole4 ,the tube is set in a brace and used like an ordinary bit1 but must be kept well smeared with emery and oil or else it will not cut4 ,this method of leading in the rat-tail is the only one to be recommended if the transmitter is one-quarter kilowatt or over in power4 ,illustration3 ,fig4 #ba4 ,high-tension ,cable and ,insulator4 ,the lead-in should be anchored just outside of the window so as to relieve the glass pane and the tube from all strain4 ,pirelli cable or the high-tension cable which is used for the secondary wiring of an automobile is the best conductor to use for the aerial in the interior of a building4 ,the way to lead it over the ceiling is to support it on a porcelain cleat similar to that shown in ,fig4 #ba4 ,many are under the erroneous impression that four times the length of the aerial is the wave length which the station will emit4 ,this is only at the best a very rough approximation1 for many undeterminable factors such as the nature and location of surrounding objects1 trees1 etc41 so affect the capacity and inductance of the aerial that the wave length must be determined empirically after the aerial is in operation4 ,the standard wave length of the ,united ,states ,navy for ship installations is #dbe meters4 ,an inverted ,l aerial1 calculated before erection to have a wave length as near as possible to this1 has the following dimensions3 ,four horizontal stranded phosphor bronze wires 7#g strands ,no4 #bj ,b4 ,s47 each #afj feet long and spaced #e feet apart1 four vertical wires #he feet long and a #ce-;foot rat-tail4 ,it is always desirable that the wave length should be as long as possible1 for the waves will then travel farther and are not absorbed to such an extent by trees1 etc4 ,the absorption due to trees is said to vary as the fourth power of the frequency4 ,it is sometimes very convenient to calculate the strain on insulators or masts caused by a horizontal antenna4 ,this is easily found by the following equation3 ,p equals ,l x ,w_/#h,s where ,p is the required strain in lbs41 ,w the weight in lbs4 per foot of aerial1 ,l the length of the aerial and ,s the sag of the wire in feet4 ,when erecting an aerial1 it is best to fasten a pulley at the top of the supporting mast and hoist the aerial up after the pole is in position4 ,then in case the wires become twisted or broken they may be lowered and repaired without any difficulty4 99,erection of an ,aerial499--,the average amateur aerial is generally from #dj to #fj feet high and supported at one end by a short pole placed on the house and at the other end by a mast set in the ground or lashed to a tree4 ,fig4 #bb illustrates such an arrangement whereby a flat-top ,t aerial is supported at one end by a short pole fastened to the house and at the other end by a pole set in the ground4 ,illustration3 ,fig4 #bb4 ,flat-top ,t ,aerial4 ,the flat-top loop aerial is preferred by some amateurs and it is to be recommended for receiving but is an inefficient radiator4 ,when this type of aerial is used the two leading-in wires should be connected to a switch so that when the switch is closed they are connected4 ,the aerial may then be used as a straight-away aerial for transmitting1 and by opening the switch1 as a loop aerial for receiving4 ,this precaution is advised when a loop aerial is to be used with a low-powered induction coil as a transmitter1 for otherwise there will be a loss of energy at the anchor gap4 ,a large aerial is of no advantage when used with a small transformer or induction coil because it cannot become properly charged4 ,to erect a flat-top ,t aerial1 first select its location4 ,if possible take advantage of two trees and lash a short pole in the top of each1 so that the aerial may be raised up clear of the leaves4 ,another good plan is to erect a pole at each end of the house4 ,in any case1 the distance separating the poles must not be greater than three times the height above ground or the directive action of the aerial will be very pronounced4 ,an aerial #ej to #fj feet high should have a length of from #hj to #ajj feet4 ,stranded wire is no advantage for receiving1 but must be used if the transmitter is other than a small induction coil4 ,secure two spruce sticks about #b inches in diameter and #aj feet long4 ,fasten an insulator #f inches from each end of the spars and two more each #c ,j feet from the ends4 ,this arrangement will separate each of the four wires which compose the aerial by three feet4 ,the two spars are then laid on the ground at a distance apart equal to the desired length of the aerial4 ,four wires1 either stranded or ,no4 #ab ,b4 ,s4 gauge copper1 are cut to equal lengths and fastened to the corresponding insulators4 ,the middle of each wire is found and a long copper wire soldered to it4 ,these four wires constitute the rat-tail or lead-in4 ,they should be of the same length1 and are not connected together until they are about to enter the building4 ,a short rope tied to each end of the spars and fastened to the rope which passes over the pulley on the top of the pole1 serves as a bridle to prevent the aerial from twisting4 ,the aerial is then hoisted up but allowed to hang slightly slack4 ,there is considerable difference of opinion among experts as to whether or not the ends of the horizontal wires should be connected1 and it is impossible to say with good reason which method is better4 ,however1 when erecting a flat top aerial1 exercise every care to make all the wires of exactly the same length4 ,an aerial of the size and type just described will send and receive the following distances4 ,these distances are only approximate and will vary with the efficiency of the operator and the location of the station4 ,when any of the transformers described later are used1 the aerial should be #hj to #ajj feet high4 ,in this case the last named receiving outfit will have a range of from #ejj to #a1jjj miles4 99,ground ,connections499--,the importance of a good earth or ground connection can hardly be overestimated4 ,whenever possible commercial stations are located on moist ground or near a body of water so that a good ground may be secured by imbedding zinc or copper plates in the earth or water4 ,a ground on shipboard is easily secured by fastening a conductor to one of the ship's plates4 ,if the ground connection is poor1 the natural period of the oscillation circuit is made irregular and short1 so that the currents are choked in passing in and out of the earth4 ,the result is an undesirable rise of potential at the lower end of the aerial and often harmful sparking at the ground connection4 ,the transmitting and receiving ranges of a station are very considerably reduced through a poor earth4 ,ground connection can often be obtained in the country by immersing metal plates in a well or a cistern4 ,where connection is made to a water supply pipe some sort of a ground clamp should be used to insure a good contact4 ,illustration3 ,fig4 #bc4 ,ground ,clamp4 ,an efficient earth for portable outfits may be quickly formed by spreading a large area of wire netting over the ground4 ,proper precautions for protection against lightning by grounding the aerial outside of the building should be taken4 ,the wisest plan is to install a heavy single pole double throw switch outside of the building where the rat-tail enters4 ,the knife of the switch should be connected to the aerial1 one contact to the house lead and the other to a heavy wire grounded on the outside of the building as in ,fig4 #bd4 ,when the apparatus is not in use the aerial should be grounded by throwing the switch on the grounded contact4 ,illustration3 ,fig4 #bd4 ,switch for ,lightning ,protection4 ,the rulings of the ,national ,board of ,fire ,underwriters governing this class of work are appended below4 #a4 ,aerial conductors to be permanently and effectively grounded at all times when the station is not in operation by a conductor not smaller than ,no4 #d ,b4 ,s4 gauge copper wire1 run in a direct line as possible to water pipe on street side of said water pipe within the premises or to some other equally satisfactory earth connection4 #b4 ,aerial conductors when grounded as above specified must be effectually cut off from all apparatus within the building4 #c4 ,or the aerial to be permanently connected at all times to earth in the manner specified above1 through a short gap lightning arrester2 said arrester to have a gap of not over 4#jae of an inch between brass or copper plates not less than #b #a_/b inches in length1 parallel to the gap1 and #a #a_/b inches the other way1 with a thickness of not less than one-eighth of an inch1 mounted on non-combustible1 non-absorptive insulating material of such dimensions as to give ample strength4 ,other approved arresters of equally low resistance and equally substantial construction may be used4 #d4 ,in cases where the aerial is grounded as specified in paragraph #a1 the switch employed to join the aerial to the ground connection shall not be smaller than a standard #ajj-;ampere jack-knife switch4 ,notice of wiring done for these installations should be sent to the ,board1 the same as for all other work4 ,,chapter ,,iv4 ,,induction ,,coils4 ,some means of charging the condenser which produces the oscillatory discharge is necessary4 ,an induction coil is the most practical for the amateur4 ,the induction coil consists of a primary coil of wire wound around a central iron core and surrounded by a secondary coil consisting of many thousand turns of carefully insulated wire4 ,the primary coil is connected to a source of direct current which also includes an interrupter to make and break the current in rapid succession4 ,every make of the circuit and consequent magnetization of the core induces a momentary inverse current in the secondary1 and every break and corresponding demagnetization a momentary direct current4 ,normally1 the induced currents would be equal1 but by means of a condenser shunted across the interrupter the circuit when made requires considerable time for the current and magnetization of the core to reach a maximum value1 while when broken the demagnetization and current drop are nearly instantaneous4 ,the value of the induced electromotive force in a circuit varies as the speed at which the magnetic lines of force cut the circuit1 and so the induced e4m4f4 at break is thus rendered high enough to leap across a gap in the shape of sparks4 ,the formulas connected with induction coils depend upon conditions which are never met in actual practice and cannot be relied upon4 ,to construct a coil of a given size1 it is necessary to use dimensions obtained empirically4 ,therefore it is well for the amateur to stick closely to lines and hints which are given here or which appear in some up to date book on induction coil building4 ,illustration3 ,fig4 #be4 ,diagram of an ,induction ,coil4 ,for a long time the induction coil was an expensive1 inefficient instrument1 until wireless telegraphy demanded of it more rigid and efficient design and construction4 ,it was the aim of manufacturers to produce the longest possible spark length with a minimum amount of secondary wire4 ,as a result of this demand1 wireless coils are now made with a core of large diameter and give heavier and thicker sparks4 ,the secondary in this case is short and uses wire of large cross section in order to reduce the resistance and minimize the heating4 ,no one part of an induction coil may be developed to its maximum efficiency without seriously influencing and lowering the efficiency of the other parts4 ,the following suggestions regarding the construction are given that they may prove a useful guide to the amateur coil builder4 ,the parts will be considered in their natural order of construction4 99,core499--,some experimenters not quite familiar with the principles of magnetism reason that if an induction coil were provided with a closed core as the transformer1 the efficiency of the coil would be materially increased4 ,but this is not so1 for the magnetization and demagnetization of the iron cannot take place rapidly enough in a closed core when an interrupted direct current is employed in place of an alternating current4 ,the core of an induction coil is therefore always straight4 ,for the same reason1 it is never solid but is made up of a bundle of soft iron wires in order that rapid changes in magnetism may take place4 ,the wires are always of as high a permeability as possible so as to create a strong magnetic field4 ,swedish or ,russian iron of a good quality is the best1 as its hysteresis losses are small4 ,the smaller the diameter of the wire the less will be the eddy current losses and heating1 but the permeability is also rendered less and the core will not be so effective1 as the amount of iron is thereby decreased and the oxidized surface increased4 ,no4 #bb ,b4 ,s4 gauge wire is the best size for the average core4 ,wires of a good quality may be purchased already cut to various lengths4 ,to buy them in this form will save a great deal of the labor required in building a core4 ,if the wires are not quite straight they may be straightened by rolling them1 one at a time1 between two boards4 ,it is best to reanneal the wires in the following manner4 ,place them in an iron pipe and plug the ends of the pipe with clay4 ,then lay it in a coal fire until the whole mass attains a red heat4 ,the fire is then allowed to die out gradually with the pipe and wires remaining in the ashes until cool4 ,when cool remove them from the pipe and rub each one with emery paper until bright4 ,after this cleaning1 the wires are dipped in hot water and dried4 ,they are then dipped in a good quality of varnish and allowed to dry again4 ,illustration3 ,fig4 #bf4 ,induction ,coil ,core4 ,the varnish serves to interpose resistance to the eddy currents generated in the core and renders the losses due to this cause much less4 ,a strong paper tube having an internal diameter equal to the diameter of the finished core is made by rolling the paper on a form and cementing with shellac4 ,when perfectly dry4 the tube is removed and the wires tightly packed in it4 ,the following table gives the core dimensions for practical coils of different sizes4 99,primary ,winding499--,the ratio of the number of primary turns of an induction coil to the number of secondary turns bears no relation to the ratio of the primary and the secondary currents4 ,it has been found in practice that two layers of wire wound tightly on the core constitute the best primary4 ,the primary should always be thoroughly shellacked or covered with insulating varnish4 ,since there is almost no ventilation in the primary the wire must be large enough to avoid all heating4 ,a table containing the various sizes of primary wires is given below4 ,in large coils1 the inductance of the primary causes a kick back and sparks are liable to pass between the adjacent turns4 ,for this reason1 it is always well to use double cotton covered wire and to further thoroughly insulate it by soaking the primary and core in a pan of melted paraffin and allowing them to harden therein4 ,afterwards the pan is slightly warmed to loosen the cake of paraffin and the excess of wax removed by scraping with a blunt instrument so as not to injure the wires4 ,paraffin contracts upon hardening1 and the proper method to impregnate a porous substance is to allow it to soak and become set in it upon cooling4 ,a good method of reducing the kick back and also the size of the condenser shunted across the interrupter is to form the primary of a number of turns of smaller wire in parallel1 the effect being to give a conductivity equal to a single wire of large diameter and at the same time to make a more compact winding of the primary on the core4 ,this method of winding is very desirable in large coils1 as it reduces the cross section of the primary and allows the secondary to be placed nearer the core1 where the magnetic field is the strongest4 ,the primary winding ought to occupy nearly the whole length of the core1 since there is no gain in carrying the end of the core very far beyond the end of the primary1 for most of the magnetic lines of force bend at the end of the primary and return without passing through the extreme ends of the core4 99,insulating ,tube499--,the successful operation of an induction coil without breaking down when under strain depends largely upon the insulating tube which separates the primary and secondary4 ,hard rubber tubes are perhaps the best4 ,a tube may be easily built up of several layers of #a_/b-;inch sheet hard rubber by steaming it so as to soften it and then wrapping it around a form4 ,the tube should fit the primary tightly and be about one inch shorter than the core4 ,after the tube is in place it is poured full of beeswax and rosin in order to fill all interstices and prevent sparks due to the condenser effect of the windings from jumping from the inside of the tube to the primary4 99,secondary499--,a coil used as a wireless telegraph transmitter must have wire of large cross section in its secondary so as to obtain a heavy disruptive discharge4 ,numbers #cd and #cb ,b4 ,s4 are generally used for small coils and numbers #cj and #bh ,b4 ,s4 for large coils4 ,silk covered wire is the usual practice1 but enameled wire is coming into use4 ,cotton covered wire takes up too much space and has poorer insulating qualities4 ,enameled wire is insulated by a coating of cellulose acetate1 which has a dielectric strength of about twice that of cotton and takes up much less room than silk4 ,there is1 then1 with enameled wire a great saving in space1 and a greater number of turns may be placed on the secondary without increasing its mean distance from the core4 ,the following table shows the comparative diameters of silk and enamel covered wires suitable in size for use on the secondaries of induction coils4 ,in winding enameled wire it must be taken into consideration that the insulation of enameled wire is rigid and has no give4 ,consequently1 to allow for expansion1 enameled wire must be more loosely wound than fiber or silk covered wire4 ,the occasional insertion of a layer of paper in winding will give room for expansion and at the same time not add greatly to the diameter4 ,illustration3 ,fig4 #bg4 ,theoretical and practical form of secondary4 ,the length of the secondary is generally not much more than one-half the length of the core4 ,coils giving sparks up to #b inches in length may be wound in two sections or in layer windings1 but the layer winding is not recommended for coils giving sparks over one inch4 ,it is best in a coil of this kind to insert an occasional layer of paper4 ,the paper should be well shellacked or paraffined and be of a good grade of linen4 ,it should project about one-quarter of an inch from the ends of the secondary as shown by the sectional drawing in ,fig4 #bh4 ,this insertion of paper increases the insulation and renders the liability of sparks jumping from layer to layer much less1 as is the case when the layers are very long4 ,illustration3 ,fig4 #bh4 ,layer ,winding for ,small ,coils4 ,the secondaries of large coils are made up of pies or pancakes from one-eighth to three-eighths of an inch in thickness4 ,the pies are separated from each other by a triple thickness of blotting paper which has been thoroughly dried and then soaked in melted paraffin4 ,in cutting the blotting paper1 much labor may be saved if a metal template of the required size is first cut from sheet brass and then laid on the blotting paper1 which is cut by scoring around the edge of the template with a sharp knife4 ,illustration3 ,fig4 #bi4 ,section ,winder4 ,the pies are wound in a bobbin or form such as is shown in ,fig4 #bi4 ,the disks or flanges are made of sheet brass and mounted on an arbor so that the form may be placed in a lathe or some other contrivance for revolving it4 ,the core is beveled in order to facilitate the removal of a completed pie from the winder4 ,the flanges of the winder are clamped against the core by two nuts placed on either side4 ,the pie is removed by unscrewing one of the nuts and removing one of the flanges4 ,in winding silk covered wire it is first passed through a mixture of beeswax and rosin or a bath of melted paraffin4 ,the excess of wax is removed by passing the wire through a slit made in a pad of paper or by rubbing against a piece of felt4 ,fig4 #cj shows such a contrivance4 ,illustration3 ,fig4 #cj4 ,impregnator for ,silk ,covered ,wire4 ,the wire passes from the reel over an ordinary spool down into the pan of paraffin1 out of the paraffin1 over another spool1 and rubs against a piece of felt to remove the surplus paraffin4 ,the spools are mounted with a screw and a washer so that they will turn without friction4 ,the wire is guided1 when winding1 by the fingers4 ,if it is wrapped with a piece of felt and held between the thumb and forefinger it will run without friction and not cut the fingers4 ,it is necessary that the wire should be closely watched for kinks1 etc4 which would cause the wire to break4 ,oftentimes the wire is broken but is held together by the insulation4 ,therefore each pie should be tested for continuity when completed4 ,this is best accomplished by means of a galvanometer and battery4 ,all imperfect pies should be rejected1 as one of them would cause serious trouble if embodied in the coil4 ,in soldering the secondary wires1 acid must not be used as it soon corrodes the fine wires4 ,rosin is the best flux for this purpose4 ,when building a small coil with a layer winding it is absolutely necessary that the wire should be wound on in smooth even layers4 ,in a built-up secondary having pies not greater than #a_/d inch in thickness such great care is not necessary4 ,illustration3 ,fig4 #ca4 ,methods of ,connecting the ,secondary ,sections4 ,fig4 #ca shows the methods of connecting up the pies or pancakes4 ,in ,a1 the inside of one section is connected to the outside of the next1 and so on4 ,the maximum voltage which can exist between the adjacent sections in this case is equal to the e4m4f4 generated by one pie and is equal throughout4 ,in ,b1 the coils are connected alternately inside and out4 ,the voltage ranges from zero at the points where they are connected1 to a value equal to twice the e4m4f4 developed by one section4 ,it would seem that there would be a saving in insulation space of one-half in the first case1 but it is not so since the connecting wire passes between the pies and therefore the insulation must be twice as thick or exactly equal to that in the second case4 ,the latter method 7,fig4 #ca ,b7 is the best and most convenient4 ,when the pies are connected in this manner the current must flow through alternate sections in opposite directions4 ,to accomplish this it is not necessary to wind every alternate coil in an opposite direction1 but merely to turn them around and connect them with the direction of their windings reversed as shown by the arrows and the bevels in ,fig4 #ca4 ,the connections between the sections must be very carefully soldered4 ,after the secondary is assembled the coil should be placed in a tight receptacle or tank containing melted paraffin4 ,the tank is then connected to an air pump or aspirator and the air exhausted4 ,the diminution of pressure causes any air bubbles in the windings to expand and be pumped out4 ,after standing a while1 the pressure of the atmosphere is readmitted and the place of the bubbles will be occupied by paraffin which has been forced in under pressure4 99,mounting499--,a coil for wireless work is best mounted as shown in ,fig4 #cb and used with an independent interrupter4 ,the coil may then be placed under the operating table or on the wall1 out of harm's way1 and the interrupter on the table1 where it is handy to the adjustment of the operator4 ,illustration3 ,fig4 #cb4 ,coil ,case4 ,the case is simply a rectangular hardwood box large enough to contain the completed coil4 ,two binding posts mounted on the side of the box connect with the primary winding and two on the top of the box lead to the secondary terminals4 ,the box is filled with boiled oil or melted paraffin and sealed up by screwing on the lid4 ,if desirable1 the secondary binding posts may be mounted on the top of a short piece of hard rubber rod as illustrated in the drawing4 ,magnetic permeability is the conducting power for lines of magnetic force4 ,see hysteresis under ,magnetic ,detector4 ,,chapter ,v4 ,,interrupters4 ,we now come to what is the greatest source of trouble and annoyance in an induction coil1 namely the interrupter4 ,too much importance cannot be attached to this instrument1 for upon it depends largely the satisfactory working of the coil4 ,the operation of an induction coil and the part played by the interrupter were fully explained in the chapter on induction coils4 ,an adjustable interrupter is necessary for large coils1 that is1 one not only whose speed may be governed1 but also the time and duration of the break4 ,illustration3 ,fig4 #cc4 ,simple ,interrupter4 ,the rapidity of oscillation of a mechanical interrupter is a very different thing from the speed of break4 ,the ideal speed of break is instantaneous4 ,in wireless telegraphy1 very faint signals are heard more distinctly in telephone receivers if the rate of interruption at the station sending them is high4 ,the human ear is somewhat more sensitive to sounds higher than those ordinarily produced in the telephone receivers of a wireless receptor4 ,this seems to argue the use of a high-speed interrupter to make and break the current4 ,but the effect on the coil must also be considered4 ,in the first place1 where a condenser is shunted across the terminals of the secondary as is the case with a wireless transmitter1 a high-speed interrupter would be very likely to set up harmful oscillations in the secondary of the coil itself4 ,second1 if too fast1 the rise and fall of the secondary currents will be caused to run into each other1 since the break will occur before the primary current has reached a maximum and the reverse secondary current has died away4 ,third1 the diameter of the core of a wireless coil is generally much larger than that of the ordinary coil1 and if a very rapid interrupter is employed there is not time enough to properly magnetize the core before the current is broken4 ,fourth1 the strength of the losses in the core caused by the eddy currents and hysteresis are proportional to the interruptions in the primary circuit and therefore a low speed will be the most efficient4 ,a rapid interrupter requires a higher voltage and amperage than the same interrupter run at a lower speed4 ,these are some of the reasons why it is very desirable to use an atomic interrupter or one so adjustable that the rate of the time and duration of the make and break may be closely regulated4 ,an ideal interrupter is designed to give the longest time possible after contact is established and before the break occurs4 ,it does not pay to construct an interrupter for an induction coil giving sparks up to #b inches in length4 ,the type of interrupter in use on automobile coils is perfectly well adapted to small coils1 and may be purchased complete with the platinum points for as low a price as #a4ej4 ,the mechanical break described below is designed so that various adjustments are possible and it may be adapted to almost any coil4 ,since it is independent1 it need not be mounted directly on the coil1 but may be placed in the position most convenient to the operator for adjustment4 ,the interrupter will not operate coils well on an electromotive force above #cj volts1 for the excessive voltage causes a spark at the contacts when the circuit is broken and prolongs the decadence of the primary current4 ,illustration3 ,fig4 #cd4 ,independent ,interrupter4 99,independent ,atomic ,interrupter499--,fig4 #cd illustrates two views of the interrupter4 ,current is furnished to the electromagnets by a six volt battery independent of the source supplying the coil4 ,the interrupter is set in operation by closing the circuit breaker on the aerial switch4 ,when the primary circuit of the transmitter is then completed by pressing the key1 the coil will respond immediately because the interrupter is already in vibration4 ,the electromagnets 7,fig4 #ce7 are a pair of four ohm telegraph sounder magnets4 ,a hole is bored in the center of the top of each magnet core and threaded with an #h-cb tap so that the pole pieces may be fastened thereto1 ,the shape and dimensions of these projections1 which must be made of soft iron1 are illustrated in ,fig4 #ce4 ,illustration3 ,fig4 #ce4 ,details of ,magnets4 ,a soft iron yoke ,y1 #b #a_/b x #g_/h x #a_/d inches1 connects the bottom of the magnets and supports them in an upright position4 ,an #h-cb machine screw passing upward through the base and yoke holds them firmly4 ,the base is preferably of hard rubber #d x #c #a_/d x #c_/d inches4 ,illustration3 ,fig4 #cf4 ,details of ,moving ,parts4 ,the moving parts are illustrated in ,fig4 #cf4 ,the main spring1 ,d1 is a strip of spring steel1 #b #a_/h inches long1 #a_/b inch wide1 and #a_/cb inch thick4 ,the soft iron armature1 ,a1 is fastened to the spring by means of two small #d-cf machine screws4 ,m is a piece of brass rod1 #a #a_/b inches long1 bent in the form of a hook and threaded with a #d-cf die to screw in a similarly threaded hole in the back of the armature ,a4 ,the hooked portion of ,m is fitted with a small piece of hard rubber rod1 ,r1 to insulate it where it comes into contact with the spring1 ,g4 ,the spring1 ,d1 carries a second hook1 ,e1 riveted to the center of the spring #a #e_/h inches from the lower end4 ,the hook1 which is about #c_/h inch long1 passes through a hole in the top of the spring1 ,f1 and engages it so that it is set in operation by the vibratory motion of the spring1 ,d4 ,the spring1 ,f1 is #a #c_/d inches long1 #e_/af inch wide1 and ir #a_/fd inch thick4 ,it carries a platinum rivet #c_/d inch from its lower end4 ,the spring1 ,g1 is #b #a_/b inches long1 #e_/af inch wide and #a_/fd inch thick4 ,a heavy platinum rivet is fastened #b #a_/d inches from the lower end4 ,an elongated hole1 #a_/d inch long and #c_/af inch wide1 permits the hook1 ,m1 to pass through the opening4 ,a #e_/cb inch hole1 #a #a_/d inches from the bottom1 allows the adjusting screw to pass through and make contact with the platinum rivet on the spring1 ,f4 ,two rectangular pieces of brass1 ,o1 #a #a_/d x #a_/b x #e_/af inches are fastened to the base to support the springs4 ,illustration3 ,fig4 #cg4 ,details of ,standard and ,screws4 ,the standard1 ,u1 supporting the adjusting thumbscrews is a piece of #c_/h-;inch brass1 #b #a_/b inches high4 ,it tapers from #a #a_/b inches at the bottom to #c_/d inch at the top4 ,a hole #b #a_/d inches from the bottom is threaded with a #aj-cb tap to receive the thumbscrew1 ,b4 ,a second hole #a #a_/d inches from the base is threaded with an #h-cb tap to fit the adjusting screw1 ,s4 ,both of the adjusting thumbscrews carry heavy platinum points4 ,the standard is held upright to the base by means of two machine screws passing through the base4 ,a #c_/cb inch brass rod #a #c_/d inches long is threaded to fit a hole in the top of the armature4 ,a sliding weight1 ,w1 may be clamped in any position on the rod by means of a thumb-screw4 ,raising or lowering the position of the weight decreases or increases the natural period of vibration of the interrupter4 ,screwing the hook1 ,m1 in or out so as to shorten or lengthen it1 decreases or increases the ratio of the make to the break4 ,illustration3 ,fig4 #ch4 ,diagram of ,connections for an ,independent ,interrupter4 ,fig4 #ch shows a diagram of the connections of the interrupter4 ,the standard1 the thumbscrew1 ,b1 and the spring1 ,g1 form part of the primary circuit of the induction coil4 ,the standard1 the thumbscrew1 ,s1 the spring1 ,f1 and the electromagnets are placed in series with a six-volt battery and connected to the circuit breaker on the aerial switch1 so that when the switch is thrown in position for transmitting1 the interrupter will be set in operation4 ,a condenser must be shunted across the larger contacts of the interrupter in order to hasten the demagnetization of the core of the induction coil and create a higher e4m4f4 in the secondary4 ,the condenser must be suited in size to the induction coil with which the interrupter is to be used and so the following table is appended to serve as a guide4 ,the condensers are built up of alternate sheets of tin foil and paraffined paper4 ,connections are made to the sheets by means of tin foil strips which project out alternately from opposite sides as in the illustration4 ,the paper should be about two inches larger each way so as to leave a one inch margin on all sides of the tin foil4 ,illustration3 ,fig4 #ci4 ,construction of a ,paper ,condenser4 ,when the alternate sheets of tin foil and paper have all been assembled1 the condenser is warmed so as to soften the paraffin4 ,it is then placed between two flat boards and subjected to great pressure in a letter press or a vice4 ,the capacity of a pressed condenser is often several times that of a condenser of the same dimensions but not pressed4 99,mercury ,interrupters499--,the mercury turbine interrupter is one of the most convenient and successful breaks in use4 ,the construction is such that a stream of mercury is made to play against a number of saw shaped metal teeth4 ,a spiral worm terminating in a nozzle at the top is rapidly revolved by an electric motor4 ,the lower end of the tubular worm dips in a mercury reservoir1 so that when the spiral is revolved the mercury is caused by centrifugal action to rise in the tube and be thrown out in the form of a jet at the upper end4 ,when the revolving jet strikes one of the metal teeth1 the circuit is closed and the current flows from the mercury jet into the teeth4 ,when the mercury jet passes between the openings between the teeth1 the circuit is interrupted4 ,by raising and lowering the saw teeth so that the mercury strikes either the lower or upper part of them1 the ratio between the make and break may be made smaller or larger4 ,by regulating the speed of the motor driving the jet1 the number of interruptions may be varied from #aj to #aj1jjj per second4 ,the bottom and sides of the mercury reservoir are ribbed to prevent the mercury from attaining a rotary motion4 ,a somewhat simpler and more easily constructed type of mercury interrupter consists of a hard rubber disk having a brass rod running through from the periphery to the center1 where it connects with the shaft4 ,the lower edge of the disk dips at an angle in a mercury bath and is rapidly revolved by an electric motor4 ,when the rod is under the surface of the mercury1 the circuit is made through the mercury to the rod4 ,the circuit is broken when the rod is above the surface4 ,the mercury is covered with a layer of alcohol1 which prevents excessive sparking and makes a quicker break4 ,an interrupter of this kind when run by a motor of the magnetic attraction type is exceedingly simple4 ,the break of any of the mercury type interrupters when properly adjusted is much quicker than the hammer spring break and gives thicker sparks4 ,after the mercury has been in use awhile it becomes churned up into small globules of a black color1 but may be easily cleaned and restored for use by shaking up with some strong sulphuric acid4 ,care must be taken that the mercury is perfectly dry and free from acid before replacing in the interrupter4 99,electrolytic ,interrupters499--,fig4 #dj shows a diagram of a ,wehnelt interrupter4 ,the cathode or negative electrode is a lead plate immersed in dilute sulphuric acid4 ,the anode is a piece of platinum wire placed in a porcelain tube and projecting through a small hole in the bottom1 so that only a very small surface of the wire is exposed to the liquid4 ,when a strong electrical current is passed through the acid electrolyte1 the current is very rapidly interrupted by the formation of gases on the small platinum electrode4 ,the speed of the interrupter is variable through great ranges by moving the platinum electrode up or down and changing the amount of surface exposed to the liquid4 ,the only disadvantage of this interrupter is that the electrolyte soon becomes heated1 and unless the interrupter is provided with a water jacket or some device for cooling1 the bubbles of gas do not form freely4 ,a potential of at least #dj volts is required to operate a ,wehnelt or other electrolytic break4 ,illustration3 ,fig4 #dj4 ,wenhelt and ,simon ,electrolytic ,interrupters4 ,a ,wehnelt interrupter may easily be made by sealing a platinum wire in a glass tube4 ,it is well to make several such tubes with the platinum projecting from one-sixteenth to one-quarter of an inch4 ,the different tubes will each have a different speed of interruption1 and one should be picked out which seems to be most suitable for the coil upon testing4 ,connection to the platinum wire is established by filling the tube with mercury and dipping a wire in it4 ,fig4 #dj also shows a diagram of a ,simon electrolytic interrupter4 ,it consists of a vessel containing dilute sulphuric acid and divided into two parts by a thin porcelain diaphragm having a small hole in the center4 ,a lead electrode dips into each of the divisions4 ,the interruption is caused by exceeding a certain current density in the small hole at the diaphragm4 ,upon the passage of the current the liquid is so heated that it becomes vaporized4 ,the vapor is a poor conductor to low voltages and so the current is broken4 ,immediately upon the cessation of the current1 the vapor condenses and the circuit is established again4 ,this cycle repeats itself with a speed depending upon the size of the aperture and the amount of current flowing4 ,a crude form of this type of interrupter may be made by heating the end of a test tube in a pin flame1 and then blowing on the open end of the tube so as to burst the soft glass and form a small hole4 ,several such test tubes should be prepared having holes varying from #a_/cb to #a_/h of an inch in diameter4 ,the one which gives the best results upon trial is selected for use4 ,a number of holes in a single tube1 if not too many or too large in diameter1 increases the efficiency and the speed of interruption4 ,the tube should be immersed in a glass jar containing dilute sulphuric acid4 ,one lead electrode is placed inside of the test tube and the other outside4 ,it makes no difference which way the current flows through this interrupter4 ,the ,caldwell interrupter is a modification of the ,simon type in which the size of the aperture is made adjustable by means of a pointed glass rod which may be raised or lowered in the hole and the speed of interruption varied4 ,an interrupter of the test tube type as described above may be modified to this form by locating the hole directly in the center of the bottom of the tube and inserting in it a hard glass rod which has been drawn out to a point4 ,electrolytic interrupters do not require any condenser connected across the break4 ,illustration3 ,fig4 #da4 ,construction of ,electrolytic ,interrupters4 ,fig4 #da shows in section more substantial forms of both the ,wehnelt and ,simon-,caldwell interrupters4 ,the containers are ordinary #e x #g inch battery jars4 ,they are fitted with covers made of two thicknesses1 ,c and ,b1 of #c_/d-;inch wood4 ,the upper piece1 ,c1 is #f inches in diameter1 while the under one should fit snugly into the interior of the jar4 ,the wood must be boiled in paraffin to protect it from the action of the acid4 ,a slit is made in the left-hand side of both covers for the passage of a lead electrode1 ,l1 #a inch wide and #a_/d inch thick4 ,the upper end of the electrode is bent over and fitted with a binding post4 ,illustration3 ,fig4 #db4 ,details of ,electrolytic ,interrupters4 ,the mechanism for adjusting the interrupters is the same in both cases4 ,the dimensions are indicated in ,fig4 #db4 ,a brass yoke1 ,y1 is mounted on the cover in the position shown4 ,a #a_/b-;inch hole is bored through the upper part of the yoke and a piece of brass tubing1 ,s1 #a inch long soldered in a vertical position in the hole4 ,a #a_/d-;inch threaded brass rod passes through the tube1 #e4 ,a groove is milled in ,a along its entire length and engages a pin in the wall of ,s4 ,the rod is thus enabled to slide up and down in the tube but is prevented from revolving4 ,a fiber head1 ,h1 is fitted with a brass sleeve or bushing in its center4 ,the bushing should fit tightly into the fiber head and is threaded to fit the rod1 ,a4 ,the electrode may then be carefully raised or lowered by revolving the head4 ,the tube1 ,v1 for the ,simon-,caldwell interrupter is a hard glass test tube4 ,a #a_/h-;inch hole is blown in the bottom of the tube4 ,a hard glass rod1 ,g1 is drawn out to a point and fastened to the lower end of the rod1 ,a1 by means of a short length of flexible rubber tubing1 ,r4 ,the tube1 ,n1 for the ,wehnelt break is made from a piece of hard rubber tubing #f inches long1 having a bore of ,j inch4 ,illustration3 ,fig4 #dc4 ,electrolytic ,interrupter4 ,the lower end is fitted with a spark plug porcelain4 ,the porcelain must fit the tube tightly and not leak4 ,the electrode1 ,p1 is a piece of brass wire which will just pass through the hole in the porcelain4 ,the upper end of the electrode1 ,p1 is soldered or fastened otherwise to the lower end of the rod1 ,a4 ,a small hole1 h1 should be made in the tubes1 ,n and ,v1 above the level of the electrolyte in the jar4 ,when the interrupter is in operation the electrolyte gradually rises in the tubes1 and would corrode the lower end of ,a if it were not able to pass out through the vents4 ,in the ,simon-,caldwell interrupter1 a strip of lead passes from the binding post mounted on the foot of the yoke down inside of the test tube4 ,the size of the hole in the tube is regulated by revolving the fiber head so that the glass pointed rod will be inserted in or withdrawn from the hole4 ,the frequency of the interruption will also depend somewhat on the concentration of the acid solution4 ,it is therefore best to start with a weak solution and add acid slowly until it is of the proper strength4 ,,chapter ,,vi4 ,,transformers4 ,where alternating current is available in commercial wireless telegraph stations1 the induction coil has been gradually superseded by the more modern transformer for charging the oscillation condenser4 ,since the transformer is less expensive to construct than an induction coil capable of transmitting the same distance1 it is favored by many amateur experimenters4 ,a one quarter kilowatt transformer has a sending range of over #ej miles when used with a properly constructed aerial about #hj feet high4 ,this is probably the size best suited to the average private installation4 ,the secondary of a wireless transformer seldom develops potentials exceeding #ae1jjj to #bj1jjj volts1 while those of an induction coil range from #a #e1jjj to #cjj1jjj volts4 ,however1 the strength of the secondary current of a transformer is so much greater than that of an induction coil1 that more powerful and penetrating waves are developed4 ,for these reasons a transformer is always rated by its output in watts or kilowatts rather than by the spark length produced at the secondary terminals4 ,the spark of a one quarter kilowatt transformer is only #j4be to #j4ej of an inch1 while the spark of a one half kilowatt transformer may be the same length but still represent more energy4 ,there are two distinct types of transformers in use1 known as the open and closed1 accordingly whether the core is straight like the core of an induction coil or in the form of a hollow rectangle4 ,the open core type is used in the government stations and by the ,united ,wireless ,telegraph ,co4 ,it is the simpler and more easily constructed of the two1 but is also less efficient and requires that more material be expended to bring it up to a definite rating4 ,in principle it is simply an induction coil operated on alternating current minus the interrupter and condenser4 ,in view of the greater currents employed1 the windings must be larger and heavier than those of the induction coil to prevent heating4 ,before commencing the construction of a transformer one should read the chapter on induction coils and use the same care emphasized there in regard to building coils4 99,open ,core ,transformer499--,the transformer described below will transmit from #bj to #ge miles and consume about #cjj watts on the no volt #fj cycle alternating current4 ,the core is #af inches long and #b inches in diameter4 ,it is built up of soft iron wires in the same manner as if it were the core of an induction coil4 ,the primary is composed of two layers of ,no4 #ad double cotton covered ,b4 ,s4 gauge magnet wire4 ,the primary is #ad inches long and is wrapped with a layer of micanite cloth #c_/h inch thick to separate it from the secondary winding4 ,it is never advisable to use shellacked cotton cloth as insulation4 ,when cotton is dried and shellacked1 it is at first a good insulator1 but soon becomes capable of absorbing moisture4 ,shellac carbonizes at a low temperature1 and if a transformer or coil having any of this sort of insulation entering into its construction is overheated1 the insulation is liable to become a conductor4 ,micanite cloth is the best insulation for transformers4 ,the dielectric strengths of the different forms of micanite are shown by the following table4 ,the secondary is wound in ten sections over the micanite insulation4 ,each section is #f inches in diameter and #a #a_/d inches thick and is wound with ,no4 #cj ,b4 ,s4 single silk covered wire4 ,the sections are separated by disks of blotting paper #a_/h inch thick and #g inches in diameter1 treated as described in ,chapter ,,iv4 ,the completed transformer should be placed in a box and covered with oil4 99,a ,one ,quarter ,kilowatt ,closed ,core ,transformer499 ,the simplest form of a closed core transformer consists of two independent coils of insulated wire wound upon an iron ring4 ,when an alternating current is passed through one of the coils1 known as the primary1 it generates a magnetic flux in the iron core4 ,the lines of force passing through the core induce in the secondary coil an electromotive force the magnitude of which is in nearly the same ratio to the primary inducing electromotive force as the number of turns of wire in the secondary is to the number of turns in the primary4 ,for example1 if it is desired to raise the potential of the no volt alternating current to #bb1jjj volts1 the number of turns in the secondary of the transformer must be at least #bjj times the number in the primary4 ,a circular ring of iron wire presents several theoretical advantages as a transformer core but it would be difficult to form and afterwards place the windings in position4 ,the core is therefore usually in the form of a hollow rectangle1 built up of very thin sheets or laminations of soft iron carefully insulated from one another by a coat of varnish4 ,if the core were solid or the separate laminations not insulated from one another1 heavy currents1 known as eddy currents1 would be set up in the iron and cause heating4 ,a considerable loss in the efficiency of the transformer would also result4 ,one half of both the secondary and the primary windings of a properly designed transformer are placed on opposite sides or legs of the core in order to reduce the magnetic leakage and increase the efficiency4 ,the only difficulty involved in such construction is the proper insulation of the primary from the secondary1 but if careful attention is given to this point no difficulty will be experienced4 99,core499--,the dimensions and method of assembling the core laminations are indicated by ,fig4 #dd4 ,long strips are cut from soft ,russian or ,swedish stovepipe iron4 ,the strips1 which are #a #c_/d inches wide are then cut up into short lengths1 one half of which are #g #c_/d inches long and the other half #d #c_/d inches4 ,enough are cut to form two piles of each size #a #c_/d inches high when compressed4 ,the completed core will then form a hollow rectangle #i #a_/b x #f #a_/b x #a #c_/d inches4 ,illustration3 ,fig4 #dd4 ,assembly and ,dimensions of ,core4 ,the strips must be dipped in some good insulating varnish such as ,p4 ,b4 compound and thoroughly dried before they are assembled4 ,both legs 7the longest sides7 are laid on a table with the alternate ends overlapping as shown by ,a and ,b in ,fig4 #dd4 ,after the short pieces ,c and ,d have been slipped between the overlapping ends the whole core is squared up4 ,the strips ,d are then carefully removed and one end of the core thus left open until all the windings are in place4 ,three or four layers of well varnished linen cloth are wound tightly over the legs preparatory to winding on the primary4 99,primary499--,four fiber heads1 ,h1 #d #c_/d inches square1 #a_/b inch thick and having a square hole #a #g_/h x #a #g_/h inches cut in the center are required4 ,one of the fiber heads is placed on each end of the assembled leg as shown in ,fig4 #dh4 ,illustration3 ,fig4 #de4 ,fiber ,head and ,separator4 ,the primary winding is wound in six layers1 #d #a_/b inches long1 three layers on each leg4 ,about three pounds of ,no4 #af ,b4 ,s4 gauge double cotton covered magnet wire are required for the winding4 ,the terminals of the two halves of the primary are led through the fiber heads at the same end of the transformer4 ,the windings are not to be carried close up to the fiber heads but begin and end about #a_/d inch from them1 so that the remaining space may be filled by winding in a strip of micanite cloth #a_/d inch wide4 ,the primary and secondary windings are separated by a strip of micanite cloth #e inches wide1 wound over both of the primary windings close up to the heads until a layer #a_/b inch thick is formed4 99,secondary499--,the form on which the secondary sections are wound is illustrated in ,fig4 #df4 ,all the parts are cut out of wood except the shaft and are made of the dimensions indicated4 ,if the center of the form is slightly tapered it will greatly facilitate the removal of the completed sections4 ,sixteen sections are required4 ,when removed from the winder they will be in the form of hollow squares #d #a_/b x #d #a_/b x #g_/af inches4 ,illustration3 ,fig4 #df4 ,section ,form4 ,about ten pounds of ,no4 #cd ,b4 ,s4 gauge silk covered wire are required to wind the sections4 ,cotton covered wire must not be used to avoid expense1 because with it a sufficient number of secondary turns cannot be secured to bring the secondary current up to the proper voltage4 ,by observing explicitly the instructions and precautions given below no trouble will be experienced in handling enameled wire and forming the sections4 ,the form should be placed in a lathe chuck or some other machine which is convenient and whereby the form may be rapidly revolved under the control of the operator4 ,saw slots are cut in the wooden flanges and the center of the form as shown in the illustration so that silk threads may be passed under and around the completed section and tied so that a possible cave in of the wire is prevented4 ,after tying up the section should be removed from the form by unscrewing the nut and taking off the flange4 ,illustration3 ,fig4 #dg4 ,methods of ,connecting ,sections4 ,when winding the wire it must be very carefully watched for loops or kinks and only be laid on in even layers4 ,it must also be borne in mind that enameled wire cannot be as tightly wound as fiber covered wire for reasons heretofore explained4 ,in case the wire becomes broken1 it must be smoothly spliced and soldered4 ,do not under any consideration use acid as a flux or heat the wire with a flame4 ,acid will corrode the fine wire1 and the flame will badly oxidize or melt it4 ,use a short piece of ,no4 #h ,b4 ,s4 gauge tinned copper wire set in a small file handle as a soldering iron1 and rosin as a flux4 ,paraffin some silk binding tape such as dressmakers use and wrap the joint with a small piece4 ,the sections as they are removed from the winder must be taped and then carefully marked with an arrow which points in the direction of the winding4 ,fig4 #dg illustrates the two methods of connecting up the sections4 ,it will be noticed in the second method that the arrow denoting the direction of winding points down on every alternate section4 ,this does not indicate necessarily that every alternate section is wound in an opposite direction from the other1 but that they have merely been turned around so that the arrows come on a reverse side of the core and point in an opposite direction4 ,this precaution must be taken in order that the current will flow through all the sections1 and is made necessary because the inside terminal of one section is connected to the inside terminal of the adjacent section and the outside terminal of that section is connected to the outside terminal of the next adjacent section4 ,the first method1 ,a1 illustrated in ,fig4 #dd1 is less complicated and does not require this reversal1 but for various reasons is not to be recommended in place of ,b4 ,eight of the completed and taped sections are placed on each leg of the transformer1 with one of the fiber separators between each pair as in ,figs4 #dh and #di4 ,when each leg has been completely assembled1 solder all the secondary terminals together so as to connect as in ,fig4 #dg4 ,illustration3 ,fig4 #dh4 ,assembly of ,leg4 ,then place the remaining fiber head1 ,s1 on each of the legs and finish assembling the core by slipping in the end strips ,d4 ,square the core up perfectly true and fasten by four fiber strips ,m1 ,fig4 #di1 #i #c_/d inches long1 #a #c_/d inches wide and #a_/b-;inch thick4 ,the strips are placed in the position shown in ,fig4 #df and a hole ,p bored in the end of each4 ,four #a_/d-;inch bolts1 two of which are #c inches long and two #c #a_/b inches1 pass through the holes in the strips1 so that when the nuts are screwed on the core is clamped firmly4 ,the two longer bolts are placed at the same end of the transformer4 ,illustration3 ,fig4 #di4 ,transformer with ,one ,secondary removed4 ,the terminals of the primary lead out to four binding posts mounted on the fiber strips4 ,the pillars which support the secondary binding posts are fiber rods1 #a inch in diameter and #b inches long4 ,the lower end of each is bored and tapped to fit the upper ends of the longer bolts which clamp the fiber strips together4 ,an insulating shield must be placed between the two secondary windings to prevent sparks from jumping across4 ,a piece of fiber #e x #e x #a_/h inches will serve nicely for this purpose4 ,if the primary windings are placed in series the transformer will consume about #cjj watts4 ,when the transformer is placed in a box and the box filled with some boiled amber petroleum1 the windings may be connected in parallel and the transformer will consume about #ejj watts4 ,it will then transmit over #ajj miles providing the aerial is at least #ajj feet high4 ,the wiring connections are diagramed in ,fig4 #ej4 ,a variable inductance or reactance coil is connected in series with the primary circuit to steady the current1 as explained in the paragraph under reactance4 ,a reactance suitable for this transformer may be constructed by winding two layers of ,no4 #ab ,b4 ,s4 gauge cotton covered wire1 six inches long1 around a hollow wooden tube made of cigar box wood4 ,the core is built up of soft sheet iron to form a rectangle #h x #a #c_/d x #a #c_/d inches which will just slide in and out of the tube4 ,the windings should be about six inches long4 ,illustration3 ,fig4 #ej4 ,wiring ,diagram4 ,five half-gallon ,leyden jars form about the right capacity for the secondary of the transformer when the windings are in series4 ,twice that number must be used when the windings are in parallel4 ,the secondary sections must always be kept in series1 as otherwise the voltage would not be high enough to properly charge the condenser4 ,construction of a #b-,k4,w4 ,transformer4 99,core499--,strips #b #a_/b inches wide are cut from soft sheet iron4 ,one half of them should be #aa #a_/b inches long and the other half #f #a_/b inches4 ,enough are cut to make two piles of each size #b #a_/b inches high4 ,both sides 7the longest strips7 of the core are built up with the ends overlapping as in ,fig4 #da4 ,the ends 7the short pieces7 are then slipped between the overlapping ends of the long strips and the whole core squared up4 ,the completed core should have a cross section of #b #a_/b inches square and form a hollow rectangle #h x #ad inches4 ,the strips of iron must be dipped in ,p4 ,b4 insulating varnish and dried before they are assembled4 99,primary499--,four fiber heads #f inches square1 #a_/b inch thick and having a hole #b #a_/b inches square are made4 ,one of these is placed on the core legs as shown by ,fig4 #dh4 ,two or three layers of well varnished linen are wound over the core preparatory to winding the primary4 ,room must be left for the other head to be placed on the opposite end after the windings are all in place4 ,the primary consists of #ajj double turns of ,no4 #ab ,b4 ,s4 gauge double cotton covered magnet wire4 ,fifty of the double turns are wound on each leg4 ,the four terminals of the primary are led out through the fiber heads4 ,care should be taken to distinguish them from each other so that they may be identified when the transformer is completed4 ,the primary is then wound with a strip of micanite or empire cloth #h inches wide until it measures #d inches square over all4 99,secondary499--,the secondary coils1 which are eight in number1 are wound on a form #d inches square and #a #a_/b inches between the flanges4 ,the construction of the form is similar to that shown in ,fig4 #df but is larger4 ,the slots are also necessary here so that the completed section may be tied up4 ,about ten pounds of ,no4 #cj ,b4 ,s4 gauge single silk covered wire are required to wind the secondary4 ,the sections are wound in smooth even layers until they are six inches in outside diameter4 ,they are then tied up and removed from the winder4 ,the sections are separated by sheets of fiber #f #a_/b inches square on the outside1 #a_/b inch thick1 having a hole #d inches square cut in the center4 ,the sections are all connected in series and the terminals soldered to strips of copper4 ,after the secondary coils are all in place and connected1 the fiber head is slipped on the end of the leg4 ,then the short lengths of the core1 which had been pulled out again after squaring the core up1 are slipped into place4 ,the core is squared up again and fastened together by boring a #c_/h-;inch hole completely through the core at each corner4 ,two strips of fiber #ab x #b #a_/b x #a_/b inches are bored with corresponding holes in their ends4 ,these strips are placed at the end of the transformer1 on top of the core1 and #a_/d-;inch bolts passed through the holes in the fiber and the core4 ,the bolts are wrapped with micanite cloth where they pass through the core1 and an insulating washer is placed under the nuts1 so that the iron core laminations are not electrically connected4 ,the nuts are tightened until the core is held firmly together4 ,the fiber strips also serve as insulated supports for the binding posts4 ,the copper terminals of the secondary lead to two binding posts mounted on two fiber or hard rubber pillars #a inch diameter and #d inches high4 ,the rods are arranged as explained in the section under the heading of a #a_/d-,k4,w4 transformer4 ,the transformer is designed for use on a #fj-;cycle #aaj-volt current4 ,it may be used on #bbj volts if the two primary coils are connected in series4 ,when the primaries are in series1 and the transformer is used on the #aaj-volt current1 it will deliver a voltage of about #ab1jjj at the secondary4 ,with either primary alone the voltage will be about #ab1jjj1 and with both in parallel about #be1jjj4 ,it will then deliver a very heavy current at the secondary and draw from the line about #bj amperes in the primary4 ,if used with a proper tuning helix1 condenser and aerial1 the transformer is capable of sending about #cjj miles under favorable conditions4 ,if the transformer is to be used for long periods at a time1 it is best to place it in a tight wooden box #ah inches square and #ab inches deep4 ,the box is then filled with boiled linseed oil or amber petroleum4 ,a rheostat or impedance and reactance coil should be placed in series with the transformer to regulate the current and also to prevent arcing across the spark gap4 99,reactance499--,in ,chapter ,i1 the lag and lead of a circuit were explained in connection with tuning4 ,this is a property of every alternating circuit and is brought to our notice again in the transformer which charges the condenser4 ,the current developed by a transformer is a leading current1 since the instantaneous values of the current do not correspond to the proportionate values of the voltage supplying the current4 ,in order to force the current values of the charging current to correspond with the voltage it is necessary to produce a lag4 ,this is accomplished by means of an adjustable reactance in series with the primary of the transformer4 ,a reactance or inductance suitable for the #b-,k4,w4 transformer may be made by building up a coil in the same manner as described under the heading of the ,j-,k4,w4 transformer4 ,the reactance will have to be somewhat larger on account of the heavier currents4 ,the core is built up of sheet iron to measure #b #a_/b x #b #a_/b x #aj inches when completed4 ,the coil is wound around a wooden form and is composed of about #ajj turns of ,no4 #h ,b4 ,s4 gauge double cotton covered magnet wire4 ,by varying the amount of core inserted in the hollow coil the energy may be adjusted as desired4 ,illustration3 ,fig4 #ea4 ,clapp-,eastham #a_/d-,k4,w4 ,transformer4 ,fig4 #ea illustrates the #a_/d-,k4,w4 transformer manufactured by the ,clapp-,eastham ,company4 ,the core is so constructed that a small metal tongue of soft iron projects from one side of the core towards the opposite side between the windings1 but is separated from the opposite side by a small air gap4 ,several objects are accomplished by this tongue1 which gives rise to magnetic leakage2 the inductance of the primary is increased thereby to such an extent that the transformer is self-controlling1 so that it may be connected directly to the source of alternating current supply of ordinary commercial frequencies and potential1 and the current flowing in this circuit be regulated by varying the number of turns in the primary coil4 ,as this magnetic leakage gives rise to a loose coupling effect1 the primary and secondary circuits may be brought into resonance by placing a suitable capacity across the secondary terminals4 ,this condition of resonance brings the power factor to a materially higher percentage4 ,while the power factor of the open or closed core transformer is seldom above #ej1 this type of transformer has a power factor of #hj to #ij when used with a suitable condenser4 ,illustration3 ,fig4 #eb4 ,united ,wireless ,motor-,generator set for supplying ,alternating ,current to the ,transformer4 ,another point of considerable advantage is the almost entire freedom from arcing at the spark gap when this type of transformer is used4 ,the spark gap is connected directly across the secondary terminals of the transformer and the condenser4 ,the primary turns of the helix and the spark gap are connected in series4 ,when the transformer is in operation1 this condenser being across the secondary1 the transformer is in resonance and the condenser is charged to such a point that it will jump the spark gap4 ,at the instant that the spark passes1 the secondary of the transformer is practically short circuited through the spark gap4 ,as this circuit is now closed and the condenser out of circuit1 the secondary circuit of the transformer is no longer in resonance and the energy immediately drops off1 destroying at once the tendency for an arc to form4 ,as soon as the spark has passed1 the condenser of course comes in to play and the condition of resonance being reestablished the same process is repeated4 ,the ,clapp-,eastham ,company have made application for a patent on any transformer employing this or any similar construction for use in charging a condenser4 ,,chapter ,,vii4 ,,oscillation ,,condensers ,,and ,,leyden ,,jars4 ,a condenser consists of two conducting surfaces separated by an insulator or dielectric4 ,fig4 #ec shows a diagram of a simple condenser in which ,a and ,b are two tinfoil sheets separated by a sheet of glass1 ,c4 ,illustration3 ,fig4 #ec4 ,simple ,condenser4 ,if ,a is connected by means of a wire to a static machine a positive charge will collect on the glass at ,a and induce a negative charge at ,b1 so that if ,a and ,b are connected to a small spark gap the charge will leap the gap in the form of a spark4 ,when a condenser discharges through a coil of wire1 the discharge consists of a large number of exceedingly rapid oscillations or surgings4 ,the first passage of current more than empties the condenser and it becomes charged in the opposite direction1 that is1 the conducting coatings change their polarity4 ,a reverse discharge then occurs which also oversteps itself and the oscillations thus go on but become rapidly weaker until they die completely4 ,the time consumed in the discharge may have been only a fraction of a second1 but during that short period the current perhaps oscillated several thousand times4 ,if a condenser is discharged through a conductor of high resistance the discharge passes out slowly1 and dies away gradually in one direction without oscillating4 ,one of the fundamental equations of wireless telegraphy is therefore that there will be oscillations in a circuit if the resistance in ohms is not greater than the square root of four times the inductance in henries divided by the capacity of the condenser in microfarads4 ,the capacity or the ability of a condenser to store electricity depends upon the area and form of the conducting surfaces1 the thickness of the dielectric between them1 and a factor known as the specific inductive capacity of the dielectric4 ,the unit of capacity is called the farad and is defined as the condenser which would be raised to a potential of one volt by a charge of one ampere flowing for one second4 ,a condenser of such a capacity is1 because of its enormous size1 impractical to construct1 and the unit ordinarily used is therefore the microfarad1 or one millionth of a farad4 ,capacity may be calculated from the following formula3 ,capacity equals ,k7,a_/,d71 where ,k equals a constant depending upon the specific inductive capacity of the dielectric1 ,a the total area of tinfoil and ,d the thickness of the dielectric4 99,leyden ,jars499--,transmitting condensers in a wireless telegraph station usually take the convenient form of a jar1 coated inside and out with tinfoil and known as a ,leyden jar4 ,the jars should be of good ,bohemian or ,jena hard glass and coated with tinfoil only for about three-quarters of their height1 as otherwise the discharge is liable to pass over the top4 ,the tinfoil must be thick to avoid blistering1 and is stuck to the glass with shellac varnish4 ,the blistering of ,leyden jars is a serious fault1 for when this condition exists1 the capacity is thereby altered to such an extent that the period of the closed circuit may be sufficiently altered to throw the system out of tune and decrease the radiation of energy4 ,considerable expense may be saved if the glass jars are purchased and coated by the amateur4 ,the best jars are those imported from ,germany1 which have wide mouths so that they may be easily coated inside with tinfoil4 ,illustration3 ,fig4 #ed4 ,leyden ,jar4 ,the jars must be thoroughly cleaned and dried before they are coated4 ,give the inside a thorough brushing over with shellac varnish1 and before it is dry1 carefully insert the tinfoil and press it smoothly against the glass4 ,the outside of the jar is treated and coated in the same manner4 ,the inside and outside of the bottom are also coated by cutting the tinfoil in circular pieces and shellacking them on4 ,illustration3 ,fig4 #ee4 ,aerial ,switch4 ,the whole upper part of the jar is given one or two coats of shellac in order to prevent the collection of moisture and brush discharging4 ,a wooden plug fitted in the top of the jar supports a brass rod1 terminating at the lower end in a chain or spiral spring which connects with the inner coating4 ,when trouble is experienced because of an imperfect contact between the coating and the chain or rod1 a layer of brass filings an inch or two deep placed in the bottom of the jar will remedy the difficulty4 ,the upper end of the rod usually terminates in a small brass ball or a binding post4 ,the wooden plug or cover is dried in an oven to expel all moisture and then boiled in paraffin4 ,small ,leyden jars may be very conveniently made from six-inch test tubes and mounted in a rack so that the capacity of the condenser will be adjustable by removing one or more of the tubes4 ,an ordinary test tube rack such as is used in chemical laboratories serves very well for this purpose4 ,the tubes should be connected in parallel1 that is1 all the outside coatings together and all the inside coatings together4 ,figs4 #ee and #ef illustrate condensers of this type which are on the market4 ,the tubes are all separately removable so that the capacity may be adjusted4 ,illustration3 ,fig4 #ef4 ,amco ,oscillation ,condenser4 99,glass ,plate ,condensers499--,glass plate condensers offer several advantages over ,leyden jars and are coming into wide use4 ,they are not so bulky or expensive and1 above all1 do not blister4 ,plate condensers are often placed in a rack and made adjustable by means of movable contacts4 ,much the better plan is to place the plates in oil1 as this eliminates all corona or brush discharges and much sharper tuning is rendered possible4 ,the container is usually a tight wooden box filled with oil or paraffin after the plates are in place4 ,it is impossible to state the size of condenser suitable for induction coils of a given power or spark length1 because many factors such as inductance1 length of aerial1 etc41 which differ in various stations1 influence the capacity4 ,a condenser of convenient size suitable for coils or small transformers consuming from #bej to #cjj watts is that described below4 ,it is about the proper size for the small open core and #a_/d-,k4,w4 closed core transformers1 described in the last chapter4 ,illustration3 ,fig4 #eg4 ,clapp-,eastham ,oscillation ,condenser4 ,the glass plates may be secured by removing the emulsion from old #h x #aj inch photograph plates4 ,hot water will soften the gelatin on the plates so that it may be very easily scraped off4 ,twenty-four plates of this size are required4 ,the tinfoil is cut #h x #h inches1 so that an inch margin is left on all sides4 ,the alternate sheets are connected together by heavy tinfoil or thin copper foil strips4 ,the condenser should be placed in a convenient sized wooden box and poured full of paraffin4 ,the plate condenser shown in ,fig4 #eg is of 4#jb microfarad capacity4 ,the condenser is mounted in a plain wooden box with several binding posts brought out1 so that the capacity may be varied by connecting in various sections4 ,the condenser is manufactured and designed by the ,clapp-,eastham ,company for use with the transformer illustrated in ,fig4 #ea4 ,it is very necessary to have the transmitting condenser adjustable so that its capacity may be varied1 for the proper value depends upon the wave length1 spark frequency1 power and persistency of the wave train4 ,when the condenser capacity is too small the spark will be somewhat flaming like an arc1 and the potential to which the aerial is charged will be low4 ,if too much capacity is used the spark will be very irregular and intermittent4 ,illustration3 ,fig4 #eh4 ,methods of ,varying ,capacity4 ,fig4 #eh shows condensers connected in series and in parallel and a combination of the two4 ,two condensers of equal capacity connected in parallel have twice the capacity of one1 while in series they will have only one-half the capacity of either4 ,this may be otherwise stated as the capacity in series is equal to the reciprocal of the sum of the reciprocals of their capacities separately4 ,by this means of connecting either in series or in parallel almost any desired adjustment of capacity may be brought about4 ,oftentimes a high voltage may be divided between two condensers by placing them in series and thus using them safely on a voltage which would rupture either one alone4 ,for example1 two condensers built for #bj1jjj volts and to be used on #cj1jjj volts could be made to perform this duty safely and only undergo a potential of #ae1jjj volts1 which is a large margin of safety4 ,it is obvious that if the capacity of the circuit were to remain constant1 four condensers connected up in series-parallel would be necessary4 ,in case of several ,ley den jars or condensers connected up in a transmitting circuit1 the leads or conducting wires connecting the various units should all be of as nearly the same length as it is possible to have them4 ,the resistance of metallic conductors to high frequency currents is several times their normal resistance to constant currents4 ,the larger the diameter of the wire the greater is this ratio4 ,this increase of resistance is due to the fact that the high frequency currents permeate wires only a very short distance4 ,in the case of copper1 the depth is only about one three-hundredth of an inch and with other metals much less4 ,therefore it is advisable to use as leads and conductors of large condensers1 stranded wires or flat ribbons of sheet copper in order to present more surface and offer less resistance than solid conductors of an equal cross sectional area4 ,iron must never be used1 as its resistance to these currents is over fifty times that of copper4 ,after connections are once established between the jars or the condenser units1 they cannot be altered nor the capacity changed without re tuning the circuits afterwards4 ,,chapter ,,viii4 ,,spark ,,gaps ,,or ,,oscillators4 ,the oscillator or spark gap is one of the most important yet often the most poorly adjusted part of a wireless station4 ,to obtain a good oscillatory discharge with little damping it is necessary that the resistance of the circuit should be kept low1 and since the greatest part of the resistance is in the spark gap it would appear as if this must be very short4 ,while there are reasons for keeping it short there are on the other hand very good reasons why it should not be made too short1 and the proper length should be a sort of compromise to be determined by experiment4 ,if the gap is too short1 the discharge will form an arc and the only oscillations taking place will be those corresponding to the frequency of the charging current4 ,power consumption is also in favor of a long gap1 since it causes the induction coil or transformer to draw less current from the line4 ,another argument in favor of a long gap is the fact that the condenser is charged to a higher voltage and more energy stored up1 which makes a greater distance of transmission possible4 ,but as stated above 7and there always is a tendency for the amateur operator to open out his gap as long as the sparks will continue to jump steadily7 the discharge will not oscillate but will merely set up a unidirectional current4 ,there exists a proper gap length for a given circuit which will cause that circuit to emit a maximum amount of energy and which may be determined accurately only by means of a hot-wire ammeter placed in the aerial circuit4 ,the proper gap length is then indicated by the maximum deflection of the meter4 ,the correct adjustment of the gap may be approximated by the experienced operator4 ,if too short1 the spark will be hissing and flaming and is in extreme cases red or yellow colored4 ,it should be lengthened out until it is thick and white and a slight increase in sound is noted4 ,the spark should not be1 as commonly thought1 stringy and crackling4 ,arcing is often caused by insufficient condenser capacity in the circuit4 ,but if the capacity is increased to remedy the arcing1 the gap length should also be increased or otherwise the potential of the condenser may not be sufficiently raised to permit a disruptive discharge to take place4 ,illustration3 ,fig4 #ei4 ,spark ,gaps4 ,the best spark gap for use with a small untuned transmitter1 making use of neither tuning helix nor condenser1 is shown at the left in ,fig4 #ei4 ,it consists of two brass balls supported on suitable double binding posts4 ,the balls tend to thicken the spark and make it more disruptive than if it passed between rods or points4 ,the balls also increase the potential required to leap the gap without increasing its length and permit the aerial to become more highly charged before a discharge takes place4 ,for this reason the balls or knobs must always be kept free from small rough spots or points by frequent polishing4 ,silver has some peculiar property which makes it the most efficient material for a spark gap1 but its cost prohibits its use and so brass or zinc1 which are next in order1 is generally used4 ,the type of gap illustrated at the right in ,fig4 #ei is very convenient and efficient for small tuned transmitters employing coils of low power4 ,illustration3 ,fig4 #fj4 ,spark ,gap4 ,the zinc tips are pieces of #c_/h-;inch zinc battery rod #c_/d inch long4 ,they are bored and threaded to fit a pair of brass rods #a_/h inch diameter and #b #a_/b inches long4 ,the rods are supported by two double binding posts and are fitted with two pieces of hard rubber rod #a_/b inch diameter and #a inch long to serve as handles4 ,if desirable one of the rods and binding posts may be threaded so that the adjustment of the gap can be accomplished by revolving the handle and screwing the gap in or out4 ,a gap of the size and type just described would not be suitable in connection with a large transformer or an induction coil4 ,the heavy discharge of such powerful instruments would very rapidly heat the small brass parts and corrode or even melt the zinc4 ,the spark gap such as is shown in ,fig4 #ei may be used with a very large coil or the two kilowatt transformer if the same proportions are kept and it is made one-half again as large4 ,using the dimensions shown in the figure1 the spark gap is suited to either the open core or the #a_/d and #a_/b kilowatt transformers4 ,two pieces of hard rubber rod1 #c_/d inch diameter and #b inches long serve as the standards4 ,three grooves #a_/h inch wide1 #a_/h inch deep and #a_/h inch apart better the appearance and reduce the liability of leakage but are not necessary4 ,two holes #b inches apart are bored in ,s1 a strip of brass #c x #c_/d x #a_/d inches4 ,two screws pass through these holes into the rubber standards ,,bb and hold ,s firmly in position4 ,the end of ,s is bent down at right angles and bored to receive a binding post4 ,a hole is bored in ,s halfway between the standards and tapped to receive a threaded brass rod #b inches long and #a_/d inch diameter4 ,the lower ends of the hard rubber standards are each bored and tapped to receive a screw which fastens them to the base4 ,the electrodes are zinc or brass cylinders #c_/d inch diameter and #e_/h inch long4 ,the upper electrode is adjustable by means of a knurled hard rubber head #b inches diameter and #a_/b inch thick4 ,the lower one is fastened to a brass plate #b inches long1 #a inch wide and #a_/h inch thick4 ,one end of the plate is fitted with a binding post4 ,the base is a piece of hard rubber #e #a_/b x #c inches x #c_/d inch4 ,,chapter ,,ix4 ,,transmitting ,,helixes4 ,the transmitting helix or tuning coil supplies the greater part of the inductance which is so necessary for the production of electrical oscillations in the transmitting circuit4 ,it consists merely of a few turns of heavy copper or brass wire wound in a helix around a form4 ,two or more movable contacts permit various amounts of the inductance to be inserted in the open or closed circuits4 ,the tuning helixes described in this chapter are offered principally to serve as guides4 ,they have been designed as carefully as possible to suit the transmitters for which they are recommended4 ,there are factors1 such as the aerial1 etc41 which vary greatly in stations of the same rated power and make it best to determine the length of the helix by actual experiment4 ,a certain amount of inductance is necessary in the closed circuit for the production of electrical oscillations and to transfer energy to the open circuit4 ,inductance beyond that necessary to receive energy from the closed circuit lessens the radiation and makes it necessary to increase the period of the open circuit by adding wires to the aerial4 ,the open and closed circuits of a tuning helix constitute an oscillation transformer1 and the two circuits if they are very close together or intertwined are said to be closely coupled4 ,when separated or far apart they are loosely coupled4 99,closely ,coupled ,helix499--,fig4 #fa illustrates a closely coupled tuning helix1 suitable for ordinary induction coils giving sparks up to #c or #d inches in length4 ,the heads of the helix are circular pieces of hard wood #a inch thick and #ab inches in diameter4 ,six rectangular notches are made at equal distances along the edges of the heads4 ,six uprights #c_/d x #a_/b inch and #h #c_/d inches long are fastened in the notches with small round headed brass screws so that the heads are separated a distance of #f #c_/d inches4 ,grooves are cut in the outside face of each of the uprights at a distance of #g_/h inch apart4 ,the wire forming the helix is #a_/d inch brass4 ,brass wire is springy and retains its shape better than copper4 ,about twenty-two feet will be required4 ,the wire is wound in the grooves in the uprights and held in place by a few double pointed tacks placed judiciously4 ,the adjacent turns of wire will then have a separation of about #e_/h inch4 ,illustration3 ,fig4 #fa4 ,closely ,coupled ,helix4 ,the helix is raised above the level of the operating bench or table by three small feet fastened to the under head1 #abj degrees apart4 ,illustration3 99,plate ,,iii4 ,transmitting ,circuits499 ,if it is desired to use this helix with the one quarter ,k4,w4 transformer1 the diameter of the wire should be increased to #e_/af inch4 ,the two ,k4,w4 transformer will require seven turns of #a_/b-;inch hard drawn brass wire two feet in diameter4 ,illustration3 ,fig4 #fb4 ,prague ,transmitting ,helix4 ,when setting up a transmitting station1 it is a good plan to coil up a long piece of the wire to be used on the helix around a rough form4 ,the adjacent turns should be the same distance apart as they are to be on the finished instrument4 ,tune up the station with this improvised helix and ascertain the amount of inductance required4 ,it is then easy to design a helix containing the proper amount of wire4 ,four or five feet extra should be included to allow plenty of range in case it is ever necessary to make any changes in the aerial or condenser4 ,illustration3 ,fig4 #fc4 ,closely ,coupled ,tuning ,circuit4 ,plate ,,iii illustrates the transmitting circuits of the various commercial systems4 ,the circuit used will determine the number of binding posts and movable clips necessary4 ,fig4 #fc gives the diagram of a very good circuit4 99,loosely ,coupled ,helix994 ,the heads of the primary coil of the loosely coupled helix illustrated in ,fig4 #fd are circular pieces of hard wood #a inch thick and #ah inches in diameter4 ,six uprights #c_/d x #a_/b inch and #aa inches long are set into notches in the upper head and fastened to the base so that the space between the heads for winding the wire is #aj inches4 ,illustration3 ,fig4 #fd4 ,loosely ,coupled ,transmitting ,helix and ,contact ,clip4 ,a square wooden pillar #a #a_/b x #a #a_/b inches and #cb inches long passes through a square hole #a #a_/b x #a #a_/b inches in the center of the heads and projects #bj inches above the upper one4 ,the heads of the secondary coil are each #ab inches in diameter4 ,the distance between them is also #ab inches4 ,a square hole #a #a_/b inches x #a #a_/b inches in the center of each of the heads permits the whole secondary coil to slide up and down on the pillar4 ,several #a_/d inch holes bored #a inch apart in the pillar admit a small peg of the same diameter4 ,the coupling between the two coils is varied by changing the height of ,s above ,p and inserting the peg to hold the upper coil in position4 ,the primary winding of the transformer should consist of about #bj turns #ae inches in diameter1 and may range in size of wire from ,no4 #b to ,no4 #h ,b4 ,s4 gauge4 ,the secondary is #aj inches in diameter and will require about #dj turns of ,no4 #aj to ,no4 #af ,b4 ,s4 gauge4 ,the largest sizes of wire are for the one-quarter and one-half ,k4,w4 transformers while the smaller sizes are best suited to small induction coils4 ,fig4 #fd also illustrates a clip for making connections to the turns of the helix4 ,the handle is a piece of hard rubber rod #b #a_/b inches long and #e_/h inch in diameter4 ,a saw slot #a inch deep is cut down the center of one end4 ,two strips of spring brass #b inches long1 #e_/h inch wide and #c_/fd inch thick are bent as shown in the illustration4 ,the straight ends are slipped in the slot in the handle and clamped together by boring a hole and passing a machine screw through4 ,the upper end may be fitted with a nut or a binding post to facilitate connection4 ,flexible copper ribbons or stranded wire should be the only conductor used for the tuning leads4 ,illustration3 ,fig4 #fe4 ,loosely ,coupled ,transmitting ,circuit4 99,tuning a ,transmitter499--,fig4 #fb shows a complete wiring diagram of a transmitter with a hot wire ammeter inserted in the aerial circuit4 ,to tune such a transmitter place both contacts ,a and ,b together on a turn of wire near the center of the helix4 ,set the transmitter in operation by pressing the key and move both contacts together along the various turns of wire until the meter shows a maximum reading4 ,then vary ,b alone until the reading is still higher4 ,shifting ,a varies the inductance in the closed circuit and ,b that of the open circuit4 ,fig4 #fe illustrates the circuit of a loosely coupled transmitter4 ,to tune such a circuit it is necessary to connect a small needle spark gap between the aerial and the ground4 ,illustration3 ,fig4 #ff4 ,united ,wireless ,helix1 ,spark ,gap and ,condenser4 ,a suitable spark gap for this purpose may be made of two darning needles mounted in double binding posts4 ,set the clips1 ,a and ,b1 at the center turns of their respective coils4 ,press the key to operate the transmitter and adjust the clip1 ,a1 until the best spark is obtained in the small needle gap4 ,then adjust ,b until the spark is still better4 ,if several wires seem to give the same results1 move the secondary a little further away from the primary and try again4 ,after securing the best spark it is possible to obtain1 remove the needle gap1 which is only used in testing4 ,the hot wire ammeter should then be placed in series with the aerial4 ,by slowly and carefully adjusting the clips and varying the coupling1 the hot wire ammeter will indicate the proper tune4 ,the secondary of the loosely coupled tuning coil produces a kick back effect on the primary1 due to induction1 and unless the two coils are somewhat separated1 the wave emitted from the transmitter will have more than one hump and a person receiving the wave will be able to tune it in on two places on his tuning coil4 ,a loosely coupled tuning coil does not radiate so much energy as a closely coupled helix1 but will1 when properly tuned1 emit a wave which is not so highly damped4 ,therefore as far as distance is concerned the loosely coupled type is perhaps the most efficient4 ,,chapter ,x4 ,,keys4 ,,the keys used in wireless work differ from those used in commercial wire telegraphy in being much heavier and stronger1 so as to conduct and break the heavier currents without heating4 ,where very powerful currents must be broken the contacts of the key usually operate under oil or in the magnetic field of a pair of electromagnets4 ,in other cases a small key is used to operate a heavy relay4 ,in the former type a metal arm projects downward from the lever of an ordinary ,morse telegraph key into a compartment filled with oil4 ,the arm is provided with a platinum point which makes contact with another similar point on the bottom of the compartment1 so that the break is made under oil and the key remains cool and does not arc4 ,in the second form the same result is accomplished by a magnetic blowout4 ,the blowout is merely an electromagnet connected in series with the key and its poles at right angles to the contacts of the key4 ,when the circuit is broken the magnetic field extinguishes the arc which tends to form between the contacts of the key4 ,an ordinary ,morse key may be used with coils operated on batteries if they do not give more than a four-inch spark4 ,larger coils or transformers1 especially if they are operated on the #aaj-volt current1 require a heavier key4 ,where an ordinary ,morse key is used with a #c-;inch or #d-;inch coil it is a very good plan to provide an auxiliary conductor1 one end of which is fastened to the metal base and the other end to the adjusting screw on the back of the lever4 ,a piece of flexible lamp cord is suitable for this purpose4 ,this precaution saves the pivots of the key from heating and possible burning by heavy currents4 ,illustration3 ,fig4 #fg4 ,morse ,key fitted with ,extension ,lever4 ,the most convenient method is to fit up an old ,morse key in the manner shown in ,fig4 #fg4 ,the lever is extended by a piece of aluminum or brass #f inches long and #e_/af inch thick4 ,the exact shape and the dimensions are indicated in the illustration4 ,the extension lever is provided with a #a_/b-;inch round brass or nickel steel contact #g_/h inch long4 ,the lower end of the contact is bored and tapped to receive a short machine screw4 ,the other contact is a similar piece projecting downwards from a small arm fastened to the top of a standard #a_/b inch diameter and #b inches long4 ,the arm is a strip of brass #a_/b inch wide1 #a_/d inch thick1 and #a #a_/b inches long1 fastened to the top of the standard with a machine screw4 ,the brass standard is held in an upright position by means of a small machine screw which passes through the base4 ,a wire connects with this screw to a heavy binding post mounted on the base4 ,connection is made with contact on the extension lever by means of a piece of heavy flexible lamp cord1 which also runs to a binding post mounted on the base4 ,the contact is insulated from the extension lever by means of two mica insulating washers and a bushing4 ,avoid running the connection to the base of the key so that the current must pass through the bearings4 ,the contacts should be filed until they are perfectly flat and square across and make contact over their entire surface4 ,when carefully constructed a key of this type will carry without heating almost any currents in reach of the amateur operator and which his induction coil or transformer will stand4 ,illustration3 ,fig4 #fh4 ,wireless ,key4 ,the plans and dimensions for a heavier key are shown in ,fig4 #fh4 ,a wooden pattern of the base and bearings is made and taken to a brass foundry where a casting in brass may be secured4 ,the pattern should be of the same shape and size as the finished article represented in the figure4 ,it is given a slight taper so that it may be easily withdrawn from the sand mold4 ,the brass casting is finished up square and smooth by grinding on an emery wheel or by careful filing4 ,the lever is a piece of brass rod #a_/b inch square and #f #a_/b inches long4 ,one end is fitted with an ordinary hard rubber ,morse key knob4 ,the knurled nuts and thumbscrews are of the same size as those used on an ordinary key1 and may be purchased from an electrical supply house4 ,illustration3 ,fig4 #fi4 ,united ,wireless ,type ,key4 ,the pivot is a piece of #c_/af inch round steel #a inch long1 and passes through the lever #a #a_/b inches from the rear end4 ,the ends are ground or turned to sharp points and rest in bearings formed by boring a recess in the ends of the thumbscrews4 ,the thumbscrews pass through the center of the bearing1 standards #c_/d inch above the base4 ,the lever is clamped to the center of the pivot by means of a small machine screw4 ,a heavy piece of spring brass1 ,s1 #a_/b inch wide and #c inches long1 is fastened to the base at one end with a short #h-cb screw4 ,the other end is bent upward so that it presses hard against the lower end of an adjusting screw1 which passes through the lever #a #a_/d inches forward of the pivot4 ,this spring serves as an auxiliary conductor and saves the key from carrying an excessive current through its bearings4 ,by adjusting the thumbscrew1 the tension of the key may be regulated to suit the operator4 ,the contacts of the key are #a_/h-;inch round nickel steel alloy or pure silver1 set in short #a_/d-;inch machine screws which fit into correspondingly threaded holes in the base and the lever4 ,this makes the contacts easily removable for renewal4 ,the lower contact is set in a longer screw than the upper one so that connection may be made to it4 ,it is insulated from the base by a hard rubber brushing4 ,the contacts must be directly above one another and in perfect alignment or else they will pit and stick4 ,,chapter ,,xi4 ,,aerial ,,switches ,,and ,,anchor ,,gaps4 ,some form of switch for quickly connecting the aerial and ground to either the transmitting or receiving apparatus is necessary4 ,low powered stations using an induction coil as a transmitter will find a #bej-volt double pole1 double throw porcelain base switch to be suitable4 ,such a switch is connected up according to the diagram shown in ,fig4 #gj4 ,as clearly illustrated1 the receiving apparatus is in use when the switch is thrown to the right1 and the transmitter is ready for operation when the switch is in the left-hand position4 ,the ease and speed with which such a switch may be thrown from right to left or vice versa may be much facilitated by fitting it with a larger and longer handle than the one usually provided4 ,illustration3 ,fig4 #gj4 ,connections for ,aerial ,switch4 ,an ordinary double pole1 double throw switch should be mounted on the wall within easy reach of the operator1 while the two types of switch about to be described are best situated directly on the operating table alongside of the transmitting key4 ,all insulated parts of an aerial switch such as the base1 insulating bar1 handle1 etc41 should be made of some good insulating material1 as porcelain1 hard rubber or ebonite4 ,all insulation which is used in power switches such as slate1 wood1 marble1 etc41 is worthless and should not be used4 ,if a loop aerial system is used1 a switch is necessary1 which will break the primary transmitting current so that in case of an accidental touch of the key while receiving1 the high voltage discharge will not pass across the anchor gap into the receptor and badly damage the same or shock the operator4 ,the connections of such a switch and the loop aerial are shown in the wiring diagram of the ,de ,forest system4 ,illustration3 ,fig4 #ga4 ,aerial ,switches4 ,a switch may be easily constructed from a #ej ampere1 single throw1 triple pole1 fuseless power switch4 ,if it is mounted on a slate base remove it and set it up on a base of the same size made of fiber or porcelain4 ,flat unglazed tiles of various sizes are obtainable from tile setters at a very low cost4 ,they may be easily bored with an ordinary steel twist drill4 ,such tiles are excellent insulators when not exposed to moisture and are useful for bases1 etc41 in many cases4 ,a heavy coat of shellac varnish will make the tile impervious to moisture4 ,a hard rubber rod1 ,s1 #c inches long and #e_/h inch diameter1 is mounted on both sides of the base in alignment with the contacts4 ,a strip of hard rubber1 ,y1 #a inch wide1 #a_/b inch thick and #f #a_/b inches long is fitted with two contacts similar to those mounted on the base of the switch4 ,the contacts are mounted at a distance apart equal to the distance between the outside knife blades of the switch4 ,a #a_/h-;inch hole is bored through the strip at both ends1 through the axis of the rods along their entire length and through the base4 ,a piece of brass rod #d inches long and threaded at both ends with an #h-cb die is passed through the holes and yoke1 so that the rods may be held firmly to the base and the strip to the tops of the rods by two nuts screwed on the ends of the brass rod4 ,illustration3 ,fig4 #gb4 ,detail of ,contacts4 ,the upper contacts should be directly over the two outside lower ones4 ,they are made from a strip of brass #a_/b inch wide1 #c #a_/b inches long and #a_/af inch thick 7bent as in ,fig4 #gb74 ,a binding post is mounted on the yoke directly above and connecting with each one of the contacts4 ,the middle pole of the switch is connected to the primary of the coil or transformer1 so that when the switch is down1 the primary circuit is completed1 and when it is up it is broken4 ,illustration3 ,fig4 #gc4 ,details of ,switch ,parts4 ,some may prefer to make the complete switch1 and in that case the dimensions given in ,fig4 #gc may be of aid4 ,the knife blades are #f inches long1 #e_/h inch wide and #a_/h inch thick4 ,three are required4 ,a #a_/h-;inch hole is bored #c_/h inch from one end1 and the other end is cut out in the shape shown in the illustration4 ,an insulating bar #e x #c_/d x #e_/h inches is made of hard rubber and three notches are cut in the back face1 one directly in the center and one #b inches on either side4 ,illustration3 ,fig4 #gd4 ,method of ,fastening ,knife4 ,three #a_/h-;inch holes are bored one in the center of each groove and at right angles to it4 ,an #h-cb machine screw #c_/d inch long is placed in the notch in the end of the knife blade and the screw passed through the hole in the insulating bar4 ,the blade may then be clamped tightly in place by putting a nut on the end of the screw4 ,the screw which holds the middle knife blade in place is longer than the other two so that a handle may be fitted on4 ,the bearings are made the same size and shape as the contacts illustrated in ,fig4 #gb1 with the exception that a #a_/h-;inch hole is bored through near the top so that a small bolt may be slipped in to hold the knife blades in place4 ,the base of the switch measures #h x #i x #c_/d inches4 ,the parts are assembled as in ,fig4 #ga4 ,another type of aerial switch called a ,t switch is illustrated in the same figure4 ,a piece of #c_/d-;inch hard rubber is sawed in the shape of a ,t1 #c #a_/b inches high and #f #a_/b inches wide at the top4 ,the upper contacts are mounted on arms of the ,t and connected to binding posts placed immediately above them1 ,a slot1 #a_/b inch wide and #c inches long1 sawed in the center of the leg of the ,t1 permits the middle knife blade to move without obstruction4 ,illustration3 ,fig4 #ge4 ,t ,aerial ,switch4 ,a double pole1 double throw switch may be easily adapted to form a ,t switch4 ,two knives are cut from sheet brass1 of the same shape as those already on the switch but twice as long4 ,the contacts at one end of the porcelain base are removed and the bearings of the knife blade fastened there in their stead4 ,this forms a single throw1 double pole switch having knife blades twice the length of the original double pole1 double throw switch4 ,a ,t shaped support for the upper contacts may be sawed out of #a_/b-;inch hard rubber and smoothed up with a file4 ,the support is fastened upright by means of two screws which pass through holes in the center of the base where the knife bearings originally were4 ,the two contacts which were removed from the base are fastened to the support directly over the knife blades so that they make a good contact when the switch is up4 ,two binding posts mounted above the contacts make connection with them4 ,if desirable the switch may be fitted with a third knife blade and contact so that when the switch is up in position for receiving1 the primary circuit of the induction coil or small transformer is open4 ,it is obvious that the dimensions1 etc41 need not be the same as those given here but may be adapted to suit the size and design of the switch which is to be altered4 ,the knives should always be as long as convenient and the contacts separated by a wide space4 ,illustration3 ,fig4 #gf4 ,united ,wireless ,lightning ,switch4 ,illustration3 ,fig4 #gg4 ,shoemaker ,tuning ,coil and ,aerial ,switch4 ,figs4 #gf and #gg illustrate the aerial switches used in the installations of the ,united ,wireless ,telegraph ,company4 ,these illustrations give a good idea of the long knife blades employed4 ,the lightning switch is fitted with a micrometer spark gap on top of the switch which is in service when the handle is up4 ,the small spark gap affords a path for the lightning to jump into the ground1 but cannot be bridged by the receiving currents4 99,anchor ,gaps499--,when a loop aerial system is employed for both transmitting and receiving1 a device known as an anchor gap becomes necessary4 ,illustration3 ,fig4 #gh4 ,united ,wireless ,anchor ,gaps4 ,the construction and connection of a simple anchor gap are shown in ,fig4 #gi4 ,a ring #a #c_/d inches outside and #a #a_/d inches inside is cut out of #e_/h-;inch hard rubber or fiber and smoothed up4 ,three #a_/h-;inch holes are bored in the periphery of the ring at #abj degrees to each other4 ,the holes are threaded with a #aj-bd tap4 ,three small binding posts are each fitted with a #c_/af-;inch brass rod #g_/h inch long1 having a #aj-bd thread so that they may be screwed into the holes in the ring4 ,illustration3 ,fig4 #gi4 ,anchor ,gap4 ,the gap between the ends of the two rods connected to the aerial and the receiving apparatus is adjusted until it is about #a_/h inch long4 ,the third point is screwed in until it all but touches the other two4 ,,chapter ,,xii4 ,,hot ,,wire ,,ammeter4 ,when a current passes through a conductor1 it generates heat in proportion to the resistance offered and the amount of current flowing4 ,heat causes metals to expand sufficiently so that these two properties may be applied to the construction of a hot wire ammeter for the measurement of alternating currents of high frequency and potential4 ,the hot wire ammeter is placed in series with the aerial1 so that by noting the deflection of the pointer1 the inductance1 capacity and spark gap may be adjusted until the meter gives a maximum reading4 ,illustration3 ,fig4 #hj4 ,simple ,hot ,wire ,meter4 ,a simple and crude form of meter which is sufficiently sensitive for most experimental work is illustrated in ,fig4 #hj4 ,a piece of ,no4 #cf ,b4 ,s4 platinum wire is sealed in the bulb of an ordinary air thermometer4 ,when the wire becomes heated by a passing current of electricity1 it causes the air in the bulb to expand and change the height of the colored liquid in the tube4 ,an air-thermometer is simply a glass tube of fine bore having a bulb blown at the upper end and the free end immersed in a reservoir of ink or some other colored liquid4 ,the instrument is put in working order by grasping the bulb in the palm of the hand1 so that the warmth of the hand will expand the air and cause some of it to escape from the lower end of the tube4 ,upon removing the hand1 the air will contract and suck some of the liquid up into the tube4 ,it should rise only about half way to the bulb1 and the tube should be about #ah inches long so as to leave room for changes in the position of the column due to variations in the outside atmosphere4 ,a cardboard scale graduated in inches and reading downward is fastened in back of the tube4 ,the tube should have a fine bore so as to make the instrument as sensitive as possible4 ,the best liquid to use is alcohol1 colored with a little aniline dye4 ,alcohol has a lower specific gravity than water1 and the column will be more sensitive to small changes of pressure4 ,the same figure shows a form of meter devised and used with success by the author4 ,two tubes are fitted to the bulb1 a large one having a bore of about #j4a of an inch and another about #j4jd inch4 ,connection is established by the aid of two corks and a short length of glass tubing one inch in diameter4 ,the tubes are bent ,u shaped1 and a little colored alcohol is placed in each1 so that the bottle reservoir is unnecessary4 ,the tube of large bore is fitted at the top with an ordinary glass stopcock such as that used in chemical laboratories4 ,the stopcock is left open and the transmitter is set in operation by holding down the key4 ,the helix1 etc41 are adjusted until the larger tube shows a maximum reading4 ,the stop-cock is then closed and the instruments further adjusted by noting the reading in the finer tube which corresponds to much smaller changes in current4 ,the finer bore cannot at first be used alone because the large changes of current would blow the liquid out of the tube4 ,in lieu of a glass stopcock1 a piece of rubber tubing may be placed over the end of the tube and closed1 when necessary1 with a pinch cock4 ,illustration3 ,fig4 #ha4 ,meter with ,case ,removed4 ,fig4 #ha shows a more elaborate and sensitive form of meter which is not only suitable for experimental outfits but may be used with good results for more careful work4 ,the advantage of the form of meter here described is that it is pivotless so to speak1 and contains no bearings which require jewels to eliminate friction4 ,the hot wire is platinum1 and in order to compensate for external changes of the atmospheric temperature1 is mounted on a strip of glass4 ,glass and platinum expand at nearly the same rate1 and the wire is thus kept taut and prevented from changing the position of the pointer except when the current passes4 ,illustration3 ,fig4 #hb4 ,glass ,compensating ,strip4 ,drill four #a_/h-;inch holes in a piece of window glass #f inches long and #a inch wide4 ,the location of the holes is shown in ,fig4 #hb4 ,the two at the ends serve to mount the standards1 ,a and ,b1 and those at the center to fasten down the strip to the base4 ,the holes are drilled with a small three-cornered file which has been broken off and set in a breast drill4 ,the broken end should be used to drill the glass and be kept thoroughly lubricated with camphor and turpentine4 ,with a little care and patience the holes may be drilled without breaking the glass4 ,illustration3 ,fig4 #hc4 ,details of ,hot ,wire ,supports4 ,two brass standards are fastened on each end of the glass4 ,they are bent out of sheet brass and are #c_/d inch high and #c_/h inch wide4 ,a brass spring of the same width and #a #a_/d inches long is clamped under one standard4 ,the standard which holds the spring in position is tapped for a small thumbscrew which may be secured from a binding post4 ,solder a small brass pin to the top of the spring and another one to the top of the standard which is fastened at the opposite end of the glass strip4 ,some paper or rubber washers must be placed between the feet of the standards and the glass strip to prevent it from cracking when the screws are tightened4 ,for a station up to one-half ,k4,w4 in power the hot wire must be ,no4 #dj ,b4 ,s4 gauge platinum4 ,for larger stations a single ,no4 #cf wire may be used or three ,no4 #dj wires in parallel4 ,the wire must be about #g inches long4 ,stretch it between the standard1 ,a1 and the spring1 ,c4 ,wrap the ends around the pins and solder them there1 using as small amount of solder as possible4 ,the tension of the wire1 which should be taut1 is adjusted with the thumbscrew4 ,take a piece of the platinum wire about #a_/b inch long and make a little eyelet at one end4 ,wrap the straight end around the center of the long hot wire and tie a piece of silk in the eyelet4 ,illustration3 ,fig4 #hd4 ,details of ,movement4 ,the glass strip and its standards supporting the hot wire may then be fastened to the baseboard of the instrument by means of two round headed brass wood screws4 ,two rubber washers must be interposed between the glass and the wood4 ,a piece of #c_/cb inch brass #a_/b inch wide and #c #a_/d inches long is bent in the shape shown by ,f in ,fig4 #hd4 ,the upper end is bored and tapped to receive a thumbscrew similar to the one in the standard on the glass strip4 ,two brass springs #a_/fd inch thick1 #c_/h inch wide and #a #a_/d inches long are soldered or riveted at opposite ends of ,f in the positions shown in ,fig4 #he4 ,the springs should project one inch from the upright4 ,a small hook made from an ordinary pin is soldered to the outside end of each4 ,illustration3 ,fig4 #he4 ,complete ,movement4 ,the movement is shown in perspective by ,fig4 #he4 ,g is a rectangle of very thin copper1 #a_/b inch long and #a_/d inch wide1 having a little projection #a_/d inch long bent in a curve so that it forms a sextant of a circle1 of which the intersection of the diagonals of ,g would be the center4 ,the pointer is a piece of steel wire #e inches long4 ,it is slightly flattened by hammering so that it will retain its shape and not curl4 ,about #a_/b inch is allowed to project through ,g and is weighted with a lead shot so as to partly counterbalance its weight4 ,two loops of wire are fastened to the corners of ,g by tying them in holes which are bored there for that purpose4 ,the wire is fine phosphor bronze 4#jjc-4jje of an inch in diameter1 which is used for suspending the movements of delicate galvanometers4 ,pass the loops over the hooks on the springs and adjust until the pointer moves horizontally4 ,then fasten the wires permanently to the hooks by means of a small drop of solder4 ,illustration3 ,fig4 #hf4 ,side ,view of ,hot ,wire and ,movement4 ,the movement is mounted in the position shown by ,fig4 #hf4 ,the silk thread tied to the eyelet runs to the little sextant and is cemented at the further end by means of a small drop of sealing wax4 ,the scale is a piece of sheet copper or brass1 covered with white paper and calibrated in degrees or made to read in amperes by connecting it in series with an ammeter and a source of direct current4 ,a rheostat should be included in the circuit and the current varied so that various values may be marked off4 ,all the different points must be located by sending an actual current of that value through the meter4 ,an error is liable to result if any of the points are marked by guesswork1 for the divisions grow smaller and smaller as they become farther away from zero4 ,for example a position of the pointer corresponding to #j4a of an ampere will not be half way between zero and #j4b but will be nearer the #j4b division4 ,the resistance of wires to high frequency currents is much higher than their resistance to constant currents4 ,this would seem at first to indicate that our meter will give a higher reading for an equal current value1 when used with a high frequency current after being calibrated with a direct current4 ,but with wires of very small diameter such as ,no4 #dj ,b4 ,s4 gauge there is almost no perceptible difference and consequently no error unless the frequency of the oscillations exceeds #a1jjj1jjj per second1 which is very unlikely with the spark method of wireless telegraphy4 ,fig4 #hg illustrates the form of hot wire ammeter used by the ,united ,wireless ,telegraph ,co4 for tuning their installations4 ,illustration3 ,fig4 #hg4 ,united ,wireless ,hot ,wire ,ammeter4 ,the pivotless meter just described should be fitted with heavy binding posts which are connected to the brass standards mounted on the glass strip by means of stranded copper wire4 ,the meter should be fitted with a case and glass cover to exclude dust and prevent injury to the working parts4 ,it should be mounted in such a position that the weight of the pointer is sufficient to keep the silk thread taut so that when the wire expands the pointer which is normally at zero will fall of its own weight4 ,when the wire cools after the current has ceased to flow1 it will contract and draw the pointer up again4 ,platinum wire will give good results1 but for more accurate work an alloy known as platinoid is most suitable4 ,detailed instructions for tuning the transmitting circuits by means of a hot wire ammeter are given in the chapter on ,transmitting ,helixes4 ,,chapter ,,xiii4 ,,oscillation ,,detectors4 ,,universal ,,detector4 ,the purpose and position of the detector in a wireless telegraph system has already received some notice in the first chapter1 but its operation and adjustment are so important that this chapter deserves the most careful consideration4 ,the receiving range of a station is not as much dependent upon the aerial system as it is upon the adjustment of the tuning circuits and the detector itself4 ,it is suggested that the amateur experimenter not confine his work to receiving only with a single type of detector but rather accustom himself to the different instruments4 ,during the past few years many wireless telegraph detectors have been invented which lend themselves readily to amateur construction4 ,it is somewhat of a convenience to have a universal detector which with a little manipulation may be used as more than one type and thus save unnecessary expense and much labor4 ,the universal detector shown in ,fig4 #hh has been so designed as to present a good appearance and at the same time be successfully operated as an electrolytic1 tantalum1 peroxide of lead1 silicon1 carborundum or any of the crystal type detectors4 ,illustration3 ,fig4 #hh4 ,universal ,detector4 ,illustration3 ,fig4 #hi4 ,details of ,universal ,detector4 ,the standard1 ,r1 is a #c_/d-;inch hard rubber rod1 #a #a_/d inches long1 with a #c_/af inch hole bored through its axis4 ,a spring1 ,s1 is made after the plan shown in ,fig4 #hf4 ,it is #b inches long and #a_/af inch thick4 ,a brass collar #a_/h inch thick and #c_/h inch diameter is soldered on the smaller end of the spring in order to so reenforce it that it may be bored and threaded with an #h-cb tap to receive a thumbscrew4 ,the brass standard1 ,d1 is a small cylinder #c_/h inch high and #a_/b inch in diameter4 ,a #c_/af inch hole is bored through its axis4 ,the arm1 ,a1 is brass and measures #a #a_/b x #a_/b x #a_/d inches4 ,the ends are rounded by filing or grinding so that they coincide with the semi-circumference of a circle having a diameter of #a_/b inch4 ,two holes are bored on the center line #a_/d inch from each end4 ,one is a #a_/h-;inch hole and the other is threaded with a #aj-cb tap to fit the large adjusting screw4 ,the adjusting screw1 ,h1 is #a #a_/d inches long and has a #aj-cb thread4 ,a hard rubber head #a inch thick and #a #a_/d inches in diameter is clamped to the upper end by means of two hexagonal brass nuts4 ,a small brass washer should be placed between the head and each of the nuts to give it a more finished appearance and prevent the nuts from marring the rubber4 ,illustration3 ,fig4 #ij4 ,parts of ,universal ,detector4 ,the brass bed plate1 ,b1 is #a_/h inch thick1 #c inches long and #b inches wide4 ,two holes are drilled on the center line #i_/af inch and #g_/h inch from either end4 ,one is #c_/h inch in diameter and the other is threaded with an #h-cb tap4 ,an insulating bushing in the shape of a hard rubber washer on the lower end of ,r1 #a_/h inch thick and #c_/h inch in diameter1 has a #c_/af-;inch hole bored in its center and is fitted in the larger hole in the bedplate4 ,the whole detector is assembled and mounted on a hard rubber base #d x #e x #d inches4 ,a brass binding rod1 ,m1 #c #a_/d inches long and having an #h-cb thread1 is passed successively through the arm1 the brass standard1 the spring1 the hard rubber standard and the bedplate4 ,a hexagonal brass nut on the under side of the base and a thumb nut on the brass arm serves to bind the whole tightly together4 ,four binding posts are mounted on the four corners of the base4 ,two are connected to the brass binding rod and two to the bedplate4 ,this completes the universal part of the detector4 ,the remaining parts are each described under the headings of the respective detectors to which they belong4 ,,electrolytic ,,detectors4 99,bare ,point ,type499--,although the electrolytic is the oldest of a long line of very sensitive detectors1 it still holds first rank when in the hands of an experienced and skillful operator4 ,it exists in two different forms1 but the more favored is that known as the ,fessenden bare point type1 which consists of a very fine ,woolaston platinum wire 74#jja-4jjjjb of an inch in diameter7 dipping in a small cup of dilute acid4 ,the acid is either #bj per cent chemically pure nitric or sulphuric4 ,illustration3 ,fig4 #ia4 ,bare ,point ,electrolytic ,detector4 ,a large electrode of platinum wire or foil dips into or is sealed in the bottom of the cup so as to make an electrical connection with the liquid4 ,the fine ,woolaston wire is clamped over the cup in a holder which permits of vertical adjustment1 by means of a thumbscrew1 so that the depth of immersion in the acid may be regulated4 ,illustration3 ,fig4 #ib4 ,effect of ,exposing too much ,wire4 ,woolaston wire is covered with a comparatively thick coating of silver1 which before using must be removed from the end for about #a_/cb inch by dipping it in strong nitric acid1 which will dissolve the silver and expose the almost invisible platinum core4 ,too much of the fine platinum core must not be exposed or else the surface tension of the acid will cause the wire to curl over and present a large flat surface instead of a fine point4 ,this is a very necessary and important precaution1 for the detector is more sensitive as the area of contact between the fine wire and the liquid is smaller4 ,whenever this condition is reached the end of the wire should be cut off with a pair of sharp scissors and a new point exposed4 ,illustration3 ,fig4 #ic4 ,electrolytic ,detector ,circuits4 ,the detector circuit is shown in ,fig4 #ic4 ,the fine bare point is always made the positive or anode of the battery circuit4 ,otherwise the detector will not operate4 ,a potentiometer must be shunted across the terminals of the battery to reduce the voltage to a value just below that which is required to break down the thin film of oxygen gas which collects on the bare point and polarizes it or insulates it from the liquid so that little or no battery current can flow4 ,this film of gas is caused by the electrolysis of the acid solution and the decomposition of the water into hydrogen and oxygen gas4 ,when oscillations are set up in the receiving aerial and they surge through the detector1 a sufficient e4m4f4 is generated to break down the film of gas and permit the battery current to flow again4 ,the passage of current causes the signals in the telephone receivers4 ,the electrolytic cup for the universal detector is illustrated in ,fig4 #ij4 ,it is made of a piece of hard rubber rod #c_/d inch in diameter and #c_/d inch high4 ,a recess #a_/b inch in diameter and #c_/h inch deep is cut in the top to contain the acid4 ,a small hole #a_/d inch deep is bored in the under side and threaded with an #h-cb tap4 ,a brass pin #a_/b inch long1 having a corresponding thread1 is fitted in the hole4 ,the pin may then be screwed into the small hole in the bedplate4 ,a piece of ,no4 #cj ,b4 ,s4 gauge platinum wire or a strip of platinum foil is clamped between the bottom of the cup and the bedplate and then bent over the top of the cup into the liquid4 ,illustration3 ,fig4 #id4 ,electrolytic ,detector4 ,a #a_/af-;inch hole #a_/d inch deep is bored in the lower end of a thumbscrew having an #h-cb thread4 ,a piece of ,woolaston wire #a_/b inch long is placed in the center of the hole and tinfoil packed into the surrounding space with the head of a sewing needle until the wire is held firmly in position4 ,the free end of the wire must then be dipped in some strong nitric acid to remove the silver4 ,the thumbscrew is placed in the collar on the end of the spring of the universal detector and lowered until the bare point almost touches the surface of the electrolyte in the cup beneath4 ,pressure must then be applied to the spring by turning the large adjusting screw until the bare point touches the liquid and a click is heard in the telephone receivers and a faint bubbling sound is also audible4 ,the adjusting screw must then be slowly and carefully turned in the opposite direction so as to raise the point until the bubbling changes to a hissing sound4 ,the point is then above the level of the electrolyte in the cup but is still in contact with it because of the capillary action of the fine wire and the liquid4 ,by using the large adjusting screw as much as possible1 instead of the small thumbscrew1 the point is raised or lowered without giving it a circular motion and much finer adjustment is made possible4 ,the potentiometer is adjusted until the hissing noise caused by excessive battery voltage just disappears4 ,the detector is then in its most sensitive condition for receiving signals4 ,when the detector is in use for long periods1 the potentiometer must be frequently readjusted to compensate the gradual loss in voltage of the battery4 ,it is well to provide a small switch which will disconnect the battery from the potentiometer when the detector is not in use4 ,in the same case the acid should be removed and placed in a tightly stoppered bottle4 ,a pipette or fountain pen filler furnishes the most convenient means for filling or emptying the cup4 ,the acid must be kept perfectly pure and out of contact with all metals other than platinum4 ,great care should be exercised in filling the cup1 for the acid1 if spilled1 will not only badly corrode the metal fittings1 but will also provide a current leak and seriously weaken the signals4 99,shoemaker and ,stone ,detectors499--,these two types of detectors make use of glass points1 so called because the fine platinum wire is sealed in a glass tube and the end of the tube is then ground down on a fine oilstone until the platinum wire is exposed4 ,this results in a very fine contact area and insures constant immersion of the point without readjustment4 ,illustration3 ,fig4 #ie4 ,forming ,glass ,point4 ,the fine platinum wire for a glass point may be secured from one of the flaming pocket cigar lighters making use of spongy platinum4 ,the center of a thick walled glass tube is softened by heat and contracted as shown at ,a-,b in ,fig4 #ie4 ,after cooling1 the tube is cut in half at the point indicated by the dotted line4 ,the platinum wire is placed in the contracted end of the tube and carefully fused in so that about one-half of the wire1 which is about #a_/b inch long1 is embedded in the glass4 ,the contracted end of the tube containing the wire should be closed4 ,connection is established to the upper end of the fine platinum wire by filling the tube with mercury and dipping a piece of flexible conductor in the mercury4 ,the upper end of the tube is closed and the mercury prevented from escaping by a small dab of sealing wax4 ,the point is slowly and carefully rubbed on a fine oilstone kept well wet with water4 ,the tube must be held in a vertical position so that the glass will be ground away at right angles4 ,when it is thought that the platinum wire has been exposed by the grinding1 connect the flexible conductor to one pole of a battery4 ,the other pole of the battery is connected to a pair of sensitive telephone receivers and the telephone receivers to a vessel containing dilute acid4 ,if the platinum wire is exposed1 a sharp click will be heard in the telephone receivers when the point is dipped in the acid4 ,do not confuse the sharp click with the sound which may be occasioned because the outside of the glass tube is damp or wet4 ,after the point has been sufficiently ground1 disconnect the testing apparatus and connect the free end of the flexible conductor to a binding post placed on the end of the detector spring1 ,s4 ,the detector circuit is similar to that of the bare point type4 ,illustration3 ,fig4 #if4 ,shoemaker ,detector4 ,the illustration shows what is sometimes called a primary cell detector because it furnishes its own current and does not require a battery4 ,a ,stone detector may be very easily changed to one of the ,shoemaker type by substituting an amalgamated zinc rod for the platinum wire anode which makes connection with the liquid in the cup4 ,this combination of platinum and zinc results in an electromotive force of about #j4g volt1 and the telephone receivers are connected directly to the terminals of the detector without any local battery or potentiometer4 ,the electrolyte in the cup must be a #bj per cent solution of pure sulphuric acid1 as nitric acid would dissolve the zinc in a very few minutes4 ,the zinc must be kept well amalgamated with mercury4 ,illustration3 ,fig4 #ig4 ,shoemaker ,detector ,circuits4 ,the ,shoemaker system makes use of a loop aerial1 and the circuits with a single and double coil tuner are illustrated in ,fig4 #ig4 ,it is not necessary to use these1 and the detector will operate just exactly as well on a straightaway aerial4 99,lamp ,detector499--,all electrolytic detectors1 more especially those of the glass point type1 are subject to the annoyance of burn-outs4 ,that is1 the fine platinum wire melts when receiving strong signals from a near-by station4 ,in such case1 the bare point must be lowered until it again makes contact with the liquid1 and the glass point reground until the wire is again exposed4 ,when this trouble comes often it is very convenient to have at hand a simple detector which will not burn out and which may be substituted for the usual one when great sensitiveness is not required4 ,illustration3 ,fig4 #ih4 ,lamp ,detector4 ,such an instrument is made by snipping off the tip of a small incandescent electric lamp and removing the filament with a wire4 ,one of the leading-in wires is broken off as close as possible to the glass stub and the globe half filled with a #bj per cent acid solution4 ,the broken wire must be made the negative or cathode and connected like a ,fessenden or ,stone detector4 ,this lamp detector though crude will give good service without burning out when used to receive from near-by stations4 ,in place of a lamp detector1 a glass point having a larger wire than that of the cigar lighter may be used instead of the usual point1 but it will not be so sensitive4 ,fig4 #ii illustrates a simple form of electrolytic detector which is not so sensitive as that shown in ,fig4 #ajj but is still very serviceable4 ,the cup is made from the carbon of an old dry cell1 the brass connecting cap serving very well to make the connections to4 ,it has a recess about #a_/b inch in diameter and #a_/d inch deep cut in the top to contain the electrolyte4 ,the cup should be about one inch high4 ,a file will smooth up any rough edges and give it a good appearance4 ,illustration3 ,fig4 #ii4 ,simple ,electrolytic ,detector4 ,the yoke is made of a piece of #a_/h-;inch sheet brass about #c_/d inch wide1 bent in the shape shown in the illustration4 ,two small holes are drilled in the feet1 to serve to fasten the yoke firmly to the base and also to make connection to4 ,the adjusting screw may be made from the screw taken from the carbon of an old dry cell4 ,to permit of accurate adjustment1 it should be fitted with a large head made from a piece of #a_/d-;inch hard rubber or fiber cut in a circle about #a #a_/d inches in diameter4 ,bore a small hole about #a_/h inch in diameter through the center of the head and force it on the screw4 ,a nut screwed on the under side will then clamp it tightly against the brass head4 ,a hole is bored in the center of the yoke and a battery nut which will fit the adjusting screw soldered directly under it4 ,the platinum wire may be either soldered to the adjusting screw or fastened with tinfoil in the method which has been described4 ,the cup and yoke are best mounted on a piece of hard rubber #a_/b inch thick1 #c inches wide and #d inches long4 ,a binding post is placed near each of the four corners4 ,it is possible to do extremely fine and long distance work with the detector illustrated in ,fig4 #ajj4 ,it is so arranged that the bare point need not necessarily be revolved when making an adjustment1 and so it is possible to place it in a very sensitive condition4 ,a brass standard1 ,u1 #a #a_/d inches long is cut from a piece of #a_/b-;inch rod4 ,a hole bored in the top and bottom of the standard is threaded with an #h-cb tap4 ,a brass rod1 ,r1 #b inches long is threaded with an #h-cb die throughout its entire length4 ,one end is screwed in the top of ,u4 ,a piece of brass tubing1 ,p1 #a #a_/d inches long and having an internal bore of #a_/b inch is slipped over ,u4 ,a slot cut in ,p fits over a small pin set in ,u and permits ,p to be slid up and down but not to turn around4 ,illustration3 ,fig4 #ajj4 ,electrolytic ,detector4 ,a head in the form of a circular brass washer1 ,e1 #a_/h inch thick1 #a_/b inch in diameter and having a #e_/cb-;inch hole bored in the center is soldered in the top of the tube1 ,p4 ,a circular piece of hard rubber1 ,h1 #b inches in diameter and #a_/b inch thick is fitted with a brass bushing having a hole in the center with an #h-cb thread to screw on the rod1 ,r4 ,a spiral spring is placed around ,r between ,u and the head ,e4 ,a small brass washer should be placed between ,h and ,e in order to eliminate friction4 ,when ,h is turned in one direction1 the spring will cause ,p to rise1 and when turned in the other direction it will be lowered4 ,a brass arm1 ,a1 #a_/d x #a_/d x #a #a_/b inches carries a small thumbscrew1 r1 at one end1 while the other end is soldered to ,p as shown in ,fig4 #if4 ,the ,woolaston wire is soldered to ,t4 ,illustration3 ,fig4 #aja4 ,details of ,electrolytic ,detector4 ,a small carbon cup #c_/d x #c_/d inch serves to hold the electrolyte4 ,a #c_/h-;inch hole is bored #a_/d inch deep in the bottom of the cup and poured full of melted lead4 ,the lead is then bored and tapped to fit a machine screw which fastens the cup to the base4 ,connection is made from a binding post to the machine screw4 ,a second binding post is connected to the screw which fits into the bottom of ,u and holds it to the base4 ,if desirable a circular piece of hard wood1 ,f1 may be turned out and glued to the base around the cup in order to give it a more finished appearance4 ,the thumbscrew1 ,t1 is used to lower the bare point until it almost touches the liquid1 and then the large head1 ,h1 is brought into play to make the finer adjustment4 99,increasing the ,sensitiveness of an ,electrolytic ,detector499 ,the sensitiveness of an electrolytic detector may be increased in three ways1 viz41 by connecting two detectors in series1 by warming the electrolyte and by agitating it4 ,the first method is clearly apparent4 ,the second is accomplished by placing the detector over a sand bath and gently warming it4 ,it will then show a marked increase in the strength of the signals at a temperature of about #cj ,c4 ,this increase will continue to rise with the temperature until it reaches a maximum at about #fj ,c4 ,illustration3 ,fig4 #ajb4 ,increasing the ,sensitiveness of an ,electrolytic ,detector4 ,branly discovered that a fine stream of gas passed through the electrolyte in order to agitate it increases the strength of the signals in the phones4 ,he devised a detector provided with two extra platinum terminals sealed in the cup4 ,when connected in series with a battery and an adjustable resistance1 these terminals cause electrolysis of the water1 and a fine stream of oxygen and hydrogen gas flows through the acid electrolyte4 ,the stream of gas agitates the liquid just sufficiently so that when oscillations strike the detector they augment the breaking down of the film of gas which collects on the fine platinum point4 ,this results in an increase in the battery current flowing through the telephone receivers of from two to four times and a corresponding increase in the volume of sound4 ,the adjustable resistance is used to regulate the decomposition of the electrolyte and formation of gas1 for if this proceeds too rapidly an undesirable rumbling noise will be produced in the telephone receivers4 ,,tantalum ,,detector4 ,the tantalum detector is especially suitable for the amateur experimenter because its change in resistance when struck by oscillations is so great that high resistance telephone receivers are not necessary4 ,its normal resistance is about #ajjj-bjjj ohms1 and this sometimes drops as low as #abe-ajj ohms when struck by oscillations of ordinary strength4 ,it is not nearly so sensitive as the electrolytic or crystal detectors1 but gives very much louder tones in the telephone receivers when used for short distance work4 ,illustration3 ,fig4 #ajc4 ,tantalum ,detector4 ,the detector is easily made by substituting a piece of tantalum wire for the ,woolaston wire of an ordinary electrolytic detector4 ,the dilute acid solution is removed from the cup and replaced by some pure mercury4 ,the connections remain the same as for the bare point4 ,the potentiometer is adjusted until the potential of the battery is in the neighborhood of #j4b-j4d volt4 ,the tantalum wire may be easily secured by breaking the globe of a tantalum lamp and using a piece of the filament4 ,it is best to snip off the lamp tip before breaking the globe4 ,this precaution admits the air and prevents an explosion which would shatter the glass and scatter the filament in fragments4 ,if the universal detector is used with a tantalum point1 turn the small thumbscrew until the wire almost touches the surface of the mercury4 ,then lower it with the large adjusting screw until the tantalum touches the surface and a sharp click is heard in the telephone receivers4 ,adjust the potentiometer until the signals are the loudest4 ,,crystal ,,detectors4 ,certain minerals and crystals1 principally members of the carbon and sulphur groups1 possess the peculiar property of rectifying electrical oscillations and converting them into a pulsating direct current4 ,these crystals conduct the current better in one direction than in the other4 ,in the case of a current having a potential of ten volts and applied to the ends of a carborundum crystal1 the current may be one hundred times greater when flowing in one direction than when flowing in the other4 ,this ratio decreases as the voltage is raised1 for with #be volts it may be only about forty times greater4 ,the crystals when properly inserted in the aerial circuit are enabled to rectify the oscillations and produce sounds in the telephone receivers without the aid of a battery4 ,the following is a partial list of the minerals and crystals exhibiting these properties to a sufficient extent that they are of value as oscillation detectors in wireless telegraphy4 ,in the case of iron pyrites the writer has found that a specimen of this mineral containing very little or no copper as an impurity does not exhibit these properties to an appreciable extent4 ,illustration3 ,fig4 #ajd4 ,united ,wireless ,carborundum ,detector 7horizontal type74 ,in order to use the universal detector for minerals1 a special contact similar to that shown in ,fig4 #ij must be made4 ,the contact is bored and threaded on its under side to fit a brass pin #c_/d inch long and having an #h-cb thread4 ,the other end of the pin screws into the hole in the bedplate4 ,the large knurled portion of the contact permits it to be raised or lowered without the fingers coming in contact with the crystal4 ,the crystal is clamped between the contact and the spring1 ,s4 ,the position is varied until a sensitive spot is found and then the pressure is carefully regulated by means of the large adjusting screw until the signals in the telephone receivers are the loudest4 ,if possible avoid touching the crystals with the fingers1 as the oil and dirt1 even though it cannot always be seen1 spoils their value for long distance work4 ,use instead a pair of steel forceps4 ,illustration3 ,fig4 #aje4 ,united ,wireless ,carborundum ,detector 7vertical type74 ,the ,united ,wireless ,telegraph ,co4 makes use of carborundum in the detectors shown in ,figs4 #ajd and #aje4 ,the principal advantage of carborundum over such substances as silicon1 etc41 is that it is not affected by the heavy discharge of the transmitting apparatus and does not require a new adjustment after each period of sending4 ,all the crystals will not work1 and so a large cake should be purchased and the desired crystals selected4 ,the dark blue portions of the mass1 which are the hardest1 will give the clearest tones in the telephone receivers1 and are preferable to the lighter colored crystals4 ,since the crystals conduct better in one direction than in the other1 as explained above1 the adjustment must be made with the view of determining in which position the particular crystal will work the best4 ,carborundum will produce sounds in the telephone receivers without the aid of any battery1 but for careful work a battery and a potentiometer are necessary4 ,the other crystals given in the column merely require that the telephone receivers be connected to the detector terminals as in the wiring diagram in ,fig4 #ajh4 ,the ,clapp-,eastham detector makes use of a crystal of iron pyrites held in a brass retaining cup beneath the metal contact point4 ,it is not affected by strong signals and requires no battery or potentiometer4 ,when adjusted it will remain in a sensitive condition for a long time without further attention4 ,illustration3 ,fig4 #ajf4 ,clapp-,eastham ,ferron ,detector4 99,silicon ,detector499--,while the silicon and perikon detectors are classed as mineral or crystal detectors they deserve special attention4 ,illustration3 ,fig4 #ajg4 ,silicon ,crystal in ,cup4 ,silicon gives fair results if a crystal is placed between two metal electrodes as1 for instance1 between the contact and spring of the universal detector1 but is much more sensitive when properly mounted4 ,a brass cup such as that shown in ,fig4 #ij is made and the interior brightened by scraping with a file4 ,the cup is then poured full of a molten fusible alloy and the silicon pressed in it until it cools and becomes set4 ,it should then present an appearance similar to that shown by ,a in ,fig4 #ajg4 ,the silicon is ground down by rubbing on the surface of a clean oilstone kept well wet with water1 until the surface is flat and shows a polish4 ,illustration3 ,fig4 #ajh4 ,silicon ,detector ,circuits4 ,the cup containing the silicon is placed over the hole in the bedplate of the universal detector4 ,a knurled brass thumbscrew having a point on its lower end is screwed into the collar on the spring1 ,s1 and brought to bear on the polished surface of the silicon4 ,the pressure may be easily regulated by means of the large adjusting screw until the signals in the telephone receivers are the loudest4 ,it is not advisable to fasten the cup to the bedplate but merely to brighten the bottom so as to insure a good contact4 ,the cup may then be moved around so that different portions of the polished surface of the silicon may be brought into play when desirable4 ,if the knurled brass thumbscrew is fitted with a platinum point which can be brought to bear on the surface of the silicon1 the efficiency of the detector will be materially increased4 ,when mounting silicon or other crystals some careless experimenters use lead or a metal having a high melting point instead of a fusible alloy4 ,this is poor policy because the high temperature coats the surface of the crystals and the interior of the cup with a non-conducting layer which destroys the sensitiveness and makes it unfit for long distance work4 ,a fusible alloy melting at about the boiling point of water or even lower should be used4 ,such alloys are usually composed of tin1 lead and bismuth4 ,the addition of a little cadmium serves to make the fusing point considerably lower in each case4 ,the alloys may be prepared by the experimenter from the following formulae1 or are obtainable from a firm manufacturing fire plugs for automatic fire extinguishers4 ,the lead should be melted first and then the bismuth1 tin and cadmium added in the order named4 99,perikon ,detector499--,the ,perikon detector is one of the latest types to come into extensive use4 ,it consists of two crystals1 zincite and chalcopyrites1 set in cups in the manner just described and placed in contact with each other4 ,the minerals are mounted similar to those in ,fig4 #aje4 ,the zincite should present a rather flat surface with the grain of the crystal parallel to the sides of the cup so that the top surface corresponds to the end of a stick of wood sawed at right angles to the grain4 ,more than one crystal of zincite is usually set in the same cup4 ,the chalcopyrites should present a rather blunt point4 ,the cup containing the chalcopyrites is the smaller and is bored and threaded to fit a thumbscrew which passes through the collar in the spring1 ,s1 of the universal detector4 ,the bottom of the cup containing the zincite is brightened so as to insure a good contact and then placed on the bed plated under the cup containing the chalcopyrites which is fastened to the thumbscrew4 ,the zincite may then be moved around until the most sensitive portion is found4 ,the chalcopyrites is lowered until it comes into contact with the zincite and then the pressure regulated by means of the large adjusting screw4 ,illustration3 ,fig4 #aji4 ,perikon ,detector ,elements4 ,the ,perikon detector gives excellent results without a battery and is preferably used in that manner4 ,if a battery is used1 a potentiometer to lower the voltage is necessary4 ,when adjusting this or the carborundum detector where a battery is used1 the pressure must be very carefully regulated until it is found to be the best4 ,when the pressure is light the signals in the phones are due to an imperfect contact1 and when it is slightly increased the rectifying properties of the crystal are brought into play4 ,the ,perikon detector illustrated in ,fig4 #aaj is somewhat similar to that used for commercial work4 ,the standards or posts supporting the cups which contain the elements are brass rods #a_/b inch square and #a #a_/b inches high4 ,a hole is bored in the bottom of each and threaded with an #h-cb tap to receive a machine screw which passes through the base and holds them in an upright position4 ,a hole is bored #a #a_/h inches from the bottom1 in the face of one standard and threaded with an #h-cb tap4 ,a brass rod #a #a_/d inches long1 carrying at one end a cup #a inch in diameter and #c_/h inch deep1 is threaded to fit in the hole in the standard4 ,the zincite is mounted in this cup4 ,illustration3 ,fig4 #aaj4 ,perikon ,detector4 ,the other standard is cut in half with a hack saw and a #a_/h-;inch hole bored #a_/d inch deep in the axis of each piece4 ,a pin1 #a_/b inch long1 is set in the lower half by soldering it in the hole4 ,the upper half of the standard is placed over the pin and left free to move when twisted4 ,a #a_/h-;inch brass tube1 #a inch long1 passes through the upper part of the standard4 ,a #a_/h-;inch brass rod1 #a #c_/d inches long1 passes through the tube4 ,the small cup containing the zincite is mounted on one end of the rod and a hard rubber handle on the other4 ,a brass spring is placed between the cup and the standard in order to press the chalcopyrites against the zincite4 ,the cup is mounted out of center so that by revolving it and twisting the standard at the same time the chalcopyrites may be brought into contact with any portion of the zincite4 ,by screwing the rod supporting the zincite cup in or out of the standard the pressure with which the two elements are pressed together may be regulated4 ,the base of the detector is hard rubber of the dimensions indicated in the illustration4 ,four binding posts on each corner of the base are necessary4 ,the detector is connected in a similar manner to the silicon detector shown in ,fig4 #ajh4 ,if a battery is used the circuit should be like that of the bare point electrolytic1 and the current must flow from the zincite to the chalcopyrites4 ,,lead ,,peroxide ,,detector4 ,the peroxide of lead detector makes use of no liquids1 but still may be classed as an electrolytic since its action is of that nature4 ,illustration3 ,fig4 #aaa4 ,peroxide of ,lead ,detector4 ,it consists of a pellet of lead peroxide held between an electrode of lead and one of platinum4 ,contrary to most other detectors1 the resistance is increased upon the passage of electrical oscillations4 ,the oscillations stimulate chemical action and increase a counter-electromotive force sufficiently so that a decrease in the current sent through the phones by the local battery takes place4 ,the action may be outlined more in detail as follows4 ,the current of the local battery decomposes part of the lead peroxide into its components1 lead and oxygen4 ,the lead ions are positively electrified and so they tend to pass upward toward the lead electrode which is negative4 ,the negative ions of oxygen gas tend to pass downwards towards the platinum4 ,but the lead and platinum electrodes with the intervening lead peroxide constitute a small cell acting independently of the local battery and sending a current in the opposite direction4 ,this counter-electromotive force tends to send the ions in an opposite direction to that in which they are sent by the battery current4 ,upon the passage of electrical oscillations this counter electromotive force is increased and sufficient ions sent out in opposition to those of the battery current so that an appreciable drop in the current flowing through the telephone receivers takes place4 ,the sudden current drop produces a sound in the receivers4 ,the lead pellets may be secured from a druggist who can mold them in his tablet press4 ,they should be subjected to as great a pressure as possible in order to reduce resistance and prevent crumbling4 ,a piece of platinum foil about #a_/b inch square is placed beneath the pellet on the crystal electrode4 ,a piece of clean1 bright sheet lead #c_/h inch in diameter and #a_/h inch thick is laid on the pellet and the whole clamped together by tightening the thumbscrew passing through the collar on the spring1 ,s4 ,the detector is connected up similar to the bare point1 ,the platinum is made the positive of the local battery4 ,adjustment is secured by regulating the pressure4 ,it is very necessary that the pellets be kept dry1 as otherwise a loud singing and hissing noise1 due to the decomposition of the water1 will render the reception of signals very difficult4 ,,the ,,marconi ,,magnetic ,,detector4 ,when an oscillatory discharge takes place through a coil of wire surrounding a needle1 it magnetizes the needle in a totally different manner from a voltaic current4 ,the needle will have several poles throughout its length1 many of them reversed4 ,rutherford applied this phenomenon to the detection of electrical oscillations1 but it remained for ,marconi to improve it and give the magnetic detector its existing form4 ,this type of detector is very sensitive1 free from all adjustment and is not made inoperative by the heavier discharge of the transmitter during each period of sending4 ,illustration3 ,fig4 #aab4 ,marconi ,magnetic ,detector4 ,a small transformer is provided with a core composed of a band or cord of iron wires in the form of an endless belt which passes around two pulleys kept in motion by a clockwork motor4 ,the band revolves in the field of a strong horseshoe magnet and passes directly over the poles after issuing from the transformer bobbin1 so that the portion approaching the bobbin are constantly in a state of increasing magnetism4 ,the actual operation is based upon the property of iron called hysteresis1 for the magnetism of the core lags behind that of the permanent magnet and is of a different degree from what it ought to be1 in view of its position in the vicinity of the permanent magnet4 ,the moment the oscillations pass through the primary coil of the transformer1 this lag is set free and the magnetism assumes its full value4 ,the change in magnetism induces a current in the secondary1 which registers as a sound in the telephone receivers4 ,illustration3 ,fig4 #aac4 ,details of ,transformer4 ,the primary coil is made up of a single layer of ,no4 #cf ,b4 ,s4 gauge silk covered wire wound on a thin walled glass or hard rubber tube4 ,the ends of the tube1 which is #b inches long and #a_/d inch external diameter1 are slightly flared so as not to chafe the band4 ,the primary is thoroughly shellacked and covered with a single layer of paper4 ,the secondary is also of ,no4 #cf ,b4 ,s4 silk covered wire and is wound between two disks of hard rubber1 #a_/d inch thick and #a #a_/b inches in diameter1 placed #c_/h inch apart in the center of the secondary and the intervening space wound full of wire4 ,the terminals of both the primary and secondary are extended to binding posts mounted on the case of the instrument4 ,illustration3 ,fig4 #aad4 ,method of ,joining ,ends of ,band4 ,the core or revolving band is made by winding #ajj strands of ,no4 #cf silk covered soft iron wire between two small pegs1 placed a distance apart1 equal to twice the circumference of the oval formed by the two pulleys4 ,the wire is all wound in the same direction4 ,it should be carefully removed from the pegs and kept taut while it is slightly twisted1 doubled1 and then further twisted into a rope or cord4 ,the ends are threaded together with a separate piece of insulated wire1 into a link which will pass easily through the primary tube4 ,illustration3 ,fig4 #aae4 ,pulley4 ,the pulleys around which the band revolves are made of hard wood4 ,they are #d inches in diameter and #c_/h inch thick and have a ,v-shaped groove cut in the edge4 ,in order to minimize friction and wear1 it is advisable to fit them with a bearing which may be made out of brass tubing and a couple of washers4 ,one of the pulleys is geared to a clockwork motor so that the band makes a complete revolution about once every two minutes4 ,an old eight day clock may be adapted for this purpose1 or1 what is much better1 the motor from an old phonograph4 ,illustration3 ,fig4 #aaf4 ,pulley ,bearings4 ,the horseshoe magnet is mounted with its north pole pointing towards and nearly touching the middle of the outside of the secondary4 ,the south pole is placed opposite the end of the primary tube which is on the side towards which the band is revolving1 that is1 the band in revolving passes first over the north pole and then over the south4 ,two magnets are sometimes used with their north poles together in the center of the secondary1 and a south pole opposite each end of the primary tube4 ,illustration3 ,fig4 #aag4 ,circuit of ,magnetic ,detector4 ,the commercial instrument is placed in a glass covered case which protects it from dust and injury4 ,the clockwork motor is concealed in the lower part of the case4 ,this is a good plan but an experimental detector may be merely mounted on a flat wooden base as illustrated in ,fig4 #aab4 ,the secondary terminals are connected directly to the telephone receivers while the primary leads to the aerial and the ground4 ,when the detector is started up it should make a very slight hissing sound in the telephone receivers as the band passes slowly through the coils4 ,this shows the instrument to be in good working order and ready for the reception of signals4 99,the ,audion499--,dr4 ,lee ,de,forest was led by the flickering of a sensitive gas flame to investigate whether or not it would respond to ,hertzian vibrations as well as to those of heat and sound4 ,his experiments led to the invention of the audion1 a peculiar instrument making use of ionized gas for its operation4 ,the audion consists of an incandescent lamp having a metallic filament1 on either side of which are a grid and a plate made of nickel4 ,when the filament is lighted it throws off ions which act as a relay to high frequency oscillations passing between the plate and the grid4 ,a properly constructed audion is exceedingly sensitive and produces very loud tones in the telephone receivers4 ,it has the further advantages of entire absence of adjustment except the governing of the battery voltage1 and is capable of extremely fine tuning4 ,illustration3 ,fig4 #aah4 ,fleming ,oscillation ,valve4 ,fleming originated the oscillation valve illustrated in ,fig4 #aah4 ,it consists of an ordinary incandescent lamp with a carbon filament1 having a metal cylinder1 ,c1 placed around the filament1 but attached to an independently insulated platinum wire sealed in the glass4 ,when the lamp is lighted by passing a current through the filament1 the incandescent carbon liberates negative ions4 ,if oscillations are then set up in a circuit which includes a pair of sensitive telephone receivers and is formed by connecting the negative terminal of the filament with the platinum cylinder1 negative electricity will be enabled to pass from the filament to the cylinder but not in the opposite direction1 and so sounds will be produced in the telephone receivers4 ,high frequency oscillations themselves could not be made to pass through the telephone receivers because of the choking action of the iron cores of the electromagnets4 ,illustration3 ,fig4 #aai4 ,flame ,audion4 ,the simple but sensitive form of detector illustrated in ,fig4 #aai is not of practical value for commercial work1 but is very interesting as the progenitor of the audion1 and provides a good field for amateur investigation4 ,its only drawback is that the gas flame is very difficult to keep steady and every flicker registers as a sound in the telephone receivers4 ,a ,bunsen burner using coal gas furnishes the flame1 and a salt of an alkaline metal heated in the flame1 the ions4 ,the hydroxides of caesium1 potassium and sodium give the best results in the order named4 ,the salt is contained in a piece of trough-shaped platinum foil1 about #c_/h inch long and #a_/af inch wide4 ,this trough is made the cathode or negative of the telephone circuit and placed in the outer oxidizing flame just above its juncture with the interior reducing flame and must be kept incandescent4 ,the upper electrode or anode is a piece of platinum wire about #a_/af inch above the trough4 ,illustration3 ,fig4 #abj4 ,circuit of ,flame ,audion4 ,the arrangement and construction of the detector is clearly indicated by the drawing so that it is unnecessary to go into details4 ,the block1 ,e1 which fits on the tube of the ,bunsen burner1 is made of fiber4 ,two double binding posts1 ,d1 are fastened to ,e to support the rods1 ,r1 which are fitted at the tops with binding posts1 ,b1 into which the electrodes may be clamped4 ,twelve dry cells are connected with a multiple point switch so that an electromotive force of #f-ah volts1 varying in steps of one cell at a time1 may be secured4 ,the flame is best provided with a mica chimney to protect it from drafts4 ,by keeping plenty of salt in the trough and carefully adjusting the voltage1 this detector may be made marvelously sensitive4 ,the different detectors in order of their sensitiveness are electrolytic1 perikon1 magnetic1 silicon1 carborundum4 ,peacock ore or bornite1 which consists of about #fj parts of copper1 #ad parts of iron and #bf parts of sulphur1 may be substituted for the chalcopyrites with excellent results4 ,,chapter ,,xiv4 ,,tuning ,,coils ,,and ,,transformers4 ,a tuning coil is merely a variable inductance wound in single layer on a suitable form4 ,fig4 #aba illustrates a double slide tuner4 ,the base is a piece of hard wood1 #ab inches long1 #a inch thick and #e #a_/b inches wide4 ,two wooden heads #d x #d x #c_/d inches support the form upon which the coil is wound4 ,illustration3 ,fig4 #aba4 ,double-slide ,tuning ,coil4 ,the form is a piece of wooden curtain pole1 #i inches long and #c inches in diameter4 ,some may prefer to use a cardboard tube in place of the curtain pole4 ,a tube can be made by winding a long strip of cardboard #i inches wide around a suitable form and cementing the layers together with shellac4 ,the liberal use of shellac will stiffen the tube and cause it to better retain its shape4 ,the tube is held tightly between the two heads by means of a brass rod which passes through the center and is clamped by two nuts4 ,a square brass rod #aj #a_/b inches long is fastened to the center of the top of the heads and a similar rod to the center of the front face4 ,illustration3 ,fig4 #abb4 ,sliders4 ,fig4 #abb shows two forms of sliders4 ,the first one is the better and to be preferred4 ,a short square brass tube1 ,s1 fits snugly upon the square brass rod1 ,r4 ,it cannot turn around but is free to slide back and forth4 ,a strip of spring brass1 ,c1 is soldered to the lower face of the square tube4 ,it is bent in a double turn and a punch mark made near the lower end as shown in the illustration4 ,the indentation is made with a center punch1 but should not be deep enough to break through the metal4 ,illustration3 ,fig4 #abc4 ,double-slide ,tuning ,coil ,circuits4 ,the little projection on the under side of ,c caused by the punch mark is the only part of the slider which should make contact with the wire on the tuning coil4 ,it should slide easily but firmly along the wires and touch only one at a time4 ,long distance signals will be considerably weakened if the slider touches more than one wire at a time and short-circuits a turn4 ,illustration3 99,plate ,,iv4 ,receiving ,circuits4 7,straightaway ,aerial4799 ,the slider1 ,b1 is similar to ,a except that it has a short length of brass tubing1 ,t1 soldered to the under side of ,s in place of the brass strip1 ,c4 ,a small ball bearing which just fits the bore of the tube is pushed down into contact with the wire by means of a small spiral spring inside of the tube4 ,both sliders are fitted with a hard rubber handle so that they may be adjusted without the ringers coming into contact with the metal4 ,illustration3 ,fig4 #abd4 ,murdock ,double-slide ,tuning ,coil4 ,illustration3 ,fig4 #abe4 ,united ,wireless ,receiving ,set4 ,two good circuits employing the double slide tuner are given in ,fig4 #abc4 ,plates ,,iv and ,v illustrate the oscillation or tuning circuits of the most prominent receptor systems4 ,if a loop aerial is used1 more than one tuning coil is necessary as shown by the loop aerial oscillation circuits in ,plate ,v4 ,figs4 #abe and #abf illustrate the instruments employed for receiving by the ,united ,wireless ,company4 ,illustration3 ,fig4 #abf4 ,united ,wireless ,portable ,receiving ,set4 ,in ,fig4 #abe the handles which are attached to the sliders of the tuning coils project through long slots cut in the top and one side of the cabinet4 ,the tuning coils in the portable outfit are mounted in a vertical position in back of the aerial switch4 99,loosely ,coupled ,tuning ,coil499--,by the use of a loosely coupled receiving tuner or transformer1 the range of a station is considerably increased1 as is also the strength of the signals1 and much finer tuning and selectivity made possible4 ,fig4 #abg illustrates the construction of such an oscillation transformer4 ,the base is wood and measures #ad x #e #a_/b x #a inches4 ,the primary winding is wound on a cardboard or fiber tube #d #a_/d inches long1 having an internal diameter of #b #c_/d inches and an external diameter of #c inches4 ,the heads1 ,l and ,m1 are the same size as those of the double slide tuning coil4 ,the head1 ,l1 has a circular hole #b #c_/d inches in diameter cut in the center in order to permit the secondary coil to slide in and out of the primary4 ,illustration3 ,fig4 #abg4 ,oscillation ,transformer4 ,the secondary coil is a piece of round curtain pole #b #a_/b inches in diameter and #c inches long4 ,a #e_/af-;inch hole is bored through its axis4 ,the head1 ,k1 of the secondary coil is #c #c_/d x #c #c_/d x #c_/d inches4 ,a ten-point switch on ,k is so connected that it divides the secondary into ten equal parts and permits any number of the divisions to be used as desired4 ,illustration3 ,fig4 #abh4 ,united ,wireless ,receiving ,transformer4 ,a wooden post1 ,j1 #b #a_/b inches high and #a #a_/d inches wide1 supports one end of a #a_/d-;inch brass rod upon which the secondary slides back and forth4 ,illustration3 ,fig4 #abi4 ,details of ,receiving ,transformer4 ,no4 #bd ,b4 ,s4 gauge copper wire may be used for winding both the primary and secondary4 ,it is also the proper size to use on the double slide tuner4 ,the best method is to use bare wire1 wound with a thread so that a thread is interposed between adjacent turns of the winding4 ,give the whole winding one or two coats of thick shellac and allow it to harden4 ,then use a strip of sandpaper to remove the shellac in a long narrow path immediately below the sliders so that they may make contact with the wire4 ,illustration3 ,fig4 #acj4 ,slider for ,loose ,coupler4 ,some may prefer to make a loosely coupled tuner in which the inductance of both coils is adjustable by means of a sliding contact4 ,in such a case the slider on the secondary coil must be constructed as illustrated in ,fig4 #acj4 ,the contact is long and narrow so that it can touch the innermost turns1 when placed within the primary4 ,by slipping the slider off the end of the rod and reversing it1 the contact can be made to touch the turns next to the head4 ,the square brass rod is set in a notch cut in the coil head so that the rod is flush with the top4 ,when tuning a receiving transformer1 place both variable condensers in a halfway position and adjust the sliding contacts1 first on the primary and then on the secondary1 until the signals are the loudest4 ,then adjust the condensers4 ,illustration3 ,fig4 #aca4 ,loosely ,coupled ,tuning ,circuits4 ,to cut out an undesirable station1 vary the coupling between the two coils by sliding the secondary away from the primary4 ,when several turns on the secondary seem to give the same results also vary the coupling4 ,illustration3 ,fig4 #acb4 ,combination ,loosely and ,closely ,coupled ,tuner4 ,fig4 #acb illustrates the wiring diagram of a combination loosely and closely coupled tuner4 ,two sliding contacts are placed on the primary coil of the receiving transformer and connected with a double pole double throw switch as in the diagram4 ,when the switch is thrown on contacts #a and #b1 the primary is connected to the detector as a double slide tuner1 and when on #c and #d both the primary and secondary are brought into use as a transformer4 ,this arrangement may seem cumbersome and is recommended only as a convenience in experimenting4 ,a loosely coupled tuning coil is capable of exact tuning1 and unless one understands how to use it1 he may not hear a station because the tuner is not properly adjusted4 ,by using the double slide tuner first and then throwing the switch so as to tune in on the transformer1 this difficulty may be eliminated4 ,illustration3 ,fig4 #acc4 ,clapp-,eastham ,loose ,coupler4 99,potentiometer499--,a potentiometer is not properly classed under the heading of tuning coils1 but the construction may be made so similar that it well appears here4 ,the potentiometer is merely a variable resistance shunted across the terminals of the detector battery in the manner illustrated in the numerous detector circuits4 ,it is used to reduce the voltage of the battery to a value slightly below the critical voltage of the detector4 ,the critical voltage of a detector is the voltage at which its action commences4 ,in the case of an electrolytic detector1 it is the voltage required to break down the thin film of gas which collects on the bare point4 ,illustration3 ,fig4 #acd4 ,a ,highly ,efficient ,form of ,loose ,coupler4 ,in construction1 the potentiometer illustrated in ,fig4 #ace is in reality a small edition of a double slide tuning coil4 ,it is wound with ,no4 #bh ,b4 ,s4 gauge ,german silver wire4 ,three binding posts are mounted on the base1 two of them connecting with the ends of the coil and one with the sliding contact4 ,illustration3 ,fig4 #ace4 ,potentiometer4 ,in a finely balanced circuit where long distance work and close tuning are desired1 the potentiometer must be non-inductive4 ,illustration3 ,fig4 #acf4 ,amco ,potentiometer4 ,this may be accomplished by using two potentiometers wound in opposite directions from one another and connected in series4 ,the two terminals of the windings are then connected across the battery and the sliding contacts led to the detector4 ,illustration3 99,plate ,v4 ,receiving ,circuits499 ,,chapter ,,xv4 ,,receiving ,,condensers4 ,condensers play an important part in tuning and adjusting the receiving circuits of a wireless telegraph station4 ,they are inserted in the circuits for various purposes4 ,in some places a small condenser shunts the detector to somewhat equalize any small changes in capacity which might occur in the detector and throw the circuit out of tune4 ,in other cases where selectivity is desired they provide a path for undesirable oscillations and allow them to flow into the ground without passing through the detector4 ,wherever the double slide tuner or the ,fessenden single slider circuit is used1 a condenser must be inserted in the circuit to prevent the wire of the tuning coil from short-circuiting the telephone receivers and battery4 ,illustration3 ,fig4 #acg4 ,tuning ,circuit with and without an ,adjustable ,condenser4 ,the value of a condenser may be readily appreciated by the following experiment4 ,connect up a detector according to the diagram shown by ,a of ,fig4 #acg4 ,this circuit will give good results and the signals will be clear4 ,but change it to that shown in ,b1 by connecting one side of a variable condenser to the upper contact of the tuning coil and leading the other side to the ground4 ,considerable selectivity may now be attained and the signals will be #ej per cent louder4 ,to be of any value for a receiving circuit the capacity of the condenser must be adjustable1 but there are many places where a fixed condenser is of service4 ,the average capacity of such condensers generally ranges around 4#jjc of a microfarad1 but cannot be predetermined1 as it depends upon many factors which vary greatly in different stations4 ,even if specific dimensions were given for the construction of a paper condenser of stated capacity1 the experimenter would very seldom succeed in constructing his condenser and have it of this value when finished4 ,the paper used as the dielectric and the pressure applied to the condenser would make the difference4 ,the best plan is to build one up in the form of a roll as follows4 ,three thin tin foil strips #c #a_/b inches wide and four feet long are separated by strips of thin paraffined paper #d inches wide and four and one-half feet long4 ,the two outside strips of tin foil are connected together and form one terminal of the condenser4 ,the middle strip of tin foil is the other4 ,the outside strips of tin foil are covered with paraffined paper and the whole rolled up4 ,if thin paper and tin foil are used the condenser will form a roll #d inches long and less than an inch in diameter4 ,two or three such condensers should be constructed1 and one of them connected up in the circuit where it is desirable to use it4 ,by unrolling a little of the condenser and cutting one or two inches off at a time the proper size may be determined4 ,as explained in ,chapter ,,vii1 two equal condensers connected in series have one-half the capacity of either4 ,by connecting them in parallel the capacity is the sum of the two4 ,in this manner it is not hard to first find the approximate capacity1 which gives the best results before cutting the condenser4 ,illustration3 ,fig4 #ach4 ,tubular ,condenser4 ,when the proper value is found1 place the condenser in a brass tube about #e inches long and #a inch in diameter4 ,the tube is fitted with hard rubber flanges to close the ends4 ,a binding post is mounted on each flange1 and connects with the terminal of the condenser to which it is nearest4 ,mounting a condenser in this manner gives it a much better appearance and it occupies less space than otherwise4 ,fixed condensers are used in two cases only1 to shunt the condenser and to prevent the tuning coil from short-circuiting the telephone receivers4 ,in any other position they are worthless4 99,variable ,condensers499--,a simple form of adjustable condenser which may be quickly made for a special experiment is constructed in the following manner4 ,a wooden curtain pole #b inches in diameter and #ah inches long is covered with a layer of tin foil4 ,the tin foil must be laid on smoothly and cemented with shellac4 ,a layer of paraffined paper is then placed over the tin foil4 ,a piece of sheet copper or tin #f #c_/d inches wide and #ah inches long is rolled up in a cylinder to fit over the rod with its tin foil and paper4 ,the rod is fastened at one end to a base board about #bj inches long and #d inches wide1 by means of a bracket1 or it may be mounted on a smaller base in a vertical position4 ,connections are made to the tin foil and to the outside metal tube4 ,by sliding the tube back and forth on the rod the condenser may be given a variable capacity4 ,illustration3 ,fig4 #aci4 ,variable ,condenser4 ,the best variable condensers are constructed so that the dielectric between the two plates is formed by air4 ,there are consequently no losses of energy in the condenser1 for this mode of construction eliminates all dielectric hysteresis4 ,fig4 #aci shows such a variable condenser and ,fig4 #adj the details4 ,it is possible to do very close1 selective tuning with this instrument4 ,the efficiency of the receiving circuit may be considerably improved if one is used wherever a condenser is required4 ,a rectangular box is built up in the manner shown in ,fig4 #ace4 ,the sides1 ,d1 are #f inches long1 #d #aa_/af inches wide and #a_/b inch thick4 ,the top1 ,a1 is #f inches long1 #a #ac_/af inches wide and #a_/b inch thick4 ,the bottom1 ,b1 has the same width and thickness but is #aa inches long4 ,eleven grooves are cut in ,a and ,b as shown in the cross section4 ,the grooves are #a_/af inch wide1 #c_/af inch deep and #a_/af inch apart4 ,they are formed by setting the blade of a circular saw so that it projects #c_/af inch above the table or bed4 ,after cutting one groove1 the guide is moved #a_/h inch and another cut made4 ,illustration3 ,fig4 #adj4 ,details of ,variable ,condenser4 ,eleven metal plates1 ,p1 are required1 six fixed and five movable4 ,they are made of ,no4 #bb gauge sheet brass and measure #d x #f inches4 ,six of them are placed in the grooves in the box in such a manner that an empty groove is left between each one4 ,the six plates are then electrically connected together by soldering a strip of brass across their rear ends4 ,illustration3 ,fig4 #ada4 ,sliding ,plate ,variable ,condenser4 ,five slots each #a_/d inch deep and #a_/d inch apart are made with a hack saw in a piece of brass1 ,c1 #a #a_/b inches long1 #c_/d inch wide and #a_/b inch thick4 ,a small pin #a_/b inch long is set in the center of ,c on the opposite side from the saw cuts4 ,a fiber handle #a_/b inch in diameter and #a #a_/b inches long is fastened to the pin4 ,the five movable brass plates are set in the grooves between the six fixed plates4 ,they are allowed to project three or four inches out of the box4 ,the yoke1 ,c1 is then soldered across the ends so that each one of the movable plates fits into its corresponding saw cut4 ,the capacity of the condenser is varied by sliding the movable plates back and forth between the fixed plates4 ,a binding post is soldered to the yoke1 ,c1 and another one to the strip which holds the fixed plates together4 ,connections are made to the binding posts with lamp cord or some other flexible conductor which will not interfere with the movement of the plates4 ,the instrument is finished by staining the woodwork and giving it a coat of varnish or shellac4 ,,chapter ,,xvi4 ,,telephone ,,receivers ,,and ,,headbands4 ,a pair of high resistance telephone receivers in nice adjustment constitute one of the most sensitive electrical instruments in existence and will detect an exceedingly weak current4 ,the only type of receiver of much service in wireless telegraphy is that known as a watch case or pony receiver4 ,it is small and compact so that it may be attached to a headband and clamped against the ear4 ,illustration3 ,fig4 #adb4 ,types of ,permanent ,magnets4 ,the permanent magnets of a watch-case receiver are usually in the form of either a ring or a horseshoe as shown by ,fig4 #adb4 ,the first form has consequent poles and is considered somewhat superior to the horseshoe1 since the lines of force are not so liable to pass across the pole pieces before they pass through the electromagnets and the diaphragm4 ,the ordinary low resistance telephone receiver is perfectly well suited to the telephone work for which it was designed and adjusted1 and will give good service on a wireless receptor for short distances1 but can be considerably improved by following the suggestions and instructions given below4 ,the principal objection to the ordinary receiver is that it does not contain enough turns of wire on its bobbins4 ,this is easily remedied by carefully rewinding them with a very fine silk covered1 pure copper magnet wire no larger than ,no4 #dj ,b4 ,s4 gauge4 ,this will increase the number of turns and also the resistance1 but it must not be inferred that resistance is to be desired4 ,this is a common impression of amateurs who do not understand the underlying principle1 that the strength of an electromagnet varies directly as the number of turns of wire1 multiplied by the amperes flowing through the magnet4 ,when a telephone receiver is wound with a finer wire the resistance is increased1 cutting down both the current and the strength of the magnet4 ,but if pure copper wire is used1 and the winding not carried beyond the point where the circumference of the outside layer becomes twice as great as the circumference of the first layer1 the number of turns increases faster than the resistance and the magnet strength is considerably greater than before the receiver was rewound4 ,no4 #dj ,b4 ,s4 gauge silk covered wire is often used for this purpose1 but the best results are obtained with enameled covered wire of the same size4 ,it is possible to wind almost three times as much of the enameled wire on a telephone bobbin as silk wire of the same size4 ,the difference is due to the thickness of the insulation4 ,an ordinary double pole watch-case receiver will have a resistance of #hjj-a1jjj ohms when wound with silk covered wire and #a1ejj-a1hjj ohms when wound with enameled wire4 ,to rewind a telephone receiver1 first unscrew the cap and remove the diaphragm1 then remove the bobbins by unloosening the screws with the aid of a screw driver4 ,unwind the old wire and examine the empty bobbins to see that wherever the wire is liable to come into contact with the metal that it is well insulated with paraffined paper or some other equally good material4 ,then wind the new wire on in smooth even layers and when it is completed fasten the bobbins back on the permanent magnets and connect them up4 ,the current should flow through in opposite directions so that the north pole of one and the south pole of the other is on top4 ,do not trust splice connections but solder them using acid as a flux4 ,the ,navy ,department specifies that its wireless receivers shall be wound with copper wire of not less than #j4jjae inch in diameter and the diaphragm to have a diameter of #a #c_/d inches and a thickness of #j4jjd inch4 ,the resistance of the coils is specified at #a1jjj-a1ajj ohms4 ,there is not much advantage in greatly exceeding the number of turns possible with this winding1 for to obtain them a much finer wire than ,no4 #dj ,b4 ,s4 gauge is necessary and the ratio between resistance and turns becomes greater4 ,the second objection to the ordinary receiver is that the diaphragms are very often too thick4 ,a receiver having a thin diaphragm is preferable because when a weak current is sent through the coils1 the change in magnet strength is greater4 ,but this may be carried to excess and the diaphragm made so thin that it cannot absorb sufficient lines of force to properly play its part4 ,the best thickness then for a diaphragm can only be determined experimentally and depends much upon the diameter4 ,the distance from the poles and the strength of the magnets will also have considerable bearing on the thickness4 ,the ordinary phone will be very sensitive and give clear tones with diaphragms ranging from 4#ja-4jjd inch4 ,the relation between the thickness and the diameter is shown by the following3 ,if the diaphragm of a receiver is increased in diameter1 the tones will become more distinct1 but if the increase is carried too far they will become indistinct and the only remedy is to thicken the diaphragm4 ,likewise if after clearness is secured the diaphragm is thickened so that the tones again become indistinct1 the diameter must be increased4 ,illustration3 ,fig4 #adc4 ,grinding ,tool4 ,the third objection is that such receivers are not carefully and properly adjusted4 ,the adjustment is also a matter of experiment and is accomplished by comparison of the receiver in question with one which is known to be in a sensitive condition4 ,the adjusting may be done by means of the tool shown in ,fig4 #adc4 ,this tool is made from an ordinary file by grinding off the teeth on one side save for a distance of about #c_/d inch in the middle4 ,the grinding may be done on an emery wheel4 ,the part 7a7 is used for filing the pole pieces and thus making the distance between them and the diaphragm greater4 ,the tool has the advantage over an ordinary file of permitting the poles to be filed without removal from the receiver and without grooving the diaphragm bed or the receiver case4 ,to lessen the distance between the poles and the diaphragm1 lay the receiver bed downward on a piece of fine emery paper and rub with a circular scouring motion4 ,if the emery paper is placed on a perfectly flat surface no trouble will be experienced in grinding the bed down evenly4 ,when filing the pole pieces rub with the same circular motion so as to grind off all sides evenly4 ,test from time to time by passing a straight edge over the bed in all directions while holding to the light and looking between the straight edge and the poles4 ,in this manner the distance separating the diaphragm and the poles may be gauged and whether or not it is the same on all sides4 ,bear in mind that if the diaphragm is thin1 the attraction of the permanent magnets will cause it to bend in towards the poles4 ,in case you have a pair of receivers built for wireless work1 which appear to be in good condition but do not give their former results1 the last thing to do is to tamper with the adjustment4 ,the most common cause1 when the tones are impaired1 is dirt or dust accumulated on the poles or diaphragm and damping its vibration4 ,the cap should be carefully unscrewed and the diaphragm examined to see if it is bent4 ,if so1 replace with a new one of the same size4 ,remove any dirt or filings1 and if the diaphragm is rusty clean it by laying it on a flat surface and rubbing it with a piece of fine emery paper4 ,then give it a thin coat of colorless lacquer4 ,examine the magnets and pole pieces to see if they have become loosened and if so tighten them4 ,or the trouble may be that the permanent magnets have lost part of their magnetism1 and almost any receiver which has been in use for some length of time will bear having its magnets strengthened4 ,if they are found to be weak they should be removed and remagnetized4 ,this is accomplished by winding a coil of ,no4 #ah ,b4 ,s4 gauge wire around them and sending a heavy direct current through for a few minutes4 ,illustration3 ,fig4 #add4 ,parts of a ,holtzer ,cabot ,receiver4 ,in carrying out any of these suggestions remember to work with one receiver at a time1 keeping the other for comparison1 so that by repeated tests you may tell whether or not an improvement is being made and when well enough is reached1 let it alone4 ,fig4 #add shows the construction of a telephone receiver manufactured by the ,holtzer ,cabot ,co4 of ,brookline1 ,mass4 ,the permanent magnets and bobbins are mounted in a metal cup1 ,b1 which supports the diaphragm1 ,a4 ,the metal cup is enclosed in a hard rubber shell1 ,c1 and fitted with a cap1 ,d4 ,the complete receivers are mounted on an adjustable headband and fitted with pneumatic ear cushions which make them set more comfortably and shut out extraneous noise4 ,these receivers are wound to all resistances used in the wireless field but1 for the experimenter1 those having a resistance of #ajjj ohms apiece will give the best all around results4 ,illustration3 ,fig4 #ade4 ,holtzer ,cabot ,head ,set4 ,it is very desirable that the receivers should be fitted with a comfortable headband which will hold the telephones in close adjustment to the ears4 ,fig4 #adf shows the construction of such a band4 ,illustration3 ,fig4 #adf4 ,adjustable ,head ,band4 ,two brass straps1 #a inch wide1 #ab inches long and #a_/af inch thick are necessary4 ,two #a_/h-;inch holes1 mm1 are bored in them #c_/af inch from one end and the end bent up at an angle along a line #c_/h inch from the end as shown by the drawing4 ,a cover is made for the straps1 by sewing two strips of leather #a #a_/d inches wide and #ab inches long1 together along their edges4 ,the covers may then be slipped over the straps4 ,two #a_/af-;inch brass strips1 #c_/h inch wide and a little longer than one-half the circumference of the watch-case receiver to be fitted to the head band1 are bent into stirrups as shown in the illustration by ,y4 ,the ends of the stirrups are fitted with two pivots1 ,,pp1 which are riveted in a hole4 ,two holes or recesses are bored in the shell of each receiver1 on the sides #ahj degrees apart4 ,the pivots1 ,,pp1 fit into these holes and form bearings in which the receivers can turn and adjust themselves to the ears4 ,the stirrup has two small holes1 hh1 bored #c_/h inch apart at the top and tapped to receive a small screw4 ,the screws pass through the holes1 mm1 and hold the stirrups at the end of their respective strap4 ,the leather-covered straps are bound together by means of two clamps which permit the head band to be adjusted to suit the wearer4 ,the clamps1 ,c1 are made from #a_/af-;inch brass #c_/h inch wide4 ,their form and construction may be best understood from the drawing4 ,a small screw eye is cut in half and soldered to the center of the upper side of the clamp so that the receiver cord may be passed through the eyelet1 ,e4 ,the telephone receivers should be connected in series by means of a flexible telephone cord4 ,,chapter ,,xvii4 ,,operation4 ,the first essential in order to manage a wireless station1 after learning the construction and handling of the instruments1 is to acquire a thorough knowledge of the telegraph codes4 ,the two codes in use in wireless service are the ,morse and the ,continental4 ,they are given below4 ,in some cases1 the intending wireless operator has had some experience with a ,morse sounder and then it is merely a matter of transition and of accustoming the ear to a new sound4 ,however it is always best to learn the ,morse code first as ,continental is merely an adaptation in which no space characters appear4 ,a beginner may learn to receive most easily by communicating with another person to whom it is also new4 ,they should first memorize all the letters of the code and practice transmitting before commencing any communication4 ,it is a great mistake for a beginner to start by writing down the dots and dashes as he receives them on paper4 ,he should make an effort to translate them and set the characters and words down directly4 ,this at first will sacrifice speed but will make a better operator and enable one to become proficient sooner than if he begins otherwise4 ,in case two complete sets of wireless apparatus are not convenient1 one may learn to read from a buzzer connected to a key and a battery4 ,the signals may be read directly from the sound of the buzzer itself1 but if a pair of telephone receivers are connected across the terminals1 a sound will be produced in the phones similar to that of a wireless receptor4 ,in sending1 avoid a short1 choppy or jerky style and handle the key with a light but firm touch4 ,keep the dots and dashes firm and of the proper relative length1 as also the spaces between letters and words4 ,the following suggestions and instructions adapted from the ,rules and ,regulations governing ,naval ,wireless ,telegraph ,stations may be of value and service to many in operating their instruments4 ,the operating room should be well lighted and free from vibration4 ,the room should have a well insulated entrance for the aerial and should be fitted with an operating table about two and one-half feet wide1 not less than seven feet long and of a convenient height for working the sending key4 ,the table should be of dry1 well-seasoned wood and the instruments should be mounted on the table at safe sparking distances from each other4 ,the connections should all be as direct as possible and well insulated4 ,high potential leads should be kept away from low potential leads and where they cross it should be at nearly right angles4 ,sending key contacts must be kept clean and flat with surfaces parallel to each other4 ,all sliding contacts1 especially in the receiving tuning coils1 should be kept clean and bright and free from foreign matter4 ,a sending set working at low power with all connections good1 closed and open circuits in resonance1 no sparking from edge of condenser1 jar or plates1 no glow from aerial and no sparking to rigging1 is utilizing its power much more efficiently than the same set pushed to the limit with high resistance connections1 sparking at all points and out of resonance4 ,illustration3 ,fig4 #adg4 ,marconi ,station at ,siasconset1 ,mass4 ,it is a good plan for any amateur to keep a note book in which he can record the various distances he has been able to receive and transmit4 ,he should try more than one circuit and jot down the results4 ,it is then possible to bring a station up to an efficiency which cannot be reached in any other manner4 ,,electrical ,,terms ,,and ,,definitions4 ,accumulator3 ,a cell whose positive and negative electrodes are formed or deposited by a current flowing from a separate source4 ,aerial3 ,a network or a number of wires insulated from surrounding objects and suspended in the air to emit or intercept electromagnetic waves4 ,alternating ,current3 ,an electric current1 of which the direction of flow reverses a number of times per second4 ,ampere3 ,the quantity of current which will flow through a resistance of one ohm under a potential of one volt4 ,the unit of current4 ,ampere ,hour3 ,the quantity of electricity passed when flowing at the rate of one ampere for one hour4 ,anode3 ,the positive terminal of a broken circuit or a source of electricity4 ,it is the carbon of a cell or the pole at which a current enters a solution4 ,capacity3 ,the relative ability of a conductor to receive and retain an electric charge4 ,circuit3 ,an unbroken conducting path for an electric current4 ,condenser3 ,a device for receiving and storing up electrostatic energy4 ,cycle3 ,the full period of reversal of an alternating current4 ,a #fj-;cycle current is one making #fj complete reversals per second4 ,detector1 ,wireless3 ,an instrument for detecting oscillations in the aerial of a receiving station4 ,it either varies its own internal resistance or generates a weak intermittent direct current similar in time and duration with the signals emitted by the transmitting station4 ,dielectric3 ,a non-conductor or insulator4 ,it usually refers to the material interposed between the oppositely charged coatings of a condenser4 ,direct ,current3 ,a current flowing in one direction only4 ,electrode3 ,the terminal of an open electric circuit or a conductor carrying a current and immersed in an electrolyte4 ,electrolysis3 ,the separation of a chemical compound into its elements by the action of an electric current4 ,electrolyte3 ,a solution which will conduct a current of electricity4 ,electromagnet3 ,a mass of iron which is magnetized by the passage of a current of electricity through a coil of wire wound around the mass and insulated therefrom4 ,farad3 ,the unit of electrical capacity4 ,a condenser having a capacity of one farad would be raised to a potential of one volt by one ampere flowing for one second4 ,field of ,force3 ,the space which is under magnetic stress in the neighborhood of a magnet or a wire carrying a current4 ,helix1 ,transmitting3 ,a coil of heavy wire which furnishes the inductance for the closed oscillation circuit of a wireless transmitter and acts as an auto-transformer to raise the voltage of the high frequency currents4 ,henry3 ,the unit of induction4 ,it is the induction in a circuit when the electromotive force induced in this circuit is one volt1 while the inducing current varies at the rate of one ampere per second4 ,inductance3 ,the property of an electric circuit whereby lines of force are developed around it4 ,induction ,coil3 ,an instrument or device consisting of two independent coils of wire wound around an iron core1 and which by magnetic induction steps up an intermittent direct current from a low to a high voltage4 ,insulator3 ,a non-conductor or a substance impervious to the passage of electricity4 ,key3 ,a device for making and breaking a current into periods corresponding to the dots and dashes of the telegraph code4 ,kilowatt3 #a1jjj watts4 ,see watt4 ,leyden ,jar3 ,a static condenser which will store up static electricity and is cylindrical in form4 ,so-called because it was originated in ,leyden1 ,holland4 ,multiple3 ,the term expressing the connection of several pieces of electrical apparatus in parallel with each other so that the current is divided between them4 ,ohm3 ,the unit of resistance4 ,it is arbitrarily taken as the resistance of a column of mercury1 one square millimeter in cross sectional area and #ajf centimeters in height4 ,parallel3 ,the same meaning as multiple4 ,parallel circuits are those which start at a common point and end at a common point4 ,polarization3 ,the collection of hydrogen upon the positive electrode of a primary cell with a consequent loss of voltage4 ,potential3 ,voltage or electrical force4 ,resistance3 ,the quality of an electrical conductor whereby it opposes the passage of an electric current4 ,the unit of resistance is the ohm4 ,rheostat3 ,a variable resistance to regulate the strength of an electric current4 ,series3 ,opposed to parallel or multiple4 ,instruments in series are so connected that the current passes from one to the other and does not divide4 ,spark ,gap3 ,an air gap or open space between two electrodes for the passage of a high voltage discharge4 ,storage ,battery3 ,see accumulator4 ,transformer3 ,a device for stepping up or stepping down the voltage of an alternating current by means of magnetic induction4 ,tuning ,coil3 ,a variable inductance for changing the period of the receptor circuit4 ,volt3 ,the unit of electrical force or potential4 ,the electromotive force which1 if steadily applied to a conductor whose resistance is one ohm1 will produce a current of one ampere4 ,voltmeter3 ,an instrument for measuring voltage4 ,watt3 ,unit of work4 ,it is the rate of work of one ampere flowing under a potential of one volt4 ,seven hundred and forty-six watts represent one electrical horsepower4 ,illustration3 99,plate ,,vi4 ,de,forest and ,marconi ,systems499 ,,chapter ,,xviii4 ,,the ,,amateur ,,and ,,the ,,wireless ,,law4 ,,what ,,it ,,is2 ,,how ,,to ,,comply2 ,,how ,,to ,,secure ,a ,,license4 ,on ,august #ac1 #aiab1 ,congress enacted a ,wireless ,law to regulate radio communication4 ,the whole law may be found in the appendix of this book1 but briefly as far as the amateur is concerned it is as follows3 ,an amateur may not use transmitting apparatus which is sufficiently powerful to send radio signals across any of the boundaries of the state in which he is located and which can be detected by a sensitive receiving set located just beyond the state boundary1 nor can he use apparatus which is powerful enough to interfere with the reception of signals by others from beyond the state boundaries unless he has a license4 ,an amateur may receive messages from anywhere at any time without a license provided that his station is not also fitted with transmitting apparatus4 ,in other words if the amateur possesses a receiving outfit only which is in working order or if he has both transmitter and receptor and the former is not powerful enough to send signals out of the state in which he lives1 or to interfere with the reception of messages by another when the messages come from beyond the state boundary a license is unnecessary4 ,this is of course somewhat unfair for those living near the center of large states for they may operate almost as they please with ordinary instruments with no fear of the signals going beyond the border1 while those living within a few miles of another state must secure a license4 ,if an amateur has a license he may transmit messages beyond the state border1 but he must not employ a wave length greater than #bjj meters or a power input into the transmitter of more than #a ,k4,w4 without special permission4 ,illustration3 ,fig4 #adh4 ,experimental ,amateur ,station of ,w4 ,haddon1 ,brooklyn1 ,n4 ,y4 ,if the amateur is within five nautical miles of an army or navy station equipped with radio apparatus his power input must not be more than #a ,k4,w4 99,complying with ,law499--,after a license is secured1 or rather as a matter of fact in order to secure it1 the wave length must not be greater than #bjj meters4 ,in order to secure such a wave length the effective portion of the aerial cannot usually be made greater than #aae feet in consideration of the amount which the lead-in1 helix and ground wire add4 ,illustration3 ,fig4 #adi4 ,complete ,receiving ,outfit ,consisting of ,receiving ,transformer1 ,detector1 ,fixed ,condenser1 ,loading ,coil1 ,two ,variable ,condensers1 ,potentiometer1 ,battery1 ,switches1 etc4 ,such an aerial will serve well for transmitting purposes1 but is too short for receiving very long distances4 ,if the amateur desires to pick up long distance messages he must employ two aerials1 a short one for transmitting and a long one for receiving4 ,if it is desirable to use the long aerial for both transmitting and receiving its wave length may be brought down to #bjj meters or under1 while transmitting by placing a large glass plate condenser of the proper capacity in series with the aerial4 ,it may be short-circuited with a suitable switch when receiving4 ,the law also says that the transmitting wave must be pure1 and must be sharply tuned1 which means that the wave must be of one length and not1 as is very often the case1 composed of two or more waves of different lengths4 ,in order to comply with this restriction1 the use of an oscillation helix or loosely coupled helix is necessary4 ,a rotary or quenched gap is also necessary in place of the ordinary spark gap4 ,the construction of all three of these instruments is described farther on4 99,how to ,obtain a ,license499--,in order to obtain a license send to the nearest ,radio ,inspector2 ,radio ,inspectors are stationed at the ,custom ,houses at the following cities3 ,boston1 ,mass42 ,new ,york1 ,n4 ,y42 ,savannah1 ,ga42 ,baltimore1 ,md42 ,cleveland1 ,ohio2 ,chicago1 ,ill42 ,seattle1 ,wash42 ,new ,orleans1 ,la42 ,san ,francisco1 ,cal42 and obtain a copy of ,the ,wireless ,law1 #h-fdab1 ,the ,regulations ,governing ,radio ,communication1 ,the ,berlin ,international ,radio-telegraphic ,convention1 and the necessary ,application ,forms4 ,look over the ,wireless ,law1 the ,regulations and the ,berlin ,convention pamphlet1 then fill out ,form #gef4 ,this is an application for an operator's license4 ,illustration3 ,fig4 #aej4 ,receiving ,outfit ,consisting of ,receiving ,transformer1 ,fixed ,condenser and ,detector4 ,if the amateur is not already in possession of a certificate of skill as an operator it will be necessary to find out1 from the commandant at the nearest one of the stations1 listed on page #d of the ,regulations as being the places where examinations are given1 on what days the examinations are held4 ,if the amateur is able to pass the examination1 an operator's license will be issued4 ,then fill out ,form #geg and forward it to the ,radio ,inspector4 ,if he thinks your station conforms to the regulations without inspection the license will be issued2 if not1 the license will be issued after inspection4 ,there are no fees to pay in connection with securing any of the licenses4 ,,apparatus ,,required ,,in ,,many ,,instances ,,in ,,order ,,to ,,comply ,,with ,,the ,,wireless ,,law4 99,,oscillation ,,helix99 ,the oscillation helix has almost become a necessity in order to comply with the regulations of the ,wireless ,law regarding wave form1 except in those stations where a quenched gap is used4 ,illustration3 ,fig4 #aea4 ,amco ,oscillation ,helix4 ,the wave emitted by many stations is not pure4 ,it is composed usually of two or three separate waves of different lengths instead of all the energy being confined to oscillations of one period4 ,it is possible to tune such a wave in two or more places or humps1 as they are called1 on the tuning coil4 ,it is obvious that a wave possessing such humps cannot be closely tuned and is liable to interfere with the signals of another station4 ,this is one of the principal causes of interference4 ,the reason for this phenomenon is simple4 ,the action of a transmitter is to first charge a condenser4 ,when the potential of the condenser rises to sufficient value it discharges across the spark gap and sets up oscillations in the closed circuit4 ,these oscillations immediately induce oscillations in the open circuit or aerial system and part of the energy passes off into the ether as electro-magnetic waves4 ,however1 the oscillations in the aerial system do not immediately die away after the oscillations in the closed circuit cease during the interim until the next condenser discharge1 but continue to surge and react upon the dosed circuit to sufficient extent to induce therein currents which surge back and forth long after the current from the condenser discharge has died away4 ,we might call the oscillations due to the condenser discharge primary oscillations and those induced in the aerial thereby secondary oscillations4 ,those which are then set up in the closed circuit by the reaction of the secondary currents are tertiary4 ,this third train of oscillations persist after the secondary currents have died away1 and induce another set of oscillations in the aerial which send out a second set of electromagnetic waves differing in length from the first4 ,the oscillations which take place after the initial surge in the closed and open circuits are naturally somewhat weak4 ,by using an oscillation helix in which the primary and secondary are separated from each other it is possible to eliminate the third and fourth trains of oscillations and all others having a tendency to follow1 by placing the circuits apart so that the weak oscillations are not strong enough99 to react across the intervening space4 ,the immediate oscillations set up by the condenser discharge are strong enough to act across the space and set up powerful oscillations in the aerial4 ,illustration3 ,fig4 #aeb4 ,details of ,oscillation ,helix ,construction4 ,a hot wire ammeter placed in the aerial circuit of a transmitter employing an oscillation transformer will not indicate as much current as if placed in the same position in a circuit using an ordinary helix2 but in spite of the fact1 a transmitter using an oscillation helix will send farther because the energy is concentrated in waves of one length4 ,the construction of one type of oscillation helix has already been outlined on page #ib4 ,the form shown in ,fig4 #aeb has no special advantages over the other but is preferred by many experimenters4 ,it is of the pancake type1 so-called because of the flat form of the windings which are made in the shape of a spiral of brass ribbon set in a slotted frame4 ,the dimensions of the helix are clearly apparent from the drawing4 ,the primary is composed of seven turns of brass ribbon #a_/b inch wide and #a_/af inch thick4 ,the secondary should have from #aj to #ae turns of ribbon #c_/h x #a_/af4 ,the coils may be slid back and forth on the brass rod so that the distance between them is variable4 ,connection is made to the coils by means of suitable clips4 ,a clip similar to that shown on page #ib1 but made to snap on a flat ribbon instead of a round wire1 will serve the purpose4 99,,quenched ,,spark ,,gap499 ,a quenched gap is made up of a number of brass or copper disks accurately turned to a true surface and separated by mica or rubber rings about 4#ja inch thick4 ,the spark discharge takes place in the air-tight space at the center of the disks1 inside of the mica rings4 ,the quenched gap has several advantages over other forms4 ,it is practically noiseless and the nuisance of a crashing discharge may be avoided by its use4 ,the large surface offered to the spark by the disks cools the spark and quickly stops the oscillations in the closed circuit1 and thereby leaves the open circuit and aerial system free to vibrate in its own period and therefore radiates pure waves4 ,by pure wave a wave of one length is meant4 ,a quenched gap cannot be used on a set of over #a ,k4,w4 power without artificial cooling by an air blast4 ,illustration3 ,fig4 #aec4 ,quenched ,gap4 ,illustration3 ,fig4 #aed4 ,quenched ,gap4 ,fig4 #aed shows an efficient form of quenched gap for use in stations up to #a ,k4,w4 in power4 ,the disks are shown in detail in ,fig4 #aee4 ,they are cast out of copper and then turned perfectly true and smooth in a lathe4 ,after surfacing1 the discharge surface should be heavily silver plated and buffed smooth4 ,illustration3 ,fig4 #aee4 ,details of ,disk and ,ring4 ,the disks are piled on a marble base with a mica ring between each4 ,they are clamped down by a strong set screw mounted on a heavy brass yoke4 ,enough pressure should be brought to bear to force the plates tightly together and make them air tight4 ,illustration3 ,fig4 #aef4 ,explanatory ,drawing of ,quenched ,gap4 ,the number of disks required is governed by the voltage of the charging condenser4 ,generally speaking it is one section of 4#ja-;inch gap for each thousand volts delivered by the secondary of the transformer4 ,it is very important to secure just the proper number of disks4 ,if properly adjusted1 the quenched gap will give one discharge for each alternation of the current and produce a musical tone4 ,the quenched gap is placed in the same position in the transmitting circuit as any other form of gap4 99,,rotary ,,gaps499 ,rotary gaps are divided into two general classes1 the synchronous gap and the non-synchronous gap4 ,the former usually consists of one or more stationary electrodes and a rotating member made like a star wheel with projecting spokes4 ,this rotary member is attached directly to the shaft of the alternator or motor generator and arranged so that a spoke always comes opposite a stationary member at the exact moment that the maximum of potential is obtained in the condenser4 ,such an arrangement permits one discharge for each alternation of the current and produces a pure musical note easily distinguished in the telephone receivers at a distant station4 ,in the non-synchronous rotary gap the wheel is driven at a high rate of speed without any regard to synchronism with the alternations of the current4 ,the rotary gap shown in ,fig4 #aeg is of the non-synchronous type4 ,illustration3 ,fig4 #aeg4 ,amco ,rotary ,gap4 ,the rotating member is cast from an alloy of equal parts of zinc and aluminum4 ,it is necessary to first make a wooden pattern from which the casting may be made4 ,the details of the wheel are shown in ,fig4 #aeh4 ,the casting must be placed in a lathe chuck and turned true4 ,it is mounted on a hard rubber disk #b #g_/h inches in diameter and #a_/d of an inch thick4 ,the disk serves to insulate the revolving electrodes from the motor shaft4 ,the rotor is mounted upon the shaft by means of a small brass bushing which passes through the center of the disk4 ,illustration3 ,fig4 #aeh4 ,details of ,revolving ,parts of ,rotary ,gap4 ,the motor must be well built and capable of running at high speed4 ,a ,juno motor will be found very satisfactory4 ,when running free its speed is about #dejj r4p4m4 ,with the rotor in place the speed is about #cfjj r4p4m4 ,the motor should be mounted on a heavy marble base capable of absorbing any little vibration that the gap may be subject to when running at high speed4 ,the stationary electrodes are made in the same manner as those for an ordinary gap and consists of two flanged zinc electrodes mounted upon threaded brass rods supported by two hexagonal standards4 ,the axis of the electrodes should be the same height above the base as that of the motor shaft4 ,the rotor should be carefully balanced so that it is practically free from vibration by boring small holes in the back face so as to make the weight on opposite sides equal4 ,illustration3 ,fig4 #aei4 ,details of ,rotary ,gap4 ,the motor may be driven by a battery or from the same source that supplies the transformer1 in series with two or three suitable lamps4 ,a motor wound to run directly from the #aaj-volt line or a higher potential must have its fields wound with very fine wire and is apt to give trouble through burn-outs1 due to kick back4 ,when the motor is operated on batteries or is wound for running in series with a lamp the danger is lessened4 ,a rotary gap is placed in the transmitting circuit in the same position as any other gap4 ,its use will result in a wonderful increase in the transmitting range of almost any station1 for not only will the amount of energy passing through the aerial be raised1 but the clear musical tone given off is more plainly distinguishable at a greater distance in the receiving station than a spark of the ordinary sort4 99,,kick ,,back499 ,the oscillations taking place in the closed circuit and aerial system of a wireless transmitter continue to surge after the current in the condenser has dropped below a certain value1 and react upon the primary winding of the coil or transformer by induction and produce high voltage1 high frequency currents termed kick back1 in wireless telegraph parlance4 ,kick back1 wherever it exists to an appreciable extent1 is liable to damage insulation and cause possible burn-outs4 ,the kick-back preventers illustrated in the accompanying diagrams will be found an efficient method of avoiding this danger4 ,illustration3 ,fig4 #afj4 ,methods of ,preventing ,kick ,back4 ,the first method shows an ordinary pressed telephone condenser of about two microfarads capacity connected directly across the ,a4 ,c4 mains near the transformer terminals1 in series with two #f-;ampere fuses4 ,the condenser is shunted by a small spark gap made of needle points with a very small space1 about 4#jje of an inch1 between them4 ,the second method is an elaboration of the first and shows two sets of condensers in series with fuses and bridged by spark gaps with a ground through a third condenser connected between4 ,this second method is the best and is often used to prevent delicate instruments1 such as a voltmeter1 from the effects of kick back4 ,a proper kick-back preventer is part of the ,fire ,insurance ,underwriters requirements for a wireless telegraph station4 ,receiving ,apparatus4 99,,the ,,variometer499 ,a variometer is a tuning device in which two coils of wire are placed in series and connected so that the turns can be made to oppose one another4 ,one coil is movable and by turning it the currents flowing through the adjacent coils oppose each other and decrease the self-induction of the whole and consequently the period of the circuit4 ,illustration3 ,fig4 #afa4 ,variometer4 ,the accompanying illustration shows the constructive details of an efficient form of variometer4 ,the coils are wound around two cardboard cylinders4 ,one cylinder is #f inches in diameter and the other #e inches4 ,both are #b inches long4 ,the large cylinder is wound with twenty-five turns of ,no4 #bb ,b4 ,s4 gauge single silk covered wire wound in two sections so as to leave a space #c_/h inch wide in the center4 ,the small cylinder is wound in the same manner with the same size of wire but contains thirty turns so as to make the length of wire in each of the coils practically equal4 ,the space in the center of each of the coils allows a supporting rod to pass through without interfering with the wire4 ,the shaft is a piece of #e_/af brass rod about #g #a_/b inches long4 ,the upper end is provided with a knob and a pointer4 ,the large coil is mounted on the under side of a wooden cover made to fit a containing case of the proper size to receive the variometer and of a style similar to that ordinarily used to enclose a variable condenser4 ,the shaft passes through the larger coil1 at two points diametrically opposite1 but should not fit tightly4 ,it also passes through the smaller coil but is fastened to the latter by means of a cross bar so that when the knob is turned the coil will revolve also4 ,the coils are connected by means of a piece of braided wire or flexible conductor1 long enough so as not to interfere with the movement of the inner coil4 ,the outside terminals of the coils terminate in binding posts mounted on the top of the case4 ,when making a variometer be careful not to employ any iron or steel in its construction1 not even iron screws4 ,the variometer is placed in the receiving circuit by connecting it in series with the aerial before it reaches the tuning coil or loose coupler4 99,,new ,,crystal ,,detectors499 99,silicon ,detector499--,the silicon detector is always interesting because it was one of the first mineral rectifiers to come into extended use4 ,the photograph shown below illustrates one of the latest forms of the silicon detector4 ,illustration3 ,fig4 #afb4 ,silicon ,detector4 ,the large cup supported by the left-hand standard contacts several pieces of fused silicon embedded in fusible alloy4 ,the right-hand standard supports a movable offset cup the same as that used on the ,perikon type of ,detector4 ,a small piece of arsenic is mounted in this cup and may be brought to bear against any portion of any of the silicon crystals4 99,pyron ,detector499--,the ,pyron detector is not new1 but the photograph shows a very simple and efficient form in which a fine wire is brought to bear against a crystal of iron pyrites mounted in a small cup4 ,illustration3 ,fig4 #afc4 ,pyron ,detector4 99,galena ,detector499--,although galena is named in the list of sensitive minerals on page #acb it has come into such extensive use as a detector since the first edition of this book to be worthy of special attention4 ,galena detectors are often spoken of as cat-whisker detectors because of the long fine wire used to secure a delicate contact with the mineral4 ,the mineral is usually placed in a cup and held in position by imbedding in fusible alloy or clamped with a set screw4 ,the best surface of the mineral should be selected by testing previous to imbedding it in the cup4 ,contact is made with the surface of the mineral by means of a piece of ,no4 #cj phosphor bronze wire mounted on the end of a short brass rod fitted with an adjusting screw so that by turning or twisting the surface of the mineral may be searched and the tension varied4 ,illustration3 ,fig4 #afd4 ,galena ,detector4 ,such an arrangement is illustrated in ,fig4 #afd4 ,the base is a hard rubber block #c #c_/d x #a #c_/d x #a_/b4 ,the binding posts are of the type commonly used on electrical instruments4 ,one of the posts is pivoted by placing a spring washer under the head of the screw which holds the post to the base4 ,a short piece of brass rod fitted with a hard rubber knob passes through the wire hole in the post4 ,a piece of ,no4 #cj phosphor bronze wire is soldered to the end of the rod4 ,by twisting the post and sliding the rod any portion of the mineral surface may be selected4 ,twisting the rod varies the tension of the contact4 ,the galena detector is connected in the receiving circuit in the same manner as other detectors of the mineral type4 99,,the ,,audion499 99,the ,audion99--is finding favor in many amateur wireless stations1 because of its almost entire lack of adjustment and of the loud clear signals which it gives even when used for long distance work4 ,the illustration shows the latest form of audion1 the plate and the grid both being on the same side of the filament4 ,the filament of an audion is usually lighted by means of a six-volt storage battery4 ,a small battery rheostat placed in series with the battery serves to regulate the amount of current flowing through the filament4 ,only one filament is used at a time1 the other being saved as a reserve in case the first burns out4 ,illustration3 ,fig4 #afe4 ,audion4 ,the higher voltage necessary to operate an audion is supplied by a battery consisting of fifteen flashlight batteries1 each flashlight battery being composed of three separate cells4 ,the batteries are connected to an eight-point switch so that throwing the switch on the first point will connect five sets of batteries4 ,the second point places five more in circuit and each additional point one set only4 ,it is also a good plan to connect a four-point switch and three separate cells of battery in series with the eight-point switch so that they may be added to the circuit one at a time and the potential varied more closely than the steps on the eight-point switch permit4 ,the maximum voltage of such a battery is approximately #ef volts4 ,the diagram in ,fig4 #aff shows exactly how an audion is connected4 ,the wires ,a and ,b are the terminals leading to the tuning coil or loose coupler4 ,it is not necessary that the telephone receivers used with an audion be wound to a high resistance in order to secure good results4 ,illustration3 ,fig4 #aff4 ,audion ,circuit4 ,the audion is placed in operation by turning the rheostat until the filament lights brightly4 ,then adjust the voltage of the high potential battery until the signals are clearest4 ,if the voltage is too high the audion will become filled with a bluish light and the voltage should be immediately reduced4 ,the signals will be loudest when the filament is brilliantly lighted4 ,no more current should be passed through the filament than is necessary to render the signals plain1 for if forced its life will be limited to only a few hours4 ,illustration3 ,fig4 #afg4 ,rotary ,variable ,condenser4 99,,appendix499 ,,public ,no4 #bfd4 ,s4 #fdab4 ,an ,act to ,regulate ,radio ,communication4 ,be it enacted by the ,senate and ,house of ,representatives of the ,united ,states of ,america in ,congress assembled4 ,that a person1 company1 or corporation within the jurisdiction of the ,united ,states shall not use or operate any apparatus for radio communication as a means of commercial intercourse among the several ,states1 or with foreign nations1 or upon any vessel of the ,united ,states engaged in interstate or foreign commerce1 or for the transmission of radiograms or signals the effect of which extends beyond the jurisdiction of the ,state or ,territory in which the same are made1 or where interference would be caused thereby with the receipt of messages or signals from beyond the jurisdiction of the said ,state or ,territory1 except under and in accordance with a license1 revocable for cause1 in that behalf granted by the ,secretary of ,commerce and ,labor upon application therefor2 but nothing in this ,act shall be construed to apply to the transmission and exchange of radiograms or signals between points situated in the same ,state3 ,provided1 ,that the effect thereof shall not extend beyond the jurisdiction of the said ,state or interfere with the reception of radiograms or signals from beyond said jurisdiction2 and a license shall not be required for the transmission or exchange of radiograms or signals by or on behalf of the ,government of the ,united ,states1 but every ,government station on land or sea shall have special call letters designated and published in the list of radio stations of the ,united ,states by the ,department of ,commerce and ,labor4 ,any person1 company1 or corporation that shall use or operate any apparatus for radio communication in violation of this section1 or knowingly aid or abet another person1 company1 or corporation in so doing1 shall be deemed guilty of a misdemeanor1 and on conviction thereof shall be punished by a fine not exceeding five hundred dollars1 and the apparatus or device so unlawfully used and operated may be adjudged forfeited to the ,united ,states4 ,,sec4 #b4 ,that every such license shall be in such form as the ,secretary of ,commerce and ,labor shall determine and shall contain the restrictions1 pursuant to this ,act1 on and subject to which the license is granted2 that every such license shall be issued only to citizens of the ,united ,states or ,porto ,rico or to a company incorporated under the laws of some ,state or ,territory or of the ,united ,states or ,porto ,rico1 and shall specify the ownership and location of the station in which said apparatus shall be used and other particulars for its identification and to enable its range to be estimated2 shall state the purpose of the station1 and1 in case of a station in actual operation at the date of passage of this ,act1 shall contain the statement that satisfactory proof has been furnished that it was actually operating on the above-mentioned date2 shall state the wave length or the wave lengths authorized for use by the station for the prevention of interference and the hours for which the station is licensed for work2 and shall not be construed to authorize the use of any apparatus for radio communication in any other station than that specified4 ,every such license shall be subject to the regulations contained herein1 and such regulations as may be established from time to time by authority of this ,act or subsequent ,acts and treaties of the ,united ,states4 ,every such license shall provide that the ,president of the ,united ,states in time of war or public peril or disaster may cause the closing of any station for radio communication and the removal therefrom of all radio apparatus1 or may authorize the use or control of any such station or apparatus by any department of the ,government1 upon just compensation to the owners4 ,,sec4 #c4 ,that every such apparatus shall at all times while in use and operation as aforesaid be in charge or under the supervision of a person or persons licensed for that purpose by the ,secretary of ,commerce and ,labor4 ,every person so licensed who in the operation of any radio apparatus shall fail to observe and obey regulations contained in or made pursuant to this ,act or subsequent ,acts or treaties of the ,united ,states1 or any one of them1 or who shall fail to enforce obedience thereto by an unlicensed person while serving under his supervision1 in addition to the punishments and penalties herein prescribed1 may suffer the suspension of the said license for a period to be fixed by the ,secretary of ,commerce and ,labor not exceeding one year4 ,it shall be unlawful to employ any unlicensed person or for any unlicensed person to serve in charge or in supervision of the use and operation of such apparatus1 and any person violating this provision shall be guilty of a misdemeanor1 and on conviction thereof shall be punished by a fine of not more than one hundred dollars or imprisonment for not more than two months1 or both1 in the discretion of the court1 for each and every such offense3 ,provided1 ,that in case of emergency the ,secretary of ,commerce and ,labor may authorize a collector of customs to issue a temporary permit1 in lieu of a license1 to the operator on a vessel subject to the radio ship ,act of ,june twenty-fourth1 nineteen hundred and ten4 ,,sec4 #d4 ,that for the purpose of preventing or minimizing interference with communication between stations in which such apparatus is operated1 to facilitate radio communication1 and to further the prompt receipt of distress signals1 said private and commercial stations shall be subject to the regulations of this section4 ,these regulations shall be enforced by the ,secretary of ,commerce and ,labor through the collectors of customs and other officers of the ,government as other regulations herein provided for4 ,the ,secretary of ,commerce and ,labor may1 in his discretion1 waive the provisions of any or all of these regulations when no interference of the character above mentioned can ensue4 ,the ,secretary of ,commerce and ,labor may grant special temporary licenses to stations actually engaged in conducting experiments for the development of the science of radio communication1 or the apparatus pertaining thereto1 to carry on special tests1 using any amount of power or any wave lengths1 at such hours and under such conditions as will insure the least interference with the sending or receipt of commercial or ,government radiograms1 of distress signals and radiograms1 or with the work of other stations4 ,in these regulations the naval and military stations shall be understood to be stations on land4 ,,regulations4 ,,normal ,,wave ,,length4 ,first4 ,every station shall be required to designate certain definite wave length as the normal sending and receiving wave length of the station4 ,this wave length shall not exceed six hundred meters or it shall exceed one thousand six hundred meters4 ,every coastal station open to general public service shall at all times be ready to receive messages of such wave lengths as are required by the ,berlin convention4 ,every ship station1 except as hereinafter provided1 and every coast station open to general public service shall be prepared to use two sending wave lengths1 one of three hundred meters and one of six hundred meters1 as required by the international convention in force3 ,provided1 ,that the ,secretary of ,commerce and ,labor may1 in his discretion1 change the limit of wave length reservation made by regulations first and second to accord with any international agreement to which the ,united ,states is a party4 ,,other ,,wave ,,lengths4 ,second4 ,in addition to the normal sending wave length all stations1 except as provided hereinafter in these regulations1 may use other sending wave lengths3 ,provided1 ,that they do not exceed six hundred meters or that they do exceed one thousand six hundred meters3 ,provided further1 ,that the character of the waves emitted conforms to the requirements of regulations third and fourth following4 ,,use ,,of ,a ,,pure ,,wave ,third4 ,at all stations if the sending apparatus1 to be referred to hereinafter as the transmitter1 is of such a character that the energy is radiated in two or more wave lengths1 more or less sharply defined1 as indicated by a sensitive wave meter1 the energy in no one of the lesser waves shall exceed ten per centum of that in the greatest4 ,,use ,,of ,a ,,sharp ,,wave4 ,fourth4 ,at all stations the logarithmic decrement per complete oscillation in the wave trains emitted by the transmitter shall not exceed two-tenths1 except when sending distress signals or signals and messages relating thereto4 ,,use ,,of ,,standard ,,distress ,,wave4 ,fifth4 ,every station on shipboard shall be prepared to send distress calls on the normal wave length designated by the international convention in force1 except on vessels of small tonnage unable to have plants insuring that wave length4 ,,signal ,,of ,,distress4 ,sixth4 ,the distress call used shall be the international signal of distress3 dot dot dot1 dash dash dash1 dot dot dot4 ,,use ,,of ,,broad ,,interfering ,,wave ,,for ,,distress ,,signals4 ,seventh4 ,when sending distress signals1 the transmitter of a station on shipboard may be tuned in such a manner as to create a maximum of interference with a maximum of radiation4 ,,distance ,,requirement ,,for ,,distress ,,signals4 ,eighth4 ,every station on shipboard1 wherever practicable1 shall be prepared to send distress signals of the character specified in regulations fifth and sixth with sufficient power to enable them to be received by day over sea a distance of one hundred nautical miles by a shipboard station equipped with apparatus for both sending and receiving equal in all essential particulars to that of the station first mentioned4 ,,for ,,distress ,,signals4 ,ninth4 ,all stations are required to give absolute priority to signals and radiograms relating to ships in distress2 to cease all sending on hearing a distress signal2 and1 except when engaged in answering or aiding the ship in distress1 to refrain from sending until all signals and radiograms relating thereto are completed4 ,,reduced ,,power ,,for ,,ships ,,near ,a ,,government ,,station4 ,tenth4 ,no station on shipboard1 when within fifteen nautical miles of a naval or military station1 shall use a transformer input exceeding one kilowatt1 nor1 when within five nautical miles of such a station1 a transformer input exceeding one-half kilowatt1 except for sending signals of distress1 or signals or radiograms relating thereto4 ,,intercommunication4 ,eleventh4 ,each shore station open to general public service between the cost and vessels at sea shall be bound to exchange radiograms with any similar shore station and with any ship station without distinction of the radio systems adopted by such stations1 respectively1 and each station on shipboard shall be bound to exchange radiograms with any other station on shipboard without distinction of the radio systems adopted by each station respectively4 ,it shall be the duty of each such shore station1 during the hours it is in operation1 to listen in at intervals of not less than fifteen minutes and for a period not less than two minutes1 with the receiver tuned to receive messages of three hundred meter wave lengths4 ,,division ,,of ,,time4 ,twelfth4 ,at important seaports and at all other places where naval or military and private or commercial shore stations operate in such close proximity that interference with the work of naval and military stations can not be avoided by the enforcement of the regulations contained in the foregoing regulations concerning wave lengths and character of signals emitted1 such private or commercial shore stations as do interfere with the reception of signals by the naval and military stations concerned shall not use their transmitters during the first fifteen minutes of each hour1 local standard time4 ,the ,secretary of ,commerce and ,labor may1 on the recommendation of the department concerned1 designate the station or stations which may be required to observe this division of time4 ,,government ,,stations ,,to ,,observe ,,division ,,of ,,time4 ,thirteenth4 ,the naval or military stations for which the above mentioned division of time may be established shall transmit signals or radiograms only during the first fifteen minutes of each hour1 local standard time1 except in case of signals or radiograms relating to vessels in distress1 as hereinbefore provided4 ,,use ,,of ,,unnecessary ,,power4 ,fourteenth4 ,in all circumstances1 except in case of signals or radiograms relating to vessels in distress1 all stations shall use the minimum amount of energy necessary to carry out any communication desired4 ,,general ,,restrictions ,,on ,,private ,,stations4 ,fifteenth4 ,no private or commercial station not engaged in the transaction of bona fide commercial business by radio communication or in experimentation in connection with the development and manufacture of radio apparatus for commercial purposes shall use a transmitting wave length exceeding two hundred meters1 or a transformer input exceeding one kilowatt1 except by special authority of the ,secretary of ,commerce and ,labor contained in the license of the station3 ,provided1 ,that the owner or operator of a station of the character mentioned in this regulation shall not be liable for a violation of the requirements of the third or fourth regulations to the penalties of one hundred dollars or twenty-five dollars1 respectively1 provided in this section unless the person maintaining or operating such station shall have been notified in writing that the said transmitter has been found1 upon tests conducted by the ,government1 to be so adjusted as to violate the said third and fourth regulations1 and opportunity has been given to said owner or operator to adjust said transmitter in conformity with said regulations4 ,,special ,,restrictions ,,in ,,the ,,vicinities ,,of ,,government ,,stations4 ,sixteenth4 ,no station of the character mentioned in regulation fifteenth situated within five nautical miles of a naval or military station shall use a transmitting wave length exceeding two hundred meters or a transformer input exceeding one-half kilowatt4 ,,ship ,,stations ,,to ,,communicate ,,with ,,nearest ,,shore ,,stations4 ,seventeenth4 ,in general1 the shipboard stations shall transmit their radiograms to the nearest shore station4 ,a sender on board a vessel shall1 however1 have the right to designate the shore station through which he desires to have his radiograms transmitted4 ,if this can not be done1 the wishes of the sender are to be complied with only if the transmission can be effected without interfering with the service of other stations4 ,,limitations ,,for ,,future ,,installations ,,in ,,vicinities ,,of ,,government ,,stations4 ,eighteenth4 ,no station on shore not in actual operation at the date of the passage of this ,act shall be licensed for the transaction of commercial business by radio communication within fifteen nautical miles of the following naval or military stations1 to wit3 ,arlington1 ,virginia2 ,key ,west1 ,florida2 ,san ,juan1 ,porto ,rico2 ,north ,head and ,tatoosh ,island1 ,washington2 ,san ,diego1 ,california2 and those established or which may be established in ,alaska and in the ,canal ,zone2 and the head of the department having control of such ,government stations shall1 so far as is consistent with the transaction of governmental business1 arrange for the transmission and receipt of commercial radiograms under the provisions of the ,berlin convention of nineteen hundred and six and future international conventions or treaties to which the ,united ,states may be a party1 at each of the stations above referred to1 and shall fix the rates therefor1 subject to control of such rates by ,congress4 ,at such stations and wherever and whenever shore stations open for general public business between the coast and vessels at sea under the provisions of the ,berlin convention of nineteen hundred and six and future international conventions and treaties to which the ,united ,states may be a party shall not be so established as to insure a constant service day and night without interruption1 and in all localities wherever or whenever such service shall not be maintained by a commercial shore station within one hundred nautical miles of a naval radio station1 the ,secretary of the ,navy shall1 so far as is consistent with the transaction of governmental business1 open naval radio stations to the general public business described above1 and shall fix rates for such service1 subject to control of such rates by ,congress4 ,the receipts from such radiograms shall be covered into the ,treasury as miscellaneous receipts4 ,,secrecy ,,of ,,messages4 ,nineteenth4 ,no person or persons engaged in or having knowledge of the operation of any station or stations shall divulge or publish the contents of any messages transmitted or received by such station1 except to the person or persons to whom the same may be directed1 or their authorized agent1 or to another station employed to forward such message to its destination1 unless legally required so to do by the court of competent jurisdiction or other competent authority4 ,any person guilty of divulging or publishing any message1 except as herein provided1 shall1 on conviction thereof1 be punishable by a fine of not more than two hundred and fifty dollars or imprisonment for a period of not exceeding three months1 or both fine and imprisonment1 in the discretion of the court4 ,,penalties4 ,for violation of any of these regulations1 subject to which a license under sections one and two of this ,act may be issued1 the owner of the apparatus shall be liable to a penalty of one hundred dollars1 which may be reduced or remitted by the ,secretary of ,commerce and ,labor1 and for repeated violations of any of such regulations1 the license may be revoked4 ,for violation of any of these regulations1 except as provided in regulation nineteenth1 subject to which a license under section three of this ,act may be issued1 the operator shall be subject to a penalty of twenty-five dollars1 which may be reduced or remitted by the ,secretary of ,commerce and ,labor1 and for repeated violations of any such regulations1 the license shall be suspended or revoked4 ,,sec4 #e4 ,that every license granted under the provisions of this ,act for the operation or use of apparatus for radio communication shall prescribe that the operator thereof shall not wilfully or maliciously interfere with any other radio communication4 ,such interference shall be deemed a misdemeanor1 and upon conviction thereof the owner or operator1 or both1 shall be punishable by a fine of not to exceed five hundred dollars or imprisonment for not to exceed one year1 or both4 ,,sec4 #f4 ,that the expression radio communication as used in this ,act means any system of electrical communication by telegraphy or telephony without the aid of any wire connecting the points from and at which the radiograms1 signals1 or other communications are sent or received4 ,,sec4 #g4 ,that a person1 company1 or corporation within the jurisdiction of the ,united ,states shall not knowingly utter or transmit1 or cause to be uttered or transmitted1 any false or fraudulent distress signal or call or false or fraudulent signal1 call1 or other radiogram of any kind4 ,the penalty for so uttering or transmitting a false or fraudulent distress signal or call shall be a fine of not more than two thousand five hundred dollars or imprisonment for not more than five years1 or both1 in the discretion of the court1 for each and every such offense1 and the penalty for so uttering or transmitting1 or causing to be uttered or transmitted1 any other false or fraudulent signal1 call1 or other radiogram shall be a fine of not more than one thousand dollars or imprisonment for not more than two years1 or both1 in the discretion of the court1 for each and every such offense4 ,,sec4 #h4 ,that a person1 company1 or corporation shall not use or operate any apparatus for radio communication on a foreign ship in territorial waters of the ,united ,states otherwise than in accordance with the provisions of sections four and seven of this ,act and so much of section five as imposes a penalty for interference4 ,save as aforesaid1 nothing in this ,act shall apply to apparatus for radio communication on any foreign ship4 ,,sec4 #i4 ,that the trial of any offense under this ,act shall be in the district in which it is committed1 or if the offense is committed upon the high seas or out of the jurisdiction of any particular ,state or district the trial shall be in the district where the offender may be found or into which he shall be first brought4 ,,sec4 #aj4 ,that this ,act shall not apply to the ,phillippine ,islands4 ,,sec4 #aa4 ,that this ,act shall take effect and be in force on and after four months from its passage4 ,approved1 ,august #ac1 #aiab4 ,,list ,,of ,,works ,,on ,,electrical ,,science ,,published ,,and ,,for ,,sale ,,by ,d4 ,,van ,,nostrand ,,company1 99#be ,park ,place1 ,new ,york499 99,,abbott1 ,a4 ,v4 ,the ,electrical ,transmission of ,energy499 ,a ,manual for the ,design of ,electrical ,circuits4 ,fifth ,edition1 enlarged and rewritten4 ,with many ,diagrams1 ,engravings and ,folding ,plates4 #hvo41 cloth1 #fge pp ,net1 #e4jj 99,,arnold1 ,e4 ,armature ,windings of ,direct-,current ,dynamos499 ,extension and ,application of a general ,winding ,rule4 ,translated from the original ,german by ,francis ,b4 ,de,cress4 ,illustrated4 #hvo4 cloth1 #abd pp #b4jj 99,,ashe1 ,s4 ,w4 ,electricity ,experimentally and ,practically ,applied499 ,second ,edition4 #dbb illustrations4 #abmo41 cloth1 #cge pp4 ,net1 #b4jj 99,,ashe1 ,s4 ,w41 and ,,keiley1 ,j4 ,d4 ,electric ,railways ,theoretically and ,practically ,treated499 ,illustrated4 #abmo41 cloth4 99,vol4 ,i4 ,rolling ,stock499 ,second ,edition4 #bhe pp ,net1 #b4ej 99,vol4 ,,ii4 ,substations and ,distributing ,systems499 #bif pp ,net1 #b4 #ej 99,,atkinson1 ,a4 ,a4 ,electrical and ,magnetic ,calculations499 ,for the use of ,electrical ,engineers and others interested in the ,theory and ,application of ,electricity and ,magnetism4 ,fourth ,edition1 revised ,illustrated4 #abmo1 cloth1 #caj pp ,net1 #a4ej 99,,atkinson1 ,,philip4 ,the ,elements of ,dynamic ,electricity and ,magnetism499 ,fourth ,edition4 ,illustrated4 #abmo41 cloth1 #dje pp4 #b4jj - 99,elements of ,electric ,lighting199 including ,electric ,generation1 ,measurement1 ,storage1 and ,distribution4 ,tenth ,edition1 fully revised and new matter added4 ,illustrated4 #abmo41 cloth1 #bhj pp #a4ej - 99,power ,transmitted by ,electricity and ,applied by the ,electric ,motor199 including ,electric ,railway ,construction4 ,illustrated4 ,fourth ,edition1 fully revised and new matter added4 #abmo41 cloth1 #bda pp4 #b4jj 99,,austin1 ,e4 ,single-,phase ,electric ,railways499 #cdf illustrations #h x #aa1 cloth1 #cjh pp ,net1 #e4jj 99,,ayrton1 ,,hertha4 ,the ,electric ,arc499 ,illustrated4 #hvo41 cloth1 #dgi pp ,net1 #e4jj 99,,baker1 ,j4 ,t4 ,the ,telegraphic ,transmission of ,photographs499 #fc illustrations4 #abmo41 cloth1 #aee pp ,net1 #a4be 99,,barham1 ,g4 ,b4 ,development of the ,incandescent ,electric ,lamp499 #be illustrations1 #b plates1 #e x #h cloth4 #bjf pp #b4jj 99,,bedell1 ,,frederick4 ,direct and ,alternating ,current ,manual499 ,with directions for testing and a discussion of the theory of electrical apparatus4 ,second ,edition1 greatly enlarged4 ,assisted by ,c4 ,a4 ,pierce4 ,illustrated4 #f x #i1 cloth1 #cgc pp ,net1 #b4jj 99,,blaine1 ,,robert ,g4 ,the ,calculus and ,its ,applications499 ,a practical treatise for beginners especially engineering students4 #gi illustrations4 #abmo41 cloth1 #ccj pp ,net1 #a4ej 99,,bonney1 ,g4 ,e4 ,the ,electro-,plater's ,hand ,book499 ,a ,manual for ,amateurs and ,young ,students of ,electro-,metallurgy4 ,fifth ,edition1 enlarged4 #fa ,illustrations4 #abmo41 cloth1 #bjh pp #a4bj 99,,bottone1 ,s4 ,r4 ,magnetos ,for ,automobilists2 ,how ,made and ,how ,used99 ,a handbook of practical instruction on the manufacture and adaptation of the magneto to the needs of the motorist4 ,second ,edition1 enlarged4 #eb illustrations4 #abmo41 cloth1 #aah pp ,net1 #a4jj 99,,broadfoot1 ,s4 ,k4 ,motors1 ,secondary ,batteries and ,accessory ,apparatus499 #af illustrations4 #afmo41 cloth4 #ajjpp4 7,installation ,manuals ,series7 ,net1 #j4ge 99,,broughton1 ,h4 ,h4 ,electric ,canes499 ,their design1 construction and application4 #fjj illustrations and plates4 #abj tables1 #f x #i1 cloth1 #hdh pp ,net1 #i4jj 99,,child1 ,c4 ,d4 ,electric ,arcs499 ,experiments upon arcs between different electrodes in various environments and their explanation4 #eh illustrations4 #e x #g1 cloth1 #bjc pp ,net1 #b4jj 99,,collis1 ,a4 ,g4 ,high and ,low ,tension ,switchgear ,design499 #id illustrations and folding plates1 #f x #i1 cloth1 #bcc pp ,net1 #c4ej - 99,switchgear and ,the ,control of ,electric ,circuits499 #dg illustrations4 #d #a_/b x #f #a_/b1 cloth1 #he pp4 7,installation ,manuals ,series7 ,net1 #j4ej 99,,comstock1 ,d4 ,f41 and ,,troland1 ,l4 ,t4 ,the ,nature of ,matter and ,electricity499 ,an outline of modern views4 ,illustrated4 #e x #g1 cloth1 #bjj pp ,net1 #b4jj 99,,cooper1 ,w4 ,r4 ,primary ,batteries3 their ,theory1 ,construction1 and ,use99 ,new ,edition in ,press 99,,craig1 ,j4 ,w41 and ,,woodward1 ,w4 ,p4 ,questions and ,answers ,about ,electrical ,apparatus499 ,third edition revised and enlarged4 ,illustrated4 #d x #f ,leather1 #bef pp ,net1 #a4ej 99,,cramp1 ,w4 ,continuous ,current ,machine ,design499 #acg illustration4 #hvo41 cloth1 #bdj pp ,net1 #b4ej 99,,creed ,y1 ,f4 ,single-,phase ,commutator ,motors499 #ih illustrations1 #f x #i1 cloth1 #abj pp ,net1 #b4jj 99,,crocker1 ,f4 ,b4 ,electric ,lighting499 ,a ,practical ,exposition of the ,art for the use of ,electricians1 ,students1 and others interested in the ,installation or ,operation of ,electric ,lighting ,plants4 - 99,vol4 ,i4 ,the ,generating ,plant994 ,seventh ,edition1 entirely revised4 ,illustrated4 #hvo41 cloth1 #dhb pp #c4jj - 99,vol4 ,,ii4 ,distributing ,system and ,lamps499 ,sixth ,edition4 ,illustrated #hvo41 cloth1 #eje pp4 99,,crocker1 ,f4 ,b41 and ,,arendt1 ,m4 ,electric ,motors3 ,their ,action1 ,control1 and ,application499 ,second ,edition1 ,revised and ,enlarged4 #afi illustrations4 #f #a_/d x #i #a_/d1 cloth1 #cae pp ,net1 #b4ej 99,,crocker1 ,f4 ,b41 and ,,wheeler1 ,s4 ,s4 ,the ,management of ,electrical ,machinery499 ,being a thoroughly revised and rewritten edition of the authors' ,practical ,management of ,dynamos and ,motors4 ,eighth ,edition4 ,illustrated4 #afmo41 cloth1 #bcb pp ,net1 #a4jj 99,,cushing1 ,h4 ,c41 ,jr4 ,standard ,wiring for ,electric ,light and ,power99 ,illustrated4 #afmo41 leather1 #aef pp #a4jj 99,,cushing1 ,h4 ,c41 ,jr4 and ,,harrison1 ,n4 ,central ,station ,management499 #e #a_/b x #g #a_/d cloth1 #dag pp ,net1 #b4jj 99,,davies1 ,f4 ,h4 ,electric ,power and ,traction499 ,illustrated4 #hvo41 cloth #bic pp4 7,van ,nostrand's ,westminster ,series47 ,net1 #b4jj - 99,foundations and ,machinery ,fixing499 #eb illustrations4 #afmo41 cloth1 #adf pp4 7,installations ,manuals ,series7 ,net1 #a4jj 99,,del ,,mar1 ,w4 ,a4 ,electric ,power ,conductors499 ,second edition revised4 #fi illustrations4 #e #a_/b x #h1 cloth1 #ccj pp ,net1 #b4jj 99,,devey1 ,r4 ,g4 ,mill and ,factory ,wiring499 #abf illustrations4 #afmo41 cloth1 #bji pp4 7,installation ,manuals ,series7 ,net1 #a4jj 99,,dinger1 ,lieut4 ,h4 ,c4 ,handbook for the ,care and ,operation of ,naval ,machinery499 ,second ,edition4 #abd ,illustrations4 #afmo41 cloth1 #cjb pp ,net1 #b4jj 99,,duncan1 ,w4 ,g4 and ,,penman1 ,d4 ,electrical ,equipment of ,collieries499 #aeg illustrations1 #f #a_/b x #h #c_/d1 cloth1 #cbi pp ,net1 #d4jj 99,,dwight1 ,h4 ,b4 ,transmission ,line ,formulas for ,electrical ,engineers and ,engineering ,students499 #bg illustrations4 #b folding plates1 #abmo1 cloth1 #adc pp ,net1 #b4jj 99,,dynamic ,,electricity399 ,its ,modern ,use and ,measurement1 chiefly in its application to ,electric ,lighting and ,telegraphy1 including3 #a4 ,some ,points in ,electric ,lighting1 by ,dr4 ,john ,hopkinson4 #b4 ,on the ,treatment of ,electricity for ,commercial ,purposes1 by ,j4 ,n4 ,shoolbred4 #c4 ,electric-,light ,arithmetic1 by ,r4 ,e4 ,day1 ,m4,e4 ,fourth ,edition4 ,illustrated4 #afmo41 boards1 #aff pp4 7,no4 #ga ,van ,nostrand's ,science ,series47 #ej cents 99,,eck1 ,j4 ,light1 ,radiation and ,illumination499 ,translated from the ,german of ,paul ,hogner4 #ei illustrations4 #e #a_/b x #h1 cloth1 #ajj pp4 ,net1 #b4ej 99,,eccles1 ,w4 ,h4 ,wireless ,telegraphy and ,telephony499 ,illustrated4 #e x #h #a_/b half leather1 #dah pp ,net1 #d4ej 99,,eddy1 ,l4 ,c4 ,laboratory ,manual of ,alternating ,currents499 #ba illustrations1 #e #a_/b x #h1 cloth1 #bf pp ,net1 #ej cents 99,,edler1 ,r4 ,switches and ,switchgear499 ,translated by ,ph4 ,laubach4 #cce illustrations4 #f #a_/b x #i1 cloth1 #dab pp ,net1 #d4jj 99,,edgcumbe1 ,k4 ,industrial ,electrical ,measuring ,instruments499 ,illustrated4 #h vo41 cloth1 #bbg pp4 99,,engineering ,,as ,a ,,career499 ,by ,prominent ,engineers4 ,edited by ,c4 ,e4 ,drayer and ,f4 ,h4 ,newell4 #e #a_/d x #g #a_/b1 #bbf pp4 ,paper #ge cents1 cloth #a4jj 99,,ewing1 ,j4 ,a4 ,magnetic ,induction in ,iron and other ,metals499 ,third ,edition1 revised4 ,illustrated4 #hvo41 cloth1 #cic pp ,net1 #d4jj 99,,fisher1 ,h4 ,k4 ,c41 and ,,darby1 ,w4 ,c4 ,students' ,guide to ,submarine ,cable ,testing499 ,fourth ,edition1 enlarged4 ,illustrated4 #hvo41 cloth1 #beb pp ,net1 #c4ej 99,,fleming1 ,j4 ,a41 ,prof4 ,the ,alternate-,current ,transformer in ,theory and ,practice499 99,vol4 ,i43 ,the ,induction of ,electric ,currents499 ,fifth ,issue4 ,illustrated4 #evo41 cloth1 #fda pp3 ,net1 #e4jj 99,vol4 ,,ii43 ,the ,utilization of ,induced ,currents499 ,third ,issue4 ,illustrated4 #hvo41 cloth1 #ehg pp ,net1 #e4jj - 99,propagation of ,electric ,currents in ,telephone and ,telegraph ,conductors499 ,illustrated4 #f #a_/b x #i #a_/b1 cloth1 #cbc pp ,net1 #c4jj - 99,handbook for the ,electrical ,laboratory and ,testing ,room499 ,two ,volumes4 ,illustrated4 #hvo41 cloth1 #aafj pp4 ,each vol ,net1 #e4jj 99,,foster1 ,h4 ,a4 ,with the ,collaboration of ,eminent ,specialists4 ,electrical ,engineers' ,pocket ,book499 ,a handbook of useful data for ,electricians and ,electrical ,engineers4 ,with innumerable ,tables1 ,diagrams1 and ,figures4 ,the most complete book of its kind ever published1 treating of the latest and best ,practice in ,electrical ,engineering4 ,seventh ,edition1 completely revised and enlarged4 ,fully ,illustrated4 ,pocket ,size4 ,leather4 ,thumb ,indexed4 #afcf pp #e4jj - 99,engineering ,valuation of ,public ,utilities and ,factories499 #ej blank forms4 #f x #i1 cloth1 #cfa pp ,net1 #c4jj - 99,electrical ,cost ,data1 ,estimates and ,working ,tables499 ,in ,press 99,,fowle1 ,f4 ,f4 ,the ,protection of ,railroads from ,overhead ,transmission ,line ,crossings499 #ce illustrations4 #abmo41 cloth1 #gf pp ,net1 #a4ej4 99,,freudemacher1 ,p4 ,w4 ,electrical ,mining ,installations499 #cf illustrations4 #afmo41 cloth1 #aib pp4 7,installation ,manuals ,series7 ,net1 #a4jj 99,,frith1 ,j4 ,alternating ,current ,design499 #bg illustrations4 #f x #i1 cloth1 #aca pp ,net1 #b4jj 99,,garrard1 ,c4 ,c4 ,electric ,switch and ,controlling ,gear499 #dbc illustrations1 #e #c_/d x #h #c_/d1 cloth1 #fef pp ,net1 #f4jj 99,,gant1 ,l4 ,w4 ,elements of ,electric ,traction for ,motormen and ,others499 ,illustrated with ,diagrams4 #hvo41 cloth1 #bag pp ,net1 #b4jj 99,,gear1 ,h4 ,b4 and ,,williams1 ,p4 ,f4 ,electric ,central ,station ,distribution ,systems4 ,their ,design and ,construction499 ,second ,edition1 revised and enlarged4 #ahg illustrations4 #e #a_/b x #g #a_/b1 cloth1 #dee pp ,net1 #c4ej 99,,gerhardi1 ,c4 ,h4 ,w4 ,electricity ,meters2 their ,construction and ,management499 ,a practical manual for engineers and students4 ,illustrated4 #hvo41 cloth1 #ccg pp ,net1 #d4jj 99,,goldsmith1 ,,rudolf4 ,the ,alternating ,current ,commutator ,motor4 ,the ,leakage of ,induction ,motors499 ,in one volume4 #bdg illustrations4 #e #a_/d x #h #c_/d1 cloth ,net1 #c4jj 99,,gore1 ,,george4 ,the ,art of ,electrolytic ,separation of ,metals 7,theoretical and ,practical7499 ,illustrated4 #hvo41 cloth1 #bie pp ,net #c4ej 99,,groth1 ,l4 ,a4 ,welding and ,cutting ,metals by ,aid of ,gases or ,electricity499 #abd illustrations4 #h vo41 cloth1 #bhj pp4 7,van ,nostrand's ,westminister ,series7 ,net1 #b4jj 99,,haller1 ,g4 ,f4 and ,,cunningham1 ,e4 ,t4 ,the ,tesla ,high ,frequency ,coil2 its construction and uses499 #abmo41 cloth1 #ef illustrations1 #acj pp ,net1 #a4be 99,,haskins1 ,c4 ,h4 ,the ,galvanometer and its ,uses4 ,a ,manual for ,electricians and ,students499 ,fifth ,edition1 revised4 ,illustrated4 #afmo41 morocco1 #ge pp #a4ej 99,,hausmann1 ,e4 ,telegraph ,engineering4 ,a ,manual for ,practicing ,telegraph1 ,engineers and ,engineering ,students499 #aib ,illustrations4 cloth1 #daf pp ,net1 #c4jj 99,,hay1 ,,alfred4 ,an ,introductory ,course of ,continuous-,current ,engineering499 ,illustrated4 #hvo41 cloth1 #cbg pp ,net1 #b4ej 99,,hayes1 ,h4 ,v4 ,public ,utilities1 ,their ,cost ,new and ,depreciation499 #e #c_/d x #h #a_/b1 cloth1 #bge pp ,net1 #b4jj - 99,public ,utilities2 ,their ,fair ,present ,value and ,return499 #e #a_/b x #h #a_/b1 cloth1 #bjj pp ,net1 #b4jj 99,,heather1 ,h4 ,j4 ,electrical ,engineering for ,mechanical and ,mining ,engineers499 #ahc illustrations4 #e x #h1 cloth1 #cdd pp ,net1 #c4ej 99,,heaviside1 ,o4 ,electromagnetic ,theory4 ,two ,volumes with ,many ,diagrams499 #hvo41 cloth1 #ajjf pp4 ,each ,vol ,net1 #e4jj 99,vol4 ,,iii499 #ebi pp ,net1 #g4ej 99,,hobart1 ,h4 ,m4 ,heavy ,electrical ,engineering499 ,illustrated4 #hvo41 cloth1 #cch pp ,net1 #d4ej - 99,design of ,static ,transformers499 #aja illustrations4 #f x #i1 cloth1 #ahi pp ,net1 #b4jj - 99,electricity4 ,a text-book designed in particular for engineering students499 #aae illustrations4 #dc tables4 #hvo44 cloth1 #bff pp1 ,net1 #b4jj - 99,electric ,trains499 #hh illustrations4 #hvo41 cloth1 #bbj pp ,net1 #b4ej - 99,electric ,propulsion of ,ships499 #dd illustrations4 #hvo41 cloth1 #afg pp4 ,net1 #b4jj 99,,hobbs1 ,w4 ,r4 ,p4 ,the ,arithmetic of ,electrical ,measurements499 ,with numerous examples1 fully worked4 ,sixteenth ,edition1 revised and edited with six additional chapters by ,a4 ,r4 ,palmer4 #abmo4 cloth1 #abf pp #ej cents4 99,,houstoun1 ,r4 ,a4 ,studies in ,light ,production499 #bb illustrations4 #e #c_/d x #h #c_/d1 cloth1 #abj pp ,net1 #b4jj 99,,hutchinson1 ,r4 ,w41 ,jr4 ,long-,distance ,electric ,power ,transmission399 ,being a ,treatise on the ,hydro-,electric ,generation of ,energy2 ,its ,transformation1 ,transmission1 and ,distribution4 ,second ,edition4 ,illustrated4 #abmo41 cloth1 #cej pp ,net1 #c4jj - 99and ,,thomas1 ,w4 ,d4 ,electricity in ,mining499 ,being a theoretical and practical treatise on the construction1 operation and maintenance of electrical mining machinery4 #abmo41 cloth ,in ,press 99,,incandescent ,,electric ,,lighting499 ,a ,practical ,description of the ,edison ,system1 by ,h4 ,latimer4 ,to which is added3 ,the ,design and ,operation of ,incandescent ,stations1 by ,c4 ,j4 ,field2 ,a ,description of the ,edison ,electrolyte ,meter1 by ,a4 ,e4 ,kennelly2 and a ,paper on the ,maximum ,efficiency of ,incandescent ,lamps1 by ,t4 ,w4 ,howell4 ,fifth ,edition4 ,illustrated4 #afmo41 cloth1 #adj pp4 7,no4 #eg ,van ,nostrand's ,science ,series47 #ej cents 99,,induction ,,coils3 ,how ,made and ,how ,used499 ,eleventh ,edition4 ,illustrated4 #afmo41 cloth1 #abc pp4 7,no4 #ec ,van ,nostrand's ,science ,series47 #ej cents 99,,jehl1 ,,francis4 ,the ,manufacture of ,carbons for ,electric ,lighting and other purposes499 ,illustrated with numerous ,diagrams1 ,tables1 and ,folding ,plates4 #hvo41 cloth1 #bcb pp ,net1 #d4jj 99,,johnson1 ,j4 ,h4 ,arc 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99,,koester1 ,f4 ,hydroelectric ,developments and ,engineering499 ,a practical and theoretical treatise on the development1 design1 construction1 equipment and operation of hydroelectric transmission plants4 ,second ,edition4 #ejj illustrations4 #dto41 cloth1 #dge pp4 ,net1 #e4jj - 99,steam-,electric ,power ,plants499 ,a practical treatise on the design of central light and power stations and their economical construction and operation4 ,second ,edition4 ,fully ,illustrated4 #dto41 cloth #dee pp ,net1 #e4jj 99,,lancaster1 ,m4 ,electric ,cooking1 ,heating and ,cleaning499 ,edited by ,w4 ,e4 ,lancaster1 ,american ,edition by ,s4 ,l4 ,coles1 #cje illustrations1 #f x #h #a_/b1 cloth #cdj pp ,net1 #a4jj 99,,larner1 ,e4 ,t4 ,the ,principles of ,alternating ,currents for ,students of ,electrical ,engineering499 ,illustrated with ,diagrams4 #abmo41 cloth1 #add pp ,net1 #a4be 99,,lemstrom1 ,s4 ,electricity in ,agriculture and ,horticulture499 ,illustrated4 #hvo41 cloth ,net1 #a4ej 99,,livermore1 ,v4 ,p41 and ,,williams1 ,j4 ,how to ,become a ,competent ,motorman399 ,being a practical treatise on the proper method of operating a street-railway motor-car2 also giving details how to overcome certain defects4 ,second ,edition4 ,illustrated4 #afmo41 cloth1 #bdg pp ,net1 #a4jj 99,,livingstone1 ,r4 ,mechanical ,design and ,construction of ,generators499 #abb illustrations4 #e #a_/b x #h #c_/d1 cloth1 #bbh pp ,net1 #c4ej - 99,mechanical ,design and ,construction of ,commutators499 #fb illustrations1 #e #a_/b x #h #c_/d1 cloth1 #ic pp ,net1 #b4be 99,,lockwood1 ,t4 ,d4 ,electricity1 ,magnetism1 and ,electro-,telegraphy499 ,a ,practical ,guide and ,handbook of ,general ,information for ,electrical ,students1 ,operators1 and ,inspectors4 ,fourth ,edition4 ,illustrated4 #hvo41 cloth1 #cgd pp #b4ej 99,,lodge1 ,,oliver ,j4 ,signalling ,across ,space ,without ,wires399 ,being a description of the work of ,hertz and his successors4 ,third ,edition ,illustrated4 #hvo41 cloth 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cloth1 #bbi pp ,net1 #b4jj - 99,lessons in ,telegraphy499 ,illustrated4 #abmo41 cloth1 #ajd pp ,net1 #a4jj 99,,sewell1 ,t ,the ,construction of ,dynamos 7,alternating and ,direct ,current7499 ,a ,text-book for students1 engineering contractors1 and electricians-in-charge4 ,illustrated4 #hvo41 cloth1 #caf pp #c4jj 99,,sheldon1 ,s41 and ,,hausmann1 ,e ,dynamo-,electric ,machinery3 ,its ,construction1 ,design1 and ,operation499 99,vol4#a43 ,direct-,current ,machines499 ,ninth ,edition1 completely re-written4 ,illustrated4 #abmo41 cloth1 #bha pp ,net1 #b4ej 99,vol4 ,,ii43 ,alternating-,current ,machines399 ,tenth ,edition1 rewritten4 cloth1 #cec pp ,net1 #b4ej - 99,electric ,traction and ,transmission ,engineering99 #abg illustration4 #abmo41 cloth1 #cag pp ,net1 #b4ej 99,,sloane1 ,t4 ,o',,conor4 ,elementary ,electrical ,calculations499 ,a ,manual of ,simple ,engineering ,mathematics1 covering the whole field of ,direct ,current ,calculations1 the basis of ,alternating ,current 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7,van ,nostrand's ,westminster ,series47 ,net1 #b4jj 99,,swinburne1 ,,jas41 and ,,wordingham1 ,c4 ,h4 ,the ,measurement of ,electric ,currents4 ,electrical ,measuring ,instruments4 ,meters for ,electrical ,energy499 ,edited1 with ,preface1 by ,t4 ,commerford ,martin4 ,folding ,plate and ,numerous ,illustrations4 #afmo41 cloth1 #bda pp4 7,no4 #aji ,van ,nostrand's ,science ,series47 #ej cents 99,,swoope1 ,c4 ,,walton4 ,lessons in ,practical ,electricity3 ,principle ,experiments1 and ,arithmetical ,problems4 ,an ,elementary ,textbook499 ,with numerous ,tables1 ,formulae1 and two large ,instruction ,plates4 ,fifteenth ,edition1 revised4 ,illustrated4 #evo41 cloth1 #dfb pp ,net1 #b4jj 99,,thiess1 ,j4 ,b4 and ,,joy1 ,g4 ,a4 ,toll ,telephone ,practice499 #bgc illustrations4 #hvo41 cloth1 #dcc pp ,net1 #c4ej 99,,thom1 ,c41 and ,,jones1 ,w4 ,h4 ,telegraphic ,connections1 embracing recent methods in ,quadruplex ,telegraphy499 #bj ,colored ,plates4 #hvo41 cloth1 #ei pp #a4ej 99,,thompson1 ,s4 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,testing of ,insulated ,wires and ,cables99 ,sixth ,edition4 ,illustrated4 #abmo41 cloth41 #aahpp #a4jj 99,,wilkinson1 ,h4 ,d4 ,submarine ,cable-,laying1 ,repairing1 and ,testing499 ,second ,edition1 completely revised4 #cac illustrations4 #hvo41 cloth1 #ehj pp ,net1 #f4jj 99,,wilson1 ,j4 ,f4 ,essentials of ,electrical ,engineering499 #cjj illustrations4 #f x #i1 cloth1 #cee pp ,net1 #b4ej 99,,wright1 ,j4 ,testing1 ,fault ,localization and ,general ,hints for ,linemen499 #ai ,illustrations4 #afmo41 cloth1 #hh pp4 7,installation ,serious ,manuals47 ,net1 #ej cents4 99,,young1 ,j4 ,,elton4 ,electrical ,testing for ,telegraph ,engineers499 ,illustrated4 #hvo41 cloth1 #bfd pp ,net1 #d4jj 99,,zeidler1 ,j41 and ,,lustgarten1 ,j4 ,electric ,arc ,lamps3 ,their ,principles1 ,construction and ,working499 #afj ,illustrations4 #hvo41 cloth1 #ahh pp ,net1 #b4jj ,a #if page ,catalog of ,books on ,electricity1 classified by subjects1 will be furnished gratis1 postage prepaid1 on application4 ,d4 ,,van ,,nostrand ,,company are prepared to supply1 either from their complete stock or at short notice1 ,any ,technical or ,scientific ,book ,in addition to publishing a very large and varied number of ,,scientific ,,and ,,engineering ,,books1 ,d4 ,van ,nostrand ,company have on hand the largest assortment in the ,united ,states of such books issued by ,american and foreign publishers4 ,all inquiries are cheerfully and carefully answered and complete catalogs sent free on request4 #be ,,park ,,place - - ,,new ,,york