,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 ,i have included the ads for other books found in the back pages of these scans4 ,,lessons ,,in ,,wireless ,,telegraphy ,a ,,systematic ,,elementary ,,course ,,in ,,the ,,principles ,,of ,,wireless ,,telegraphy ,,and ,,the ,,electrical ,,laws ,,upon ,,which ,,it ,,depends ,,by 99,a4 ,p4 ,morgan99 ,,third ,,edition1 ,revised and ,enlarged ,,published ,,by ,,cole ,,morgan ,publishers of ,the ,arts and ,sciences ,series ,p4 ,o4 ,box #adgc ,,new ,,york ,,city ,printed in ,u4,s4 ,a4 ,,copyright #aiab4 #aiag ,,by ,,cole ,,morgan ,,lessons ,,in ,,wireless ,,telegraphy ,,introduction ,this little book has been brought forward in order to supply the demand for a systematic elementary course in the principles of wireless telegraph apparatus and the electrical laws upon which it depends4 ,many operators1 both amateur and professional1 although perfectly well able to send and receive messages1 do not thoroughly understand the rudimentary theory of the instruments4 ,it is readily realizable that it is quite impossible to enter into all the engineering details in a book of this size1 but at the same time it has been possible to present a very comprehensive treatise of the subject and embody sufficient material to give a thorough grounding in the subject4 ,in order to avoid repetition and confusion and to make each instrument or principle which has been discussed stand distinctly by itself1 the text has been divided into separate lessons following in their arrangement1 as far as has been possible1 the logical sequence4 ,for the same reason1 and also because of lack of space all details pertaining to the actual maintenance and adjustment of the instruments has been embodied in another book called ,the ,operation of ,wireless ,telegraph ,apparatus4 ,,lesson ,,one4 ,,magnetism4 99,natural ,magnets4 ,artificial ,magnets4 ,magnetic ,field of ,force499 ,it was known to the ancients that certain hard1 black stones1 an iron ore consisting of iron and oxygen found notably at ,magnesia in ,asia ,minor1 possessed the power of attracting small pieces of iron or steel4 ,this almost magic attribute of the stone was early turned to account in navigation and secured for it the name of ,lodestone 7leading-stone7 because of its remarkable property of pointing north and south when suspended by a thread4 ,the name of magnet 7magnes lapis7 was also given to these stones4 ,magnetism is the peculiar property occassionally possessed by certain bodies 7more especially by iron and steel7 whereby they attract or repel one another4 ,if a piece of hard iron or steel be rubbed with a lodestone it will be found to have also acquired the properties of the stone4 ,if hung up by a thread it will point north and south1 will attract light bits of iron and if dipped into iron filings will cause the latter to cling in two small tufts near the ends with few1 if any1 near the middle4 ,illustration3 ,,fig4 #a4 ,lodestone which has been ,dipped in ,filings to show ,poles ,this indicates that the attractive power of the magnet is concentrated in two opposite parts4 ,these parts are called the ,poles4 ,the line joining the poles is the ,magnetic ,axis4 ,artificial ,magnets are those made from steel by the aid of a lodestone or some other magnetising force4 ,the principal forms of artificial magnets are the ,bar and ,horseshoe1 so called from their shape4 ,illustration3 ,,fig4 #b4 ,bar and ,horseshoe ,magnet4 ,if a magnet 7either artificial or natural7 is suspended by a thread so that it may swing freely1 and a second magnet held in the hand is presented successively to the two poles of the first1 it will be observed that one pole is attracted and swings toward the magnet held in the hand1 but that the other is repelled and swings away4 ,illustration3 ,,fig4 #c4 ,lodestone suspended from thread so as to point ,north and ,south4 ,furthermore1 if the poles of the suspended magnet are marked so as to easily be identified it will be found that it is always the same pole that swings towards the north4 ,there would therefore appear to be two kinds of magnetism or at least two kinds of magnetic poles4 ,the end swinging toward the north is termed the north seeking pole and the opposite end called the south seeking pole4 ,in common parlance they are simply termed the ,north and ,south poles4 ,it is usual to mark the ,north ,pole with the letter ,n4 ,there is no known insulator of magnetism3 it passes through everything4 ,a magnetic substance is one which offers little resistance to the field of force4 ,magnetism flows along certain lines called ,lines of ,magnetic ,force4 ,these lines always form closed paths or circuits4 ,the region in the neighborhood of a magnet through which these lines pass is called the ,field of ,force and the path through which they flow is called the ,magnetic ,circuit4 ,illustration3 ,,fig4 #d4 ,lines of ,force around a ,bar ,magnet4 ,the paths of the lines of force can be demonstrated by placing a piece of paper over a bar magnet and then sprinkling iron filings over the paper which should be jarred slightly in order that the filings may be drawn into the magnetic paths4 ,the filings arrange themselves in curved lines1 diverging from one pole of the magnet and meeting again at the opposite end4 ,the lines of force are considered as extending outward from the ,north pole of the magnet1 curving around through the air to the ,south pole and completing the circuit back through the magnet4 ,the phenomena of magnetism and its laws form a very important branch of the study of electricity1 for they play a part in the construction and operation of almost all electrical apparatus4 ,,lesson ,,two4 ,,magnetic ,,induction4 ,in #ahca ,michael ,faraday1 the great physicist1 made the valuable discovery that electric currents are induced in a closed circuit by moving a magnet near it or vice versa1 by moving the circuit across the field of force1 ,if a coil of insulated wire be connected in circuit with a sufficiently delicate galvanometer 7a galvanometer is an instrument for detecting feeble electric currents7 and a bar magnet suddenly plunged into the hollow of the coil as shown in the illustration1 a momentary current will be indicated as flowing through the galvanometer while the magnet is being moved in the coil4 ,if the magnet is then rapidly pulled out of the coil another momentary current will be observed to flow in the opposite direction from the former4 ,illustration3 ,,fig4 #e4 ,magnetic ,induction4 ,so long as the magnet lies motionless in the coil it induces no currents4 ,the field of force in the neighborhood of a magnet grows weaker as the distance from the magnet increases4 ,when the magnet is plunged into the coil1 the strength of the magnetic field in the vicinity of the coil grows stronger due to the approach of the magnet1 and when it is withdrawn the field becomes weaker4 ,currents are only induced in the coil when the magnet is moving1 or in other words when the strength of the magnetic field is changing1 either increasing or decreasing4 ,the currents generated in the coil are called induced currents4 ,the action of the magnetic field in producing induced currents is termed ,induction4 ,,lesson ,,three4 ,,primary ,,cells4 ,,secondary ,,cells4 ,if a piece of zinc is dipped in dilute sulphuric acid1 the zinc will be attacked by the acid and replace hydrogen in it1 the hydrogen appearing as bubbles on the zinc and passing off as a gas4 ,illustration3 ,,fig4 #f4 ,simple ,voltaic ,cell ,if the zinc is connected by means of a wire1 ,w1 with a strip of copper1 ,c1 dipping in the same solution1 the zinc will still to continue to dissolve but the hydrogen bubbles will now form on the surface of the copper strip as well as on the zinc4 ,it will be found that the wire ,w becomes heated4 ,if the copper and zinc are connected to a galvanometer it will show the presence of an electric current passing through the circuit4 ,the cell may be considered as a sort of chemical furnace in which fuel is burned to drive the current4 ,the zinc is the fuel4 ,the copper is merely present to pick up the current and takes no part chemically4 ,if a number of such simple cells are properly united1 the zinc of one being joined to the copper of the next and so on1 a battery is formed4 ,the current flows from the copper1 called the positive pole1 through the wires 7when they are joined7 to the zinc or negative pole and back to the copper through the solution4 ,the electricity generated by the cells exerts a certain pressure or tendency to pass through the wires4 ,this tendency is called the potential4 ,the potential is measured in volts4 ,the potential 7also called the electromotive force7 in the case of the ,voltaic ,cell just described is #a4jg volts4 ,if the copper strip is replaced with one of graphite or carbon1 the voltage will rise to #a4gc volts4 ,after a cell has been in action for a short time1 the positive plate 7copper or carbon1 as the case may be7 becomes covered with a film of hydrogen4 ,the cell is then said to be polarized4 ,the film of gas bubbles partially shields the plate from contact with the liquid4 ,when the plate becomes in this condition1 the current is much feebler than when it is clear4 ,the most effective way of removing the hydrogen is to add some chemical to the sulphuric acid solution which will combine chemically with the hydrogen as soon as it appears4 ,the usual substance is bichromate of potash4 ,the voltage of the battery will rise to #b4b volts and the polarization be stopped when bichromate of potash is added4 ,the bichromate of potash enters into chemical action with the sulphuric acid and forms chromic acid4 ,such cells are usually termed chromic acid cells4 ,one of the principal disadvantages of a cell such as that just described lies in the fact that the zinc is continuously consumed whether the cell is in action or not and in order to prevent its rapid waste must be lifted out of the solution and washed each time after using4 ,various methods have been devised for overcoming this objection1 the most prominent of the resulting cells being known as the ,fuller1 ,gordon and ,edison-,lalande ,cells4 ,illustration3 ,,fig4 #g4 ,edison ,cell4 ,the liquid excitant of the ,gordon and ,edison-,lalande cells is a strong solution of sodium hydroxide4 ,the positive pole of these cells is a block of compressed copper oxide and the negative a pair of zinc plates4 ,in the ,gordon cell the positive is enclosed in a porous chamber4 ,illustration3 ,,fig4 #h4 ,dry ,cell4 ,one of the best known forms of cell is the dry cell4 ,it consists of an outer shell of zinc forming the negative electrode and a central rod of carbon as the positive4 ,the active agent of the cell is a paste composed principally of sal ammoniac lining the interior of the zinc shell4 ,the depolarizing agent of the cell is manganese dioxide mixed with crushed carbon and packed tightly around the carbon rod4 ,the cell is not as its name implies perfectly dry inside1 but the chemicals are in paste form4 ,the cell is sealed at the top by a bituminous compound making the cell air tight and portable4 ,dry cells are only successful for intermittent work1 that is1 where they are not required to deliver a heavy current continuously4 ,they deteriorate after long standing because the moisture evaporates4 ,dry cells1 however1 are a very convenient source of current where the demand is not too great and portability is desired4 ,the cells so far described are all of the type known as primary cells4 99,,secondary ,,cells499 ,the storage cell or secondary cell is made up of plates of lead1 or an alloy of lead1 cast in the form of a grid or framework of bars4 ,the spaces formed in the plate by the little bars are filled with a paste of lead oxide4 ,the paste for the positive plates are made of red lead while litharge is used for the negatives4 ,illustration3 ,,fig4 #i4 ,a ,storage ,battery ,grid4 ,the positive and negative plates are placed alternately in a bundle with a wooden or rubber separator between1 there always being one more negative plate than positive4 ,the negative plates are all connected in parallel at one end of the cell by means of lead connecting strips4 ,the positive plates are connected at the other end4 ,the plates are placed in a jar1 usually glass or hard rubber1 and covered with a dilute sulphuric acid solution4 ,the storage cell is then connected to a dynamo1 the positive pole of the cell being connected to the positive pole of the dynamo and the current allowed to flow through until the plates are formed1 that is to say1 until the paste in the positive changes to peroxide of lead and that in the negative to spongy lead4 ,when the cell is disconnected it will give out a current of its own lasting until it becomes discharged4 ,the charging and discharging must be repeated several times before the cell really becomes efficient4 ,illustration3 ,,fig4 #aj4 ,storage ,cells4 ,what is effected in the storage cell is really the storage of chemical energy and not the storage of electricity1 for1 properly speaking1 the energy is put into the form of chemical affinity and there is in reality no more electricity actually in the cell at the end of a charge than there is when the cell is discharged4 ,the storage battery is the most convenient means of absorbing electrical energy at one time or place and using it at another time or place4 ,storage cells are very often employed in wireless stations for emergency purposes so that in case the dynamo supplying current fails the station will not be thrown out of operation4 ,the voltage of a storage cell is about two volts4 ,,lesson ,,four4 ,,electric ,,currents4 99,the ,units of ,measurement4 ,direct and ,alternating ,currents4 ,ohm's ,law499 ,electric ,currents may be divided into two classes known as direct and alternating current4 ,either one may be measured or qualified by two electrical units called the ,ampere and the ,volt4 ,the volt may be explained by likening it to the unit of pressure of the current1 while the ampere measures the unit rate of current flow4 ,for example1 in the case of water the voltage corresponds to the pressure in pounds while the amperage would indicate the rate of water flowing4 ,illustration3 ,,fig4 #aa4 ,hydraulic ,analogy between ,voltage and ,amperage4 ,the accompanying sketches show graphically the analogy between the voltage and amperage of an electric current and the pressure and volume of a stream of water4 ,in the first illustration a tank is shown at a high elevation from which a small pipe leads4 ,the voltage or pressure in such a pipe would be high in comparison with that in a pipe leading from a lower tank4 ,in the second illustration the pipe leading from the tank is much larger than that from the first and consequently the amperage or volume flowing is greater in comparison4 ,from this it may be readily seen that every circuit through which a current is flowing must exhibit both quantities4 ,the unit of electrical work or energy is the ,watt4 ,seven hundred and forty-six watts constitute an electrical horse-power4 ,the number of watts is indicated by the voltage times the amperage4 ,thus the amount of energy in a circuit in which #ej amperes at #ajj volts pressure are passing is #ej x #ajj or #e1jjj watts4 ,the ,couloumb represents the quantity of electricity flowing in a circuit-where the rate of flow is one ampere per second4 ,in order to properly indicate comparative amounts of energy the element of time must also be taken into consideration4 ,one watt passing for one hour is a watt-hour4 ,seven hundred and forty-six watts passing for one hour or one watt passing for seven hundred and forty-six hours is a horse-power hour4 ,the instruments used for measuring the amperage and voltage of a circuit are called respectively the ammeter and the voltmeter4 ,that used for registering watt-hours is called the integrating watt-meter4 ,illustration3 ,,fig4 #ab4 ,diagram ,showing ,alternating and ,direct ,current4 ,direct current is current that passes or flows in one direction only4 ,the current of all primary and secondary cells and of certain forms of dynamos is direct4 ,alternating current is current that repeatedly reverses its direction of flow4 ,a direct current may be represented by a straight line4 ,an alternating current is shown by a wavy line crossing and recrossing a straight line4 ,the current gradually rises from zero to a maximum and then dies away4 ,it does not stop at this point however1 but starts to rise again1 this time flowing in a reverse direction4 ,after reaching a maximum it dies away again and the cycle is repeated4 ,from a to c represents a cycle and from a to b an alternation4 ,alternating currents usually have a frequency of #cj1 #fj or #abj cycles per second4 ,sixty is the most common frequency4 ,many wireless telegraph stations now employ currents having a frequency of #ejj cycles4 99,ohm's ,law499 ,mention has been made above of certain electrical magnitudes1 namely1 voltage or electromotive force and amperage or strength of current4 ,these bear an important relation in determining a property of an electric circuit called resistance4 ,no conducting body possesses perfect electrical conductivity1 but presents a certain amount of obstruction or resistance to the passage of electricity4 ,the practical unit of resistance is the ,ohm4 ,it is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice1 #ad4deba grams in mass1 of a constant cross sectional area and of the length of #ajf4c centimetres4 ,the resistance of a conductor is proportional to its length1 that is1 provided two conductors are made of the same material and of the same diameter and one is twice as long as the other1 the resistance of the longer will be twice that of the shorter conductor4 ,the resistance is inversely proportional to the cross sectional area1 which is to say that a conductor of smaller cross section has a greater resistance than one of larger section4 ,the laws of resistance are conveniently expressed by the following formula called ,ohm's ,law4 ,c ,e_/,r where ,eelectromotive force in volts4 ,ccurrent in amperes4 ,rresistance in ohms4 ,if two factors are known1 the third can be found by substitution4 ,,lesson ,,five4 ,,electromagnetism4 99,the ,electromagnet4 ,the ,solenoid499 ,if a current of electricity is passed through a copper wire1 the wire will attract to itself iron filings1 etc41 as long as the current continues to flow4 ,there is then a magnetic field around the wire4 ,as soon as the current is shut off the filings drop away because the field immediately disappears with the cessation of the current4 ,illustration3 ,,fig4 #ac4 ,magnetic ,phantom about a ,wire ,carrying ,current4 ,the lines of force flow around the wire in a circle4 ,the circular lines of the field of force surrounding a straight wire may be shown by passing a wire vertically through a hole in the centre of a horizontal card4 ,iron filings are sifted over the card and a strong current passed through the wire4 ,on tapping the card gently1 the filings near the wire set themselves in concentric circles round it4 ,the creation of a magnetic field by a conductor in its own neighborhood when carrying a current of electricity is one of the most important phenomena of electrical science4 ,electrical energy must be expended in producing a magnetic field4 ,when a current of electricity is turned on in a wire the magnetic field grows around the wire1 some of the energy of the current being used for the building process4 ,this reactive effect of the surrounding magnetic field is one reason why electric currents do not instantly rise to their full value4 ,illustration3 ,,fig4 #ad4 ,diagram showing how ,lines of ,force ,form about a ,loop of ,wire4 ,if a wire is connected to a battery or some other source of electric current and a portion of the circuit twisted so as to form a loop1 the entire space enclosed by the loop will be a magnetic field and possess magnetic properties4 ,by forming a wire into a spiral coil the combined effect of each individual turn is concentrated in a small space and a powerful field of force is produced4 ,if the coil is provided with an iron core1 the lines of force can be concentrated and will exercise a very powerful attractive effect upon any neighboring masses of iron or steel4 ,such a coil is called an electromagnet4 ,a hollow coil without any core is called a solenoid4 ,illustration3 ,,fig4 #ae4 ,magnetic ,phantom about a ,coil of ,wire4 ,solenoids and electromagnets play a very important part in the construction of most electrical instruments4 ,the strength of an electromagnetic coil is proportional to its ampere turns4 ,the ampere turns of a coil are obtained by multiplying the number of amperes flowing through the coil by the number of turns of wire composing it4 ,,lesson ,,six4 ,,dynamo ,,electric ,,machinery4 99,the ,dynamo4 ,the ,alternator4 ,the ,motor499 ,the discovery of the induction of currents in wires by moving them across a magnetic field led to the construction of electrical machines1 called dynamos1 to generate current in place of batteries4 ,the dynamo is perhaps the most important piece of electrical apparatus there is for it is the source of ninety-nine percent of all the electricity now in use4 ,it is practically necessary in any case where a considerable quantity of electricity is used to have a dynamo on the spot or else bring the currents over a wire from some supply station where dynamos are kept running4 ,the operation of a dynamo is dependent upon current induction4 ,it contains a system of closed conductors revolving in a magnetic field in such a way as to continuously vary the number of lines of force threading among them4 ,illustration3 ,,fig4 #af4 ,diagram showing the principle of the ,dynamo4 ,the illustration show's the ideal simple dynamo1 which consists of a loop of wire arranged to revolve between the poles of a permanent magnet in the direction of the arrow and around a horizontal line as an axis4 ,the lines of magnetic force 7represented by the fine straight lines7 pass across from ,n to ,s as indicated4 ,when in the position shown1 the coil of wire encloses the largest possible number of lines of magnetic force4 ,when it has revolved ninety degrees or a quarter of a turn as shown by the dotted lines1 the lines of force will be parallel to the plane of the coil and none will pass through4 ,during this quarter of the turn the number of lines of force has been decreasing4 ,during the next quarter of a turn the lines will increase again1 but will this time pass through from the opposite side of the loop4 ,this decrease and increase of the number of lines of force passing through the loop generates therein a current of electricity4 ,the same process is repeated during the next half of a revolution4 ,however1 since the lines of force flow through from opposite sides of the coil every half revolution1 the current reverses twice during the same period4 ,in the illustration the loop is represented as forming a complete closed circuit in itself4 ,in order to draw any current for external use some method of establishing connection to the terminals of the coil must be had4 ,this is furnished by two circular rings called collector rings4 ,the little strips of metal or carbon employed to form contact with the rings are called brushes4 ,illustration3 ,,fig4 #ag4 ,simple ,alternator4 ,such a machine1 so equipped will deliver alternating currents and illustrates the principle of the alternating current dynamo or alternator4 ,with the aid of a device called a commutator and consisting of a ring split in sections as shown in the illustration1 all the successive current impulses may be turned in the same direction and the current made direct4 ,in practice many coils of wire wound around an iron core called the armature1 the purpose of which is to concentrate the magnetic lines of force1 are made to revolve in a powerful field between the poles of adjacent electromagnets4 ,electromagnets are used because they are capable of producing a stronger magnetic field than magnetized bars of steel4 ,the electromagnets used for this purpose are called field magnets4 ,the central iron portion upon which the revolving coils are wound1 called the armature1 is usually built up of a number of thin sheets of soft steel called armature disks or laminations4 ,illustration3 ,,fig4 #ah4 ,simple ,dynamo showing ,commutator4 ,the modern armature is very complex4 ,a simple coil such as those shown in ,figs4 #ag and #ah will not yield a steady current for twice in each revolution the electromotive force dies away to zero4 ,the coils of large dynamos are grouped so that some of them are always active4 ,there are three general methods of supplying current to the held magnets of a dynamo1 known as the series1 shunt and compound windings4 ,the series dynamo is arranged so that the coils of the held magnets are in series with those of the armature4 ,in the shunt dynamo1 the coils of the held magnet form a shunt to the main circuit and being made of many turns of thin wire1 draw off only a small fraction of the whole current4 ,illustration3 ,,fig4 #ai4 ,diagram of ,dynamo ,field ,windings4 ,the compound dynamo is partly excited by shunt coils and partly by series coils4 ,illustration3 ,,fig4 #bj4 ,motor ,generator4 ,each variety of dynamo winding has a certain advantage depending upon the condition of use4 ,in the case of alternating current dynamos1 the field magnets are sometimes supplied from a separate dynamo called an exciter4 ,in other cases the dynamo is provided with two sets of windings1 one connected to a commutator producing a direct current which excites the field coils and the other connected to a set of rings and supplying the alternating current4 ,in case a supply of either direct or alternating current is available and it is desirable to change the supply from direct to alternating or vice versa1 it may be accomplished by employing a ,motor-,generator4 ,a motor-generator consists of an electric motor operating from the source of current supply on hand and driving a dynamo which supplies current of the kind desired4 ,a motor is exactly the reverse of a dynamo4 ,if a current of electricity is passed into a dynamo1 the armature will be dragged around by the mutual action of the currents flowing in the copper conductors and the magnetic field in which they lie4 ,such a device constitutes a motor and may be employed to do useful work4 ,motors are classified as alternating and direct current machines accordingly as they are built to operate on either kind of current4 ,,lesson ,,seven4 ,,the ,,induction ,,coil4 ,the ,induction ,coil is an apparatus for producing currents of a very high electromotive force4 ,it consists of a helix of large1 insulated wire surrounding an iron core1 and this again surrounded by a second coil consisting of many thousand turns of very fine wire carefully insulated4 ,the inner or primary coil is connected in series with a battery1 the circuit also including a device called an interrupter4 ,the object of the interrupter is to make and break the primary circuit in rapid succession4 ,every time the current is turned on in the primary circuit1 the primary coil creates a magnetic field which induces a current in the secondary in accordance with the laws of induction4 ,illustration3 ,,fig4 #ba4 ,diagram of ,induction ,coil4 ,likewise at every break in the circuit caused by the interrupter1 the lines of force disappear and a second current impulse is induced in the secondary coil4 ,as the number of lines of magnetic force created and destroyed at each make and break is the same1 the two electromotive impulses in the secondary are equal4 ,by adding a condenser1 however1 the current at make is caused to take a considerable fraction of time to grow1 while at break the cessation is instantaneous in comparison4 ,the rate of cutting of the lines of force is very much more rapid at break than at make therefore4 ,the currents at break manifest themselves as a brilliant torrent of sparks between the ends of the secondary wires when they are brought near enough together4 ,the central iron core around which the coils are wound is for the purpose of increasing or concentrating the number of lines of force that pass through the coils4 ,magnetic lines flow more easily through iron than through air and so prefer that path4 ,it is made up of a bundle of fine iron wires in order to avoid induced currents which would be set up in the iron were it a solid mass and so retard its rapidity of magnetization or demagnetization as to hamper the efficiency of the coil4 ,,lesson ,,eight4 ,,the ,,principle ,,of ,,the ,,transformer4 ,the transformer is a device for raising or lowering ,a the electromotive force of an alternating current4 ,in principle it consists of two insulated coils of wire called the primary and the secondary wound around an iron ring as shown in the illustration4 ,illustration3 ,,fig4 #bb4 ,diagram showing the principle of a ,transformer4 ,if the primary coil is connected to a source of alternating current it will rapidly magnetize and demagnetize the iron ring4 ,the magnetic lines thus created will pass through the secondary coils setting up induced currents4 ,the ratio of the electro-motive force of the induced current to that of the primary current is in direct proportion to the ratio of the number of turns in the two coils4 ,for example1 if the secondary contains twice as many turns as the primary1 its electro-motive force will be twice as great4 ,illustration3 ,,fig4 #bc4 ,open and ,closed ,core ,transformers4 ,transformers are of two general types1 the open core and the closed core4 ,closed core transformers are the most efficient4 ,the open core transformer is similar in construction to an induction coil1 the core being a straight bar1 while that of the closed core machine is usually in the form of a hollow square or rectangle4 ,in practice1 the cores of transformers are built up of laminations1 usually of thin1 soft sheet iron strips piled together and shaped so as to constitute a closed magnetic circuit of rectangular shape in order to avoid constructional difficulties incurred in making a ring4 ,,lesson ,,nine4 ,,the ,,leyden ,,jar ,,and ,,condenser4 ,the ,leyden ,jar1 called after the city of ,leyden1 ,holland1 where it was invented1 is a form of condenser consisting of a glass jar coated up to a certain height inside and out with tinfoil4 ,illustration3 ,,fig4 #bd4 ,leyden ,jar4 ,a ,leyden jar may be charged by holding the rod to the prime conductor of an electric machine1 the outer coating being held in the hand4 ,if a piece of wire connected to the outer coating is then brought near the rod a brilliant snapping spark will pass across the space4 ,any two conductors1 separated by an insulating medium termed the dielectric1 constitute a condenser and possesses the property of receiving and retaining an electric charge4 ,if a charged condenser or ,leyden jar is discharged slowly by allowing the electricity to pass through a high resistance conductor the flow of current increases in strength at first and then gradually dies away4 ,if1 however1 the condenser is discharged through a coil of wire of one or more turns1 the discharge consists of a number of excessively rapid oscillations or surgings4 ,the first rush of current serves to more than empty the condenser and charges it the opposite way1 then follows a reverse discharge1 which also oversteps itself and charges the condenser the same way as the first and so on1 each successive oscillation being weaker than the one before until the discharge dies away as in ,fig4 #cf4 ,the discharge of a condenser under such conditions consists of a number of successive sparks in reverse directions4 ,the ability of a condenser to receive and retain an electrical charge is termed the capacity and is measured by a unit called the farad4 ,the farad is so large a quantity1 however1 that it is never met in practise and for convenience the micro-farad which is one millionth of a farad has been adopted4 ,a condenser of one farad capacity is such as would be raised to a potential of one volt by a charge of one coulomb of electricity4 ,the capacity of the condenser is dependent upon the thickness and nature of the insulating medium or dielectric4 ,the quality of a dielectric which decides the capacity of a condenser in which it may be a part is called its specific inductive capacity4 ,the following table shows the relative specific inductive capacity of several materials1 air being the standard3 ,,table ,,of ,,specific ,,inductive ,,capacities4 ,substance4 ,constant4 ,air #a4jj ,paraffin #a4fh--b4dg ,petroleum #b4jb--b4ai ,gutta ,percha #c4jj ,hard ,rubber #b4bh ,mica #f4fd ,glass #f4gb--g4ch ,,lesson ,,ten4 ,,the ,,ether ,,and ,,the ,,electromagnetic ,,theory ,,of ,,light4 ,all space is filled with a weightless1 invisible medium called ,ether4 ,it is the substance with which the universe is filled1 it reaches to the stars and through the very earth itself4 ,it has been known for some time that light consists of vibrations or motions in the ether4 ,in #ahfg1 ,clerk ,maxwell offered the theory that these light waves are not merely mechanical motions of the ether1 but are electrical undulations4 ,according to this theory1 the phenomena of electro-magnetism and the phenomena of light are all due to certain modes of motion in the ether4 ,twenty years later1 ,heinrich ,hertz discovered convincing proofs of ,maxwell's theory and succeeded in producing electro-magnetic waves in such a manner that they possessed the same properties1 traveled at the same speed1 and were capable of being reflected1 refracted1 polarized1 etc4 ,illustration3 ,,fig4 #be4 ,hertzian ,oscillator and ,resonator4 ,hertz employed an apparatus consisting of two metallic balls connected by metal rods to two metal sheets4 ,the two balls were also connected to the secondary terminals of an induction coil4 ,this apparatus comprised the oscillator and served to create the electro-magnetic waves4 ,in order to detect the waves1 he employed a resonator consisting of a circle of wire having in it a minute spark gap capable of fine adjustment4 ,as soon as the coil is set in operation a spark snaps across the gap and sets up a temporary conducting path for the surgings that follow4 ,each spark sent by the coil across the gap consists of a dozen or so oscillations1 each lasting less than a millionth of a second4 ,then if the resonator is placed a few feet away from the oscillator and turned broadside on to the oscillator1 it will be found that small sparks jump across the gap4 ,hertz employed various arrangements for reflecting and polarizing the waves and definitely proved that their nature is the same as that of light4 ,,lesson ,,eleven4 ,,electric ,,waves4 ,when a ,leyden jar discharges under the conditions set forth in one of the previous lessons1 portions of the energy of the current or discharge are thrown off from the conductor and do not return to it1 but go traveling on in space4 ,if a current is sent through a circuit1 as the current increases1 the magnetic field also increases1 the magnetic lines enlarging and spreading outward from the conductor like the ripples on a pond4 ,if the current is decreased1 the magnetic lines all return back and close up upon the conductor1 the energy all being re-absorbed into the circuit4 ,if electrical oscillations of extreme rapidity such as those generated by a condenser discharge are substituted for a current slowly rising and falling1 part of the energy radiates off into the ether as electromagnetic waves and only a part returns back4 ,the discharge of a ,leyden jar or condenser only oscillates when the circuit contains a certain amount of capacity and inductance in proportion to the resistance of the circuit4 ,inductance is the property of a circuit by virtue of which lines of force are developed around it4 ,circuits containing a certain amount of inductance1 capacity and resistance tend to oscillate electrically at a certain frequency4 ,illustration3 ,,fig4 #bf4 ,electric ,waves4 ,the electromagnetic waves thrown off by the aerial system follow the contour of the earth and so may cross mountains or travel anywhere4 ,the waves emitted by the ordinary wireless station1 making use of an aerial and a ground are half waves terminating in the earth as shown in the illustration4 ,in passing over the earth they are accompanied by ground currents which waste a certain amount of their energy in overcoming ohmic resistance and so reduce the intensity of the waves4 ,for this reason propagation is always the best over water or moist earth whose resistance is low4 ,a further peculiar weakening of the waves due to the absorbtion taking place in the air during sunlight4 ,the difference between the signals in the day and their strength at night is very marked1 being much stronger in the later case4 ,,lesson ,,twelve4 ,,principles ,,of ,,wave ,,telegraphy4 ,wireless ,telegraphy as practiced to-day is merely a method of setting up electromagnetic waves in the ether and then detecting their existence at a distant point4 ,it may be divided into four distinct and individual 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 ,we have already learned how electrical oscillations may be generated by the discharge of a ,leyden jar or a condenser4 ,in order to perform the first two operations named above1 it is therefore merely necessary to arrange a condenser in such a way that it is most effective4 ,the induction coil or transformer is employed to charge the condenser because the currents of these instruments are much more powerful than those of a static electric machine4 ,the induction coil is connected to a set of batteries and a key so that the periods during which the current is on and off may be controlled at will by the pressure of the fingers4 ,illustration3 ,,fig4 #bg4 ,diagram of ,wireless ,transmitter4 ,the secondary of the coil is connected to a battery of ,leyden jars or a condenser4 ,the fact was mentioned above that a certain amount of inductance in the circuit is necessary for the production of electrical oscillations ,this is furnished1 or at least the greater part1 by a device called a helix which consists of a coil of heavy wire wound around a suitable framework4 ,the spark discharge takes place across a device called a spark gap4 ,when the key is pressed1 the high potential currents of the induction coil charge the ,leyden jar or condenser and cause it to discharge through the helix and across the spark gap4 ,high frequency oscillations are immediately created in this part of the circuit4 ,the spark gap1 condenser and that part of the helix included1 constitute the closed circuit4 ,the electromagnetic waves thrown off by such an oscillatory system would not be very far reaching in their effects because the disturbances would be confined to the immediate neighborhood of the apparatus1 so recourse is had to the aerial and ground4 ,the aerial consists of a network of wires elevated high in the air4 ,the ground or earth connection is simply a large metal plate buried in moist earth or thrown into the sea4 ,by connecting the aerial and ground to the helix in the manner shown in ,fig4 #bg1 the high frequency currents are caused to surge up and down the aerial system into the ground and create very powerful electromagnetic waves which possess the power of exciting electrical oscillations in another aerial even though it may be located many miles away4 ,the existence of these oscillations is made known to the receiving operator by a device known as a detector1 described fully in one of the following lessons4 ,,lesson ,,thirteen4 ,,the ,,aerial4 ,the aerial system or antenna might be termed the mouth and ear of the wireless station1 for it is this huge network of wires stretching high into the air that emits or intercepts the electromagnetic waves upon which such systems of communication depend4 ,illustration3 ,,fig4 #bh4 ,general ,types of ,aerials ,the value of an aerial is dependent upon its height above the surface of the earth4 ,the greater its height the wider will be the field of force or strain set up in its neighborhood and consequently more powerful electric waves will be developed4 ,proximity to all large conductors1 such as smokestacks1 telephone lines1 etc41 is always avoided because these obstacles would absorb appreciable amounts of the energy sent out from the station and also shield it somewhat from the incoming waves4 ,aerials are usually constructed of conductors made up of a number of wires stranded together4 ,high frequency currents only travel near the surface of conductors and stranded wires consequently offer less resistance because they possess more surface than a solid conductor of equal cross section4 ,the aerial is always carefully insulated by means of special high tension insulators1 made of insulating composition molded into a corrugated bar having iron rings embedded in each end to which the wires may be fastened4 ,aerials take many different forms1 but may be classified into two general groups called the vertical aerials and flat top aerials4 ,vertical aerials compose the grid1 fan1 cage and umbrella forms4 ,flat top aerials are known as the ,t1 inverted ,u1 ,l and ,v types1 according to their shape4 ,the ,pyramid ,aerial is only employed in ultra-powerful stations and is becoming an obsolete form4 ,the ,fan ,aerial is a good type of especial value in crowded quarters4 ,the ,grid ,aerial is probably the best form of vertical aerial1 but is gradually giving way to those of the flat top class4 ,the ,cage ,aerial is rarely used nowadays and may be considered obsolete4 ,the ,umbrella ,aerial is a very good type now being employed in many high power stations4 ,a metallic pole or mast insulated at the base used to support the wires1 so that it is part of the aerial itself4 ,the ,t ,aerial is the most nearly perfect and gives the best all around results4 ,the ,l or ,horizontal type of aerial is used wherever it is desirable for any reason to send the most powerful waves in one direction4 ,the ,v type is used where the highest point must be near the station4 ,the wire leading into the station1 from the aerial is called the rat-tail or lead-in4 ,it is always very carefully insulated and usually enters the station through a hole in the window or wall by means of a window pane bushing or leading-in insulator4 ,certain aerials possess a directive action1 that is they radiate and receive messages in some directions better than others4 ,flat top aerials possess this peculiarity more noticeably than the vertical types4 ,flat top aerials receive and radiate waves coming from and going towards a direction opposite to that in which the free end points4 ,illustration3 ,,fig4 #bi4 ,spiral ,aerial4 ,the free end is the opposite end to that to which the rat-tail is connected4 ,there are two free ends on a ,t aerial and so this form radiates and receives its waves equally well in two directions4 ,the inverted ,l and ,v types possess a very decided directive action4 ,certain aerial forms may be classed as loop and straightaway accordingly as they are connected and led into the station4 ,in the straightaway form of antenna1 the wires are connected together as a whole and one rat-tail led into the station4 ,in the loop form the wires are all connected together and divided into two sections4 ,two wires are led into the station4 ,the loop form gives slightly better results in a short aerial1 but in most cases the straight away is decidedly the most efficient4 ,,lesson ,,fourteen4 ,,the ,,wireless ,,coil4 ,the induction coil used for wireless telegraph purposes differs from the ordinary coil commonly employed in the laboratory in that it is usually built in a more substantial manner and gives a heavier1 more powerful discharge from the secondary4 ,induction coils of this type are usually enclosed in a strong wooden case filled with insulating compound and are sometimes termed box coils4 ,they are fitted with an interrupter arranged to give a very long period of make and a short break4 ,coils giving sparks greater than six inches in length are usually provided with an independent interrupter which may be one of several types4 ,illustration3 ,fig4 #cj4 ,wireless ,spark ,coil4 ,the ordinary independent interrupter consists of the usual form of interrupter1 but is operated by the magnetism of a separate electromagnet in place of that of the coil primary itself4 ,an independent interrupter of this type is usually provided with screws for adjusting the speed1 and the duration of make and break4 ,illustration3 ,,fig4 #ca4 ,independent ,interrupter4 ,the ,mercury ,turbine form of interrupter is a very unsuccessful type in which 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 into a mercury reservoir so that when the spiral is revolved1 the mercury rises in the tube by centrifugal action and is thrown out from the upper end in the form of a jet4 ,when the revolving jet strikes one of the metal teeth the circuit is made and when it passes between it is broken4 ,raising and lowering the saw teeth so that the mercury strikes either the lower or upper part varies the ratio of time of the make and break4 ,illustration3 ,,fig4 #cb4 ,electrolytic ,interrupter4 ,the electrolytic interrupter consists of a cathode or negative electrode of sheet lead immersed in diluted sulphuric acid and an anode composed of 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 portion of the wire is exposed to contact with the liquid4 ,when a strong electric current is passed through the acid electrolyte1 the current is very rapidly interrupted by the formation of gases on the small platinum electrode4 ,the number of breaks per second possible with an electrolytic interrupter is extremely high4 ,a potential of at least #dj volts is required to operate such an interrupter1 however4 ,,lesson ,,fifteen4 ,,the ,,high ,,potential ,,transformer4 ,the transformer1 like the induction coil1 steps up the voltage of the current to a value where it is sufficient to charge the condenser4 ,the transformer for wireless work should have a potential of from #ae1jjj to #dj1jjj volts4 ,several manufacturers claim advantage for low voltages and build machines having a potential of only about #h1jjj volts1 but experiments have shown that under most ordinary conditions higher voltages permit greater range of transmission4 ,both open and closed core machines may be used with good results4 ,probably1 however1 neither one is the best4 ,the core of a wireless transformer is built up of sheet iron laminations to reduce core losses and eddy currents4 ,illustration3 ,,fig4 #cc4 ,high ,potential ,closed ,core ,transformer4 ,illustration3 ,,fig4 #cd4 ,method of ,protection against ,kick-,back ,the secondary windings are very carefully insulated with empire cloth or paper and may or may not be immersed in oil accordingly as they are designed4 ,a transformer1 more especially than an induction coil1 produces a kick-back on the line4 ,kick-back is a high potential current caused by the counter action of currents in the condenser and aerial system1 due to the fact that they continue to surge after the current has dropped to zero or so low that it is unable of its own accord to produce secondary currents which will jump the spark gap4 ,kick-back destroys insulation and is liable to cause burnouts of other electrical instruments supplied from the same system4 ,it may be guarded against by providing the line with a protective device which consists of a condenser having a capacity of one or two micro-farads placed directly across the terminals of the transformer in series with two five-ampere fuses4 ,a small spark gap open about #a_/fd of an inch wide is connected across the terminals of the condenser4 ,in case special protection is desired for some instrument in the circuit1 such as a meter1 a protective device should be connected directly across its terminals4 ,,lesson ,,sixteen4 ,,the ,,oscillation ,,condenser4 ,the ,oscillation ,condenser might almost be termed the most important part of a wireless station4 ,transmitting ,condensers usually take the form of a battery of ,leyden jars arranged in a suitable case or container4 ,very often they are placed in a tank of oil to eliminate brush discharges or leakage which takes place from the edges of the tinfoil4 ,illustration3 ,,fig4 #ce4 ,plate ,condenser4 ,leyden jars are usually covered with very heavy tinfoil or thin sheet copper to prevent blistering4 ,the best method1 however1 is to deposit a metallic covering electrolytically4 ,the principle objection to ,leyden jars is their bulk4 ,glass plate condensers are not so bulky or expensive and do not blister4 ,plate condensers are sometimes merely placed in racks1 but more often in a tank of oil to eliminate all brush discharges4 ,condensers are always made so as to be adjustable in order that the capacity of the circuit may be carefully regulated4 ,only the finest selected glass of the greatest dielectric strength is used in making condensers1 in order to avoid all losses and possibility of breakdown4 ,whenever condensers must withstand a very heavy voltage1 they may be connected in series so that the voltage is divided between them and the strain is not so great4 ,this method reduces the capacity just one-half1 however1 and when used requires four times as many plates or jars1 as the case may be1 than if they were connected in one multiple set4 ,,lesson ,,seventeen4 ,,the ,,helix4 ,the ,helix supplies the greater part of the inductance to the closed circuit of the transmitter4 ,it also acts as a transformer1 serving to raise the voltage of the currents surging through the closed circuit and impress them upon the aerial system4 ,the turns of the helix included in the closed circuit constitute the primary of the transformer1 while those in the open circuit form the secondary4 ,a helix consists of a heavy conductor1 either brass or copper1 wrapped around a suitable frame of wood or hard rubber4 ,some forms consist of a spiral of copper ribbon clamped between two cross-shaped frames4 ,illustration3 ,,fig4 #cf4 ,helix4 ,helixes are of two kinds1 known as close or direct coupled and loose or inductively coupled4 ,in an inductively coupled transmitter the primary and secondary are wound upon separate frames and are not connected together4 ,the ,u4 ,s4 ,government ,radio regulations place a limit on the amount of damping permissable in a transmitter4 ,it has already been explained in one of the previous lessons how the oscillations or surgings of the spark discharge rapidly die away4 ,a spark which thus rapidly dies away is said to be rapidly damped4 ,the damping of a loose coupled transmitting set is never as great as that of a close coupled set4 ,illustration3 ,,fig4 #cg4 ,a ,damped ,oscillation4 ,illustration3 ,close-,coupled ,transmitter vs4 ,loose-,coupled ,transmitter ,for this reason the old style helixes are now practically obsolete and the loose or inductively coupled helix is the one most commonly used4 ,loose coupled helixes are also often termed oscillation transformers4 ,illustration3 ,,fig4 #ch4 ,an ,inductively ,coupled ,helix4 ,an ordinary transmitter tends to emit two sets of waves of different length4 ,by carefully adjusting the coupling1 pure trains of waves are formed by attracting the apices of the two sets of waves into one4 ,,lesson ,,eighteen4 ,,spark ,,gaps4 ,a ,spark ,gap is the medium across which the oscillatory discharge takes place4 ,it usually consists of two electrodes of zinc alloy1 nickel steel or brass1 suitably mounted on an insulating base and standards4 ,illustration3 ,,fig4 #ci4 ,spark ,gap4 ,the electrodes are usually provided with flanges or radiators which tend to dissipate the heat and keep them cool4 ,if the electrodes should become very hot the spark would arc1 that is1 pass across the gap without generating any electrical oscillations4 ,spark gap electrodes are usually flat or else hollow on the sparking surface4 ,the proper adjustment of the gap1 i4e41 the distance between the electrodes is a matter of the utmost importance for there is a point just where the maximum amount of energy will be radiated4 ,illustration3 ,,fig4 #dj4 ,quenched ,spark ,gap4 ,the ,quenched ,gap1 consists of a number of brass or copper disks placed in a pile1 each disk being separated from the other by a thin mica ring4 ,the distance between two adjacent disks is usually only about 4#ja inch4 ,the effect of the quenched gap is to considerably reduce the damping of the system and make it possible to send signals very great distances with the consumption of only comparatively small amounts of energy4 ,illustration3 ,,fig4 #da4 ,rotary ,spark ,gap4 ,the ,rotary ,gap consists of a number of electrodes mounted on a motor shaft and arranged to revolve rapidly4 ,the spark discharge takes place between the revolving electrodes and one or two fixed contacts4 ,the effect of a rotary gap is to considerably increase the efficiency of the transmitter by allowing the condenser to become highly charged before it discharges and also reducing the possibility of arcing by keeping the electrodes cool and moving4 ,rotary gaps are of two types1 synchronous and non-synchronous4 ,synchronous rotary gaps are mounted directly on the shaft of the generator supplying current to the transmitter and arranged so that the electrodes are opposite each other once during each alternation of the current4 ,the rotary gap1 commonly used by amateur experimenters and consisting of a toothed disk mounted on the shaft of a small motor is of the non-synchronous type4 ,rotary gaps are sometimes enclosed in an air tight case and the electrodes arranged so that the results obtained are characteristic of both the quenched and rotary gaps4 ,this type of gap is known as the rotary quenched4 ,,lesson ,,nineteen4 ,,the ,,key4 ,some means of controlling the currents flowing through the transmitter in order to divide them into periods corresponding to the dots and dashes of the ,morse ,code is necessary4 ,this is supplied by a hand operated switch1 called a key4 ,a key used for wireless purposes must be much larger and heavier than an ordinary key employed for line work in order to carry the more powerful currents4 ,in spite of the size and weight of a wireless key1 if it is properly balanced1 it may be handled with perfect control and ease4 ,the contact points of a wireless key are necessarily large and heavy4 ,special alloys found to be the most suitable for the purpose are usually employed4 ,a large condenser having a mica dielectric is very often connected across the contacts to reduce the sparkling4 ,illustration3 ,,fig4 #db4 ,wireless ,key4 ,in very large stations where extremely heavy currents must be handled1 the key controls a large switch operating in oil4 ,every time the key is pressed the switch closes and when the key is released1 opens4 ,the currents of the transmitter are made and broken by the switch without passing through the key4 ,,lesson ,,twenty4 ,,aerial ,,switches4 ,since the same aerial is used both for transmitting and receiving1 some method of quickly connecting it to either the transmitter or receiving apparatus must be provided4 ,this is accomplished by means of an aerial switch4 ,the best and most efficient switch adopted generally by the commercial stations is the ,t type1 consisting of a double pole1 double throw switch having very long blades4 ,one set of contacts is mounted on the switch base and the second are carried on a ,t-shaped support from which the switch derives its name4 ,the aerial and ground are connected to the blades of the switch4 ,the lower contacts lead to the transmitting apparatus and the upper ones to the receiving instruments4 ,by simply moving the switch up or down the aerial and ground may be connected to either the transmitter or the receptor at will4 ,illustration3 ,,fig4 #dc4 ,aerial ,switch4 ,a third blade1 much shorter than the other two is usually provided and connected by means of an insulating bar to the other blades so that when they are moved it also moves4 ,it connects with a contact arranged so that when the switch is thrown into position for transmitting the two come together4 ,this blade and contact are made a part of the circuit supplying current to the primary of the coil or transformer so that in case the key should be accidentally touched while receiving the powerful discharge of the transmitter would not destroy the adjustment of the detector4 ,,lesson ,,twenty-,,one4 ,,anchor ,,gaps4 ,certain types of aerial switches require the use of what is known as an anchor gap4 ,an anchor gap consists of a small insulating ring1 usually hard rubber1 having two and sometimes three electrodes set in the periphery and almost touching each other at the sparking points4 ,anchor gaps having two electrodes are used in the aerial circuit of most ,break-in-,systems to prevent the receiving currents from flowing directly into the ground through the transmitter without passing through the detector4 ,illustration3 ,,fig4 #dd4 ,anchor ,gaps4 ,a ,break-in ,system enables the operator to hear the signals of any other station which may be transmitting at the same time when he is operating his own key4 ,the three-electrode anchor gap is commonly used on loop aerial systems4 ,two of the points are connected to the aerial1 one to each half and the other to the lead from the helix4 ,the high potential currents from the helix easily leap across the little gap and divide between the two halves of the aerial4 ,,lesson ,,twenty-,,two4 ,,detectors4 ,the little bobbins of the telephone receivers exert a very powerful choking action upon the currents of high frequency which effectually blocks their passage and prevents them from having any action upon the receiver4 ,the purpose of the detector is to change these currents into such as will flow readily through the magnets of the telephone receiver and manifest themselves as sounds recognizable from their duration and periodicity as signals of the telegraph code4 ,illustration3 ,,fig4 #de4 ,electrolytic ,detector4 ,probably the most well known form is the electrolytic detector which consists of an exceedingly fine platinum wire dipping into a cup of dilute nitric acid far enough to just touch the surface of the liquid4 ,the telephone receivers are connected to the detector1 in series with a battery4 ,the current from the detector causes bubbles to continuously form on the end of the wire and insulate it from the liquid so that the current cannot flow4 ,when the aerial is struck by a wave1 the feeble alternating currents break down the bubbles and permit the currents to flow1 causing a sound in the telephone receivers4 ,the detectors in most common use to-day are of the crystal or rectifying type4 ,there are a great many different forms of this type of detector1 each one of which possesses certain features making it peculiarly adaptable under certain circumstances4 ,illustration3 ,,fig4 #df4 ,silicon ,detector4 ,the silicon detector consists of a flat surface of highly polished silicon upon which rests a brass point4 ,the ,pyron detector is composed of a crystal of iron pyrites embedded in a cup of fusible metal4 ,a small wire spring bears against the surface of the crystal4 ,the ,pyron detector is somewhat harder to adjust than other forms of crystal detector1 but remains in a sensitive condition much longer4 ,illustration3 ,,fig4 #dg4 ,perikon ,detector4 ,the ,perikon detector consists of a cup of fusible alloy in which are imbedded several pieces of a mineral called zincite4 ,another cup containing a fragment of chalcopyrites or bornite is held in a cup carried on the end of a rotating rod4 ,the chalcopyrites is brought into contact with one of the crystals of zincite and the pressure adjusted by means of a spring4 ,the ,perikon detector will operate without a battery1 but that latter is necessary in order to obtain the best results when receiving faint or far away signals4 ,illustration3 ,,fig4 #dh4 ,galena ,detector4 ,the ,perikon ,electra detector is a very sensitive form of the regular ,perikon detector fitted with a micrometer adjustment4 ,the ,galena detector consists of a crystal of that material to which contact is made by means of a fine wire spring exerting very light pressure4 ,illustration3 ,,fig4 #di4 ,audion ,detector4 ,crystal detectors act as rectifiers and change the alternating currents ,into direct currents1 which will pass through the telephone receivers4 ,minerals used for this purpose are said to possess unilateral conductivity1 that is1 they conduct currents better in one direction than the other and act much the same as a valve which allows water to flow in one direction1 but not in the other4 ,another well known detector of the valve type is that known as the ,audion1 consisting of a small incandescent lamp containing a small grid and plate of nickel4 ,when the lamp is lighted by connecting a battery to the filament1 a flow of ions passing from the hot filament through the grid to the plate is set up4 ,the grid and plate form part of the receiving circuit containing the telephones4 ,the flow of ions carries the oscillatory currents from the grid to the plate1 but does not allow them to pass back again4 ,in this manner1 the alternating oscillatory currents are converted into direct currents1 which will pass through the telephone receivers4 ,illustration3 ,,fig4 #ej4 ,carborundum ,detector4 ,the ,carborundum detector1 as its name implies1 is a device making use of the unilateral conductivity of carborundum4 ,this form of detector is very sensitive and has been employed for a number of years in all the installations of the ,united ,wireless ,telegraph ,co4 ,it consists of a small crystal of carborundum clamped tightly between two carbon electrodes4 ,it may be used with or without a battery4 ,the battery is preferred4 ,the ,magnetic detector is a very sensitive device utilizing the changes in the magnetic state of iron1 which are caused by rapidly oscillating currents4 ,if a core of iron wires be placed in a varying magnetic field1 the magnetization of the iron will lag behind the magnetizing force on account of hysteresis or magnetic friction4 ,illustration3 ,,fig4 #ea4 ,marconi ,magnetic ,detector ,but if a rapidly oscillating current is passed through a coil surrounding the iron1 a sudden change in magnetization occurs1 sufficient to induce an ,e4 ,m4 ,f4 in a second coil surrounding the core and thus operate a telephone receiver in series with this coil4 ,the usual form of magnetic detector consists of a belt of fine iron wires passing over two pulleys which are driven by clockwork4 ,a pair of permanent magnets supply the field which induces a continuously varying magnetization in the moving core4 ,the core passes through the centre of a double coil1 one part of which is connected to the telephone receivers and the others to the aerial and ground4 ,,lesson ,,twenty-,,three4 ,,tuning ,,coils4 ,the tuning coil is a device consisting of a large number of turns of wire wound in the form of a cylinder and provided with one or more sliding contacts which can be brought into touch with any one of the turns at will in order to increase or decrease the electrical length or period of the circuit to suit the incoming waves4 ,illustration3 ,,fig4 #eb4 ,double ,slide ,tuning ,coil4 ,a circuit containing a certain amount of inductance1 capacity and resistance tends to oscillate at a certain frequency4 ,therefore1 the oscillations in every transmitting set have a certain frequency depending upon these factors4 ,it is necessary to adjust the receiving apparatus so that it possesses the same frequency as the transmitter4 ,the electro magnetic waves from the transmitting station will strike the aerial of the receiving station at a certain frequency and induce currence in it4 ,if the receiving station is tuned to the same period as the transmitter each wave will give a slight impulse to the readily excited oscillations1 which will grow in intensity just as small impulses given to a pendulum at the right times will make it swing violently4 ,the purpose of the tuning coil is to adjust the receiving circuit to the same period as that of the transmitter4 ,tuning coils are wound of bare copper wire over a core composed of a specially treated cardboard tube4 ,the wires are spaced apart so that they do not touch one another4 ,either one1 two or three variable contacts or sliders are provided4 ,the coils are consequently known as single1 double or three slide tuners4 ,a loading coil is a supplementary coil sometimes placed in series with the regular tuning coil to give a greater inductance to the circuit so that it may be given a much lower frequency in order to receive waves of greater length4 ,,lesson ,,twenty-,,four4 ,,loose ,,couplers4 ,a ,loose ,coupler or ,receiving ,transformer is a tuning coil in which the coupling1 as well as the inductance1 is variable4 ,we have already explained that an ordinary transmitting set throws off two sets of wave trains of slightly different length1 one being somewhat weaker than the other4 ,illustration3 ,,fig4 #ec4 ,loose ,coupler4 ,the purpose of the loose coupler is not only to adjust the receiving set to the period of the transmitter in the manner of the tuning coil1 but by varying the coupling to attract the apices of the weaker trains of waves to the same apex as the stronger waves and so really create a pure wave out of the other two4 ,this may be more easily understood from the accompanying illustration which represents diagrammatically a double train of waves and a pure train4 ,in construction1 the loose coupler consists of a primary winding much the same as an ordinary tuning coil provided with a single slider4 ,a second winding called the secondary1 divided into a number of sections and adjustable by means of a multi-pointed switch mounted on one end1 slides in and out of the primary4 ,,lesson ,,twenty-,,five4 ,,fixed ,,condensers4 ,a fixed condenser usually implies the condenser used in the receiving circuit to furnish part of the necessary capacity and to shunt the telephone receivers1 or as in cases where a battery is used in connection with the detector to force the current to choose a path through the comparatively low resistance turns of the tuning coil4 ,illustration3 ,,fig4 #ed4 ,fixed ,condenser4 ,a fixed condenser1 as its name implies1 has a fixed value or capacity4 ,it is usually constructed of sheets of tinfoil interposed between sheets of thin paraffined paper or mica4 ,the capacity of a fixed condenser usually varies from 4#jjb to 4#jje microfarads4 ,an alternating current passes readily through a condenser but a direct current is effectually blocked4 ,when a direct current is led into a condenser as shown in the diagram1 the half of the condenser represented by ,a becomes positively charged4 ,when ,a receives a positive charge it repels the positive charge from ,b and attracts the negative thus making ,b negative4 ,there is no change in the direction of the current after the first connection and the charge remains fixed and no currents pass4 ,illustration3 ,,fig4 #ee4 ,if an alternating current is applied to the condenser when ,a receives a positive charge1 ,b becomes negative4 ,when ,a reverses and becomes negative ,b becomes positive4 ,this process goes on1 the two halves constantly changing their charge with the result that the current continues to flow4 ,a fixed condenser may occupy one of two places in a receiving circuit1 either in series with the tuning coil and detector or directly across the telephone receivers4 ,in the illustration ,a shows a detector requiring a battery with a fixed condenser in series with it and the coil4 ,the oscillations set up in the circuit by the incoming waves can readily pass through the condenser and effect the detector because they are alternating4 ,if it were not for the condenser the direct battery current would pass through the tuning coil instead of the detector because of the comparatively low resistance of the former4 ,crystal detectors do not require a battery and may be connected to a tuning coil with a condenser in series and the telephone receivers either across the terminals of the detector or across the terminals of the condenser4 ,when in the latter position1 the proper capacity for the fixed condenser will depend upon the resistance of the telephone receivers1 the higher the resistance the less the capacity that will be required and vice versa4 ,,lesson ,,twenty-,,six4 ,,variable ,,condensers4 ,the point of sharpest resonance does not always happen to come on a turn of the tuner where it can be reached by the slider4 ,the variable condenser makes it possible to adjust the circuit to the exact point of resonance4 ,illustration3 ,,fig #ef4 ,rotary ,variable ,condenser4 ,variable condensers are of two general types1 the ,sliding ,plate and the ,rotary ,variable4 ,the rotary variable is the most convenient and easy to manipulate4 ,it consists of a number of fixed semi-circular metal plates between which swings a set of smaller movable semicircular plates4 ,the fixed plates form one half of the condenser and the movable plates the other4 ,in this way the capacity of the condenser is very closely adjustable4 ,the movable plates are provided with a pointer moving over a graduated scale so that the comparative amount of capacity in the circuit is indicated4 ,the sliding plate type of condenser consists of a number of rectangular fixed plates between which slide a set of movable plates4 ,the dielectric between the plates of a variable condenser is air4 ,there are no losses of energy due to hysteresis in a condenser having an air dielectric4 ,rotary condensers employing silk or some such material are not to be recommended4 ,,lesson ,,twenty-,,seven4 ,,telephone ,,receivers4 ,telephone receivers employed for wireless telegraphy are the same in principle as the ordinary telephone receiver but differ in construction and detail slightly4 ,they are always of the watch case type1 this style being small and light1 and consist of a ring or horseshoe shaped permanent magnet upon the poles of which are mounted two small bobbins containing many turns of fine insulated wire4 ,over the magnets1 very close to but not quite touching1 is placed a circular diaphram of thin sheet iron4 ,the lines of force created by the permanent magnet pass through the cores of the little bobbin and exert a constant pull on the diaphram4 ,the little bobbins of wire or electromagnets are connected in series4 ,if a current of electricity is sent through them they will create a little field of force of their own which will strengthen or decrease that of the permanent magnets according in which direction the current flows4 ,each change in the pull exerted on the diaphragm causes it to move and send out little sound waves which may be heard when the receiver is held close4 ,we have already learned that the strength of a magnet depends upon the ampere turns4 ,suppose that a current of one ampere passed through a coil containing #ajj turns x #a amp4 #ajj ampere turns4 ,if only one-tenth of an ampere was available and we wished to retain the same magnetic strength in the coil1 the number of turns would have to be increased to one thousand in order for the ampere turns to remain equal2 #a_/aj amp4 x #a4jjj turns #ajj ampere turns4 ,illustration3 ,,fig4 #eg4 ,types of ,telephone ,head ,sets4 ,the currents passing through the receiver from the detector are exceedingly weak1 and so in order to produce the maximum effect on the diaphragm1 the electromagnets must be wound with a large number of turns of very fine wire4 ,the resistance of fine wire is very great and for this reason wireless telephone receivers are usually termed high resistance receivers4 ,winding a receiver with many turns of fine wire does not make it more sensitive in the true sense of the word or from the standpoint of efficiency1 but makes it better suited to the minute fluctuations of a weak current4 ,the classification of receivers1 according to their resistance is a method of indicating the comparative number of turns and the finess of the wire used in winding the electromagnets4 ,receivers should be wound with copper wire only4 ,wireless receivers come in pairs provided with a head-band so that they may be securely clamped on the ears4 ,the receiver cases are made of rubber1 composition1 brass and aluminum depending upon the design and manufacture4 ,it is immaterial which4 ,,lesson ,,twenty-,,eight4 ,,the ,,hot ,,wire ,,ammeter4 ,the hot-wire ammeter is a device for indicating when the transmitting circuits are properly adjusted and arranged to emit the maximum amount of energy4 ,it is placed in series in the aerial circuit so that the high frequency currents surging in the latter must pass through the meter and indicate their strength by moving the pointer a certain distance over a graduated scale4 ,when a current of electricity flows through a wire it develops a certain amount of heat therein4 ,if the wire is of high resistance the heat will be great enough to cause the wire to expand4 ,advantage has been taken of this fact in the construction of the hot-wire ammeter4 ,this device consists of a piece of platinum wire or a platinum alloy stretched taut between two posts4 ,the wire is included in the aerial circuit4 ,the platinum wire is connected to a spindle carrying a pointer in such a manner that when the heat causes the wire to expand the expansion is conveyed to the spindle and the pointer moves over the scale magnifying the motion4 ,the greater the current flowing through the wire the greater will be the deflection of the pointer4 ,the scale is calibrated by comparison with a standard meter to read in amperes4 ,illustration3 ,,fig #eh4 ,diagram showing the ,constructive ,principle of a ,hot ,wire ,ammeter4 ,when a hot-wire ammeter is placed in circuit the latter is tuned by moving the position of the helix clips on the helix1 altering the length of the spark gap and the condenser capacity until the maximum deflection is indicated4 ,it is then removed from the circuit4 ,,lesson ,,twenty-,,nine4 ,,potentiometer ,the potentiometer is an instrument for carefully regulating the voltage of the battery supplying a detector of the electrolytic or carborundum types with current4 ,it is necessary to bring the potential of the battery to a certain critical point where it is just insufficient to break down the detector1 that is1 overcome the resistance which it offers to the oscillatory currents4 ,in construction1 the potentiometer usually consists of a small rod wound with ,german silver wire and provided with an adjustable contact4 ,graphite resistance rods are merely a cheap method of making a potentiometer and are to be avoided as entirely unsatisfactory for the purpose4 ,illustration3 ,,fig4 #ei4 ,potentiometer4 ,,lesson ,,thirty4 ,,dead ,,end ,,losses ,,and ,,no ,,dead ,,end ,,switches4 ,practically every radio circuit includes an adjustable inductance of some sort1 usually consisting of a layer of wire wound over a tube and arranged so that the amount of wire in the circuit can be varied by means of a switch1 a plug or a slider4 ,these methods of variation are familiar in the ordinary tuning coil1 loose coupler1 loading coil1 etc4 ,illustration3 ,,fig4 #fj4 ,diagram representing the effect of ,distributed ,capacity4 ,if the plug1 switch or sliding contact1 depending upon the method of variation employed1 is at ,e as in ,fig4 #fj so that only the portion of the coil ,a ,e ,b is in the circuit1 then the portion ,e ,f together with ,a ,e may form an oscillator which1 in order for the reader to obtain a better conception1 may be likened to a sort of secondary winding1 with ,a ,e considered as the primary4 ,the oscillations of this part of the system may produce some very undesirable disturbances1 especially so when the frequency of the currents in the circuit ,a ,e bear a certain relation to the natural frequency of the oscillator or ,e ,f4 ,the losses due to the disturbance of these undesirable oscillations and also those resulting from eddy currents induced in the free portion or oscillator ,e ,f by the magnetic flux of ,a ,e are known as dead-end effects4 ,these losses are very much more noticeable in receiving circuits than in transmitters on account of the very weak currents in the former and the importance of preserving all the energy when it is already very small4 ,dead end losses take place principally in receiving transformers1 loading coils and tuning coils4 ,the losses are much more marked on short waves than long waves4 ,the presence of these highly objectionable losses1 and they are large enough to not only seriously decrease the strength of signals but also to make selective tuning impossible1 may be avoided by only using coils which are just the right size so that they can be entirely included in the circuit4 ,this is a very easy matter when only one wave length or at the most1 two or three wave lengths are to be received1 because it is then easily possible to quickly connect the coil of the proper size in the circuit4 ,it is desirable however in most stations1 and especially so in amateur stations that the apparatus be universal so as to be quickly and easily tunable to any wave length within its range4 ,many amateurs build large loose couplers having a very wide wave length range under the impression that they have an ideal instrument4 ,the truth of the matter is however that such an arrangement is decidedly inefficient especially on the shorter waves when only a portion of the windings are in circuit and there is a large dead end portion4 ,the better types of receiving transformers are now provided with no dead end loss switches which automatically break the windings up into a number of groups so that only that portion which is actually required to tune the circuit to a certain wave length is in circuit and the remainder of the coil is entirely disconnected4 ,these switches are located at certain definite points as previously determined by measurements of the coil with the aid of a wave meter4 ,illustration3 ,,fig4 #fa4 ,diagram explaining how end losses are eliminated ,the diagram in ,fig4 #fa illustrates the principle of such an arrangement4 ,the points marked #a1 #b and #c are the places in the coil where the switches are located so as to divide the winding up into separate parts4 ,suppose that it is necessary to move the slider or switch to such a point on the coil as represented by its position in the illustration marked ,e4 ,the switch located at #a would then automatically close as the slider or switch moved past #b and #c would however still remain open because that part of the winding which they connect would not be required4 ,if it became necessary to include more of the winding in the circuit1 #b and #c would automatically close as the slider or switch was moved along the coil and open again as it was moved back4 ,the automatic arrangement of the switches is easily accomplished in a number of different manners by means of levers1 cams1 trips1 or some other mechanical means4 ,,lesson ,,thirty-,,one4 ,,distributed ,,capacity ,,and ,,capacity ,,losses4 ,every coil of wire possesses the property1 not only of carrying a current of electricity but of holding a charge of electricity as well4 ,this property is called capacity4 ,the capacity of a condenser is its property for holding a charge of electricity4 ,the capacity of a coil is termed its distributed capacity in order to distinguish it from the capacity of a condenser4 ,the distributed capacity of a coil is due to the condenser effect which exists between the adjacent turns of the wire4 ,the effect of this distributed condenser is exactly the same as if a small condenser was connected across the ends of the coil as shown in the accompanying illustration4 ,distributed capacity is very objectionable in most receiving circuits because a radio detector depends upon voltage for its operation and when a circuit contains an appreciable amount of distributed capacity the voltage is considerably lower than it would be otherwise4 ,the usual method of reducing the distributed capacity of a coil is to use wire having comparatively thick insulation so that the wires are spaced farther apart4 ,certain shellacs and varnishes used in impregnated windings increase the specific dielectric capacity of the space between the turns and increase the distributed capacity of the winding4 ,the same objection to distributed capacity also holds good in the case of what might be termed capacity losses which are due to improperly arranged connections1 contact points1 etc4 ,every pair of leads or taps from a coil possesses capacity4 ,they really form a miniature condenser1 the wires corresponding to the tinfoil or metal sheets of the condenser and the air between being the dielectric4 ,for that reason the leads should always be as far apart from one another as possible and contact points should be as small as possible4 ,it is unwise to use double conductor having two parallel conductors bound together for leading out connections or connecting radio apparatus4 ,if capacity losses and distributed capacity are reduced to a minimum in a circuit1 it is possible to employ more inductance than would be otherwise in order to tune the circuit to a certain frequency and the voltage is thereby preserved and full benefit derived therefrom by the changes which it produces in the detector4 ,,lesson ,,thirty-,,two4 ,,the ,,poulsen ,,arc ,,or ,,generator4 99,method of ,producing ,undamped ,oscillations for ,radio ,telegraphy and ,telephony499 ,a radio transmitter whose waves are generated by undamped oscillations has many advantages over the ordinary spark transmitter1 the oscillations of which are necessarily damped4 ,the efficiency of an undamped wave transmitter is far greater in almost every respect4 ,the selectivity at a receiving station listening to undamped wave signals is very marked in comparison to that when spark signals are received4 ,the problem of producing undamped oscillations by means of an arc was first solved by ,poulsen and is known as the ,poulsen arc or generator4 ,this type of generator is used for radio work in this country1 by the ,federal ,telegraph ,co41 in the stations at ,sayville and ,tuckerton1 in many ,u4 ,s4 ,naval stations and on board all the ,u4 ,s4 first line battleships4 ,illustration3 ,,fig4 #fb4 ,the ,poulsen ,arc for generating ,undamped ,oscillations4 ,an arrangement by which such oscillatory currents may be produced is shown in its simplest form in ,fig4 #fb4 ,it consists of an arc1 around which is shunted a condenser in series with an inductance4 ,the arc is connected to a source of direct current1 preferably having an ,e4 ,m4 ,f4 of #ejj volts or more4 ,the positive electrode of the arc is copper1 kept cool by circulating water through a hollow interior or a water jacket4 ,the gap in itself is enclosed in a chamber filled with hydrogen gas or a gas containing hydrogen4 ,the arcs in practical use for generating undamped oscillations are arranged so that they operate in a strong magnetic field4 ,the carbon electrode is constructed so that it is slowly revolved by a small electric motor4 ,the hydrogen gas atmosphere in which the arc is enclosed is produced by a small feed cup1 similar to the ordinary lubricating oil cup1 located over the case and filled with alcohol which continuously drips into the flame chamber1 where it is vaporized by the heat4 ,arc transmitters of large capacity are not as expensive or as bulky as spark transmitters of equal power4 ,the difficulties of handling and controlling a large amount of power in connection with a transmitter of this sort are also not as great as in the case of a spark transmitter4 ,the condenser used with an arc is not nearly so large as that required for a spark transmitter of equal capacity and the voltage of the current is much lower4 ,condenser breakdown1 leakage and insulation problems are therefore not as great4 ,for telegraphing with damped transmitters1 a key which alternately makes and breaks the primary circuit is sufficient4 ,this is not possible1 however1 with an arc4 ,the distance between the arc electrodes is usually greater than the gap length which the dynamo voltage would jump and form an arc whenever the key should be closed4 ,it is therefore usual to arrange a key or relay so that it short circuits a portion of the aerial inductance or helix when closed4 ,this short circuit is sufficient to throw the circuit out of tune so that it cannot be heard at the receiving station without readjusting the instruments4 ,the ,poulsen arc may be used for radio telephony4 ,a telephone receiver is arranged so as to vary the currents and impress the vibrations of the voice upon the oscillations set up by the arc4 ,,lesson ,,thirty-,,three4 ,,receiving ,,undamped ,,waves4 ,,the ,,ticker4 ,a decided difference is encountered between damped and undamped oscillations when receiving signals4 ,the ordinary detector cannot be used for receiving undamped oscillations without first being properly modified4 ,when telegraphing the dots and dashes of the code by undamped oscillations the change taking place in the detector circuit would merely move the telephone receiver diaphragm from its normal position at the beginning of each dot or dash1 causing a click to be heard and nothing more4 ,the telephone receiver diaphragm would remain in a fixed position just as long as the waves from the transmitter kept coming in during each signal4 ,both dots and dashes would be heard simply as clicks and not appear distinguishable from one another4 ,the most common and perhaps also the best method is to employ a device called a ticker in place of the detector for receiving undamped oscillations4 ,this arrangement is illustrated in ,fig4 #fc4 ,the left hand part of the illustration is the circuit diagram4 ,a detail of the ticker wheel is shown at the right4 ,the condenser ,f ,c is of comparatively large capacity and is fixed4 ,the condenser ,c is also fixed but is of much smaller capacity4 ,f ,c is usually a condenser having a capacity of several tenths of a microfarad while ,c has only a few thousands of a microfarad capacity4 ,illustration3 ,,fig4 #fc4 ,the ,poulsen ,ticker for receiving undamped ,waves4 ,t is the ticker wheel and consists of a small brass wheel having a groove in the periphery like a pulley4 ,this wheel is mounted on the shaft of a small motor so that it can be revolved at high speed4 ,a fine wire is arranged to rub against the groove in the wheel and make contact with the latter4 ,when the wheel is revolving at high speed1 the wire does not make perfect contact at all points but tends to vibrate and to act as the equivalent of a very high speed interrupter by rapidly opening and closing the circuit4 ,the basic idea in employing a device and a circuit of this sort in receiving undamped waves is as follows3 ,when the contact is broken at the ticker wheel and the condenser ,f ,c is disconnected from the oscillating circuit formed by the condenser ,c and the secondary of the receiving transformer1 the condenser ,c accumulates a relatively large amount of energy4 ,then when the ticker connects the condenser ,f ,c in parallel with ,c1 ,f ,c takes the major part of the stored energy and discharges it through the telephones ,p1 causing a click to be heard in the latter4 ,the interruptions of the ticker are very rapid1 a great many taking place during the duration of a dot or a dash1 so that the resultant clicks occur very close together and the dots and dashes sound very similar to the spark signals of a transmitter sending forth damped waves4 ,the sensitiveness of the ticker arrangement is very great1 in fact much greater than that of any detector4 ,,lesson ,,thirty-,,four4 ,,the ,,audion ,,amplifier4 ,the audion amplifier is an arrangement whereby an ,a audion bulb such as that which has already been described in the ,lesson on ,detectors is so connected that it acts as a relay and also amplifies minute pulsating electric impulses4 ,an ordinary audion detector bulb will serve as an amplifier bulb but it is usual to modify it somewhat and provide a grid and a wing on both sides of the filament as this arrangement gives the best results4 ,the audion amplifier is of especial advantage in amplifying weak wireless signals from a detector which would otherwise be unreadable4 ,it is not necessary that the audion amplifier be used in connection with another audion serving as a detector4 ,it will amplify the signals of any other form of detector such as an electrolytic1 crystal1 magnetic1 etc4 ,illustration3 ,,fig4 #fd4 ,the ,audion ,amplifier ,circuit4 ,figure #fd shows an audion amplifier connected to an audion amplifier connected to an audion detector so that the signals from the latter will be greatly increased in strength4 ,l ,c is a loose coupler connected to the aerial and ground in the ordinary manner4 ,p and ,s are respectively the primary and secondary of the loose coupler4 ,b is the wing battery of the detector circuit and ,b is the wing battery of the amplifier circuit4 ,t is the telephone receiver headset in which the amplified signals are heard4 ,p and ,s are the primary and secondary of a small open core transformer called the ,amplifier ,coil4 ,the windings contain a great many turns of very fine wire4 ,the primary of the transformer is connected so as to be included in the wing circuit of the detector4 ,it should be noticed that only one terminal of the secondary is connected to the amplifier circuit1 this one terminal being connected to the grid of the amplifier bulb4 ,an arrangement of this sort1 where one amplifier bulb is used is called a one step amplifier4 ,amplifiers having two and three bulbs1 respectively known as two step and three step amplifiers give much greater amplification than a one step amplifier and are often used4 ,,lesson ,,thirty-,,five4 ,,hook-,,ups4 99,or ,methods of ,connecting the ,instruments499 ,hook-ups or circuit diagrams showing the manner of connecting various instruments are well worth considerable study if one is desirous of securing the greatest selectivity and distance from his apparatus4 ,there are almost an endless number of ways and combinations of ways of connecting apparatus1 and strange to say1 different people seem to be able to secure the best results with widely different methods4 ,in spite of the fact that circuits of this kind are very numerous they can all be reduced to a few fundamental forms and an understanding of these forms will enable a person to devise his own hook-ups at will4 ,transmitting circuits are fundamentally almost the same4 ,the only real difference in arrangement is made by interchanging the condenser and spark gap4 ,either one may be placed across the terminals of the induction coil or transformer4 ,there is no difference in the results4 ,illustration3 ,,fig4 #fe4 ,consider the circuit shown in the accompanying illustration4 ,the action of the transformer is to charge the condenser to such a point that the voltage is sufficient to leap the spark gap and cause a discharge4 ,the rush of current which is oscillatory takes place through the condenser1 spark gap and primary turns of the helix1 or in other words through the closed circuits4 ,the secondary turns of the helix1 which are those forming part of the aerial circuit1 are larger in number than those of the primary1 and because of this ratio cause currents of higher voltage than those of the condenser to be impressed upon the aerial system4 ,the currents in the aerial system surge up and down the aerial through the helix into the ground4 ,illustration3 ,,fig4 #ff4 ,receiving ,circuits4 ,a shows a simple receiving circuit wherein a single slide tuning coil is connected to a detector4 ,the high frequency currents generated in the aerial surge up and down the system and pass through the detector on their way to the ground4 ,by moving the slider back and forth the electrical length of the circuit may be varied to suit the length of the incoming waves4 ,oscillations may be forced upon such a circuit1 that is1 if the waves are very powerful they will pass through the system and effect the detector no matter whether the slider is adjusted to suit them or not4 ,this would cause interference and confusion in case more than one station were operating at a time4 ,by adding a second slider and a condenser as shown in ,b1 this may be avoided to a considerable extent1 for slider ,no4 #a may be adjusted to the desired signals and slider ,no4 #b placed in a position such as will give the branch of the circuit from the aerial1 through the coil and into the ground of which it is a part1 a period suited to the objectionable wave and so carry off the latter into the ground without effecting the detector4 ,the desired signals will pass into the ground through the other branch of the circuit and operate the detector which lies in their path4 ,the selectivity of the outfit may be further increased by the addition of a variable condenser4 ,a variable condenser may be placed in one or more of a great many positions4 ,the accompanying illustrations show several4 ,the effect of a condenser placed in series with the ground or aerial is just the opposite of that of a loading coil4 ,it decreases the period and shortens the wave length to which it is adapted4 ,the ,amateur's ,wireless ,handy ,book shows over one hundred wiring diagrams starting from the simplest and going to the most complicated in a natural sequence4 ,any of the ,following ,practical ,books 99will be sent ,at ,once1 ,post-paid on receipt of price499 ,there is very little danger of losing currency in a letter if the following directions are observed3 ,cut a circular hole the diameter of the coin in a piece of cardboard1 of sufficient size to fit closely in the envelope4 ,the cardboard should be no thicker than the coin4 ,insert the coin in the hole and paste a piece of paper on both sides of the cardboard to prevent the coin from falling out4 ,,cole ,,morgan ,publishers of the ,arts and ,sciences ,series ,p4 ,o4 ,box #adgc ,new ,york1 ,n4 ,y4 99,the ,boy ,electrician99 ,practical ,plans for ,electrical ,toys and ,apparatus1 with an ,explanation of the ,principles of ,everyday ,electricity4 99,by ,,alfred ,p4 ,,morgan499 ,author of ,wireless ,telegraph ,construction for ,amateurs and ,wireless ,telegraphy and ,telephony1 etc4 99,with full-page ,illustrations and #cbd ,working ,drawings and ,diagrams99 99by the author4 #hvo41 ,cloth1 ,net ,price1 #b4jj499 ,this is the age of electricity4 ,the most fascinating of all books for a boy must therefore be one dealing with the mystery of this ancient force and modern wonder1 even a mere list of whose services is impossible4 ,the best qualified of experts to instruct boys1 ,alfred ,p4 ,morgan1 has in a book far superior to any other of its kind told not only how to make all kinds of motors1 telegraphs1 telephones1 batteries1 etc41 and to do so economically1 but has explained the principles upon which these depend for operation1 and how the same thing is done in the every-day world be well presented and so attractive is this really great book that it will be an education for any bright boy to have it1 as well as the best kind of a moral safeguard1 by leaving no time or thought for evil1 and a means of future benefit beyond the power of any one to reckon4 ,glancing over the pages of this book1 one cannot but be impressed by the excellent illustrations1 clearness of expression and the large number of subjects that are covered4 ,it is beyond doubt the best book in this line that has ever been written or published4 ,it is a book that will delight every boy who has a leaning towards electrical experiments4 ,the author writes in a clear and chatty style and while he has a thorough technical knowledge of his subject he has succeeded in treating it in a simple manner so that it is readily intelligible to his young readers4 99,among the ,chapter ,headings and ,contents are399 ,magnets and ,magnetism--,static ,electricity--,static ,electric ,machines--,cells and ,batteries--,electro-,magnetism and ,magnetic ,induction--,electrical ,units--,electrical ,appurtenances--,electrical ,measuring ,instruments--,bells1 ,alarms and ,annunciators--,electric ,telegraphs--,microphones and ,telephones--,induction ,coils--,transformers--,wireless ,telegraphy--,wireless ,telephony--,electric ,motors--,dynamos--,an ,electric ,railway--,miniature ,lighting--,miscellaneous ,electrical ,apparatus4 99,,read ,,what ,,has ,,been ,,said ,,of ,,it499 ,even a casual glance through the many pages of the book does not fail to emphasize the fact that ,mr4 ,alfred ,p4 ,morgan has indeed succeeded well in giving the juvenile electricians a work that has long been sought4--,popular ,electricity4 ,we have no hesitation in commending the book to the attention of the juvenile audience for which it is intended4--,boston ,post4 ,a great book for enterprising boys4 ,bright boys will highly appreciate it and feel like thanking the wideawake publishers for putting such a reliable and interesting work in the field4--,new ,haven ,journal4 ,the book covers the subject of electricity thoroughly in all its phases and is a splendid acquisition to any boy's library4--,detroit ,times4 ,in this age of electricity a book like the present one is both fascinating and valuable especially to boys4 ,the book is attractive with its many illustrations and will prove of much educational value for any bright boy4--,zion's ,herald4 ,this is an admirably complete and explicit handbook for young boys who fall under the spell of tinkering with electrical apparatus4--,boston ,transcript4 ,well presented and attractive this book will be a source of great benefit and delight for any bright boy4--,new ,orleans ,times-,picayune4 99,price1 #b4jj1 ,postpaid99 ,,countless ,,other ,,magazines1 ,,newspapers ,,and ,,libraries ,,have ,,endorsed ,,this ,,great ,,book4 ,,send ,,for ,a ,,copy ,,now4 99,if you are interested in this great book1 write for our #h-page special99 99descriptive circular499 99,wireless ,telegraphy and ,telephony ,simply ,explained99 ,by ,,alfred ,p4 ,,morgan4 99,a ,,new ,,book by the author of ,wireless ,telegraph ,construction for ,amateurs499 ,this is undoubtedly one of the most complete and comprehensive treatises on the subject ever published1 and a close study of its pages will enable one to master all the details of the wireless transmission of messages4 ,the author has filled a long-felt want and has succeeded in furnishing a lucid1 comprehensible explanation in simple language of the theory and practice of wireless telegraphy and telephony4 ,the book treats the subject from an entirely new standpoint4 ,several very novel and original ideas have been carried out in its making4 ,it is well illustrated by over one hundred and fifty interesting photographs and drawings4 ,all diagrams have been made in perspective showing the instruments as they actually appear in practice4 ,the drawings are carefully keyed and labeled4 ,many of the photographs are accompanied by phantom drawings which reveal the name and purpose of each part4 ,it is a book which the wireless experimenter cannot afford to be without4 ,it will prove even more valuable to the layman4 ,among the contents are3 ,introductory4 ,wireless ,transmission and ,reception4 ,the ,ether4 ,electrical ,oscillations4 ,electromagnetic ,waves4 ,the ,means for ,radiating and ,intercepting ,electric ,waves4 ,aerial ,systems4 ,earth ,connection4 ,the ,transmitting ,apparatus4 ,current ,supply4 ,spark ,coils and ,transformers4 ,condensers4 ,helixes4 ,spark ,gaps4 ,anchor ,gaps4 ,aerial ,switches1 ,etc4 ,the ,receiving ,apparatus4 ,detectors1 ,etc4 ,tuning ,coils and ,loose ,couplers4 ,variable ,condensers4 ,tuning and ,coupling4 ,directive ,wave ,telegraphy4 ,the ,dignity of ,wireless4 ,its ,applications and ,service4 ,wireless in the ,army and ,navy4 ,wireless on an ,aeroplane4 ,how a ,message is ,sent and ,received4 ,the ,wireless ,telephone4 ,the ,ear4 ,how ,we ,hear4 ,sound and ,sound ,waves4 ,the ,vocal ,cords4 ,the ,structure of ,speech4 ,the ,telephone ,transmitter and ,receiver4 ,the ,photophone4 ,the ,thermophone4 ,the ,selenium ,cell4 ,handsomely ,bound in ,cloth with ,embossed ,cover4 7,postpaid1 #a4jj7 ,build ,your ,own ,wireless ,instruments ,complete ,up-to-the-,minute ,authentic ,practical ,,wireless ,,telegraph ,,construction ,,for ,,amateurs ,by ,,alfred ,,powell ,,morgan #c;d ,,edition #bbj ,pages #afc ,illustrations 99,price991 #a4ej1 99,postpaid99 99,handsomely ,bound in ,silk ,cloth99 ,thoroughly up to date and unusually complete4 ,gives in minute detail1 full directions for constructing wireless apparatus and various outfits capable of receiving from #ajj to #a1ejj miles and transmitting #c to #ajj miles4 ,also clearly explains the purpose and action of each instrument4 ,directions for ,operating and ,adjusting1 etc4 99,a ,,splendid ,,treatise ,,of ,,wireless ,,along99 99,,constructive ,,lines99 ,price1 #a4ej1 ,postpaid ,the value of this book has been greatly increased by the addition of much new subject matter and many illustrations of recent interest4 ,the new text explains fully how to build the most recent forms of ,quenched ,gaps4 ,rotary ,gaps1 ,dough-,nut ,tuners1 ,kick-back ,preventers1 ,audion ,detectors and numerous other instruments1 accompanied by dimensioned working drawings4 ,several very interesting and instructive photographs have been included4 ,i4--,introduction4 ,,ii4--,the ,apparatus4 ,,iii4--,aerials and ,earth ,connections4 ,,iv4--,induction ,coils4 ,v4--,interrupters4 ,,vi4--,transformers4 ,,vii4--,oscillation ,condensers and ,leyden ,jars4 ,,viii4--,spark ,gaps or ,oscillators4 ,,ix4--,transmitting ,helixes4 ,x4--,keys4 ,,xi4--,aerial ,switches and ,anchor ,gaps4 ,,xii4--,hot ,wire ,ammeter4 ,,xiii4--,oscillation ,detectors4 ,,xiv4--,tuning ,coils and ,tuning ,transformers4 ,,xv4--,receiving ,condensers4 ,,xvi4--,telephone ,receivers and ,headbands4 ,,xvii4--,operation4 ,,xviii4--,the ,amateur and the ,wireless ,law4 ,how to ,secure a ,license4 ,oscillation ,helix4 ,quenched ,spark ,gap4 ,rotary ,gaps4 ,kick-,back4 ,the ,variometer4 ,new ,crystal ,detectors4 ,the ,audion4--,appendix4 ,,endorsed ,,by ,,wireless ,,clubs ,,throughout ,,the ,,country ,,as ,,being ,,the ,,most ,,practical ,,book ,,published ,,on ,,wireless4 ,,if ,,you ,,are ,,interested ,,in ,,wireless ,,you ,,need ,,this ,,book 99,model ,flying ,machines99 99,,how ,,to ,,build ,,and ,,fly ,,them99 ,will prove interesting and valuable4 ,have you ever built and flown a ,model ,racer8 ,if not1 you have missed something4 ,price1 #be ,cents1 ,postpaid4 ,model ,aeroplaning is one of the most fascinating and instructive of sports4 ,thousands of young men and boys have formed ,model ,aero ,clubs and organized ,flying ,contests throughout the country4 ,,model ,,flying ,,machines of the ,arts and ,sciences series is the only book giving reliable data and instructions for the construction of practical ,model ,aeroplanes4 ,,if ,,you ,,are ,a ,,beginner1 this is the book that you ought to have4 ,it will start you right4 ,it tells how to build seven different types of machines1 starting with the simplest ,monoplane and finishing with several ,long ,distance ,racing ,models4 ,,if ,,you ,,are ,,interested ,,in ,,model ,,aeroplaning1 this book will prove the one you have been looking for4 ,gives valuable ,kinks4 ,tells how to carve propellers1 make winders1 adjust and fly machines1 etc4 ,fully illustrated with large size1 detailed working drawings1 showing the exact size of each part4 ,twelve full-page plates4 ,printed on first-class paper4 ,heavy cover in three colors4 ,sent postpaid by return mail upon receipt of #be cents4 99,,every ,,model ,,aviator ,,ought ,,to ,,have ,a ,,copy99 99,experimental ,wireless ,construction99 99,,eighty-,,six ,,pages ,,ninety-,,three ,,illustrations99 99,only #be ,cents1 ,postpaid99 ,here at last is the book which every young experimenter interested in constructing his own wireless apparatus has been looking for4 ,a book which tells how to build apparatus which anyone would be proud to own4 ,it is a more advanced book than ,wireless ,construction and ,installation for ,beginners1 and describes apparatus which is much more elaborate and sensitive4 ,the instruments have all been the subject of considerable experimental work and study4 ,all the apparatus has been put to practical test and carefully improved by clever experts4 ,by purchasing this book you get the benefit of vast knowledge and experience and are enabled to build far better instruments than by following your own designs and haphazard methods4 ,,the ,,tremendous ,,popularity ,,of ,,this ,,valuable ,,little ,,book ,,is ,,only ,,an ,,indication ,,of ,,its ,,great ,,worth4 ,it has only been on the market a short time1 yet the sales will undoubtedly soon reach a point which would indicate that experimenters unquestionably consider1 that in proportion to its size1 it is the best book on the market4 ,it does not describe any old or obsolete forms of wireless apparatus but only the latest types of aerials1 spark coils1 keys1 gaps1 condensers1 helixes1 oscillation transformers1 loose couplers1 tuning coils1 detectors1 loading coils1 variable condensers1 aerial switches1 etc4 ,,it ,,is ,,one ,,of ,,the ,,most ,,detailed ,,and ,,thorough ,,books ,,ever ,,published4 ,the information is all intensely practical4 ,complete directions and dimensions are given4 ,nothing is left to be guessed at4 ,the book must really be seen to be appreciated4 99,partial ,contents99 ,chapter ,i4--,,the ,,aerial4 ,the ,location of the ,station4 ,the ,construction of an ,operating ,bench4 ,the ,aerial and ,ground4 ,the ,supports or ,masts4 ,types of ,aerials4 ,how to ,erect an ,aerial4 ,protection from ,lightning1 ,etc4 ,chapter ,,ii4--,,spark ,,coils4 ,the ,construction of ,spark ,coils4 ,a #a_/d-;inch ,spark ,coil4 ,a #a_/b-;inch ,spark ,coil4 ,a #a-;inch ,spark ,coil4 ,a #a #a_/b-;inch ,coil4 ,a #b-;inch ,coil4 ,sources of ,current4 ,dry ,cells4 ,storage ,cells4 ,wireless ,keys1 ,etc4 ,chapter ,,iii4--,,transmitting ,,apparatus ,,and ,,its ,,construction4 ,step-down ,transformers4 ,spark ,gaps4 ,the ,oscillation ,condenser4 ,leyden ,jars4 ,helixes4 ,oscillation ,transformers1 ,etc4 ,chapter ,,iv4--,,the ,,receiving ,,apparatus ,,and ,,its ,,construction4 ,a ,silicon ,detector4 ,a ,galena ,detector4 ,the ,double ,slide ,tuning ,coil4 ,how to ,make a ,fixed ,condenser4 ,building a ,loose ,coupler4 ,the ,loading ,coil4 ,how to ,make a ,variable ,condenser1 ,etc4 ,chapter ,v4--,,arrangement ,,and ,,operation ,,of ,,the ,,apparatus4 ,aerial ,switches4 ,the ,buzzer ,test4 ,using ,more ,than ,one ,detector4 ,shunting the ,detector4 ,complete ,outfits4 ,portable ,sets4 ,the ,operation of the ,station1 ,etc4 99,the ,new ,amateur's ,wireless99 99,handy ,book99 ,,fourth ,,edition ,completely ,revised and ,enlarged ,you ,cannot ,afford ,to ,be ,without ,this ,book ,price #be ,cents1 ,postpaid ,if you want to be an expert and an authority you must surround yourself with all available aids and helps4 ,you have one of the best in the ,,amateur',s ,,wireless ,,handy ,,book4 ,,there ,,have ,,been ,,more ,,copies ,,of ,,this ,,great ,,book ,,sold ,,than ,,of ,,any ,,other ,,wireless ,,book4 ,it contains nearly ,,six ,,thousand calls of ,wireless ,stations1 including all ,land ,stations1 ,ship ,stations1 ,u4 ,s4 ,army and ,navy ,stations and all ,,amateurs licensed to date of publication4 ,every registered station of the ,u4 ,s4 is included4 ,they are all there4 ,all the calls are classified alphabetically4 ,the list is the most reliable and complete in existence4 ,all obsolete stations have been abolished4 ,all corrections and changes have been made from the official lists4 99,,but1 ,,that ,,is ,,not ,,all499 ,,the ,,codes1 ,,both ,,morse ,,and ,,continental1 are shown in the form of two large full-page charts printed in heavy black type so that they can be read from a distance4 ,a ,,beginner',s ,,speed ,,chart of both ,codes so arranged that the codes may be quickly learned or consulted is provided4 ,,all ,,this ,,abbreviations used so constantly by the wireless operator to save time and labor are included4 ,there are a couple of pages of them4 99,,and ,,last ,,but ,,not ,,least99 ,nearly #ajj large hook-ups of wiring diagrams fully illustrated in a concise and clear manner4 ,loop and straightaway aerials1 grounds1 helixes1 spark gaps1 anchor gaps1 leyden jars1 induction coils1 transformers1 keys1 aerial switches1 tuning coils1 loading coils1 loose couplers1 variometers1 fixed condensers1 silicon1 electrolytic1 carborundum1 perikon and audion detectors1 telephones1 potentiometers1 etc41 you can find them all and how to connect4 ,a hook-up for any set accompanied by full explanation4 ,none are missing4 ,they are all there4 ,there are no two alike4 ,the most complete and reliable data ever collected4 ,the result of thousands of experiments by some of the most famous wireless experts in the country4 ,read now before the supply is exhausted or you forget4 ,you will be sorry if you don't4 99,,sent ,,anywhere ,,postpaid ,,for #be ,,cents99 ,note3 ,this book is always kept up-to-date by frequently issuing new editions4 ,send for the latest copy4 99,wireless ,construction and ,installation for ,beginners99 ,,seventy-,,three ,,pages ,,sixty-,,seven ,,illustrations4 7,second ,edition47 ,a ,practical ,handbook giving detailed instructions for the ,construction and ,operation of a ,boy's ,wireless ,outfit4 99,only #be;c4 ,prepaid99 ,an indispensible book for the young wireless experimenter4 ,it not alone shows how to build the various instruments but describes their actual workings and tells how to operate them4 99,,every ,,boy ,,is ,,advised ,,to99 99,,send ,,for ,a ,,copy99 ,written in a very clear and simple style1 the book is invaluable to a beginner4 ,he will be able with its aid to construct simple apparatus of the latest and approved type4 ,the instruments described in the book have been the subject of considerable experimental work and special study4 ,they are modeled along simple lines so that they will be easy and inexpensive to construct1 but at the same time combine features which make them very sensitive and capable of receiving or transmitting messages greater distances than some more complicated apparatus4 99,,this ,,book1 ,,considering ,,its ,,worth1 ,,is ,a ,,gift ,,at #be;c499 ,there are no old or obsolete forms of wireless apparatus discussed1 but only the latest types of tuning coils1 receiving transformers1 fixed condensers1 keys1 spark coils1 detectors1 etc4 ,the book is illustrated by numerous detailed working drawings giving all dimensions4 ,several full-page views of the apparatus enable the beginner to fully comprehend the text4 99,,the ,,most ,,thorough ,,and ,,complete ,,elementary ,,wireless99 99,,construction ,,book ,,published99 ,the pages on the construction and installation of aerials will be found to be of considerable help to the experimenter1 for it is here that the most trouble is experienced by the beginner4 ,the practical and helpful information on this subject is alone worth several times the cost of the book4 99,,partial ,,contents99 ,chapter ,i4--99,,wireless ,,telegraphy994 ,an intensely interesting subject2 amateur wireless telegraphy2 the purpose of the aerial and ground2 the apparatus used to send messages2 the apparatus used to receive messages4 ,chapter ,,ii4--99,,aerials ,,and ,,grounds994 ,where to put up the aerial2 types of aerials2 the ,t aerial2 the masts2 the wire2 insulators2 leading in the wires2 the ground4 ,chapter ,,iii4--99,,how ,,to ,,build ,,and ,,operate ,,the ,,simplex ,,double ,,slide ,,receiving ,,outfit994 ,the tuning coil2 the tube2 the sliders2 the fixed condenser2 the detector parts2 assembling the set2 connecting the instruments2 operation4 ,chapter ,,iv4--99,,how ,,to ,,build ,,the ,,simplex ,,loose ,,coupler1 ,,detector ,,and ,,condenser994 ,the base2 the primary2 the secondary2 the pillar2 the switch2 ,how to make the ,simplex cat whisker detector2 ,how to make the ,simplex fixed condenser2 ,how to connect the apparatus2 ,how to tune with the loose coupler2 ,how to adjust the detector4 ,chapter ,v4--99,,telephone ,,receivers ,,and ,,headbands499 ,chapter ,,vi4--99,,how ,,to ,,build ,,the ,,simplex ,,spark ,,coil499 ,the core2 the secondary2 the condenser2 the coil heads2 the base2 the interrupter parts2 the bridge4 ,chapter ,,vii4--99,,how ,,to ,,make ,,the ,,simplex ,,key994 ,chapter ,,viii4--99,,how ,,to ,,connect ,,and ,,operate ,,the ,,apparatus994 ,how to connect and operate a complete wireless station2 ,how to operate2 the code1 etc4 99,the ,operation of ,wireless ,telegraph ,apparatus99 ,do your ,wireless friends come to you for advice on constructing and operating their apparatus or do you go to them for information8 ,here is a chance for ,,you to become the authority4 99,this book is a necessity to every ,progressive ,experimenter499 99,it shows how to obtain the very highest efficiency from any station1 and how to comply with the law4 ,how to tune1 adjust your detector1 spark gap1 phones1 etc499 ,price1 #be ,cents1 ,postpaid4 ,this book was written for the wireless experimenter who has passed the amateur stage1 but explains how the beginner also can obtain the very best results from his station4 ,it contains much useful information to this end and many kinks4 99,,it ,,shows ,,how99 to receive or send on long or short wave lengths with highest efficiency1 to tune for longest distance reception of messages1 to use the buzzer test1 how to test and connect condensers1 receivers1 etc41 how to use receiving transformers1 variometers1 etc41 all with highest efficiency in view4 99,,it ,,also ,,describes99 the construction and use of a simple1 inexpensive wave meter to tune the station to any desired wave length1 and tells how to obtain a sharp wave and a pure wave4 99,,extracts ,,from ,,the ,,law99 are also given in such a manner that they are easily understood4 ,if you want to get the best results from your station this is your opportunity4 99,three ,new ,books on ,home ,made99 99,electrical ,apparatus99 or rather1 three parts of one book1 each #be cents per copy1 are now in preparation and should be ready in ,june1 #aiag4 ,they will cover every kind of electrical apparatus1 including primary and storage batteries1 dynamos and motors1 induction coils1 rectifiers1 transformers1 telegraphs and telephones1 etc4--all of which have actually been built4 ,the three parts will also be furnished as a single volume in cloth covers at #a4jj per copy1 postpaid4 ,if interested1 simply send us a postal and when the books are ready we will send you full descriptions4 99,,cole ,,morgan99 ,publishers of the ,arts and ,sciences ,series ,p4 ,o4 ,box #adgc ,,new ,,york1 ,n4 ,y4