Popular Science Monthly 



Sustained Wave Telegraphy Between as shown by AB. 

 the United States and Germany 



451 



BEFORE 19 13 there was no direct means 

 of communication between Germany 

 and the United States, except by submarine 

 cables. The Allies cut these cables im- 

 mediately war was declared. Between 

 that time and our own break with Germany, 

 communication was established by two of 

 the most important 

 pairs of wireless sta- 

 tions ever known. 

 And now that all 

 active amateur and 



Curve representing progressive values of the 

 cuirent generated by a radio alternator 



semi-professional work has been discon- 

 tinued, this ought to be just the time for our 

 friends to study the "workings" of these 

 great stations. 



The quenched singing spark systems, 

 which were used for almost all radio work 

 at the time these stations were erected, 

 were first tried at Sayville, but proved 

 entirely too feeble for the distance that 

 had now to be covered, about 4000 miles. 

 The sustained-wave system was therefore 

 installed at Sayville, and it was found 

 to be reasonably successful. Exceedingly 

 high frequency sustained alternating cur- 

 rents were used in all four stations. For 

 generating these, the stations at Eilvese 

 (Germany) and Tuckerton (New Jersey) 

 used the Goldschmidt "reflection" system, 

 while those at Nauen (Germany) and 

 Sayville (Long Island) used the Arco-Joly 

 "multiplication" system. 



The secret of the success of sustained- 

 wave telegraphy lies in the fact that high 

 frequency alternating currents — that is, the 

 currents which go through many changes 

 in direction in a second — are better radi- 

 ators of energy from the sending sta- 

 tion, while they also enable the receiving 

 instruments to respond more strongly. 

 As an alternating current generator re- 

 volves, the strength of the electromotive 

 force it produces varies as shown in Fig. 1. 

 The strength of the electromotive force 

 first increases until it reaches its maximum 



It then decreases and 

 finally becomes negative, reaching a maxi- 

 mum negative value CD. It then reduces 

 to zero again and becomes positive in 

 value once more. By greatly increasing 

 the speed of the generator or by increasing 

 its number of poles it is possible to increase 

 greatly the number of times the electro- 

 motive changes in direction per second, 

 and in this way, to increase greatly the 

 radiation efficiency of a station. However, 

 due to the fact that a machine cannot 

 easily be made sufficiently strong in the 

 one case and that the electrical efficiency 

 may be too greatly reduced in the other 

 case, this simple machine method was not 

 used for these high power stations. The 

 transformer methods of Goldschmidt or of 

 Joly were therefore adopted, rather than 

 the radio frequency dynamo of Fessenden 

 and Alexanderson, used so extensively be- 

 fore the war. 



The Goldschmidt system depends on the 

 phenomenon called "reflection." That is, 

 the currents set up in the rotating part of 

 the alternator (the rotor) can be "reflected" 

 back into the stationary part of an alterna- 

 tor (the stator) so that the frequency of 

 the original rotor current is increased to 

 double the original. This can be made to 

 take place by a suitable electrical connec- 

 tion on the stator. Again, the induced 

 current set up in this manner in the stator 

 can be "reflected" back into the rotor. 

 The frequency of this new current last set 

 up will be increased to three times the 

 original frequency. Finally, on reflecting 



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FIG.Z 



Goldschmidt "reflection" alternator for quad- 

 rupling the frequency of the original current 



this once more into the stator, the resulting 

 current frequency will be once more in- 

 creased, and to four times the fundamental. 

 This is the current that was used in the 

 antenna. 



