1905.] on Recent Advances in Wireless Telegraphy. 



35 



d 



concentric cylinders, or in other forms of closely adjacent conductors. 

 The electrical capacity of such conductors, as shown in Fig. 6, is 

 very large compared with that of a single vertical wire, with the 

 result that the amount of electrical energy stored up in the system 

 referred to in the first case is much larger, and does not radiate or get 

 away in one or two waves, but forms a train of timed impulses which 

 subsist for a certain time, which is what is required. 



An arrangement consisting of a circuit containing a condenser and 

 a spark gap. Fig. 8, constitutes a very persistent oscillator. Sir 

 Oliver Lodge has shown that by placing it near to another similar 

 circuit, it is possible to demonstrate effects of tuning. The experi- 

 ment is usually referred to as "Lodge's syntonic jars," and is 

 extremely interesting, but as Lodge himself points out in his book, 

 the " Work of Hertz," a closed circuit such 

 as this is "a feeble radiator and a feeble 

 absorber, so that it is not adapted for action 

 at a distance." 



If, however, such an oscillating circuit is 

 inductively associated with one of the author's 

 elevated radiators, it is possible to cause the 

 energy contained in the closed circuit to 

 radiate to great distances, the essential con- 

 dition being that the natural period of elec- 

 trical oscillation of the radiator should be 

 equal to that of the nearly closed circuit. 



All the latest syntonic transmitting ar- 

 rangements are based on modifications of this 

 combination. 



The general arrangement is indicated in 

 Fig. 7. 



The arrangements for syntonising or tun- 

 ing the receiving stations are shown in Fig. 5. 

 Here is shown the usual vertical conductor 



connected to earth through the primary of a transformer," the 

 secondary circuit of which contains a condenser, which is connected 

 across the coherer or detector. In this case also it is necessary that 

 the period of electrical oscillations of the vertical wire, which 

 includes the primary of the transformer and earth connection, should 

 be equal to that of, or in tune with, the secondary circuit of the said 

 transformer, which circuit includes a condenser. Therefore, in order 

 that a transmitter (Fig. 7) should be in tune with the receiver 

 (Fig. 5), it is necessary that the periods of oscillation of the several 

 oscillating circuits at both stations should be equal, or very approxi- 

 mately so. 



It is easy to understand that if we have several stations, each 

 tuned to a different period of electrical oscillation, the periods of 

 resonance of which are known, it will not be difficult to transmit 



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Fig. 



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