Transmitting Antenna in Wireless Telegraphy. 15 



Method of Direct Excitation (Slaby-Arco). 



In the method of directly exciting the oscillations, one point 

 of the condenser circuit is joined to the antenna, another point 

 to earth. 



A diagram of the connections is shown in fig. 10.* A and 

 B are the terminal binding posts of the secondary of the induc- 



10 



Anleruia 



tion coil, the distance between them being 22 cms . The spark- 

 knobs, K, K were 16"5 mm in diameter and the spark-length was 

 from 1 to 2 mm . The Leyden jar had a mean diameter of 5'7 cms , 

 with walls about 4 mm thick. The coatings were 10 cms in height 

 and of area about 180 sq cms . The lengths of the various parts 

 of the circuit are indicated on the figure, the entire condenser 

 circuit having a length of approximately 



53 + 23 + 22 + 23-5 + 16 = 137'5 cms . 



The wire CD wrapped about the jar was heavily insulated and 

 consisted of 2f turns. This corresponds to Slaby's u syntoniz- 

 ing coil," though, of course, it was not used for syntonization 

 in my experiments. The turns were about 2 cms apart, so that 

 its self-induction was practically the same as that of an equal 

 length of straight wire. It was put in this form, however, 

 through a desire to have the arrangement as nearly as possible 

 like that used in actual practice.f 



It will be seen that Y5 cms of the closed condenser circuit are 

 a part of the open antenna circuit. According to Braun,^: the 

 larger this portion of the condenser included in the antenna 

 is, the better will be the effect, and it performs a role other 

 than simply as a portion of the antenna. 



Four different arrangements were employed to balance the 

 antenna wire. 



* The arrangement was taken from that described by the Allgemeine Elek- 

 tricitatsGesellschaft in their circular regarding the Slaby-Arco system, 1902. 

 See also Boulanger et Ferrie, Telegraphie sans Fil, p. 156, 4th ed., 1902. 



f Several good illustrations of the latest apparatus are given in C. Arldt, 

 Die Funkentelegraphie, pages 48-51 (Leipzig, 1903). 



$F. Braun, Ann. der Physik., viii, p. 199, 1902. 



