I9I3J 



AUSTIN— ENERGY IN RADIOTELEGRAPHY. 



411 



formula for this purpose have been given by Rudenberg," and at- 

 tempts have been made to apply them to the case of the scout cruisers 

 Birmingliam and Salcm by H. Barckhausen' and myself.^ 



The formulc-e are based on the assumption that if an antenna be 

 erected on a conducting surface, its field will be the same as that of 

 an antenna in space of twice the height, the lower portion being 

 exactly like the real antenna but inverted beneath it; that is, the 



T 



I 



Fig. I. 



length of the equivalent Hertzian oscillator will be twice the height 

 from the earth to the center of capacity of the antenna. As Ruden- 

 berg observes, however, the imaginary portion does not contribute 

 to the energy radiated by the antenna. Then since the energy is 

 proportional to /, the length of the oscillator, squared 



[2hf 



L' = 



or /=//V2. 



Hence to get the length of the equivalent Hertzian oscillator we must 

 multiply the height h to the center of capacity of the antenna by V^- 

 In order to determine the theoretical value of the received current 

 we must determine the electromotive force on the receiving antenna 



®R. Rudenberg, Ann. d. Phys., 25, p. 446, 1908. 



" H. Barckhausen, Jahrb. d. drahtlosen Telegraphie, V., p. 261, 1912. 



^ Jottrn. Wash. Acad., i, p. 275, 191 1. 



