RADIATED AND RECEIVED ENERGY IN RADIO- 

 TELEGRAPHY. 



By L. W. AUSTIN. 

 {Read April 19. IQIS-) 



Duddell and Taylor^ were the first experimenters to attempt to 

 determine the laws relating currents in the sending and receiving 

 antennas used in radiotelegraphy. Their first experiments were car- 

 ried on near London with distances of only a few hundred yards 

 between the antennas. A little later these experiments were re- 

 peated on a larger scale on the Irish Sea between a land station and 

 the steamer Monarch, the experiments in this case being extended 

 up to about sixty miles. Their work served to show that up to the 

 distances mentioned the received current fell ofif directly in propor- 

 tion to the distance in accordance with the Hertzian equation for the 

 electric force in the equatorial plane of an oscillator. 



The determination of this law at once aroused great hopes in the 

 minds of all workers in radiotelegraphy for the establishment of 

 long distance communication. It was well known that with 2 K.W. 

 and with moderate sized antennas it was quite possible to send mes- 

 sages over distances of three hundred miles in the daytime. From 

 this it was easily calculated in accordance with the Duddell and 

 Taylor law, that it would be necessary to use only 10 K.W. with 

 antennas 400 feet high to carry oh communication up to 3,000 miles. 

 When the attempt was made, however, it was found that only on 

 exceptionally favorable nights was any communication at all possible, 

 even with two or three times the calculated power, and of course 

 none at all in the daytime. This showed at once that the Duddell 

 and Taylor law was not applicable at great distances, and it began 

 to be assumed that for communication over water an absorption 



'Duddell and Taylor, Electrician. 55, p. 260, 1905. 



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