408 AUSTIN— ENERGY IN RADIOTELEGRAPHY. [April 19, 



existed similar to that which had long been recognized in overland 

 communication. 



In 1909/10 the United States Navy carried on experiments be- 

 tween the high power Fessenden station at Brant Rock and the scout 

 cruisers Birmingham and Salemr In these experiments regular day 

 communication^ was obtained up to 800 miles between the ships, and 

 about 1,200 miles between the high power station and the ships. 

 Quantitative experiments on the effect of the height of sending 

 and receiving antennas were also carried on at this time, which 

 verified the results of Marconi, Duddell and Taylor, and Pierce. 

 The results of all this work were finallv summarized in the formula 



(0 In = 4.2S^'Ise ^'^ 





where /^ is the receiving antenna current, /^ the sending antenna 

 current, h^ and /z, the heights to the centers of capacity of the two 

 antennas, A the wave-length, and d the distance ; the currents being 

 measured in amperes and the lengths in kilometers. In this formula 

 the resistance of the receiving antenna was arbitrarily taken as 25 

 ohms, that being the resistance of the Brant Rock station under the 

 conditions of experiment. That the resistance was the same at both 

 wave-lengths used (1,000 meters and 3,750 meters) was due to the 

 fact that a series condenser was used in the Brant Rock antenna at 

 the shorter wave-length. On the ships, however, there was un- 

 doubtedly a very considerable difference in resistance at the different 

 wave-lengths. As a matter of fact, we have never had an oppor- 

 tunity to measure accurately the antenna resistance on these ships. 

 From measurements on other ships, however, it is estimated that the 

 antenna resistance at 1,000 meters would be from 15 to 18 ohms, 

 while at 3,750 meters it would probably be about 35 ohms. No more 

 quantitative work at long distances was carried on by the Navy De- 

 partment until the autumn of 1912, although in the meantime a 

 number of observations were made at moderate distances which all 



-Bulletin Bureau of Standards, 7, p. 315, 1911. 



^ Night signals, while generally stronger than those in the day time, are 

 freakish and irregular and unfitted for quantitative comparisons. 



