AUSTIN: RADIOTELEGRAPHIC TRANSMISSION 571 



and continued in 1912 in connection with the testing of the high 

 power radio station at .Aj'Ungton, Virginia. This station is 

 equipped with a 100 kw. Fessenden rotary gap sending set 

 which gives an antenna current of approximately 100 amperes 

 at a wave length of 3800 meters. The aerial is triangular in 

 shape and suspended between three steel towers, two of which are 

 450 feet in height while the third has a height of 600 feet. The 

 capacity of the antenna is 0.01 mf said the height to the center 

 of capacity 400 feet. Short range experiments showed that the 

 effective height of the .li'lington station was only about one-half 

 the height to the center of capacity of the antenna. This ap- 

 pears to be generally true of land stations and is probably due 

 to the fact that they are not erected on sufficiently good conducting 

 surfaces as assumed in the theory. The main scientific object 

 of the experiments was the determination of the correctness of 

 the Sommerfeld transmission formula 



hi Jh L 



■ 0.0019 (i 



(1) /K = 120r'-^^^.e ^x 



XdR 



where hi is the effective height of the sending antenna, ho the 

 corresponding height of the receiving antenna, h the sending 

 antenna current, X the wave length, e the distance between the 

 two stations, and R the effective high frequency resistance of 

 the receiving antenna system. 



The strength of the received signals was measured on the U.S.S. 

 Birmingham which made a voyage to Gibraltar and return for 

 the carrying out of the tests. The total height of the Birming- 

 ham's antenna w^as 130 feet and the height to the center of capac- 

 ity 114 feet. The effective high frequency resistance was 50 

 ohms at 8800 meters. Signals were received by means of an 

 electrolytic detector and their intensity was measured by the 

 shunted telephone method which was described in the paper 

 already cited. From the data thus obtained it was possible to 

 determine the received antenna current Jr. 



The table shows the results. Column five gives the experi- 

 mental values as obtained from the smoothed curve of obser- 

 vations, and column three the values as calculated from the 



