AUSTIN: HIGH SPARK FREQUENCY IN RADIO-TELEGRAPHY 5 



The striking similarity of the two columns is evident at a glance. 

 The Dittmar figures are the mean of 77 analyses. 



RADIO-TELEGRAPHY. — High spark frequency in radio-teleg- 

 raphy. L. W. Austin. Naval Wireless Telegraphic Labora- 

 tory. 



In 1908 I published a paper 1 on the subject of the advantages 

 of high spark frequency in radiotelography in cases where inte- 

 grating detectors were used. 2 In this I called attention first to 

 the great increase in sensitiveness of the telephone with increasing 

 frequency, and second to the advantage to be obtained by dis- 

 tributing the energy of the sending station over a large number of 

 sparks instead of concentrating it in a few. Since that time spark 

 frequencies of approximately one thousand per second have come 

 info common use in radiotelegraphy, 3 but the expected increase in 

 sensitiveness of the telephone at these frequencies has not been 

 obtained. This is illustrated by Table I which contains a com- 

 parison of the received energy as measured on a zincite rectifier 4 

 with galvanometer and the telephone audibility as measured 

 with the same rectifier by the shunted telephone method. The 

 measurements were taken at the Bureau of Standards. From 

 this it is seen that the sensitiveness of the telephone is approxi- 

 mately the same for sixty cycle and five hundred cycle stations. 

 This failure to obtain the increased sensitiveness at the higher 

 frequency is the more remarkable, since, for sine waves at least, 

 it has been shown independently by a number of observers. 6 



We can, however, from the data of Table I determine what 

 the actual current sensitiveness of the telephone under wireless 

 conditions is. We shall assume as a rough average that 1 mm. 



1 Bull. Bur. Standards, S: 153. 1908. 



2 Experiments have shown that the electrolytic and most of the rectifying 

 detectors depend only on the energy. 



3 Prof. R. A. Fessenden was already experimenting with high spark frequencies 

 at the time my paper was being written. 



4 Bull. Bureau of Standards, 7: 295. 1911. 



5 Lord Rayleigh, Phil. Mag. 38:294. 1894. Wien, M., Ann. d. Phys. 4:450. 1901. 

 Austin, L. W., loc. cit. 



