I 



Audio Frequency Atmospherics * 



By E. T. BURTON and E. M. BOARDMAN 



Various types of musical and non-musical atmospherics occurring within 

 the frequency range lying between 150 and 4000 c.p.s. have been studied. 

 Particular attention is directed to two types of the former, one a short 

 damped oscillation, apparently a multiple reflection phenomenon, and the 

 other a varying tone of comparatively long duration, probably related to 

 magnetic disturbances. Several quasimusical atmospherics which appear to 

 be associated with the two more distinct types are described. Dependence 

 of atmospheric variations on diurnal, seasonal and meteorological effects is 

 discussed. Characteristics of audio frequency atmospherics are shown in 

 oscillograms and graphs. 



Introduction 



N connection with a study of communication problems, observations 

 of submarine cable interference were made over periods totaling 

 about 20 months during the years 1928 to 1931. These experiments 

 were conducted at Trinity, Newfoundland ; Hearts Content, Newfound- 

 land; Key West, Florida; Havana, Cuba; and at Frenchport, near 

 Erris Head, Irish Free State. A few supplemental measurements of 

 audio frequency atmospherics received on large loop antennas were 

 made in 1929, 1931 and 1932. These experiments were made at 

 Conway, New Hampshire, at two locations in New Jersey and in 

 Newfoundland. Work carried out at the Newfoundland and New 

 Hampshire locations has been commented upon in previous reports.^ 



Since, for the most part, industrial and communication interferences 

 were of small magnitude at all locations, it has been possible to select 

 for presentation data confined to atmospherics. These data will be 

 limited mainly to the frequencies between 150 and 4000 c.p.s., although 

 measurements were made over the range from 40 to 30,000 c.p.s. 



The principal apparatus used at each location consisted of an 

 especially designed vacuum tube amplifier with which all other 

 apparatus was associated. The overall gains of the amplifiers used 

 at the various locations varied somewhat according to the conditions 

 to be met, the frequency characteristics being adjusted approximately 

 complementary to that of the pick-up conductors. The Ireland 

 amplifier consisted of seven transformer coupled stages grouped to 

 form three units. The impedance at the junction points of units was 



* Presented at U. R. S. I. convention, Washington, D. C, April 27, 1933. Proc. 

 I. R. E., 21, p. 1476, October, 1933. 



IE. T. Burton, "Submarine Cable Interference," Nature, 126, p. 55, July 12, 

 1930; and E. T. Burton and E. M. Boardman, "Effects of Solar Eclipse on Audio 

 Frequency Atmospherics," Nature, 131, p. 81, January 21, 1933. 



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