Audio Frequency Atmospherics

I 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, Newfoundland; 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. 1 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.