CXII. The use of atmospherics to study the propagation of very long radio waves

Abstract

The “level” of integrated atmospherics received on narrow-band receivers tuned to a series of different frequencies between 3·5 and 50 kc./s. has been recorded. The band-width of the receivers was about 200 c./s. and the time of integration about one minute. The results were analysed so as to eliminate the unknown spectral distribution of energy at the source, and so as to show up the way in which propagation conditions changed with distance and with time of day. The results are shown in fig. 4, from which the most significant effect is seen to be a marked attenuation of waves of frequency below 10 kc./s. when travelling over distances of 1000 km. or more. This attenuation is discussed and is related to the quasi-sinusoidal waveform often assumed by atmospherics which have travelled great distances. A decrease in the level of atmospherics has been found to occur during sudden ionosphere disturbances (S.I.D.'s) on frequencies below about 10 kc./s. This contrasts with the known increase on frequencies above about 20 ke./s.