Further Results of a Study of Ultra-Short-Wave Transmission Phenomena

Further Results of a Study of Ultra-Short-Wave Transmission Phenomena * By C. R. ENGLUND, A. B. CRAWFORD and W. W. MUMFORD Earlier published work has shown that, while the chief features of ultra-short-wave transmission over "air line" ranges are calculable from optical theory, there are deviations from this theory at the greater distances where a bending around the earth occurs. In this paper the results of a further study of these phenomena are given. It is shown that transmission to regions beyond the optical range is determined by conditions which are not constant and which, in fact, can produce great signal strength changes. The variable percentage of water vapor normally present in the atmosphere is suggested as a possible cause. The explanation seems, therefore, to involve a combination of diffraction and refraction, this latter variable with time, and at times predominant.