June 1955 | NTIA Technical Report NBS Report 3554
The Extreme Range of Regular Propagation of VHF Radio Waves by Ionospheric Scattering
Richard C. Kirby
Abstract: Initial results through December 1954 are reported from a continuing investigation of the extreme distance range of regular VHF propagation by scattering in the lower ionosphere. Signal strength observed at 36/Mc/s over an experimental path from Newfoundland to the Azores, 1411 statute miles distant, has been recorded without interruption except for equipmental reasons since 4 October 1954. October and November results indicate a medium value of 85 decibels loss relative to the Cedar Rapids- Sterling path, 743 miles, after normalization of frequencies and antenna systems; during weakest signal periods, the loss diminished to about 3 decibels relative to the Cedar Rapids- Sterling path. Smaller diurnal and seasonal variations are observed over the long path, but much greater indicence of Es-type propagation. Signal fading and correlation coefficients of about .3 to .4 are observed for a spacing of 4a, and about 0.2 to 0.3 for a spacing of 10A. Some of the geometrical aspects of extreme-range propagation are discussed and results of calculations given for vertical angles of arrival and departure, and required antenna heights vs. path lengths.
Keywords: fading; VHF; ionospheric propagation; propagation measurement
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