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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Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

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