G. D. Gierhart and M. E. Johnson

Abstract: This report provides a description of the computational details in the IF-77 (ITS-FAA-1977) radio wave propagation model. The IF-77 model is useful in estimating service coverage for radio systems operating in the 0.1 to 20 GHz frequency range. It is applicable to many air/air, air/ground,air/satellite, ground/ground, and ground/satellite systems. Irregular terrain and propagation beyond the line-of-sight range are considered in the model. However, the terrain feature is keyed to the lower (or facility) antenna and the radio horizon for the upper (or aircraft) antenna is (1) determined from the facility horizon obstacle (common horizon) or (2) taken as the smooth earth radio horizon when a common horizon is negated by the earth's bulge. Previous publications concerning IF-77 include (l) an applications guide for computer programs that use IF-77, (2) an extensive comparison of predictions made using IF-77 with measured data, and (3) an atlas of propagation curves applicable to aeronautical systems. Details concerning the computer programs are not included in this report.

Keywords: air-to-ground propagation; propagation model; transmission loss; air/air; earth/satellite; protection ratio

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.

For questions or information on this or any other NTIA scientific publication, contact the ITS Publications Office at ITSinfo@ntia.gov or 303-497-3572.

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