Institute for Telecommunication Sciences
the research laboratory of the National Telecommunications and Information Administration

M. E. Johnson; G. D. Gierhart

Abstract: The United States Department of Commerce (DOC) has been active in radio wave propagation research and prediction for several decades, and has provided the Federal Aviation Administration (FAA) with many propagation predictions relevant to the coverage of air navigation and communications systems. During 1960-1973, an air/ground propagation model applicable to irregular terrain was developed by the Office of Telecommunications/ Institute for Telecommunication Sciences (OT/ITS) for the FAA and was documented in detail. This IF-73 (ITS-FAA-1973) propagation model has evolved into the IF-77 model, which is applicable to air/ground, air/air, ground/satellite, and air/satellite paths. It can also be used for ground/ground paths that are line-of-sight, smooth earth, or have a common horizon. Model applications are restricted to telecommunication links operating at radio frequencies from about 0.1 to 20 GHz with antenna heights greater than 0.5 m. In addition, the elevation of the radio horizon must be less than the elevation of the higher antenna. The radio horizon for the higher antenna is taken either as a common horizon with the lower antenna or as a smooth earth horizon with the same elevation as the lower antenna's effective reflecting plane. This propagation model has been incorporated into ten computer programs. These programs may be used to obtain a wide variety of computer-generated microfilm plots such as transmission loss versus path length and desired-to-undesired signal ratio at a receiving location versus the distance separating the desired and undesired transmitting facilities. Such capabilities are useful in estimating the service coverage of aerospace radio systems, and are currently being used to establish station separation requirements for VHF/ UHF/SHF air navigation aids. This paper provides (1) a brief discussion of the IF-77 propagation model, (2) a summary of the prediction capabilities available, and (3) remarks concerning model validation work.

Keywords: atmosphere; radio wave propagation; upper ionospheric forecasting; ionospheric radio wave propagation

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Institute for Telecommunication Sciences
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Paul M. McKenna
Institute for Telecommunication Sciences
(303) 497-3474

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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