January 1971 | NTIA Technical Report OT/ITS Research Report 7

A New Method for Predicting HF Ground Wave Attenuation Over Inhomogenous, Irregular Terrain

Randolph H. Ott

Abstract: Several examples of the numerical evaluation of an integral equation for the calculation of the attenuation of a radio wave are given. These waves are assumed to be propagated over realistic, smoothly varying irregular, inhomogeneous terrain. Results for propagation over a cylindrical earth show an accuracy to 3–4 significant figures when compared with the classical residue series. Calculations for propagation over smooth mixed land-sea paths agree with classical methods. The applicability of the program to permit computation of propagation over terrain with smooth height variation is demonstrated by calculations of propagation over one and two Gaussian-shaped hills. The ability of the program to allow treatment of variations in both ground conductivity and height combined is illustrated by calculations of propagation from the sea up a sloping beach and by calculations of propagation over an island. Thie last example illustrates the importance of the terrain profile in mixed path calculations.

Keywords: irregular terrain; HF; inhomogeneous terrain

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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