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Radio Science

Theory of HF and VHF Propagation Across the Rough Sea, 2, Application to HF and VHF Propagation Above the Sea


  • Donald E. Barrick


This paper deals with an estimation of the effect of sea state on HF and VHF ground-wave propagation loss across the ocean. For this estimation, an expression is employed that was derived in part 1; it gives the effective surface impedance in terms of the spatial height spectrum of the surface. Two empirical models are employed for the height spectrum of the ocean, the directional Neumann-Pierson model and the isotropic Phillips wind-wave model. These effective surface impedances accounting for sea state are then inserted into a standard ESSA computer program giving the basic transmission loss above a spherical earth. The dependence on sea state is plotted in curves which show the excess loss in decibels over a smooth sea. The propagation loss to points at various heights above the sea is also calculated. Normal sea state variations are seen to be negligible below about 2 MHz but produce a maximum excess loss at about 10 to 15 MHz.

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