A Reflection Theory for Propagation Beyond the Horizon

It was pointed out several years ago1 that power propagated beyond the radio horizon at very short wavelengths greatly exceeds the power calculated for diffraction around the earth. This beyond-the-horizon propagation has stimulated numerous experimental and theoretical investigations. 2 Booker and Gordon, 3 Villars and Weisskopf 4 and others have developed theories based on scattering of the radio waves by turbulent regions in the troposphere. This paper proposes a theory in which uncorrected reflections from layers in the troposphere are assumed responsible for the power propagated beyond the horizon. In developing this theory, some arbitrary assumptions of necessity have been made concerning the reflecting layers since, at the present time, our detailed knowledge of the atmosphere is insufficient. However, calculations based 011 the theory are found to be in good agreement with reported measurements of beyond-the-horizon propagation. Measurement of the dielectric constant of the atmosphere 5 has shown that relatively sharp variations in the gradients of refractive index exist in both the horizontal and vertical planes. Although the geometrical structure of the boundaries formed by the gradients is not well known, one may postulate an atmosphere of many layers of limited extent and * This material was presented at the I.R.E. Canadian Convention, Toronto, Canada, October 3, 195G. 627