Radio Propagation at Frequencies above 30 Megacycles

TLDR

Radio propagation at frequencies above 30 MHz is influenced by distance, antenna height, earth curvature, atmospheric conditions, and terrain, and the paper discusses these quantitative effects using nomograms. The authors provide simplified spherical‑earth propagation charts that enable rapid estimation of received power and field intensity, incorporating empirical corrections for hills, buildings, and atmospheric refraction. Experimental comparisons demonstrate that the empirical methods for terrain and atmospheric effects accurately predict shadow losses and fading ranges.

Abstract

Radio propagation is affected by many factors, including the frequency, distance, antenna heights, curvature of the earth, atmospheric conditions, and the presence of hills and buildings. The influence of each of these factors at frequencies above about 30 megacycles is discussed, with most of the quantitative data being presented in a series of nomograms. By means of three or four of these charts, an estimate of the received power and the received field intensity for a given point-to-point radio transmission path ordinarily can be obtained in a minute or less. The theory of propagation over a smooth spherical earth is presented in a simplified form that is made possible by restricting the frequency range to above about 30 megacycles, where variations in the electrical constants of the earth have only a secondary effect. The empirical methods used in estimating the effects of hills and buildings and of atmospheric refraction are compared with experimental data on shadow losses and on fading ranges.