Propagation of Short Radio Waves over Desert Terrain

Results are given of an experimental investigation of the effect of relatively simple topography and meteorology upon the propagation of short radio waves over an optical 26.7-mile path and a nonoptical 46.3-mile path. Two types of meteorological conditions were encountered during the course of the experiments performed in the Arizona desert. In the daytime the atmosphere was well mixed with the index of refraction distribution nearly standard. At night a small scale duct was formed, due to a temperature inversion arising from the cooling of the ground by radiation. Measurements of the vertical distribution of field strength over a 190-foot interval were made under these two meteorological conditions for frequencies of 25, 63, 170, 520, 1,000, 3,300, 9,375 and 24,000 Mc. The effect of the diurnal meteorological cycle on the field strength is discussed for both the optical and nonoptical path. Diffraction effects on the short path due to small scale irregularities of the terrain are also discussed.