Some aircraft measurements of beyond-the-horizon propagation phenomena at 91.3 Mc/s

Field-strength measurements at distances extending far beyond the horizon from a transmitter on a frequency of 91.3 Mc/s have been carried out in an aircraft flying at a height of 10000 ft. The analysis of the results obtained and their correlation with meteorological data suggest that many phenomena of long-distance propagation could possibly be explained by the simple hypothesis of specular reflection from temperature-inversion layers at the tropopause.