Some Characteristics of Persistent VHF Radiowave Field Strengths Far beyond the Radio Horizon

The most recent results of a continuing research program devoted to the study of long-distance VHF radiowave propagation are presented. Data obtained from measurements made at 50 and 220 mc on the surface and in the air are given which extend our previous results and clarify some important aspects of tropospheric and ionospheric propagation at extreme distances and heights.