VHF propagation by ionospheric scattering - a survey of experimental results

A brief survey is given of results from an experimental program extending over the last five years to investigate the nature and characteristics of high-loss regular VHF propagation by means of scattering and other mechanisms in the lower ionosphere. Short-term characteristics as well as diurnal, seasonal and geographical variation of the observed signals are described. The results of pulse-determination of height of scattering, spaced-antenna and polarization experiments, and observations of realized gain of directive antenna systems are given. The dependence of the strength of the signals on path length, scattering angle and frequency is described. Considerations for communication applications are summarized.