Progress of tropospheric propagation research related to communications beyond the horizon

It is proposed to give a simple elementary review of tropospheric mechanisms believed to be capable of propagating short radio waves well beyond the earth´s horizon together with some selected experimental data indicatine the potential communication capacity of these tropospheric propagation mechanisms. In view of the wide general interest in the useful applications of the propagation of short radio waves, well beyond the horizon to communications systems, it is hoped that the rather simplified method of presentation will serve to introduce those communications engineers, not intimately associated with past radio propagation research, to the subjects to be discussed. The simplified presentation of theoretical models and discussion of selected experimental results discussed in this paper was intended to give communications engineers a general physical picture of tropospheric scattering. The results of experimental measurements have shown that reliable communications with useful bandwidths can be obtained at UHF and SHF over paths 150 to 300 miles in length utilizing radio waves scattered by the troposphere provided that several kilowatts of power and highly directional antenna system are utilized. The angular measurements of pulse signals scattered by the troposphere indicate that the mechanism of scattering is highly directive and that nmltipath delays are less serious than were originally anticipated.