The Role of Meteors in Extended-Range VHF Propagation

The main factors influencing the propagation of continuous radio signals by reflection from meteoric ionization trails are reviewed and summarized. A procedure is given for calculating the system parameters required to maintain the signal received over a given path above the cosmic background noise level for 95 per cent of the time. It is pointed out that the variation of signal level with frequency and path length measured for certain "ionospheric forward scatter" circuits, agrees well with calculations based on the assumption that the propagation is entirely by scattering from meteor ion trails. It is suggested that ionospheric scatter is predominantly meteoric at night in the lower latitudes. To the extent that this is true, the minmum performance level of existing circuits could be improved by use of antennas designed to maximize the meteoric component of the signal. Present designs actually tend to discriminate against meteors.