Abstract :
This paper reports the results of a study of short pulses (typically less than ten cycles) with carrier frequencies in the range 30 MHz-1 GHz. The results were generated by a particularly simple model in which ionospheric anisotropy is ignored (since the frequencies and bandwidths considered are large compared with typical electron gyrofrequencies) and only vertically-launched plane waves are considered. Quantitative predictions of pulse spreading are presented, and several possible extensions of the model are described briefly