Some ionospheric factors affecting the coverage of an HF/VHF direct broadcasting satellite service

A study has been undertaken to assess the effects of the ionosphere on the performance of a direct broadcasting satellite service operating in the high frequency (HF) band. Results relating to two issues of performance are presented: (1) determining under what conditions a frequency allocated to the broadcasting service can be expected to reach the surface of the earth from a satellite and (2) the loss of signal strength due to passage through the ionosphere. It was found that if high frequency broadcast services are to be provided on a worldwide basis using satellite platforms, the satellites need to be optimally configured for the intended service area. Also, a 3 dB loss of signal strength is expected due to ionospheric absorption.