Oblique-Sounding and HF Radio Communication

The sweep-frequency oblique sounder is a powerful tool for the study of ionospheric propagation over actual communication circuits. In addition, since it provides the pulse response of the ionosphere as a function of frequency it is potentially a powerful tool for improving communication via the ionsphere. The Defence Research Telecommunications Establishment's (DRTE) experience in using sweep-frequency sounding for the study of HF radio propagation over both short and long paths is described. These include difficult communication circuits in the auroral zone where unreliability is frequently encountered. These studies have revealed many inadequacies in our present prediction systems. Preliminary attempts to use oblique-sounding information for improving present HF communication circuit reliability have been made, but to obtain full advantage of this technique improved communication systems are required. A description is given of a proposal, which is only one of many possible, for using the obliquesounding technique on HF radio circuits to obtain more reliable long distance communication.