Prediction of Coverage for Trans-Horizon HF Radar Systems

Coverage patterns for trans-horizon radar systems can be predicted both analytically and empirically. Empirical methods are preferred because of their rapid application and lack of need for elaborate computing facilities. In addition, the coverage techniques introduced may be used eventually to determine the slant range, absorption, and effective noise temperature of trans-horizon radar systems. Some of the fundamental considerations which influence the prediction of coverage, such as geographical location, and the diurnal, seasonal, and anomalous behavior of the ionosphere, are discussed qualitatively. In spite of these factors, however, it is shown how HF radar systems overcome the line-of-sight limitations imposed upon conventional microwave radar systems and theoretically permit up to four or five times the range for a single hop.