Synthesis of radio signals on overwater paths

The fluctuations of radio signals at microwave frequencies on overwater paths are explained on the basis of a periodic rise and fall of the water level. From this study, it is seen that the variations in the radio signal strength will contain the frequency of the water-level cycles and also the second and third harmonics of the water-level cycles. This same model predicts that the cross-correlation function of the fluctuations of the radio signal at two vertically-spaced antennas will drop from unity to zero as the separation distance is changed from zero to one-half of a lobe width of a height-gain interference pattern. Although the model assumes reflection from a plane surface, the results of the study successfully explain most of the features of the observed fluctuations of the radio signals on two overwater paths.