Observations of UHF Propagation Variability on Low-Altitude Ray Paths

This paper reports on two measurement campaigns aimed at investigating the importance of atmospheric variability in several applications, including passive radar. First, UHF wide-band spectrometry analyses seek to quantify diurnal statistics, power series correlation, and signal reliability. Second, long-term radar detection data further enhances the understanding of how this variability affects both clutter and moving targets. Results demonstrate the dynamic nature of the illumination environment as well as enhancement of clutter and targets. Beyond ducting enhancement, phenomena seen in the data include station dropout, unexpected illuminators, rainstorms echoes, and other unexplained diurnal features.