Simultaneous measurements of microwave fading and lower atmospheric conditions were carried out in Georgia in 1986 as a part of the continuing effort to study the line-of-sight digital radio performance. Acoustic sounding was a principal means of exploring the mechanism that causes dispersive fading. It was found that dispersive multipath fading occurs during nights with strong radiation inversion accompanied by a subsiding air mass. Subsidence inversion causes dispersion, and the origin of the air mass affects the mean received power level under multipath propagation conditions. When the height of the nocturnal boundary layer coincides with the height of the ground-based radiation inversion layer and is at 100–150 m, fading is heavy, active, and dispersive for a 57-km path with both transmitting and receiving antennae at 60 m above grade. Case studies of the significant episodes are presented, and the statistics of the different types of fading associated with the types of meteorological conditions are summarized for the 5-month study period.
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