Atmospheric effects on ultra high frequency radio propagation

Abstract

The dependence of received power on range witnin and belcvv atmospheric ducts was measured in conditions of elevated, nonhomogeneous , multilayered ducts. An aircraft with UHF transmitter covered the range to 150 nm. from a shore based receiver. Range dependent maxima and minima in received power were detected at tne surface in elevated duct conditions. The results were compared to predictions from ray, waveguide multi- mode, and single mode theories. Ray and single mode theories were inadequate to predict power patterns over the horizon. Multi-mode theory yielded qualitative agreement for conditions of deep, low elevated ducts. Agreement for higher, thinner ducts was poor. Multilayered duct systems were observed and produced interference patterns without recognizable period with range.