Microwave propagation studies and correlation with sodar structures observed over a hilly terrain in Southern India

Abstract

Simultaneous observations of sodar echograms and microwave amplitude measurements are carried out to study radio wave propagatIon characteristics on a line-of-sight microwave link over a hilly terrain using an operational communication link between Tirupati and Tiruttani situated in Southern India. The studies show that convective conditions do not affect the microwave signal amplitude, whereas ground-based inversions of thickness < 100 m cause an average fade depth of 5 dB. The ground-based inversions of thickness > 100 m, multilayered structures and wave motions are mostly responsible for severe fading and cause deep fades of 20 dB or even more. The observed fade-outs are largely due to rising inversions, as they generate sub-refractive conditions in the convective region during the morning transition hours.