Effect of Fresnel zone clearance on propagation characteristics of microwave links in hilly terrains

29-38The effect of Fresnel zone clearance on microwave propagation over a hilly terrain has been studied. The ray tracing technique for radio rays through the troposphere has also been discussed. The ray paths were traced for different elevation angles under varied meteorological conditions. Under subrefraction conditions, there was insufficient Fresnel zone clearance which leads to fade-outs of the received microwave signals. The antenna height at the transmitting end at Tiruttani was increased from 50 to 90 m to provide enough Fresnel zone clearance. A comparison of the performance of the microwave link before and after the modification of the antenna height has been presented. Propagation characteristics of Elagiri-Tirumala and Pallavaram-Tirumala microwave links situated over a hilly terrain are also presented. The field strength data have been analysed in terms of fade rate, average fade depth and scintillating index. The diurna