Multipath Effects Observed over Long Hop Hilly Terrain Line-Of-Sight Microwave Links

Microwave signal strength measurements have been carried out for a period of 3 years over two long hop line-of-sight microwave links situated in southern India between Elagiri-Tirumala and Pallavaram-Tirumala over a pathlength of 142 and 117.5 Km. The recordings have been supplemented by the acoustic sounding data being probed at Tirupati. Deep fading periods are correlated with different atmospheric structures and also with the radiosonde data collected from the India Meteorological Department observatories. It is found that most of the fading observed is associated with the layered structures that are below the transmitter and can exist upto a height of 500 metres. It is suggested that since high fading is associated with the layers in the regions below the transmitter height, the antennas should be lifted upwards to reduce the fading during the convective conditions.