Study on rain attenuation and fading on a terrestrial microwave link

Signal strength fluctuations on the 11 GHz line-of-sight microwave link situated in Southern part of India between Puducherry and Madras with a hop length of 31.2 km have been recorded at the receiving end, Madras. The signal strengths have been recorded on a strip chart recorder on 24 hour basis from August 1989 to February 1990. The rain rate at this location is recorded with a conventional rain gauge. A preliminary examination of the records shows prominent effects of rain attenuation. The diurnal and seasonal variation of field strength and fading characteristics of this microwave link are discussed. A detailed study of median signal (dBm), fade rate/hour, fade depth (dB) and scintillation index (percent) is made. The fading effects, particularly noticeable at night during the winter months, can be classified into three distinct types. The first is characterised by slow fading of small amplitudes, the second is also slow fading with deep fades superposed and the third is characterised by fast fading.<>