Beyond the line-of-sight propagation of VHF and UHF radio signals in the Middle East Arabian Gulf areas

The refractivity parameter, N, in general, is written in terms of the climatic variable of the atmosphere, namely the pressure, temperature, and partial water vapour pressure, at the considered height. N, under normal atmospheric conditions (temperate, or civil aviation), decreases uniformly with height up to a generally accepted height of 10 km. If, however, there is an anomaly in, especially the temperature profile, the refractivity profile is no longer uniform and propagation effects such as sub-refraction, super-refraction and ducting can occur, and the radio signals can be directed into the diffraction region. There was evidence that unusual propagation conditions occurred in the public land mobile radio bands in the State of Qatar. Also signals clearly could travel over large distances. To examine the happenings more rigorously, a set of fixed frequency CW beacons were installed on existing radio masts at various outposts in the State