Mountain cliffs constituting knife edges influence radio wave propagating from VHF to microwave frequencies. The diffraction phenomena caused by these single or multiple knife edges are a dominant propagation mechanism that has to be taken into account in planning TV, FM networks, cellular radio, microwave network, etc., in mountainous regions. In order to investigate the above mechanism field strength measurements were conducted over five double knife edge paths and the measured signal levels are compared with several prediction techniques. The deviations of the prediction techniques and their suitability are presented in this paper. It is seen that out of all the prediction methods Giovanelli’s method gives best agreement with the observed results.