Radio propagation over a cylindrical hill including the effect of a surmounted obstacle

An analysis is presented for wave propagation over a smooth cylindrical surface of constant curvature when the boundary impedance is specified. High-frequency approximations are introduced which permit a universal plot of the diffraction loss as a function of a hill-height parameter. The results are extended to allow for the presence of a knife-edge obstacle located on the crest of the rounded hill. For the conditions considered, the latter produces a substantial gain which, to some extent, overcomes the diffraction loss associated with the hill. The results have direct application to HF and VHF radio propagation over heavily vegetated and forested terrain.