U.H.F. propagation over rounded hills

Several features of the diffraction of electromagnetic waves by large obstacles are examined both theoretically and by optical experiments using a laser source and idealised models. The underlying purpose of the work was to establish and verify, where possible, working methods of estimating the field strength in the shadows of rounded hills. The emphasis throughout is largely on the propagation conditions which arise in u.h.f. broadcasting, where ordinary terrain has a near-dielectric behaviour and its surface becomes effectively rough. Guided by the results of the simulation experiments, an attempt is made to deal with hill crests whose surfaces are randomly rough and with those of irregular shape.