Mountain obstacle measurements

During 1955 several hundred paths were tested for mountain obstacle transmission loss in approximately 40 different locations in California, U.S.A. Thorough investigations were made of representative frequencies from 50 to 500 mcs. Limited measurements were made at 900 and 1800 mcs. Almost without exception all paths planned provided the anticipated obstacle-gain phenomena. Suitable techniques were evolved whereby these phenomena may be used to extend radio communication ranges in mountainous areas along non-line-of-sight radio paths. It has been shown that 20- 30 db reduction in comparison to tropospheric scatter paths in path loss is readily obtainable in mountainous areas. In comparison with smooth earth paths the obstacle "gain" figures are in the order of 70 to 80 db. A reliable and accurate means for computing the mountain obstacle transmission loss, and a simplified siting procedure were developed.