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Several authors have suggested that hills, earth walls, excavated pits, or same other such obstacle might be used to shield ground-terminal antennas of satellite-to-ground communication links from radiated interference propagating at low angles (troposcatter, groundwave, etc.). As the tradeoff is between access or look angle and shielding efficiency, such pits would be most useful for synchronous satellite systems, but they might be applicable for other systems. This paper presents measured isolation provided by three representative pits at two frequencies (2.3 and 9.0 Gc) in the band presently proposed for communication satellite systems (1-10 Gc). One pit had a vertical wall, one a sloping wall, and the third a rounded sloping wall. Isolation of 40 dB appears feasible, and possibly more could be achieved with specially designed pit walls.