Satellite System Interference Tests at Andover, Maine

Tn order that satellite communication systems and terrestrial microwave systems may share successfully the same frequency band, it is in general necessary that the earth station of the satellite system and microwave station be separated physically so that line-of-sight transmission between them is not possible. Under these conditions, either the scatter mode or diffraction mode of transmission predominates, depending on the path profile. While a considerable amount of data on such transmission is available with transmitting and receiving antennas pointed at one another and only elevated sufficiently to graze the horizon, very little data have been taken with one of the antennas, the earth station antenna in this case, randomly oriented in azimuth and elevation. Predictions have been made that it should be possible to operate point-to-point microwave systems in the same radio frequency band as the satellite system at distances of some 45 to 150 miles removed from the earth station, or even less, provided that (a) the earth station antenna is not operated at an elevation angle less than some minimum value, for which 7.5 degrees has been suggested, (b) suitable terrain blocking exists, and/or (c) a certain amount of angular discrimination is provided by the antenna of the radio relay terrestrial station. 1,2