Gain of Electromagnetic Horns

Recently, a standard horn was used as a calibration reference in measuring the gain of a 400-square foot aperture horn-reflector antenna at 4080 mcs.1 Since the horn-reflector antenna is currently being used for precision measurement of the absolute flux of stellar radio sources, it is desirable that the gain of the standard horn be known as accurately as possible. From previous work,2 the calculated gain7 of a standard horn was believed to be within ± 0 . 1 db of its true gain. Our purpose was to measure the absolute gain of the standard horn to an accuracy better than that previously achieved. The gain of a standard horn can be determined by measuring the transmission loss versus separation between two identical standard horns. In the technique of measurement commonly used, the separation distance is not large, and it is well known that the far-zone power transmission formula PR/PT = (GX/^r)2 5*27 (1)