A Phase Tracking Interferometer

A series of radio telescope receivers has been developed to operate in a switched interferometer system of the type described by Ryle. The new features of the equipment include automatic tracking and recording of the phase difference of a coherent signal at the two receiver input terminals. Chart recorded outputs of total power, signal power, and signal phase are provided. The receiver utilizes dual low-noise rf amplifiers with a high degree of frequency selectivity. Fixed delay lines are available in both receiver channels to allow operation on the higher order lobes of the interference pattern. Front panel controls include a precision gain control, a receiver bandwidth selector, manual and automatic phase tracking controls, and signal power and total power integration time constant switches. Background and signal noise sources are provided for direct calibration of the receiver. Three of these receivers are currently in operation on frequencies of 53 mc, 108 mc, and 470 mc in a two-antenna drift interferometer at the National Bureau of Standards Laboratory in Boulder, Colo.