Radio Receiver Testing Equipment

Abstract

The difficulties of measuring radio receivers and the lack of standardized equipment has made necessary the development and construction of special apparatus for this purpose. Generally speaking, determining the characteristics of the input signal to the receiver, the conditions of receiver operation, and the character of the resulting output will serve as a proper measure of performance. The "transmitter" utsed in the measuring setup has associated equipment in the way of attenuators, vacuum-tube voltmeters, modulationt meter, and monitor and frequency supervision, so as to control rigidly and to know wlith great accuracy the character of the inpult signal. T'he design and usage of these various units are described in detail. Emphasis is placed on the proper design and use of vacuumn-tube voltmeters. A novel modulation meter is described, being simple and accurate.Power meassuring panels, screening, and other precautions are noted for mainltaining the receiver under test in proper operating condition. The output power may be measured under different conditions of usage. A "distortometer" of new design is described, enabling the distortion and overload of the output to be directly measured.Proper operation of thts test equipment will measure radio-frequency amiplification, audio-frequency amplification, and detector sensitivity. It will show thle radiofrequency selectivity, the audio-frequency fidelity, the overall fidelity, and the overall selectivity. Thefrequency range of the receiver may be measured. The "hum" voltage of the output may be noted. The maximtum undistorted ouitput of thle receiver and the percentage of overload at acny output can be found. The miethods of obtaining these data are given in the paOpe-.