Vector-response indicator

THE performance characteristics of a communication circuit are often conveniently described in the form of a response curve which indicates the steady-state transmission of the circuit at frequencies within the range of interest. These curves can be obtained by making a sufficient number of individual measurements of transmission at various frequencies within the band of interest and plotting the results; however, considerable time may be saved by the use of a device which indicates directly the desired curve. Many such response-curve tracers are found in radio laboratories, the same frequency, is a vector quantity having an angle as well as a magnitude — the angle being the phase angle between the output voltage and the input voltage. The response-curve tracers now in general use indicate only the magnitude of the amplification as a function of frequency. The vector-response indicator described in this paper is a unique apparatus that indicates directly both the magnitude and phase angle of the transmission as a function of frequency. This vector response of the circuit is indicated by a special type of pattern on the screen of a simple cathode-ray tube.