. The Bell System technical journal . condition is a measure of the delay of the system being 1* Compare Phase Compensation III—Nyquist Method of Measuring TimeDelay da/dw, E. K. Sandeman and I. L. Turnbull, Electric Communication, Vol. \II,p. 327, 1929. MEASUREMENT OF PHASE DISTORTION 541 measured. If the detector were balanced with a zero delay system and,then, rebalanced with the system under question inserted, the differ-ence in these readings as given by the phase shifter would indicatethe delay of the system. An integral multiple of tt might not be takencare of in this measurement, but t
. The Bell System technical journal . condition is a measure of the delay of the system being 1* Compare Phase Compensation III—Nyquist Method of Measuring TimeDelay da/dw, E. K. Sandeman and I. L. Turnbull, Electric Communication, Vol. \II,p. 327, 1929. MEASUREMENT OF PHASE DISTORTION 541 measured. If the detector were balanced with a zero delay system and,then, rebalanced with the system under question inserted, the differ-ence in these readings as given by the phase shifter would indicatethe delay of the system. An integral multiple of tt might not be takencare of in this measurement, but this is of little consequence. For the modulating frequency of 25 cycles, a phase shift of ninedegrees in the envelope of the 25-cycle modulation corresponds to adelay of .001 second. For convenience, therefore, the phase shifterused in this set is arranged in steps so that each step corresponds to aphase shift of nine degrees, or a delay of .001 second. In order toread intermediate values of delay, an auxiliary phase shifter, which. Fig. 8—Arrangement for direct measurement of envelope delay at low frequencies. consists of a variable condenser bridged across the output circuit ofthe detector tube, is used and calibrated directly in steps of .0001second. This particular delay measuring set has been found quite useful inthe frequency range of 300 to about 10,000 cycles per second. Theabsolute value of delay, of course, is not that which is measured,but this can usually be determined from the measured value byadding this measured value to the integral multiple of .04 second,which is suitable for the case in hand. (2) For measurements below 300 cycles, the circuit arrangementshown in Fig. 8 can be advantageously used. This is based on princi-ples exactly the same as those just described but differs considerablyin the application of these principles. Here a relatively low frequency must be used for modulation. Oneand a quarter cycles per second has been chosen because it is sati
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