Frequency deviation measuring and adjusting system

摘要

A calibrated unipolar signal is used to deviate a frequency modulator by a predetermined amount DELTA f from a carrier f2. An automatic frequency control circuit operates to bring the carrier back on frequency and a meter connected in the control circuit will read this departure from normal. During the test for correct deviation, a frequency shifter compensates for the predetermined frequency deviation and the meter would so indicate, e.g., would not change reading from that of carrier alone, if the deviation caused by the calibrated unipolar signal is equal to that incorporated in the frequency shifter. If the reading does change, the modulation sensitivity of the frequency modulator is adjusted until the readings before test (using carrier only) are the same as those under test.