| 摘要 |
PURPOSE:To shorten the time required for presetting by varying the value of tuning voltage data slowly in the opposite direction after a detection signal is inputted from a tuning detecting means. CONSTITUTION:A computer 30 increases the value of the tuning voltage data the value of a tuning signal also varies with the duty ratio of a PWM wave generator 38. Then when an oscillator 14 varies in frequency toward the frequency at the time of the reception of two channels, the frequency of an IF signal from a mixer 16 also varies, so that the variation in the voltage data is stopped at 45.75 MHz with the detection signal of an IF frequency detecting circuit 36. The PWA signal, however, is delayed by a low-pass filter 26 and the IF frequency is as high as the frequency at a point (b), so the value of the tuning voltage data is varied slowly in the opposite direction a certain time later and the computer 30 stores the tuning voltage data when the IF frequency detecting circuit 36 outputs the detection signal again.
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