| 摘要 |
PURPOSE:To eliminate the need for the change in the oscillating frequency at each channel selection operation by impressing an impulse signal using the same frequency as the channel interval of a broadcast band as a fundamental frequency as an adjusting signal to a receiver input terminal. CONSTITUTION:For example, a position change in a channel selection variable resistor is given to a tuning control circuit 9 as a voltage change, the tuning control circuit 9 changes over a switch circuit 10 to be a position Shown in figure, and changes gradually a reverse voltage of a tuning varactor diode inlcuded in a tuning amplifier circuit 2. In inserting an IF filter of narrow band into a peak detection circuit 8, many harmonics are subject to frequency conversion into an IF signal by the tuning amplifier circuit 2, a mixer 3 and an IF amplifier circuit 6, only a harmonic having the same frequency as a reception desired frequency is selected from the IF signals and its peak value is detected. Since the output of a pulse generating circuit ll includes frequencies corresponding to all broadcast stations in this way, it is not required to change the oscillating frequency at every channel selection.
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