| 摘要 |
PURPOSE:To perform the tracking adjustment for a tuner, by holding the control voltage, which is given to a varactor diode, in a prescribed voltage value by a control voltage holding circuit. CONSTITUTION:When a switch 17 is operated to operate the channel selecting operation system, a channel selecting operation detector 16 becomes the detection state to detect a channel selecting operation detection signal. An RF input connector/disconnector 11 makes the RF input system disconnected, and an RF oscillating circuit 18 set an RF amplifying circuit 12 to the oscillation state. Then, a signal of the differential frequency between the oscillation frequency of the RF amplifying circuit 12 and the local oscillation frequency of a local oscillator OSC is outputted from the output terminal of a mixer 13. This output signal is supplied to an IF comparator 14 and is compared in phase with a reference IF signal, and a control voltage corresponding to the phase difference is given from the output terminal to a varactor diode VCD through a control voltage holding circuit 15. The capacity of the diode VCD is changed to make the output signal of the mixer 13 coincident with the reference IF signal. |
