| 摘要 |
PURPOSE:To eliminate noises, by performing the changeover between a radio reception mode and a TV reception mode when a varicap voltage exceeds the prescribed value. CONSTITUTION:The varicap voltage of a tuning varicap D1 is 6V in 90MHz and 8V in 95.75MHz, respectively, No current flows to a Zener diode D2 in the varicap voltage of 6V or so when the Zener voltage of the diode D2 is about 7V. The varicap voltage becomes 8V in the tuning frequency of 95.75MHz, and the current flows to the diode D2. Thus an pulselike noise eliminating circuit 46 is earthed, and as a result, the signals supplied to the circuit 46 are delivered as they are. Accordingly, the malfunction of the circuit 46 caused by the effect of the subcarrier wave used for the multiple voice broadcast of TV is prevented to produce no noise. |
