| 摘要 |
PURPOSE:To remove the interruption of operation at a channel selecting time by obtaining an RFAGC signal by two IF circuits. CONSTITUTION:An RFAGC signal is outputted from respective IF circuits IFv, IFs and sent to an RFAGC switching circuit 10 and the gain of an electronic tuner 1 is controlled by a channel selection control circuit 5 on the basis of the RFAGF signals from both the IF circuits IFv, IFs. In the normal receiving state, said AGC is controlled by the RFAGC signal outputted from the video IF circuit IFv. If a tuning voltage is not a correct voltage value at the time of channel selecting operation, a video IF carrier in the IF signal is shifted from a regular frequency. If the IF frequency is shifted to the positive side (e.g. +500kHz-1MHz), the RFAGC signal is not outputted from the video IF circuit IFs, but the gain of the electronic tuner 1 is controlled by the RFAGC signal outputted from the voice IF circuit IFs and the channel selecting operation due to the generation of spurious can be prevented from bad influence or interruption.
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