| 摘要 |
PURPOSE:To eliminate essentially the image interference in a UHF-VHF tuner device, by setting an intermediate frequency between 325MHz and 340MHz. CONSTITUTION:A television signal of the VHF or UHF band received by an antenna 1 is amplified by an RF amplifier 2 or 8, and the signal of the VHF band is supplied to a mixer circuit 3 and has the frequency converted into a prescribed IF signal in a range of 325-340MHz by the local oscillation signal from a local oscillator 4. Meanwhile, the signal of the UHF band amplified by the RF amplifier 8 is supplied to a mixer 9 and is converted to the same frequency as the VIF frequency by the local oscillation signal from a VCO10. This converted UHF signal is supplied to the mixer circuit 4 which is operated as a mere VIF amplifier at a UHF receiving time. Thus, the VIF frequency is set to a frequency higher than the conventional that to eliminate essentially the image interference. |
