| 摘要 |
PURPOSE:To automatically perform a tracking adjustment between a high frequency amplifier circuit and a local oscillation circuit by changing tuning frequencies in the first and the second tuning circuits, and setting a video carrier wave level and a sound carrier wave level at maximum. CONSTITUTION:A tuner part A is constituted with a pre-selector, 1 a high frequency (RF) amplifier 2, a band-pass filter 3, a mixing circuit 4, an intermediate frequency transformer 5, and a local oscillation circuit 6 on which a tuning voltage is applied. Voltages corresponding to the video carrier wave level and the sound carrier wave level detected at a tracking detection part 18 are supplied as data to a microcomputer 21 through an A/D converter 19. The voltage impressed on variable capacitance diodes in the pre-selector 1 and the band-pass filter 3 is made change through D/A converters 23, 25, and 26, and the gain of the RF amplifier 2 is controlled through an AGC controller 24, and the voltage corresponding to the video carrier wave level, and the voltage corresponding to the sound carrier wave level can be maximized.
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