| 摘要 |
PURPOSE:To adjust easily a tuning characteristic of a high frequency amplification part by controlling variably a tuning element of a selective amplifier in the high frequency amplification part by using a microcomputer so that the intensity of an IF signal is maximized. CONSTITUTION:A broadcasting signal intensity level output 4 is taken out to an A/D converter 5 through the high frequency amplification part 1, a frequency conversion part 2 and an IF amplification part 3 which are constitutional elements of a synthesizer tuner. The output of the A/D converter 5 is sent to the microcomputer 6, the output of the computer 6 is D/A converted by a D/A converter 7 and the analog signal is supplied to the amplification part 1 as a varicap control voltage 8. At that time, the voltage 8 is set up to an initial value and the broadcasting signal intensity is read out by the converter 5 and stored in the computer 6. Subsequently, the voltage 8 is change and the broadcasting signal intensity at that time is read out by the converter 5 and compared with the preceding intensity by the computer 6. If the read out value is larger than the preceding value, the current value is stored, and if smaller, the operation is stopped at that time. Thus, the varicap control voltage is set up to the maximum point of the radio broadcasting signal intensity by repeating said operation. |
