| 摘要 |
PURPOSE:To make after-tuner adjustment unnecessary, by using a mechanical filter having an inherent frequency selectivity and a resistor having no frequency selectivity and compensating the loss in the IF signal level caused by the above- mentioned filter by means of an amplifier having no frequency selectivity. CONSTITUTION:The output of a tuner 3 is amplified by means of a high-gain amplifier 44 and the intermediate frequency of the amplifier 44 is subjected to frequency selection at a mechanical filter 55. The signal obtained by the filter 55 is supplied to a video detector 7 and video signals are obtained. An amplifier having an amplification factor which can compensate the loss of the filter 55 is used as the amplifier 44. Since the filter 55 has a sharp inherent frequency selectivity, interference can be eliminated. A resistor 99 having no frequency characteristic, for example, can be used for the video detector 7 instead of conventional IF amplifiers and tank circuits of detectors. In other words, a wide band detector 66 can be used as the detector, because the filter 55 has the sharp frequency selectivity.
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