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在电视信号较弱的山区,如果把差转机的高频调谐器直接安置在接收天线下方,只经一米左右的同轴电缆把信号馈入高频调谐器内进行放大和第一次混频,这样,由于在最靠近天线处进行放大和第一次混频,相应地提高了信号电平及信噪比,使转发出来的电视信号图象及伴音质量明显提高。具体联线看附图。图中+12V电源直接由差转机内取出,并与中频信号共同由一根同轴电缆输送。由3k电阻及3V稳压管组成简单3V稳压源向高频头AGC端提供偏压,保证高频头内高放级处于最佳放大状态。
In the weaker mountain area of the television signal, if the high-frequency tuner of the transcoding machine is placed directly under the receiving antenna, only one meter or so of coaxial cable feeds the signal into the high-frequency tuner for amplification and the first mixing In this way, the signal level and the signal-to-noise ratio are correspondingly increased due to the amplification and the first mixing at the closest position to the antenna, so that the quality of the transmitted television signal image and sound quality is obviously improved. Specific line to see the drawings. The figure + 12V power directly from the transfer machine removed, and jointly with the IF signal from a coaxial cable. By 3k resistor and 3V regulator composed of a simple 3V regulator source to the AGC-side high-frequency head to provide bias to ensure high-frequency head high-grade amplifier in the best state of enlargement.