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目前市面上流行的有线电视频道变换器大体分为两种:二次变频式变换器和解调调制(中频)式变换器。 二次变频式变换器利用二次变频技术,首先将射频电视信号频谱上移到1GMHz完成第一次变频,再将变频后的信号通过选频回路频率下移到1频道,供电视机用户收看,实现第二次变频。理论上每次变频有3dB的信号衰减,二次变频式变换器理论上应有6dB的损耗,实际一般损耗均为9～10dB左右。 笔者介绍的ADD电视频道变
Currently on the market popular cable channel converter can be divided into two types: the second frequency converter and demodulation modulation (IF) converter. The second frequency converter using frequency conversion technology, the first radio frequency television signal spectrum shifted to 1GMHz to complete the first frequency conversion, and then the frequency of the signal through the frequency of the selected frequency down to 1 channel for TV users to watch , To achieve the second frequency conversion. In theory, every time there is a 3dB signal frequency attenuation, the second frequency converter should theoretically 6dB loss, the actual average loss of about 9 ~ 10dB. The author introduced ADD TV channel change