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(上接第 16期 )变频调谐部分电路的核心是在进行变频的同时预选接收频道 ,它将第一中频信号 (95 0～ 145 0ＭＨｚ)变成解调前的固定第二中频信号 (如 140ＭＨｚ或 4 79.5ＭＨｚ) ,在 5 0 0ＭＨｚ的带宽内均能工作 ,并能选择 2 4个频道内的任一个频道。变频调谐部分的工作原理 :
(Continued from the 16th) Frequency tuning part of the circuit is the core of the pre-selected receive channel frequency conversion, which will be the first IF signal (95 0 ~ 145 0MHz) before the demodulation into a fixed second IF signal (such as 140MHz Or 4 79.5MHz), can work within the bandwidth of 500MHz, and can choose any one of 24 channels. Frequency tuning part of the working principle: