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两次变频收音机电路并不是什么新花样.一般的收音机是把外来的高频信号变为中频信号(不论中波或短波,大都变为465千赫),然后进行中频放大、检波等过程;而两次变频式收音机首先把外来高频信号变成第一中频信号,然后再把第一中频信号变为第二中频信号(大都为465千赫),以下同样是中频放大、检波等过程(图1);在实际应用过程中,第一中放级可要可不要.第一中频一般选在1-5兆赫,第二中频仍可
Two frequency conversion radio circuit is not a new tricks.General radio is the external high-frequency signal into an IF signal (regardless of the medium or shortwave, most into 465 kHz), and then the IF amplification, detection and other processes; and Two frequency conversion radio first foreign high-frequency signal into the first IF signal, then the first IF signal into the second IF signal (mostly 465 kHz), the following is the same IF amplification, detection and other processes (Figure 1); In the actual application process, the first release level may not want to. The first IF generally selected at 1-5 MHz, the second IF is still