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德生PL737数字调谐收音机在接收短波电台时,其自动搜索功能只能在几个小范围内进行,还有一大部分的短波频率(约占该机短波覆盖的80%)在自动搜索时则自动跳过。为此,笔者为该机增加了寻台附加电路,现简述如下。电路原理如图1所示。NE555及外围阻容元件组成多谐振荡器,周期为0.1～1s可调,振荡器输出的信号控制两个模拟电子开关
When the German PL737 digital tuned radio receives shortwave radio, its automatic search function can only be carried out in a few small areas, there is a large part of the shortwave frequency (about 80% of the aircraft shortwave coverage) in the automatic search is automatically jump over. To this end, the author added to the aircraft to find additional circuits, are summarized below. Circuit shown in Figure 1. NE555 and external RC components form multivibrator, the period is 0.1 ~ 1s adjustable, the oscillator output signal control two analog electronic switch