普通袖珍收音机大多采用CXA1019系列集成电路。这种集成设置LED调谐指示,但没有设静噪。FM调谐到电台时,指示灯点亮;调谐不到电台时,指示灯不亮,并伴有较大的“沙沙”声,令人生烦,收听时不得不减小音量再调台,十分不便。针对这个缺点,笔者利用调谐指示加装静噪功能,并且不影响指示。加装的电路如图所示。本静噪电路实质上是由V1、V2组成的电子开关管。当没有调谐到电台时,⒆脚没有电流输出,V1因得不到基极电流而截止,+3V经R2、R3加到V2的基极而使其导通,把信号V0旁路到地,达到静噪的目的。当调谐到电台时,⒆脚有电流输出, Most pocket radios using CXA1019 series integrated circuits. This integration sets the LED tuning indication, but no muting is set. When the FM is tuned to the radio, the indicator light is on; when the radio is not tuned in, the indicator light is not on and accompanied by a large “rustle” sound, it is annoying to listen to, . In response to this shortcoming, I use the tuning instructions to install the mute function, and does not affect the instructions. The installation of the circuit as shown. The squelch circuit is essentially composed of V1, V2 electronic switch. When not tuned to the station, there is no current output pinch, V1 because the base current can not be cut off, +3 V by R2, R3 added to the base of V2 and make it turn, the signal V0 bypass to ground, Squelch to achieve the purpose. When tuned to the radio, the pin has a current output,