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伴音通道电路的作用是将从预视放输出的第二伴音调频中频信号经6.5MHz带通滤波器、中频放大器和中频限幅放大器、鉴频器和音频功率放大器后,送到扬声器还原成伴音。 预视放输出的信号除包含有第二伴音中频信号之外,还有全电视信号,这两种信号混合在一起,但频率不同。用6.5MHz带通滤波器可从中取出第二伴音中频信号,而频率低于6.5MHz的全电视信号被滤除。 由带通滤波器取出的第二伴音中频信号,送入中放级进行电压放大,以使中频信号的幅度达到鉴频器所需要的电平值。因为只对中频信号放大,所以中频放大器是调谐放大器。由于调频信号的幅度变化通过鉴频器电路后会引起干扰,为此要在鉴频器前加一级限幅放大器,削去干扰成分,
Audio channel circuit is the role of the second sound from the pre-amplifier FM IF signal through the 6.5MHz band-pass filter, IF amplifier and IF limiting amplifier, discriminator and audio power amplifier, sent to the speaker to restore sound . In addition to the pre-broadcast signal output contains the second audio IF signal, there are all television signals, the two signals mixed together, but the frequency is different. With 6.5MHz bandpass filter can be taken out from the second audio intermediate frequency signal, and the frequency of less than 6.5MHz full television signal is filtered out. The second audio intermediate frequency signal taken out by the band-pass filter is sent to the intermediate amplifier stage for voltage amplification so that the amplitude of the intermediate frequency signal reaches the level value required by the frequency discriminator. Because only the IF signal amplification, so the IF amplifier is tuned amplifier. As the FM signal amplitude changes through the frequency discriminator circuit will cause interference, this should be in front of the frequency discriminator plus a limiting amplifier, cut off the interference components,