As far as I know, most squelch circuits work by simply comparing the AGC voltage to a threshold and only enabling the audio amp chain when they detect a total signal strength over a certain value. Why bother with trying to detect white noise if you have access to the AGC voltage (which is what is causing the majority of the quieting effect anyway - the AGC turns down the gain when a strong signal is detected) Sean On Sun, Jun 24, 2012 at 3:23 PM, Dave wrote: > This might be easier to solve in analog since squelch circuits are easy. > > Manu Abraham wrote: > >>Hi, >> >>Maybe a filter could help ? >> >>Regards, >>Manu >> >>On Sun, Jun 24, 2012 at 10:50 PM, wrote: >> >>> >>> >>> =A0 =A0 Hi, >>> >>> =A0 =A0 I want to build a FM radio squelch using a microprocessor with = an ADC. >>> =A0 =A0 The ADC will be sampling the FM radio audio output and turn on = a >>> LED when there is only noise present. The LED will be off when someone >>> is using the channel (no noise, just voice). >>> >>> =A0 =A0 What is the best way of doing this in software? >>> >>> =A0 =A0 Thanks for any idea. >>> =A0 =A0 Mark Jordan >>> >>> >>> >>> >>> >>> -- >>> http://www.piclist.com PIC/SX FAQ & list archive >>> View/change your membership options at >>> http://mailman.mit.edu/mailman/listinfo/piclist >>> >>-- >>http://www.piclist.com PIC/SX FAQ & list archive >>View/change your membership options at >>http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .