Shooting from the hip here... never done it or delved into DSP functions mu= ch. An FFT to get amplitudes of a number of frequency bands. Without looking into things I imagine white noise will have a flat average = amplitude over these bands, while transmissions will have varying amplitude= s [With some the newer styles of music this may not hold true ;) ] Manu Abraham wrote: Hi, Maybe a filter could help ? Regards, Manu On Sun, Jun 24, 2012 at 10:50 PM, wrote: > > > Hi, > > I want to build a FM radio squelch using a microprocessor with an ADC= .. > 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). > > What is the best way of doing this in software? > > Thanks for any idea. > 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 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .