It is easier than it sounds.
Sample the audio above the highest expected audio. Any signal above 4khz=20
in a radio with a 3khz bandpass is white noise. Logically speaking,=20
(White noise) =3D NOT (Audio). Be careful of Patents though. I know there=20
was a patent issued in the mid-1980's for selecting the best usable comm=20
channel of a redundant set of channels.

Don't let this discourage software/DSP discussion. I am really=20
struggling with especially the DSP aspect.

On 6/24/2012 1:20 PM, enkitec@gmail.com wrote:
>
>       Hi,
>
>       I want to build a FM radio squelch using a microprocessor with an A=
DC.
>       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
>
>
>
>
>

--=20
John Ferrell W8CCW
=93During times of universal deceit,
   Telling the TRUTH becomes a revolutionary act=94
      George Orwell




--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.