I think the noise will be filtered by the audio circuits in the=20
radio, so there will be little noise above 3kHz.
     Voice or noise will use the same bandwidth.

     Mark



On 24-Jun-12 17:48, John Ferrell wrote:
> It is easier than it sounds.
> Sample the audio above the highest expected audio. Any signal above 4khz
> in a radio with a 3khz bandpass is white noise. Logically speaking,
> (White noise) =3D NOT (Audio). Be careful of Patents though. I know there
> was a patent issued in the mid-1980's for selecting the best usable comm
> channel of a redundant set of channels.
>
> Don't let this discourage software/DSP discussion. I am really
> 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=
 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
>>
>>
>>
>>
>>


--=20
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