[Elecraft] [K3] AGC White Paper

[Alan Bloom]

If the AGC is working right, it is equivalent to manually riding the RF 
gain control.  It shouldn't affect the decoding.

If the AGC time constant is too fast then, yes, it can cause distortion 
and degrade the decoding.  But that should never happen in a 
properly-designed AGC system.

AGC makes the decoder's job easier, not harder, because it reduces the 
dynamic range the decoder has to deal with.

Alan N1AL


On 03/07/2017 01:19 PM, Ed Muns wrote:
> Decoders operate on the audio stream presented to them from the receiver.
> The decoding algorithms use the difference in audio level at each instant in
> time to make bit decisions.  AGC reduces those differences and thus
> increases the bit error rate.
>
> Of course, it is important to adjust the absolute audio levels so that the
> dynamic range of the signal(s) is placed within the dynamic range of the
> decoder.  But, compressing the dynamic range, i.e., AGC, increases the error
> rate of the decoder.
>
> Ed W0YK
> _________________________________________________________________
>
> -----Original Message-----
> From: Bill Frantz [mailto:frantz at pwpconsult.com]
> Sent: 07 March, 2017 13:05
> To: ed at w0yk.com
> Cc: elecraft at mailman.qth.net
> Subject: RE: [Elecraft] [K3] AGC White Paper
>
> What I get using a relatively flat AGC is automation of my
> riding the RF gain control. I don't see how this kind of
> automation affects decoder performance. It should help
> performance as the decoder has a nearly constant level signal to
> work with. Please explain.
>
> Thanks - Bill AE6JV
>
> On 3/7/17 at 11:37 AM, ed at w0yk.com (Ed Muns) wrote:
>
>> Just the opposite.  Most digital signal decoders work best with the least
>> AGC action possible, even AGC Off.  AGC constrains decoder performance.
>>
>> Ed W0YK
>> _____________________________________________________________________
>>
>> -----Original Message-----
>> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill
>> Frantz
>> ...
>> Now to use SLP=15 for digital, where I want the AtoD to not
>> have to deal with a big range, while using something with more
>> dynamic range for voice/CW.
>
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