Re: Q regarding DSP filtering [K3]

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Re: Q regarding DSP filtering [K3]

Vic K2VCO
DaleJ wrote:

> Are the DSP filters within the agc loop?  I can't seem to find anything about
> this in the manual.  

Yes, the main AGC loop includes the DSP filters. But there is also a
'hardware' AGC that kicks in on very strong (S9+30) signals that are
within the crystal passband but outside of the DSP passband. This
hardware AGC acts before the DSP (but usually does not act at all).

I believe the above to be essentially true but maybe a bit oversimplified.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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Re: Q regarding DSP filtering [K3]

David Woolley (E.L)
Vic K2VCO wrote:
DaleJ wrote:
>
>> Are the DSP filters within the agc loop?  I can't seem to find

For the K2 no.  For the K3 read on.

>> anything about
>> this in the manual.  
>
> Yes, the main AGC loop includes the DSP filters. But there is also a

More precisely, the main AGC function is entirely implemented in
firmware.  The Elecraft schematics do not include the equivalent signal
flows in the firmware, and they can vary from release to release,
however, I would expect the AGC function to be implemted betwee IF and
AF filters, but the AGC loop not to actually contain either filter, so
that the IF signal processing is done with maximum signals, to maximise
dynamic range.  Doing it before the AF DSP would, I think, be essential
in order to support FM and full carrier AM.

> 'hardware' AGC that kicks in on very strong (S9+30) signals that are

I would expect this loop to sense the signal immediately after A/D
conversion, to allow the rig to prevent the A/D convertor from clipping.

> within the crystal passband but outside of the DSP passband. This

I think the function is needed for signals within the passband, as well,
as it will be there to prevent the A/D convertor saturating.


--
David Woolley
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