K2 AGC, Seems a bit soft

[Paul Pollock]

I am enjoying my recently completed K2-6148 very much, but I had a  
couple of questions and thought others might have some constructive  
thoughts.

While some folks like a slightly soft AGC in the receiver, I'm one of  
those folks that finds that soft signals received softer than loud  
signals (especially SSB) is tiring. I prefer a very stiff and level  
AGC. Mind you, this has nothing to do with the fast/slow delay rates  
or anything along those lines.

1). My K2 exhibits good AGC performance and I believe it works as  
designed, but it is a soft AGC. Are there any ideas on modifications  
to the AGC IC (LM833) that might stiffen the AGC performance?

2). I'm another of those folks where my AGC threshold voltage will  
not go above 3.7x volts. It is my feeling that a threshold set so  
that the AGC actually releases at the noise level is better than a  
setting where the AGC is ON at all levels. On my K2 the AGC never  
releases at any level. Any thoughts on getting the AGC to release  
correctly?

Thanks in advance!
-Paul Pollock KD7BWB

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[Don Wilhelm-4]

Paul,

You may find some information in the archives that could possibly help
your situation.  Jack Smith K8ZOA has documented a good amount of info
on the AGC operation on his website and Dave White VE6DRW has created a
mod to give more control over the various AGC characteristics.
Look for their posts to the reflector in the February and March 2007
timeframe.

It is quite likely that neither of those sources will produce the
'strong AGC' that you seem to desire (most of us like the softer K2
AGC), but may be worthwhile for study as a prelude to your re-design of
the K2 AGC.

On the lack of ability to get the AGC Threshold up to 3.8 volts - do not
be overly concerned about that - the maximum voltage is related to the 8
volt regulator actual voltage.  Furthermore, if your AGC is active even
with no signal, you should *lower* the AGC Threshold voltage.  I know it
sounds counter-intuitive, but results from the point where the voltage
is measured.  Warning, if your AGC Threshold voltage is too low, your
S-meter settings will become a bit 'squirrelly', and for that reason I
recommend that you do not reduce the AGC Threshold below 3.65 volts in
any case.

Changes from the 'standard' designs and settings may be made, that is
part of the K2 'fun' - try it and see what happens, you can always set
it back to the 'standard'.

73,
Don W3FPR

Paul Pollock wrote:

> I am enjoying my recently completed K2-6148 very much, but I had a
> couple of questions and thought others might have some constructive
> thoughts.
>
> While some folks like a slightly soft AGC in the receiver, I'm one of
> those folks that finds that soft signals received softer than loud
> signals (especially SSB) is tiring. I prefer a very stiff and level
> AGC. Mind you, this has nothing to do with the fast/slow delay rates
> or anything along those lines.
>
> 1). My K2 exhibits good AGC performance and I believe it works as
> designed, but it is a soft AGC. Are there any ideas on modifications
> to the AGC IC (LM833) that might stiffen the AGC performance?
>
> 2). I'm another of those folks where my AGC threshold voltage will not
> go above 3.7x volts. It is my feeling that a threshold set so that the
> AGC actually releases at the noise level is better than a setting
> where the AGC is ON at all levels. On my K2 the AGC never releases at
> any level. Any thoughts on getting the AGC to release correctly?
>

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[Darwin, Keith]

Yes, Paul the K2's AGC is definitely "soft".  Soft in that it has some
slope to it with quiet signals sounding quieter than loud.

And I love it that way.  In fact that is one of a handful of factors
that make the K2 such a sweet sounding radio and such a pleasure to
listen to.  I've had rigs (good rigs) with hard AGCs and they leave me
feeling assaulted after a whle under the headphones.

Obviously, this is only my opinion, and YMHV (your mileage has varied) -
but in my book the K2's AGC is top notch.

73!

- Keith N1AS -
- K2 5411.ssb.100 -

-----Original Message-----

While some folks like a slightly soft AGC in the receiver, I'm one of
those folks that finds that soft signals received softer than loud
signals (especially SSB) is tiring. I prefer a very stiff and level AGC.
Mind you, this has nothing to do with the fast/slow delay rates or
anything along those lines.

-Paul Pollock KD7BWB
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I completely agree about the K2's great sounding AGC. The fact that
there *is* some slope to the AGC to still allow the perception of
various signal levels while still maintaining control, is a testament to
the radio's excellent dynamic range. IMHO, it actually reduces listening
fatigue by  not excessively raising the noise floor for weak signals.

73, Dale
WA8SRA

Darwin, Keith wrote:

> Yes, Paul the K2's AGC is definitely "soft".  Soft in that it has some
> slope to it with quiet signals sounding quieter than loud.
>
> And I love it that way.  In fact that is one of a handful of factors
> that make the K2 such a sweet sounding radio and such a pleasure to
> listen to.  I've had rigs (good rigs) with hard AGCs and they leave me
> feeling assaulted after a whle under the headphones.
>
> Obviously, this is only my opinion, and YMHV (your mileage has varied) -
> but in my book the K2's AGC is top notch.
>
> 73!
>
> - Keith N1AS -
> - K2 5411.ssb.100 -
>
> -----Original Message-----
>
> While some folks like a slightly soft AGC in the receiver, I'm one of
> those folks that finds that soft signals received softer than loud
> signals (especially SSB) is tiring. I prefer a very stiff and level AGC.
> Mind you, this has nothing to do with the fast/slow delay rates or
> anything along those lines.
>
> -Paul Pollock KD7BWB
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft   
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
>  

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