[Elecraft] K2 AGC, Seems a bit soft

[Don Wilhelm]

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?
>