[Elecraft] K3 AGC THR doesn't go low enough

[Don Wilhelm]

  I seem to have trouble convincing some to raise the threshold to 
combat the noisy effect.  Please read all below carefully, and I believe 
I can offer some explanation.

Let's study what the AGC SLP and AGC THR settings do and try to relate 
them to the perception that the K3 is noisy.

IF --
the threshold is so low that the noise triggers the AGC (and that will 
be happening if the noise is causing the S-meter to have a reading with 
no signal)
AND --
If the slope is set to a high value which makes all the signals have 
more or less the same audio volume,
THEN --
The noise will appear at about the SAME audio volume as the signals.
RESULT --
A K3 that sounds noisy :-( !  It is a combination of both the threshold 
and the slope that create this condition.

The cure for that situation is to increase the threshold and reduce the 
slope.
How much?
That is an individual decision, but I have mine set to the extremes of 
THR at 008 and SLP at 002.
I really believe the defaults are OK for a band where the ambient noise 
level is lower, but certainly gives problems on a band that is 
inherently noisy.

Please make your evaluation while listening to signals and the breaks 
between signals - if you are hearing only noise, you will naturally turn 
the AF Gain up, and yes the noise will increase - not only that, with 
only noise, the perception is that one should use a lower threshold setting.
That is because as you lower the threshold, the AGC response to the 
noise gets stronger, and the audio level is reduced by the AGC - what 
you are perceiving is  exactly the opposite of what you wish to achieve.

In addition, turn the attenuator on and the preamp off - again, if you 
hear an increase in the band noise when the antenna is connected, you 
have all the sensitivity that you can use for that band and antenna.  
The K3 remembers those settings by band, so you don't have to make 
changes as you switch bands.

73,
Don W3FPR

On 10/8/2010 2:23 PM, Mike Scott wrote:
> I have thought about John's wish for more AGC control. The K3 has a lot of
> gain, I wonder if greater attenuator control would be more useful. I would
> like to rotate in another 10 or 20 dB attenuation at times when operating
> lower bands. I would guess my that wishes would require hardware
> modifications and John's may not.
>
>
>
> AE6WA
>
> Mike Scott
>
> K3, KX1
>
>
>
>> John G3XRJ said: I've played around with various AGC settings and in
> particular the
>
> AGC THR - which if it would go 2 or 3 points lower would appear to
>
> address the problem.
>