Posted by
David Gilbert on
Feb 06, 2010; 7:43am
URL: http://elecraft.85.s1.nabble.com/K3-in-a-cw-pileup-needs-work-tp4523884p4524374.html
Not true. Read the Clifton labs link that I posted and you'll see that on the K3 AGC SLP = 000 actually gives a slope around 2 ... i.e., it takes 4 times the signal strength to sound twice as loud.
The concern is not about having loud signals sound louder than weaker ones ... the concern is having the least nonlinearity in the signal chain to minimize in-band intermod products. Loud signals override weak signals so intermod isn't an issue there. The problem occurs when multiple signals are approximately the same strength and they lie at or near a nonlinear portion of the gain curve. Take a look at the severe knee in the Clifton Labs AGC plots and you'll see what I mean. The best way to avoid distortion in the presence of multiple signals for the majority of conditions (especially when receiving multiple weak ones) is to set the AGC threshold to maximum (008) and the slope to minimum (000), but that still leaves the opportunity for multiple STRONG signals to find the knee in the curve and generate distortion. It also, of course, leaves you less protected against really strong signals.
And please don't try to sound so condescending ... I know exactly what the AGC SOFT setting is and I use it exclusively.
Lastly, you should pay attention to whom is posting what. The original poster who complained about the AF LIM situation is Dave, K6LL.
73,
Dave AB7E
------Original Mail------
From: "The Smiths" <
[hidden email]>
To: "Elecraft Reflector" <
[hidden email]>
Sent: Sat, 6 Feb 2010 06:04:58 +0000
Subject: Re: [Elecraft] K3 in a cw pileup - needs work
Having the Slope set to 000 is like not having the AGC on at all.
If you're going to have a theshold, then why bother to keep the AGC from actually doing anything? At least put that Slope to 04 or something where it actually makes a difference. If your concern is having loud signals be louder than the low signals underneath it, and you want to compress the lower signals to sound as loud as the loud ones (or Vs Versa, have the loud ones squashed to the same level as the low signals), you have to actually set the slope compression to do something, not turn it off by setting it to 00. I agree with Guy completely.
Also, there's a setting in the menu that will allow you to have a "soft" Agc which was designed JUST for this Contest/Pile up situation your describing. If you don't know what or where it is, please let us know and I will dig it up for you.
As for the AGC off level limiter, and creating distortion... Yea, I've noticed that with the loud ones too. I belive that Wayne did something with that setting in the last 2 beta software releases... I don't know if you have access to it yet.
M
> From:
[hidden email]
> To:
[hidden email];
[hidden email];
[hidden email]
> Date: Fri, 5 Feb 2010 22:48:19 -0700
> Subject: Re: [Elecraft] K3 in a cw pileup - needs work
>
>
> Wrong ... you have that totally backwards. AGC SLP = 000 gives the LEAST amount of AGC action you can get in the K3. AGC SLP = 015 is the setting that makes all signals above the threshold sound the same, and potentially creates mushy distortion for multiple signals depending on what setting you use for AGC THR. Read the manual, or check out
http://www.cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm if you want to see it graphically.
>
> K6LL's AGC settings are exactly the same as those I use for contesting.
>
> 73,
> Dave AB7E
>
>
> ------Original Mail------
> From: "Guy Olinger K2AV" <
[hidden email]>
> To: "Dave Hachadorian" <
[hidden email]>,
> "Elecraft Reflector" <
[hidden email]>
> Sent: Sat, 6 Feb 2010 00:17:32 -0500
> Subject: Re: [Elecraft] K3 in a cw pileup - needs work
>
> Hi Dave,
>
> Using slope 000 is likely most of your problem. With that setting all
> signals regardless of strength are set to the same level regardless of
> how loud they are coming in. If they are zero beat or close, it will
> mush the dickens out of the copy by making them all the same level in
> your ear. I set AGC SLP to 15 for contests. I also use slow AGC the
> entire time. If there are key clicks, I use NB with IF off and dsp to
> t3-7 or t2-7. It rounds off CW bauds some but does not make them
> uncopyable.
>
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