[Elecraft] New K3 guide by KE7X

[Wayne Burdick]

Dave,

The K3 provides two alternatives to turning off AGC in this situation.  
We closely examined the effect of these on multiple close-spaced  
signals, and both reduce IMD considerably:

1. CONFIG:AGC DCY sets the AGC decay characteristic, and applies to  
both AGC-S and AGC-F (slow and fast AGC). The default setting NOR,  
provides a traditional linear decay. The SOFT setting applies a "soft"  
exponential decay. It typically reduces in-band IMD by 10-15 dB.

1. CONFIG:AGC HLD adds a "hold" timer to slow AGC-S (slow AGC) only.  
It behaves as if you were manually (and very quickly) riding the RF  
GAIN control, reducing gain when a very strong signal comes in, then  
turning it back up N seconds later. The normal setting is 0.00 (no  
hold time); a typical setting for pileup conditions might be 0.40.  
This can reduce in-band IMD as much as turning AGC off.

Please give these AGC alternatives a try.

73,
Wayne
N6KR


On May 31, 2011, at 1:42 PM, Dave Hachadorian wrote:

> The KE7X Guide has an interesting discussion about the
> shortcomings of the K3's AGC in a CW pileup situation.  I have
> complained about this AGC issue several times, but there has not
> yet been any effective solution.
>
> The K3's AGC, even at SLP=0 and THR=8, compresses CW signals at
> too low a threshold and too flat a slope.  Signals in a pileup
> are all mushed together by the AGC.  It's not an IMD problem,
> it's a compression problem.  The usual solution, turning AGC OFF,
> is thwarted by the AF Limiter's extreme distortion on even
> moderately loud signals, even at its max setting AF LIM = 030.
>
> If you have extremely sensitive headphones, and a very quiet
> shack, you can turn AGC OFF and turn the overall receiver gain
> down to where the AF Limiter rarely triggers, but one shouldn't
> have to jump through these fiery hoops.  With a TS-850, you could
> turn AGC OFF, and a loud signal would not blow your ears off, and
> would not be severely distorted.  If they could do that in 1989,
> it should be doable today.
>
>
> Dave Hachadorian, K6LL
> Yuma, AZ
>
>
>
> -----Original Message-----
> From: T Gahagan
> Sent: Tuesday, May 31, 2011 12:06 PM
> To: Elecraft List
> Subject: [Elecraft] New K3 guide by KE7X
>
> For those that don’t know about the new K3 guide by KE7X check
> out the link in this message.  Fred has done an outstanding job
> of explaining many of the intricacies of the K3 that have puzzled
> me.  Block diagrams and step by step instructions on just about
> every facet of operation are really helpful.  Fred’s guide doesn’t
> replace the K3 manual by any means but it sure  has helped me
> determine if I have my K3 set up properly for what I am trying to
> accomplish.  I have no financial interest in this product but
> thought reflector members might like to know about this new
> offering.
>
> Todd, WA7U
>
>
>
> http://www.ke7x.com/home/guide-to-the-k3
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