K1 AGC action

[Ron ZL1TW]

Hi,
      I have just pulled the old K1 out and blown the dust off it ready for
a QRP Sprint coming up on 80m here this weekend, and while the set seems to
work fine in most respects I can't help but wonder if I have a problem with
the AGC.
If I (say) call CQ and a strong station answers me, I get an enormous burst
of tone from the calling station for the first letter he (she) sends, and
then the AGC kicks in and everything is sweet again. ( until there is a
pause in his/her sending)
  It has always done this since I built it some 4 years ago, and before I
got the K2, I used to put up with it, but in hindsight, I have to wonder if
it is "normal".??
I realize the AGC is a pretty basic setup in the K1, but would be
interested to know if I have a problem ? It sounds to me like the AGC is
waiting for a capacitor to charge before controlling the gain of the
mixers. I seem to recall there was a mod to make C31 something like 1uf and
having a resistance in series to speed up the AGC action, and I think that
is in the set.
I would be interested in comments from other K1 owners.........at the
moment I think I will use the K2 @ 5w tomorrow, to save what I have left of
my hearing.
73.......Ron ZL1TW

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[Evan Roberts-3]

   My K1 (SN # 301) is so uncomfortable to use that I generally leave the
   attenuator  on.   Otherwise, the first keystroke of any character will
   be too loud for comfort.

   I would like to have better AGC on this otherwise great little rig.

   Last comment, How can I get display illumination on my K1?

   Evan, W5IQS
   >From: Ron ZL1TW <[hidden email]>
   >To: [hidden email]
   >Subject: [Elecraft] K1 AGC action
   >Date: Fri, 13 May 2005 20:52:56 +1200
   >
   >Hi,
   >      I have just pulled the old K1 out and blown the dust off it
   >ready for a QRP Sprint coming up on 80m here this weekend, and while
   >the set seems to work fine in most respects I can't help but wonder
   >if I have a problem with the AGC.
   >If I (say) call CQ and a strong station answers me, I get an
   >enormous burst of tone from the calling station for the first letter
   >he (she) sends, and then the AGC kicks in and everything is sweet
   >again. ( until there is a pause in his/her sending)
   >  It has always done this since I built it some 4 years ago, and
   >before I got the K2, I used to put up with it, but in hindsight, I
   >have to wonder if it is "normal".??
   >I realize the AGC is a pretty basic setup in the K1, but would be
   >interested to know if I have a problem ? It sounds to me like the
   >AGC is waiting for a capacitor to charge before controlling the gain
   >of the mixers. I seem to recall there was a mod to make C31
   >something like 1uf and having a resistance in series to speed up the
   >AGC action, and I think that is in the set.
   >I would be interested in comments from other K1 owners.........at
   >the moment I think I will use the K2 @ 5w tomorrow, to save what I
   >have left of my hearing.
   >73.......Ron ZL1TW
   >
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   >You must be a subscriber to post to the list.
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[Mike Morrow-3]

Ron wrote:

>I seem to recall there was a mod to make C31 something like 1uf and
>having a resistance in series to speed up the AGC action, and I think that
>is in the set.

There have been several proposals for altering (speeding up) the stock AGC
response of the K1.  The most common is just reducing C31 on the RF board
from 2.2 uF to 1 uF or less.  Some who have the KNB1 noise blanker installed
do likewise with NB C10, though I haven't found that necessary.

Most people find fast AGC to be appropriate for CW operation, so I've been
at a loss to understand why the stock K1 uses such a high value of C31 to
produce such a terribly slow AGC response.

You might want to verify that C31 in your K1 has been changed.

73,
Mike / KK5F

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