[Elecraft] pre series "B" AGC adjustment.

[Ron Willcocks]

Hi folk,
           I have been reading the mail about setting the AGC levels in the
latest "B" series K2's and noted the comments therin about tuning to a quiet
part of a band and switching the AGC ON/OFF and noting the whether the
background noise has a marked change in level. If it does change quite a bit
then apparently the AGC is acting too soon.
I tried it on my K2 (pre "B" series no. 2204) and I had a very marked
difference in level when the AGC was turned ON/OFF, so I had a look through
my saved items of interest from the Elecraft team, and found the article put
out by Gary Surrency AB7MY back in Dec 2001, relating to "Poor S-Meter
action". The main content of the article is about changing a diode to
improve the S-Meter action, but as a related alteration, Gary wrote:-
"If you notice a fairely large drop in RX hiss when you turn off the AGC,
then you may want to decrease the value of R1 (also on the control board)
from 51k to 33k. This has the same effect as if you could turn the RF gain a
little further clockwise, and RX sensitivity will be better than before on
weak signals."
Anyway, I did change R1 to 33k and it has made a very noticeable difference
in the sensitivity of my K2. There is now only a very small change in "hiss"
when the AGC is turned ON/OFF, and it sure beats turning the AGC off when
copying weak signals as I had been doing.
I did have to alter the "S LO" and "S HI" setting a wee bit, but the overall
AGC action is unchanged.

Cheers.....Ron ZL1TW