[Elecraft] K2 Frequency Stability

[John Grebenkemper, KI6WX]

Roy;
In a normal home indoor environment with the temperature changes you
describe, I would expect a K2 that is left on would drift less than 50 Hz
over your time period.  If you are operating outdoors with much larger
temperature excursions, the drift will be greater.

The results of the frequency stability measurements and changes I made to my
K2 are located on my web site, http://home.pacbell.net/johngreb/KI6WX.html .
In about the worst case torture test I could design, I was able to make my
unmodified K2 drift about 150 Hz in one hour.  As Wayne pointed out to me,
my test method is not reflective of the operating methods of most K2 owners,
and the real values that they see will be considerably better.  The note on
my web site shows a method that was used to reduce the drift to about 60 Hz
using the same torture test.  These changes are not recommended for most K2
owners because of their complexity.
-John
 KI6WX

----- Original Message -----
From: <Unifiedtx@aol.com>
To: <elecraft@mailman.qth.net>
Sent: Wednesday, February 06, 2002 1:13 PM
Subject: [Elecraft] K2 Frequency Stability


> John Grebenkemper, KI6WX, has recognized the need for better frequency
> stability and has made modifications to reduce frequency drift.  He has
asked
> others about their K2 drift rates.  I have not heard about his findings,
but
> I would not be surprised if all K2s have a slow drift rate of from 130Hz
to
> 170Hz over a period of 8 to 12 hours with an ambient temperature of 60 to
68
> degrees F.  This drift is considerably greater than most of the late model
> commercial American and Japanese made transceivers.  I have also noticed
that
> the VFO range tends to shift depending on whether the bale is retracted or
> down.  It may be that the bale in the retracted position is pushing
against
> the cabnet bottom plate causing a change in L33 parameters.  With the bale
> down the cabnet bottom may be further away from L33.  During construction
I
> carefully positioned L33 tightly in the grommet and pulled L33 leads
tightly
> into the PCB during the soldering process.  I made a check of the
proximity
> of L33 to the cabnet bottom plate by removing a side panel and observed
the
> clearance.  The clearance does not seem to be a problem.
> I would like to know if anyone else has notices this subtle frequency
> difference.  It can only be noticed by looking at the drift from a cold
start
> to the point of no apparent further drift.  I also would like to know if
> anyone has come up with a way (perhaps change in components) to
substantially
> reduce this drift.  John Grebenkemper was able to cut his drift from 155Hz
to
> 65Hz.  His mod, however, is not for the faint of heart and appears to be
> quite involved.
> Roy Morris  W4WFB