[Elecraft] [K1] VFO Drift Problem

[Don Wilhelm]

  Matt,

I would first suspect the stability of the voltage regulators.  That VFO 
is tuned with a varactor, if the voltage changes, the frequency will 
change.  If that does not settle it down, I would wind L1 on a new core 
on the suspicion that the present one is more temperature sensitive than 
usual.

73,
Don W3FPR

On 5/5/2011 1:40 AM, Matt Scholz wrote:
> Hi -
>
> I am trying to reduce my K1's VFO drift to an acceptable level. The VFO
> frequency drifts up at a rate of about 30Hz/minute (after a 5 minute warm
> up). Even after one hour, the drift is still about 15Hz/minute. This is
> too much, obviously.
>
> I have been trouble shooting this with the help of Gary, AB7MY. So far I
> have done the following:
>
> * Removed C2 to isolate D3 from the rest of the VFO circuit. No change.
> * Replaced all three VFO poly caps (one at a time). See above.
>
> I was wondering if anybody had any ideas on how to further trouble-shoot
> and resolve this issue...
>
> Thanks in advance and 73,
>
> -Matt / W6ZBA
>