[Elecraft] [K1] VFO Drift Problem

[Matt Scholz]

Thanks Don.

So here's another question. My first step was to remove C2, which
effectively removes the varactor (D3) from the equation. I was still
observing an excessive amount of drift. Doesn't this rule out the voltage
regulators as the cause of this problem?

73,
-Matt W6ZBA

On 5/5/11 7:19 AM, "Don Wilhelm" <w3fpr at embarqmail.com> wrote:

>  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
>>