http://elecraft.85.s1.nabble.com/TCXO-drift-and-calibration-tp7656815p7656854.html
I had the same problem. After 3 years, I had to replace the TCXO which had clearly become defective.
I don’t operate HF, so hearing WWV is sometimes difficult. A good way to calibrate is to have a local, who is dead-on calibrated, send CQ on FT8. You can adjust the ref cal to get it right.
> On Dec 6, 2019, at 2:24 PM, Edward R Cole <
[hidden email]> wrote:
>
> To add a little to what Wes said:
>
> The K3 TCXO rest freq is 49,380 KHz. It is a temperature corrected oscillator so will still drift with radio warm up but less than a non-compensated oscillator. So best to calibrate after at least 30-minutes warmup. If you have the 100w model K3, there will be some temperature drift when transmitting (varies with mode and frequency band).
>
> I have the EXREF installed with the TCXO-03 and that holds my 50-MHz signal within 3 Hz. But if you check the TCXO frequency (CONFIG: REF CAL) you will see the frequency drift. Mine seems to top out at about 49.380.090 and then hold within a few .001.
>
> The EXREF takes the need for periodic re-calibration away. But your 10-MHz reference needs to be very accurate/stable. I use a surplus OCXO that needs re-calib about every 4-6 months (usually only 1-Hz drift). My OCXO runs 24/7 to avoid warm up drift.
>
> Hope that helps.
>
> 73, Ed - KL7UW
>
> From: "Gary Peterson" <
[hidden email]>
> To: <
[hidden email]>
> Subject: [Elecraft] TCXO drift and calibration
> Message-ID: <C8C8661341DC47FCB5BF558A94B08417@WIN7LowProfile>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Last February, I purchased a factory assembled K3S including a 1 ppm TCXO. The transceiver is serial number 11803 and the firmware was updated on May 5th of this year.
>
> Last July, I noticed that many of the signals on 50.125 MHz sounded as if they were a bit off frequency as they were higher pitched. This led me to believe that the reference oscillator may have drifted, possibly due to crystal aging.
>
> Subsequently, I used method 2 and WWV, as described on page 53 of the Elecraft K3S manual. The REF CAL frequency was lowered from 49.999.996 to 49.379.448. That seemed to make the signals on the 6 meter calling frequency sound like they should.
>
> A few days ago, I caught a six meter opening and signals on 50.125 sounded higher pitched again. I repeated the reference oscillator calibration again, using method 2. Now, the REF CAL frequency is set to 49.379.110. I have not had the opportunity to hear any six meter signals, since I changed the reference oscillator.
>
> I am wondering if the REF CAL frequency change that I have seen in less than a year is normal, or whether I have a TCXO problem.
>
> Any thoughts would be most appreciated. Thanks in advance for any time taken to reply.
>
> Gary, K0CX
> Rapid City, SD
>
>
> 73, Ed - KL7UW
>
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