[Elecraft] TCXO drift and calibration

[John Stengrevics]

Gary,

I had the same problem.  After 3 years, I had to replace the TCXO which had clearly become defective.

I still need to recalibrate periodically.

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.

73,

John
WA1EAZ 

> On Dec 6, 2019, at 2:24 PM, Edward R Cole <kl7uw at acsalaska.net> 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" <kzerocx at gmail.com>
> To: <elecraft at mailman.qth.net>
> Subject: [Elecraft] TCXO drift and calibration
> Message-ID: <C8C8661341DC47FCB5BF558A94B08417 at 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
>  http://www.kl7uw.com
> Dubus-NA Business mail:
>  dubususa at gmail.com 
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