[Elecraft] TCXO drift and calibration

[Edward R Cole]

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
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