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TCXO drift and calibration

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Gary Peterson

TCXO drift and calibration

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
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Wes Stewart-2

Re: TCXO drift and calibration

Your first number is bogus, but generally speaking if your other numbers are
correct, that does seem excessive. That said, crystals do age and some of this
depends on power on/off cycles. I'm now to the point of leaving my K3S powered
continuously.

I recently ran some drift tests and found that it takes about 25 minutes for my
reference to settle to a point limited by measurement jitter. There is an
initial positive increase of a few Hz at power up (at room temperature) then a
non-linear decrease of about 25 Hz.

(Direct measurement of the synthesizer output with a FA-2 counter by BG7TBL,
with a Bodnar GPSDO reference)

Wes N7WS

On 12/4/2019 1:33 PM, Gary Peterson wrote:

> 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

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Edward R Cole

Re: TCXO drift and calibration

In reply to this post by Gary Peterson

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
http://www.kl7uw.com
Dubus-NA Business mail:
[hidden email]

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stengrevics

Re: TCXO drift and calibration

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 <[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
> http://www.kl7uw.com
> Dubus-NA Business mail:
> [hidden email]
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]