[Elecraft] K3S KTCXO3-1 possible problem

[Mike Cizek W0VTT]

Hello Gary,

Elecraft reported having problems with the TCXOs a while back.  Mine isn't very well behaved, either, but it stays within a few Hertz compared to WWV on 10 MHz.

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73,
Mike Cizek W0VTT

-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Gary Peterson
Sent: Tuesday, 9 March, 2021 13:40
To: elecraft at mailman.qth.net
Subject: [Elecraft] K3S KTCXO3-1 possible problem

I have a K3S, purchased factory built, February 2019.  This included the 1 ppm TCXO3-1-F option.  

A few months later, I noticed that SSB signals heard on 50.125.000 MHz all sounded a bit off frequency.  Hence, I performed a reference oscillator calibration, using method 2.  Because of my relatively short distance to WWV, the variability in the signal strength made its use difficult.  Instead, I used a GPS disciplined TCXO as my 10 MHz standard.  The GPSDO had been on for several hours before any calibration and the transceiver had been on for, at least, three hours.  The frequency display on the K3S was set to 10.000.000 MHz.  Beats were displayed on a Weston VU meter, driven by an opamp, connected across the external speaker output.  This allows beats to be easily seen, that are less than one per second.

The REF CAL as received from the factory was 49.379.766 On 7/10/2019, I changed the REF CAL setting to 49.379.448  (I chalked this change up to possible crystal aging.) On 11/30/2019, the REF CAL setting was changed to 49.379.110 On 3/1/2020 the REF CAL setting was changed to 49.378.926 On 1/16/2021 REF CAL was changed to 49.378.495 On 1/30/2021 REF CAL was changed to 49.378.484 On 2/22/2021 REF CAL was changed to  49.378.508 (the first time the setting has been increased)

I have also noticed a change of several Hz in the beat note between the transceiver having been on for half an hour and having been on for three or four hours.  This seems odd behavior to me for a high stability, 1 ppm TCXO.  The transceiver is in a room, with a temperature of 70, plus or minus, 3 degrees Fahrenheit.  There is nothing on top of the transceiver and there is plenty of space below, behind and on either side of the radio.  There are no other heat sources near the transceiver.  

Am I being overly critical, or do you think this is unusual behavior for a KTCXO3-1?

I posed this question to Elecraft tech support.  The reply did not address my question as to whether this KTCXO3-1 is misbehaving.  The reply only said that “We have no KTCXO3-1 and have no orders to restock at this time.”  The tech, who replied, also gave me sourcing information for, apparently, the oscillator part on the board.

Thanks in advance for any time taken to reply to my post.

Gary, KØCX







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