I -think- the way it works is that when the K3EXREF is locked with the external frequency standard on 10 MHz, this is used to measure the frequency of the TCXO. The value of that frequency measurement is then put into the K3 REFCAL setting. If the TCXO drifts slightly as they all will, then the frequency difference is detected and the value in REFCAL is changed to match, hence keeping the frequency of the K3 correct, without actually phase locking the TCXO to an external reference which could degrade the low phase noise performance of the K3's synth.
Basically the K3EXREF is doing the same thing automatically as you would manually when doing the calibration, by measuring the TCXO frequency and storing that value in REFCAL. The K3EXREF acting a frequency counter with a high stability external 10 MHz reference. Hope I have that right. So, it would be normal for the value in REFCAL to change as things warm up even with the external reference into the K3EXREF, because the TCXO is not locked, just measured. 73 from David GM4JJJ > On 7 Mar 2016, at 11:01, David Pratt <da...@g4dmp.fsnet.co.uk> wrote: > > Andy - Without the K3EXREF connected, the REF CAL frequency will be > fixed and the K3 will drift, albeit very slightly, particularly when it > is first switched on. With K3EXREF locked with your 10MHz standard the > REF CAL frequency will vary to correct any drift in the K3. If you > measure the output frequency of your K3 with an accurate frequency > meter, such as a digital counter locked to a standard, you will find > that your K3 is stable to within +/- a couple of Hertz. > > 73 de David G4DMP > > In a recent message, ANDY NEHAN <andy.ne...@btinternet.com> writes >> Sometime ago I installed the K3EXREF which I feed from an external >> 10MHz double oven Xtal oscillator. I am confident the K3EXREF is >> installed and configured correctly as when in use and the external >> oscillator is connected the front panel says REF*CAL with the * >> blinking. Attempting to change the local oscillator frequency gives the >> message "Locked" just as the manual says. >> However, I am puzzled as the local oscillator frequency display slowly >> drifts down from 49.379.675Hz to 49.379.622Hz over a period of at least >> an hour from K3 switch on. I leave the external oscillator on >> permanently. I was expecting the local oscillator to rapidly get to its >> final frequency. Can someone explain whats happening as I am puzzled?? >> My firmware is the latest version. >> Andy G4HUE > -- > + - - - - - - - - - - - - - - - - + > | David M Pratt, Kippax, Leeds. | > | Website: http://www.g4dmp.co.uk | > + - - - - - - - - - - - - - - - - + > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to gm4...@yahoo.co.uk ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
