Re: K3EXREF and Trimble Thunderbolts

Posted by Julian, G4ILO on Apr 05, 2011; 9:52pm
URL: http://elecraft.85.s1.nabble.com/K3EXREF-and-Trimble-Thunderbolts-tp6242158p6243940.html

Thanks to Leigh for his detailed explanation. Also to you, Rich, for explaining how the frequency standard is applied to the K3.

I still have a couple of questions.

If, as I believe is the case, the K3 REF CAL has fairly large discrete steps, is there any benefit in using a reference oscillator that is many times more accurate than that? All one is looking for is something that will keep the K3 as accurate as it can be without the need to perform regular manual checks. A standard that has extra precision is not going to make the K3 any more accurate because the reference oscillator is being controlled using discrete steps.

Has anyone tested the effect of these small stepwise adjustments of frequency on the WSPR mode, in which the data is transmitted using a frequency shift of about 1.5Hz?

Julian, G4ILO

Rich Heineck wrote

The K3EXREF uses the 10 MHz standard as it's time base to measure the K3's TCXO and passes
an error value to the K3's MCU every few seconds.  No TCXO frequency control takes place,
thus no increase in phase noise.  Frequency compensation is done in software by
automatically updating the REF CAL function.  A relatively simple mechanism but effective :)

For my installation, I'm using a Thunderbolt, an $11 active antenna from Digi-Key, and a
30' run of RG-6, which works nicely with the F connector on the Tbolt.