[Elecraft] K3(s) main oscillator calibration

[Don Wilhelm]

With the main K3 fine tuning at 1 Hz steps, I don't know that 0.1Hz or 
even 0.25Hz doppler shift will matter much in the final result.

My frequency counter is good to 10 exp-9 which equates to +/-0.1 Hz at 
the TCXO frequency, so the WWV method provides as good or better 
accuracy, even considering the doppler shift possibility.

The main problem is chasing the beat note down to a stable solid note. 
You usually can't truly get there, but you can get close enough that you 
hear about 10 or 20 seconds between peaks.  Close enough for me.

It can be quite expensive to obtain stability better than the K3S in an 
analog oscillator.  My HP8640B signal generator will do that, but it 
takes at least a 3 hour warmup before it becomes stable.  Yes, all the 
internal enclosures in my '8640 have covers with all the screws 
installed - that helps.  OK, that is 'old iron', but I am not going to 
spend several $10,000 for something better.  I have better things to do 
with my money, and no longer have access to modern lab quality equipment 
to achieve that kind of stability.

We have a ham band transceiver - not a precision lab instrument.  As 
long as we can stay inside our ham bands, that is all that matters to 
me.  I would not put a carrier exactly on 7,000.00 kHz with any transceiver.

73,
Don W3FPR

On 6/6/2020 5:42 PM, Dave Cole wrote:
> Hi,
> 
> As the other station siad, you will have Doppler issues.  Also the K3 
> tunes in steps, which make sustained .1 hz accuracy a dream, not 
> attainable.  It looks to tune in .25 Hz., or larger steps.  I am going 
> from memory here, so it may be something different.
> 
> I wanted to use my K3 to watch Ionospheric shifting, via Doppler shifts, 
> from WWV.  I am unable to as a result of the method Elecraft chose for 
> tuning.
> 
> I have the TXCO, and that just provides a reference for the radio, it 
> does not make the steps go away...
> 
> I was quite disappointed when I discovered this, but, the good stuff in 
> the rest of the radio makes up for that small loss.  I'll buy some 
> stable rig that uses analog tuning.
>