[Elecraft] Re: K2's 4 MHZ Master Oscillator.

[Ron D'Eau Claire]

Nigel, ZL2DF wrote:
You are probably aware that WWV and WWVH broadcast alternately 500hz and
600hz tone for 45 secs of most minute periods.    It is possible to
inadvertently zero beat to these tones which will also cause a
miss-calibration.  

--------------------

It's very easy to do just that! As Nigel said, "To avoid this check the zero
beating when there is no
tone present." Note that what you'll hear the tone during the silent minute
if you've inadvertently zero-beated with the sideband! You'll be hearing the
BFO beating at the same frequency against the carrier. 

My "final check" is to compare the pitch of the tone on opposite sidebands.
Remember, you can switch back and forth between sidebands just like you do
between CWn and CWr. While in either USB or LSB mode, just push and hold the
AGC button. That avoids you having to step through CW mode using the MODE
button.

I certainly do NOT have "perfect pitch" but I can tell when one note is
higher or lower than the other. Switching back and forth between sidebands,
I tune for the spot where they are as close as possible. Often there is some
difference, since the K2 tunes in 10 Hz steps. But I can hear when the tones
reverse as I change sidebands. Then I know I'm as close to zero beat with
the carrier as the K2 can tune. 

Then, switching to CW mode and hitting SPOT you should be within 20 or 30 Hz
of zero beat. Again, the resolution of the DAC's make getting closer a
matter of chance. 

Just checking mine to be sure I'm describing the button-pushing right, WWV
is zeroed in SSB (tones match best switching between sidebands) at 10000.01.
Zero beat with SPOT in CW mode is 9999.98 in CWn and at 10000.00 in CWr. So
the spread is a maximum of 30 Hz. 

Ron AC7AC