[Elecraft] Determining zero-beat

[Guy Olinger K2AV]

Set mode to CW.  Set width to 200 Hz.  Do a HOLD on MON. Set level to
20-25. Tap MON to turn off beat.  Tune to 10.000.000.  Tap SPOT.
Should hear a beat, albeit a slow one.  Advance or retard AF gain to
get the obvious beat. In CONFIG: go to REF CAL.  This will have turned
off SPOT.  Tap it again. Adjust VFO A to get slowest beat.

With some patience and careful listening this is usually clearly a
specific setting, in my case 49.379.737.  You will find that the beat
frequency wavers around due to changing propagation path length so you
have to listen for a while.  Having accounted for the variation in
propagation it is quite clear in my case, albeit subtle, that 738 is
too high, and 736 is too low.  It is also more clearly heard at some
times of day on a given frequency than others.  There are also times
where there is a fast QSB on the signal that can be confusing and you
may just have to wait until the signal steadies.  When you have it
spot on, there will be periods of several seconds or more where the
beat does not vary, something which does not happen nearly as much up
or down one Hz on the REF CAL frequency.

After this adjustment it is clear that my K3 is within +/- 0.5 Hz at
10.000000 MHz with no drift, probably within +/- 0.2 Hz though I won't
claim that.  I have the KTCXO3-1 option in mine.  It may be that a K3
without it may be a bit more cranky, I would imagine so, but I'm not
pulling it out to see  :>)

0.5 Hz at 10 will be less than 2.5 Hz at 50, though I don't know the
formula.  It's not a straight multiply because of the conversion
scheme.  With this adjustment in the menu, the chief contribution of
the KTCXO3-1 is no drift, not an absolute accuracy.

My K3 is way more accurate than they spec, and accurate enough to show
up the propagational variations in the WWV frequencies. I would think
that if you have left it on for a while, and calibrate it before an
"exercise", you can count on it for spot on.

73, Guy.

On Fri, Dec 3, 2010 at 6:09 AM, Pete Smith <n4zr at contesting.com> wrote:
> I want to use my K3 to calibrate the QS1R receiver used here as part of
> the Reverse Beacon Network.  For technical reasons, it's desirable to
> calibrate the QS1R at as high a frequency as possible, so I wanted to do
> so in the 6-meter band.  I thought that if I knew how accurate the K3's
> frequency display was at 10 MHz WWV, I'd know whether I needed to
> compensate for any systematic error when comparing the two up on 6M.
>
> Here's where the problem comes in.  AM mode isn't usable for finding
> zero-beat, of course.  On CW, it appears that the zero-beat frequency is
> displayed as 10 MHz minus the "pitch" frequency (which can only be
> adjusted down to 300 Hz).  I'd like to know the frequency accuracy of
> the K3 within 20-30 Hz if possible for this exercise.
>
> How to proceed?
>
> --
> 73, Pete N4ZR
>
> The World Contest Station Database, updated daily at www.conteststations.com
> The Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com,
> spots at telnet.reversebeacon.net, port 7000
>
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