K2 VFO band to band accuracy?

[Solosko, Robert B (Bob)-2]

I recently added a CW tuning indicator to my K2 (a very useful addition). The other night I was listening to W1AW code practice and wanted to see how well I picked it up one each of the bands on which code practice is sent. Tuning to W1AW on 160m, the side tone of the W1AW signal was essentially right at 600 Hz, as indicated by the CW tuning indicator. Switching to 80m and tuning to the W1AW frequency, there was a slight but noticeable difference in side tone and I had to tune up about 20 Hz to be in the center of the CW tuning indicator band width. On one of the other bands on which I could pick up W1AW (either 20m or 40m, I don't recall which one), the difference in side tone when tuned to the W1AW frequency was even more noticeable, and the CW tuning indicator didn't even light up until I tuned up about 40Hz. So, either W1AW's transmitting frequency accuracy isn't very good (not likely), or there is this noticeable variation in VFO frequency display accuracy from band to !
 band in my K2. The difference is not very large (max of about 40 Hz) and is really not a problem, but it's enough that it's clearly detectable, both audibly and with the CW tuning indicator. Has anyone else noticed this, and is there anything I can do to get the tuning accuracy better across all of the bands?

Thanks

Bob
W1SRB
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[Darwin, Keith]

I remember the day when 1000 Hz readout was considered very good.  That
got you close enough that you could find the net or your scheduled QSO.
Xtal calibrators told us where the band edges were and we were in good
shape.

Then came digital displays with resolution to 100 Hz.  Wow!  Was that
slick.  Now our rigs display frequency to 10 Hz.

I'm not convinced having that additional resolution is worthwhile.  It
may even be distracting.  We tune WWV, the display says 9.999.94 and
somehow we feel we're off frequency.

Do you remember the days when we tuned in a signal based on how it
sounded rather than based on what the display said?

- Keith KD1E -
- K2 5411 -

-----Original Message-----
From: Solosko, Robert B (Bob)

... Switching to 80m and tuning to the W1AW frequency, ... I had to tune
up about 20 Hz to be in the center of the CW tuning indicator band
width. On one of the other bands ... the difference ... was even more
noticeable, ... about 40Hz.
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[Don Wilhelm-3]

Robert,

First, W1AW frequencies may vary from time to time - I have found the
frequency on 14 MHz off as much as 40 Hz from their nominal frequency in the
past few months - I don;t know if they have corrected that yet or not.

40 Hz accuracy is not too bad at all!  It has not been long ago when we had
analog dials, and if the accuracy was 1 kHz or better we considered that it
was quite accurate.  Transceiver dials are just not precision frequency
counters (my precision frequency counter cost more that a K2 and it was
used).

Due to digitizing steps and the fact that the dial readout is limited to 10
Hz steps, the best expected dial accuracy for the K2 should be in the
vicinity 20 to 30 Hz.  It is even possible to get it within 10 Hz with a lot
of work.  Add to that the region of uncertainty for the CW tuning indicator
(which will vary with signal strength - mine is about 30 Hz wide) and you
can easily add up a 40 Hz uncertainty error with only a 10 Hz inaccuracy in
the K2 dial reading.

If you want to try to improve your K2 dial accuracy, check out the K2 Dial
Calibration article on my website http://w3fpr.qrpradio.com - that will give
you several resources as well as the procedure for accurately setting the K2
dial.

The variation from band to band comes as a result of the K2 displaying the
calculated result of the VCO setting that is stored in EEPROM.  The K2 does
not actually measure the frequency on a real-time basis.  The calibration
process (CAL PLL and CAL FIL) determines the dial readings, and these are in
turn dependent on the accuracy you achieved when setting the 4 MHz reference
oscillator.  Use the N6KR method for the greatest accuracy, but you must
tune the reference standard station in exactly to be successful.  Note that
the 4 MHz oscillator only needs to be accurate during the CAL PLL and CAL
FIL process, it does not have to remain stable for subsequent accurate dial
readings because the dial readings do not depend on the 4 MHz reference for
a real-time reference.

73,
Don W3FPR

> -----Original Message-----
>
> I recently added a CW tuning indicator to my K2 (a very useful
> addition). The other night I was listening to W1AW code practice
> and wanted to see how well I picked it up one each of the bands
> on which code practice is sent. Tuning to W1AW on 160m, the side
> tone of the W1AW signal was essentially right at 600 Hz, as
> indicated by the CW tuning indicator. Switching to 80m and tuning
> to the W1AW frequency, there was a slight but noticeable
> difference in side tone and I had to tune up about 20 Hz to be in
> the center of the CW tuning indicator band width. On one of the
> other bands on which I could pick up W1AW (either 20m or 40m, I
> don't recall which one), the difference in side tone when tuned
> to the W1AW frequency was even more noticeable, and the CW tuning
> indicator didn't even light up until I tuned up about 40Hz. So,
> either W1AW's transmitting frequency accuracy isn't very good
> (not likely), or there is this noticeable variation in VFO
> frequency display accuracy from band to !
>  band in my K2. The difference is not very large (max of about 40
> Hz) and is really not a problem, but it's enough that it's
> clearly detectable, both audibly and with the CW tuning
> indicator. Has anyone else noticed this, and is there anything I
> can do to get the tuning accuracy better across all of the bands?
>
> Thanks
>
> Bob
> W1SRB
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