Re: Tuning the K1 using W1AW or WWV.

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Re: Tuning the K1 using W1AW or WWV.

Mike Morrow-3
Gil wrote:

> Did I explain the procedure correctly?

I'm not sure I understand everything in your statements there:

> With WWV on 10mHz (30m), you move the tune pot until their tone matches
> your sidetone frequency on the screen, meaning, if you did set your tone
> to 600Hz, you move the tuning pot until their "main" tone (thicker line)
> shows on the 600Hz mark on the screen. If your display shows 10,000.6,
> you're right on.

Try this really simple test for proper K1 display adjustment:

Assume that the transmitter offset adjustment RF-C13 has been set for
the desired 600 Hz sidetone.  Because the K1 receiver operates in LSB
mode, the transmitter frequency is 600 Hz *below* the frequency of any
calibration signal with which the K1 receiver is zero beat.  The K1
should display transmitter frequency, not receiver cal signal zero beat
frequency.  So...

If K1 transmitter offset is set to 600 Hz and the K1 receiver is zero
beat to 10 MHz WWV, the display should show 9,999.4 kHz.


It is sufficiently accurate to zero beat WWV by tuning until the voice
announcements sound natural. Tests have shown that most people can easily
tune a receiver within 25 Hz of a calibration frequency in this manner.

Once the K1 receiver is zero beat with 10 MHz WWV, the OPF display cal
function may be used to set the LCD to indicate the transmit frequency
as 10,000.0 kHz - 0.6 kHz = 9,999.4 kHz.

That doesn't mean that the LCD will always reflect the actual transmit
frequency from that point on.  

The inputs that generate receiver frequency are the filter board
heterodyne oscillator frequency (HFO, crystal-controlled, not adjustable),
the receiver BFO frequency (X5, crystal-controlled, adjustable with C20),
and the VFO frequency.  Receive Frequency = HFO - X5 - VFO .

The inputs that generate transmitter frequency are the filter board
heterodyne oscillator frequency (HFO, crystal-controlled, not adjustable),
the transmitter mixer frequency (X6, crystal-controlled, adjustable with C13),
and the VFO frequency.  Transmit Frequency = HFO - X6 - VFO .

However, the K1 MPU counts *only* the VFO.  It assumes a fixed band-specific
value for HFO, assumes a fixed value of X5, counts the VFO frequency, and
applies the stored user-adjustable band-specific OPF datum to generate a
frequency display that is unmodified between receive and transmit conditions.
The display must be manually adjusted during the OPF cal process to reflect
the *transmit* frequency.

Any subsequent changes to HFO or X6 (due to temperature change and, for
X6, C13 change/manual adjustment) will *not* be indicated as a change
to displayed frequency.

The value of X6 is rather stable, but not so much that there is a lot
of value in using sophisticated methods to set RF-C13, IMHO.

Performance of the OPF calibration must be done for *each band*.  WWV can
serve for the 30m filter board, if the 170 kHz VFO span option has been
utilized.  An accurate cal signal must be found for each of the other
bands on a filter board.  I have never considered W1AW to be an adequate
frequency standard, but it's better than nothing.

Also, OPF data are stored in the K1 front panel circuitry...and not on the
filter board.  Only *one* OPF cal datum can be stored for each band between
160m to 10m.  If one has, say, a filter board for 40/30/20/15m and another
for 17/15m, only one OPF datum can be stored for the duplicated 15m band.
Small variances in heterodyne crystals will result in less accurate 15m
frequency display when one filter board is in place, compared to that of
the filter board in place during the latest 15m OPF cal.

Mike / KK5F
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