Gareth,
That is NOT correct.
You must do things in order and all will work out properly.
First, the 100 Hz WWV subcarrier should be outside the passband of the
SSB filters, so it will have a very low amplitude.
It is better to use the alternating 500 and 600 Hz as well as the 'on
the minute' tone at 1000Hz to determine the correct tuning of WWV. The
tone at 2 minutes after the hour is 440Hz.
If your SSB OP1 (or FL1 if no KSB2) filter passbands are not properly
aligned, do an initial alignment of the LSB and USB filters so the
filter passband low frequency slope -5dB point is at 300 Hz (use
Spectrogram to observe the passband position).
Once the SSB FL1 filter is adjusted, then receive WWV and use the
Spectrogram (or other audio spectrum analyzer) to properly tune the WWV
transmitted tones. Once tuned properly, lock the VFO to prevent moving
the VFO knob.
With WWV properly tuned, set to CAL FCTR and alternate the internal
counter probe between TP2 and TP1 while adjusting Control Board C22.
Since all WWV transmissions are on '000.000 kHz boundaries, all you need
to do is observe the 4 low order digits in the CAL FCTR display and you
do not have to do the subtraction in every case.
Once C22 is properly adjusted, put the counter probe in TP1 and run CAL PLL.
When CAL PLL finishes, then go to CAL FIL.
Even though the FL1 passband has been previously set, you must still
change the BFO settings. Move them up one DAC count and back down to
where they were before.
Then adjust the BFOs for SSB FL2 thru FL4. I set the low frequency
slope of FL2 at 350Hz, FL3 at 400Hz, and FL4 at 500Hz.
Adjust the BFOs for the CW filters (and RTTY filters if you have them
enabled) to properly position the filter passbands. If they were set
correctly before, move them by one DAC step and back again - this is to
force the BFO frequencies to be recorded into EEPROM with the current
4MHz reference frequency.
After those steps, re-check the WWV tuning. It should be correct within
20 Hz. The BFO DAC steps are approximately 20 Hz wide, so you may see a
shift in the tuning by that amount. If it is greater than 20 Hz, re-do
the entire procedure from the beginning.
I do this procedure more than 3 times a week on K2 repairs, and it
always works.
73,
Don W3FPR
On 3/2/2015 11:11 AM, Gareth - M5KVK wrote:
I realise this is close to becoming an obsession, but I really want to
understand what's going on.
Once I'd gone through my modified version of Wayne's process for adjusting
the VCO (i.e. adjusting the VFO to have the WWV 100Hz sub-carrier on
100Hz), I realised that this applied only to LSB FIL1. As soon as I
switched to FIL2, the sub-carrier moved and I needed to use CAL FIL to
adjust it back.
Also, if you want to move the position of the filter in the audio spectrum
(e.g. to change where the skirts are), and thus change the BFO; you need to
run Wayne's process again.
Is that right?
73, Gareth - M5KVK
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