I can't remember if I've raised this problem before; if I have, I apologise!
My OmniVI frequency readout is consistently 130Hz high on all bands and
all modes; in other words if I accurately tune in a station on 14,200KHz
the frequency read out will be 14,200.130.
I've adjusted all the BFO settings and the TCXO setting as accurately as
I can with a frequency meter whose calibration I checked against a DDS
source zero-beated to WWV.
Here's what's puzzling me:
1) I'm reluctant to suspect the BFO frequencies - it's too much of a
coincidence that USB, LSB and CW are all out by exactly the same amount
in the same direction. In any case they are within 5 Hz as measured on
the counter.
2) If the TCXO was out, I would expect the 5MHz VFO, the Xtal
frequencies, and the final LO frequency all to be out by the same
percentage. That would result in approximately 3 times the frequency
error on 10m as on 160m; but I see the same on all bands.
3) Interestingly, I recently swapped the oven oscillator for the TCXO.
The same 130Hz shift was there before and after the change. Again it
seems too much of a coincidence that the two reference oscillators were
out by exactly the same amount. I needed to make a very small adjustment
to the TCXO to get it on 20 MHz, but that had no effect on the "offset".
I could always deliberately "misadjust" the BFO frequencies to
compensate, but that seems a retrograde step and would likely alter the
Tx audio characteristics by moving the carrier relative to the filter
skirts.
I can't think of anything that would produce the same offsets on all
bands and all modes. Am I missing something?
It's not a showstopper - just an annoyance.
73,
Steve G3TXQ
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