The attached document may help understand the OmniVI mixing scheme a bit
better:
http://www.karinya.net/g3txq/temp/omni_mix.pdf
Note that - ignoring the RTTY mode - the BFO is only ever on one of
three frequencies, _irrespective of the side-tone pitch selection_:
9,000.000 kHz (for LSB Rx, LSB Tx, and CW Rx)
9,000.400 kHz (for CW Tx)
9,003.000 kHz (for USB Rx and USB Tx)
Other things to note:
* The LO is altered during CW Rx so that the received audio matches the
selected side-tone pitch
* Whatever the selected side-tone pitch, the LO always shifts back to
the same frequency on CW Tx (23,100.400 kHz in this example)
* The LO is offset between USB and LSB modes so that the displayed
frequency is always the carrier frequency
The micro which controls the LO to apply the various offsets has no way
of "knowing" the actual BFO frequency - it "assumes" the BFO is on the
appropriate frequency for the mode. So any error in the BFO frequencies
has a direct impact on the transmit or receive frequencies.
Hope that helps,
Steve G3TXQ
On 30/07/2014 23:07, Jim Allen wrote:
That makes sense because adjusting the sidetone during the test did not
change anything, as I think about it.
I'll have a go at your further suggestions tomorrow.
It is good to have the VI+ to compare to, which is known to be working
"right."
I notice that the alignment info in the manuals shows that on the VI, CW
tune is C16, LSB receive is C10 and USB receive is C12. In the VI+, CW
tune is C10, LSB receive is C16 and USB receive is C12. I guess that is to
keep everyone hopping.
Many thanks again.
73 de W6OGC Jim Allen
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