Many thanks to Dan, N4VET.
Dan was correct: in the Omni VI Plus manual, the instructions for
adjusting transmit bias are incorrect. A crucial sentence had been
left out from this 1997 version of the manual by TT. As a result, I
had improperly adjusted Omni VI plus xmit bias, and failed to get
linearty, and so SSB speech was garbled in on the air tests.
After correct bias adjustment, SSB speech quality reports have been
consistently excellent.
These corrected instructions may also apply to other TT rigs that
followed the Omni VI+, assuming the error was "carried forward."
Here are corrections to Section 4-16, page 4-28 (First Printing,
01/97, Omni VI + manual):
Note the arrows on the aluminum panel, bottom, and set pots (decrease)
R15 and R19 for minimum current. Here, you are measuring current
across the red "B Plus" line into the power amp module. You need a
DMM rated to at least 20 amps, preferably 30. The bias adjustments are
made with drive into the PA disconnected ("idle"), but the front panel
is set for full power in USB at 14 mHz.
Now, adjust pot R15 to produce an increase in current by 50 milliamps.
Then adjust pot R19 to produce an additional increase of 500 milliamps.
To get the alc and meter reading correctly, you now need to adjust
three pots under "Alignment", Section 4-5 page 4-6 as described in the
Omni VI Plus manual.
73s,
Peter
VE1CHS
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