Adjusting Transmit Bias on the Omni VI Plus

From the Ten-Tec Reflector March 20, 2007

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.




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