Omni V Passband Tuning Adjustment

From the Ten-Tec Reflector January 16, 2003

In another previous post, I mentioned that the Passband Tuning board in this Omni V had been switched to one from a Paragon at some point. I compared the schematics and noted the differences. I have since found out that crystal Y1 is the same frequency in the Paragon and the Omni V (at least as far as the versions I have info on-my Omni manual shows it as 15.302.3, but it's actually 15.301.2). The only difference is that the Omni is adjusted for greater range.

Since I've not seen this explained elsewhere, here's what I did to adjust the Passband tuning control:

  1. Find a good spot to connect the freq counter! The manual doesn't say, so I tried several places. First place I tried was the emitter of Q4. Bad spot! The counter displayed the freq, and I readjusted everything. After I disconnected the counter and checked it on the air, it was off considerably. Basically the counter/cable was pulling the oscillator. The best place I found was the emitter of Q7 (easiest place to make a connection is where R44 connects to the emitter of Q7).
  2. Turn the Passband control to the extreme that places the lowest voltage on the varactor. I have to admit I can't remember which direction this is! Basically turn it to whichever extreme show's the highest freq on the counter.
  3. Adjust C22 (small trimmer cap) for a frequency of 15.3023 MHz
  4. Move the Passband Tuning control to Center.
  5. Adjust R18 (trimmer pot) for a freq of 15.300 MHz
  6. Repeat steps 3-5. Actually I didn't have to repeat it, but it doesn't hurt!

Hope this information will be of help!

Anthony, NT4X

Comments by email from I1OWT/5 - June 10, 2007

I had to adjust the PBT of Omni V transceiver and I could not adjust the PBT with the test point indicated by Anthony.

The difference from the procedure described by Anthony, NT4X, is in the test point. It's possible that my frequency counter is not enough sensitive.

This is the procedure I used to adjust the PBT freq:

  1. Connect a frequency counter to L-3 on the PBT bd.
  2. Turn the PBT control full CW and adjust C-22 to 15.302.300
  3. Turn PBT control to 12 o'clock position and adjust R-18 to read 15.300.000

73 de I1OWT/5


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