(note: before performing frequency calibration, you need to make sure the BFO oscillators are correctly aligned/calibrated per the procedure in the manual; also, be prepared for the real possibility that C31 has aged and needs replacement - N1EU)
From the Ten-Tec Reflector August 17, 2003
To verify/check for any soundcard error, you can use the sidetone. It is generated by the DSP and is independent of the TXCO/crystal oven. Just run DigiPan/MixW and verify that the sidetone is where it is supposed to be…if not, then your soundcard is in need of calibration. Like George, I have found my integral soundcard chip to be spot-on. Note that MixW has instructions for calibrating your soundcard that you can use to check/verify soundcard calibration without using your rig.
Re calibrating an Omni VI/VI+ using WWV, I didn't/don't use George's method, but one similar to it.
[Note that this method assumes that the BFO crystal trimmer caps are set so that the resultant BFO frequencies are at factory specs (unless you've dinked with them or something in the BFO circuit, e.g., crystals, trimmer caps, resistors, has been replaced, this is a safe assumption). You will need a frequency counter to set these, or another rig that you know is calibrated to transmit and receive a CW signal on exactly the same frequency (you can get around the lack of a frequency counter if you can trim your rig to transmit and receive CW on the same frequency using a separate rig as a reference… but that is an involved procedure so we'll assume that the BFO board is aligned to spec).]
Undo the screws on your top but leave it on your radio, and then let your radio warm up for at least 10 minutes, and after that time transmit into a dummy load for 5-10 seconds at 25 watts. Then, do the following:
A good check on your BFO trimmer cap settings is to have the VFO set to 10 Mhz and then switch back and forth between USB and LSB. There should be no change in the tone you are receiving from WWV. If there is, then your BFO board needs calibrating, and you will need a frequency counter or accurate separate rig.
I'm open to any suggestions for corrections and/or improvements on this method.
John Clifford KD7KGX