[TenTec] Closing the loop (sort of) on the Orion II Freq alignment issue

Scott Sheppard scott.vy1co at gmail.com
Mon Jan 2 20:32:59 EST 2023

Well, I think I have taken more than my  share of bandwidth on the
TCXO issue. For whats it worth, I thought I would share what I have
learned despite not actually having cured the problem.

The rig was purchased with the understanding from the prev owner, it
was about 100 hz off in freq. The testing I have done to date, by
various means and methods has confirmed the following in terms of how
out of tune the rig is.

5Mhz/35hz    10Mhz/74hz     15Mhz/114hz    25Mhz/194hz

 From these numbers you can envision 80m being close, 10m way off.
Also note that when I compensated and tuned the dial up for however
much the rig was out, the Delta between UCW and LCW was 6hz or less
across the above mentioned freqs. The TCXO was dialed in as best as it
could--numerous times. Its actually quite linear in its tuning...just
not enough range--perhaps.

Transmit freq: For sake of discussion, the displayed freq is 'on Freq'
during Tx, it's the Rx that's off.

Voltages, measurements etc. As best as I can determine, all the
voltages are to spec--again, measured more than once. I did not peel
the lids off any of the cans, but given the tcxo is getting close to
5v bang on, I am satisfied.

TCXO. The TCXO is not the Siward version often referenced
online...this is of course a 45.550 Mhz device, but of a different
manufacturer. I found a few on line at some Japanese auction site but
don't seem eligible to purchase. Any TCXO's of that freq are rare to
say the least. If you know of a source, please tell.

Next steps: I honestly don't know what those might be...The radio
performs well and there are no signs of any other issues at all. I
could live with the amount its out, but it is annoying. I would like
to replace the TCXO if I could, but to be honest, given the way it is
performing and repeating the same, consistent results, I am not sure
its the culprit...I have read something on the TT site about the
synthesizer alignment, but that seems a bit beyond my level of
expertise. Perhaps others have gone through the process?

So there you have it. Still a great rig--albeit systematically and
incrementally out of alignment as you increase frequency.

To those who chimed in online and off, many thanks.


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