If your Opt3 is using the crystal oven, then you can, as another poster
pointed out, just leave the power supply on at all times (with the rig off
unless it's being used). This will power the crystal oven to keep it at a
constant temperature. When you power the rig on (via the power switch) it
should remain very close to its calibrated setting, i.e., with rig warmed up
tune to WWV @ 10 Mhz, turn the rig off for several hours, turn it on, and it
should still be tuned.
You can also upgrade your Opt3 to the newer TXCO from Ten-Tec. It's a
matter of removing a few parts, soldering a few wires, and then installing
the TXCO in an unused hole in the chassis. I find that, with this done, the
rig starts much closer to its calibrated/aligned setting, and quickly moves
to and stays at that point. In other words, the warmup drift is much less.
Ten-Tec will tell you that the TXCO is no more frequency-stable than the
crystal oven (but it is cheaper and can't cook out the reference crystal
like the oven, which is one reason I didn't like to leave my rig constantly
powered on). I think it is a better solution. Of course, if you want the
ultimate, at least one Omni VI owner on this list has modified his rig to
accept the 10 Mhz signal from a GPS clock to keep within 1 Hz.
However, the big problem I've encountered with my Opt1 is drifting during
high duty mode QSOs (PSK31 and other digital modes, and especially painful
in MFSK where tuning is critical). This drifting is caused by the BFO
crystals on the TX Audio Board (drifting as the rig heats up during
transmit). The drift is within Ten-Tec specs, but then again the rig was
designed for CW and SSB usage where this isn't a problem (and it drifts much
less in those modes, if at all). I did some research, and was able to
modify my Opt1 to stay within 10 Hz during digital mode QSOs, after spending
about $100 for closer-tolerance parts. Check the archives to find out the
details.
I wonder why Ten-Tec didn't just use PLL feedback with these crystals (as
they did with the L.O. Board) so that they too could be controlled. But
they didn't (probably because it isn't needed for CW/SSB).
I also wonder how stable the Orion and Jupiter are in high duty modes (like
PSK31).
- jgc
John Clifford KD7KGX
Heathkit HW-9 WARC/HFT-9/HM-9
Elecraft K2 #1678 /KSB2/KIO2/KBT2/KAT2/KNB2/KAF2/KPA100
Ten-Tec Omni VI/Opt1, Centaur, 238B
Alinco DR-605TQ, DJ-V5
Icom T90A
IRLP #3978
email: kd7kgx@arrl.net
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