Hi Everyone,
Once again I am compelled to comment on this thread having spent a lot of
time seeking to improve this very specific Omni VI problem. It's real and it
does exist.
After 5 1/2 years of Omni VI ownership (prior to selling it this past
Spring), I chased improved frequency readout accuracy on this radio and came
up with the following conclusions. My Omni VI suffered from both frequency
repeatability and accuracy problems considerably greater than other
transceivers I have owned. In fairness to Ten Tec though, the Omni VI and
VI+ were never spec'ed to super-precise frequency accuracy. Nevertheless
this problem bugged the heck out of me over time. So I embarked on a series
of modifications seeking an improvement. Funny, I thought that
experimentation was in the true spirit of ham radio from days gone by.
Anyway......
The frequency repeatability problem was vastly improved if not solved
outright by substituting the 2ppm TCXO for the original crystal oven in the
reference oscillator. A tremendous modification for older Omni VI's. About
$40 and hours work. As I have said before, it is the best change Ten Tec
has come up with for the Omni VI and VI+. While many crystals do exist in
the radio's L/O circuit, unlike in the Omni V, the VI's L/O crystals are
tied to the reference oscillator and cannot be individually trimmed per se,
for improved frequency accuracy. Small deviations do exist from band to band
but are not a real bother IMO.
Th real culprits in the Omni VI are the BFO crystals located on the board
directly under the in-board speaker. This circuit is subject to significant
thermal drift coming and going in response to rig-generated heat and even
changes in ambient room or Wx temperature. Attempting to fix this problem I
first removed the speaker to allow for convective cooling up through the
speaker grill. Good but not great results. Then I substituted higher
quality ceramic trimmers for the USB and LSB trimmers. No real improvement.
Finally I ordered custom built USB and LSB BFO crystals from ICM in
Oklahoma. About $70 and an hour's work later, I had them installed. This
change removed about 99.5% of the thermal drift resulting in better than
spec'ed display accuracy. The BFO circuit is the culprit in this rig
causing the problem with frequency accuracy. It is noticeable in SSB over
periods of extended TX activity. New custom crystals and its just about
gone.
I must join with Adam and George in telling you that my new IC 756 Pro II
has provided me with amazing frequency accuracy and repeatability. And to
those of you commenting that it does not matter I beg to differ. It matters
to many of us a whole lot. I simply got sick and tired of always being off
everyone else's frequency. It also matters if you want to work MARS. Check
out the MARS rig requirements of late.
I will also add that some of the snide comments including "sell your Omni
and keep you Jap rig then you won't be so stressed out" once again
demonstrate to me the developing intolerance of some on this list.
Regrettable.
I have both ICOM and Ten Tec gear here now but hold no blind allegiance to
any manufacturer. Competition breeds the best product for us all. To each
his own. This specific problem was/is important to me and many others who I
have spoken with but who care not to comment on the reflector.
And on a final unrelated note, I wish TT would put some good quality Orion
photos on the TT Web site. It needs to be seen better than is being shown.
73 de N1LQ-Dave
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