No subject

FREQUENCY ACCURACY    +/- 50 Hz @ 25 degrees C. (NOTE: the frequency will
shift noticeably for  1 - 2 minutes while the oven heats up when first
turned on.  Leave DC power connected to the rear panel el eliminate this
turn-on drift).

And I see all the P'n and Moanin' over 10 Hz.

I use my Omni VI+ on 20M PSK31 and yes I see many signals in the 500 Hz
passband.  Never have a problem finding my schedule or frequency.  Guess my
tuning knob works and I know how to use it.


73
Bob, K4TAX

----- Original Message -----
From: "David Hammond" <dhhdeh at concentric.net>
To: "tentec reflector" <tentec at contesting.com>
Sent: Wednesday, October 02, 2002 8:58 PM
Subject: [TenTec] Omni VI Plus freq. readout


> 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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