Folks,
For those who may be interested, here are the comments from TT's service
department:
1) Spurii
"Some spurii, but not all, can be reduced by making sure that the mounting
screws for the boards and ALL chassis screws are tight. You may have to move
some cables and or put a twist in them. Also on the Band Pass Filter board, any
part that passes through the top ground plane to ground or earth, should be
soldered on the TOP side of the board. No two rigs are the same, some it is
cables, others it is grounds or a combination of both."
2) "Dim" display
TT say they had a few Omni VI runs where the "smoked glass" insert on the front
panel was a lot darker than the rest of them. Unfortunately they don't carry
any replacements. It's not a big deal, but if you saw the Omni lined up
alongside the Hercules and the TT ATU you'd think the Omni meter bulbs were
running on half-voltage (they are not - I've checked) :)
If I make any significant improvement on the spurii, I'll report back.
The good news from TT was that they carry replacement AF/RF gain controls, and
they still stock the 15 way multipole connector to make up a lead between the
Omni and my Hercules II
73,
Steve G3TXQ
----- Original Message -----
From: Ken Brown
To: geraldj@storm.weather.net ; Discussion of Ten-Tec Equipment
Sent: Wednesday, November 29, 2006 9:38 AM
Subject: Re: [TenTec] Shields in Omni VI
>
> Doesn't NAR change the filter bandwidth and then the controller adjust
> the BFO frequency and the main oscillator frequencies to keep the offset
> from BFO to IF filter the same and the main oscillator to compensate to
> keep the received zero beat frequency the same?
>
In a word, no.
The Omni VI has only five discreet selectable BFO frequencies and they
are selected depending on mode CW TX / LSB (TX or RX), or CW RX / USB
(TX or RX) / FSK TX space, FSK TX mark. They are not dependent on
either 9 MHz or 6.3 MHz filter selection.
If the BFO were more finely controllable, there would be no need to
produce both the 219 and 221 filters, which are both 250 Hz BW 6 pole
filters. The only difference between them is their center frequencies.
The fact that switching the NAR 9MHz filter in and out changes the
birdie frequency in Steves Omni suggests to me that that part of the IF
chain is also part of the feedback loop generating the spurious
oscillation. Or as someone else has suggested, the spur is created in
part of the digital circuitry and changes due to the added current used
by the NAR LED.
I'm sure glad mine does not have that problem. I hope Steve can find an
easy way to make it go away in his rig.
DE N6KB
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