The Omni 5, 6, Paragon series all use the same basic method of cw carrier
generation and the cw offset is determined by small trimmer capacitors
located on the TX-Audio board. The Omni 5 and 6 has a trimmer capacitor for
the BFO which has a habit of changing value with age, temperature and dirt.
I'm not 100% sure if the trimmers on the "real" 6+ were improved or not but
at any rate these little trimmers are not the best.
When you press your key, the T voltage is applied to a switching transistor
which in turn, inserts one of these trimmers across the crystal for proper
offset. This is what tends to cause the distinctive keying note to the Omni
6. The sudden change in frequency causes a slight micro-chirp in the
transmitted carrier. After a few years, the crystal ages and the trimmer
changes value and realignment is necessary. This doesn't help the chirp but
it does cure the offset problem.
Look in your manual for the TX-Audio board discription. There you will find
instructions for alignment of the various trimmers on the board. When I had
an Omni 6, I used my IC-706 as a frequency meter to align these. You could
use a frequency counter or just another receiver. Once aligned, you should
have no more trouble keeping on frequency.
Steve
N4LQ
----- Original Message -----
From: "Al Williams" <alwilliams@olywa.net>
To: "Tom Delker" <k1ky@bellsouth.net>; "Bill Hawkins" <w5ec@knology.net>;
<tentec@contesting.com>
Sent: Monday, February 21, 2000 12:49 AM
Subject: Re: [TenTec] Zero beat?
I am not sure that I understand this subject correctly--i.e.
is the main frequency off or the rit/xit off? On my year-
old Omni6+, with the rit/xit off I have to tune about 30 hz
above what others say the frequency is. That sort of
annoys me because the rig costs twice as much as
my kenwood ts440 and Icom706 which I havent
noticed has the problem--but my ear hasn't been as
critical.
But the main reason for this posting is that I heard
in a 75 fone group discussion one who said that
TenTec rigs were notorious for being off frequency!
If this can be corrected somewhat easily, how to do
so and why isnt it set at the factory?
k7puc
-----Original Message-----
From: Tom Delker <k1ky@bellsouth.net>
To: Bill Hawkins <w5ec@knology.net>; tentec@contesting.com
<tentec@contesting.com>
To: <tentec@contesting.com>
Date: Sunday, February 20, 2000 9:01 PM
Subject: Re: [TenTec] Zero beat?
Interesting subject Bill! I noticed that on RIT my offset required is
about +.04, but on XIT it seems to be different. I'm sure there are
separate adjustments for this and they are prone to drift after
manufacture.
--
Thomas M. Delker - K1KY CFO#395 - Smyrna / Gallatin / Short Mtn. TN
A.R.R.L. District Emergency Coordinator - Tennessee District #4
C.A.T.S. (W4CAT) - 147.30/145.23/145.49/145.17/223.98/444.45/444.65
Stones River A.R.C. (K4FUN) - http://www.members.home.com/srarc
Tennessee Contest Group (K4TCG) - http://www.k4ro.net/tcg.html
CODE WARRIOR © #2 - Mobile CW Operator
"Putting code on the road using the primary mode"
--
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