Hi Paul,
I'm sorry, but I can't really contribute anything to the keying
'issue'. I do not share Steve's opinion that the Omni VI has lousy keying
characteristics. Over the six years that I've had my Omni VI, I've never had
anyone mention the keying was chirpy; I have had many compliments on the keying
characteristics, running at 20 wpm all the way up to the max keying speed of 68
wpm, BEFORE they knew what kind of radio I was using. I have briefly monitored
the rf output on a HP spectrum analyzer, and I always monitor the keyed rf
envelope on an oscilloscope, and have yet to observe problems. Admittedly, it
would be very difficult to observe chirp on a spectrum analyzer unless it was
pretty severe.
Unfortunately since I've started using TenTec radio's, I've kinda lost
my urge to 'tinker' with circuitry! These things just don't break often
enough..hi! When I got my Omni, I also had an IC-781. I compared them
side-by-side for about seven months, both on-the-air signal comparisons and
many hours of listening and wound up selling the 781 in favor of the slight
rcvr advantage of the Omni in it's ability to hear weak signals on 40m and 80m
that the 781 at times just could not pull out of the noise.
Just yesterday, I purchased another used IC-781 and just yesterday I
received my Omni back from the factory with the Mod 3 installation. So I'm
going to go through the comparison process again...which do you think will win?
Good luck in chasing down the keying issue.
73,
From: "Paul Christensen" <<paulc@mediaone.net>
To: <<chestert@pressroom.com>
Subject: Omni Six Keying
To: <tentec@contesting.com>
Date: Mon, 21 Jul 1997 15:54:59 -0400
X-MSMail-Priority: Normal
X-MimeOle: Produced By Microsoft MimeOLE Engine V4.71.1008.3
Chester:
I recently copied you in on a post to Steve Ellington about the Omni Six
keying issue. Is there anything more you can contribute? The problem
doesn't appear to be timing related. Rather, as the 9 MHz crystal is
shifted during transmit, its capacitive loading changes when a variable
capacitor is switched in parallel with the crystal. A slight chirp is heard.
What's perplexing is that the Omni is capable of beautiful keying if the 9
MHz trim capacitor is set to it's minimum value. Only when that occurs, the
frequency display is off by 3 kHz.
I've ordered several crystals to continue experimenting with this in an
attempt to find a crystal that can be shifted 400 Hz and results in a
chirp-free 9 MHz signal.
-Paul, W9AC
Chester Alderman
<color><param>0000,0000,ffff</param>W4BQF -- Tom
</color><color><param>ffff,0000,0000</param>chestert@pressroom.com
</color>
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