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Omni VI and Corsair II comparison

To: <tentec@contesting.com>
Subject: Omni VI and Corsair II comparison
From: junger@usgs.gov (Unger)
Date: Fri, 10 Jan 1997 14:03:15 -0500
As promised a while ago, I have written this look at the Omni VI is from 
the perspective of a Corsair II user (and fan!) for hams on the TenTec 
reflector to read.  This purely subjective information comes from using 
my new Omni VI for a grand total of five weeks after having a Corsair II 
in constant use for Dxing, contesting, and general all around ham radio 
for over 3 years. I should add that I operate CW about 99% of the time.

Similarities:

1. Both made by TenTec; this fact speaks for itself and conveys the idea 
of quality construction and legendary service.

2. The two rigs use the same filters in the 6.3MHz IF; e.g., you can use 
your Corsair II filters in the Omni VI. I am also using my TenTec 961 
power supply that came with the Corsair II; it works fine.

3.  The two rigs "sound" alike when listening to CW; this may be a 
function of using the same IF filters and is hard for me to define, but 
that=92s the only way I know how to say it. I should add that I mostly use 
the 500Hz filter for CW.

4.  Both rigs have internal keyers that I can=92t comment on; I use an 
external keyer.


Differences I have noticed:

1. When you are in the CW mode, the CW sidetone is always on the "upper" 
side of the zero beat frequency on the Omni VI; on the Corsair II it is 
on the upper side on 30 Meters and below and on the lower side above 30 
Meters.

2. The noise blanker on the Omni VI works. I never saw any effect of the 
Corsair II=92s noise blanker on any interference I experienced. I don=92t 
think it was just my rig either; I have two friends with Corsair II=92s 
who have had similar experiences.

3. The CW sidetone frequency and the transmit offset from the receiving 
frequency are identical on the Omni VI and can be changed, but if your 
transmit offset gets far from 700 Hz the CW bandpass filters won=92t work 
right because they are centered on 700 Hz (you can compensate with the 
passband tuning, though). On the Corsair II the transmit offset is fixed 
and you can adjust the=20sidetone frequency by itself. The sidetone 
quality on the Omni VI is much nicer and easier on the ears.

4. The top-mounted speaker and/or better audio output make the Omni VI 
sound better than the Corsair II on SSB and CW; the audio seems clearer 
and stronger. I almost always used the speaker in the 961 power supply 
with the Corsair II; now the power supply is tucked away out of sight.

5.  The passband tuning in the Omni VI just works better than the one on 
the Corsair II. It seems to cut out interfering signals cleanly with a 
minimum of distortion both on CW and SSB.


Operating Impressions: 

When I first sat down in front of the Omni VI I noticed two things: the 
frequency display is larger and reads to the 0.01 KHz, and the tuning 
knob feels smoother and, well, just nicer. The tuning rate on the Omni 
VI can be set from 0.85 to 5.12 KHz per revolution, but the fastest 
rate, 5.1 KHz per revolution, is much slower than the Corsair II=92s 17 
KHz per revolution. After a short adjustment period for my fingers, I am 
now used to and like the slower tuning rate on the Omni VI better.

The Omni VI makes use of some coaxial control knobs rather than having 
all single function knobs like the Corsair II. However, usually only one 
of the coaxial knobs=92 functions is used frequently, and the other is 
"set and forget". For example, AF and RF gain are ganged, as are drive 
and mic gain. In case you didn=92t guess, I=92m not a fan of coaxial knobs=
=85

The receiver in the Omni VI is HOT! At first I thought that the Corsair 
II was quieter, but then I realized that the Omni VI=92s receiver is more 
sensitive and that I was hearing more signal, too. The AF gain control 
seems more sensitive in the Omni VI than in the Corsair II; with head 
phones on the control goes from very quiet to very loud in only about 90 
degrees of  rotation. It would be nicer to have a more gradual, linear 
"volume control". I use both transceivers with their RF gains set from 
about the 1 to 3 o=92clock position under normal conditions. I rarely have 
the RF gain "cranked up" all the way.

The Omni VI is definitely more selective than the Corsair II for CW 
contest-type operating with lots of adjacent strong signals - even 
without using the 500 Hz filter in the 9 MHz IF. With the 500 Hz, 9 MHz 
filter, the performance is awesome; you can work very close to strong 
signals and not even be bothered by interference. I am using exactly the 
same 6.3 MHz filters in my Omni VI that I had in my Corsair II. I have 
experienced absolutely no ringing or signal deterioration using the 500 
Hz or 250 Hz filters either with or without the addition of the 9 MHz 
filter.


Things I miss:

1. The big one - being able to listen to two frequencies at once and 
vary their relative volume like I can with the Corsair II and its 
external VFO. But with the A/B split on the Omni VI you can alternately 
listen to two frequencies, even on different bands, just by holding and 
releasing the REV button, very nice.

2. With the Corsair II, I used its QSK output jack to key my venerable 
Drake L-4B amplifier through an external QSK switching box that I built 
using Jennings vacuum relays. The Omni VI does not have a direct QSK 
output analogous to the Corsair II=92s, so I have to use the T/R relay 
output and run my amp essentially non-QSK. There may be a possibility to 
use the QSK out and enable jacks on the Omni VI, which are designed for 
use with the TenTec amps to drive my QSK box; I=92m looking into that 
possibility.

Omni VI features I now can=92t live without:

1. Moving around the bands with direct frequency entry and switching 
from band to band and always returning to the same frequency-filter-mode 
on a band.

2. Having a computer interface to the rig so that my contesting and 
logging programs can automatically control the rig=92s frequency and 
vice-versa.

3. The additional selectivity of that 500Hz filter in the 9MHz IF.

4. The DSP notch filter is "magic" on SSB. You just hit the button an 
tuner-uppers and heterodynes simply vanish.


Regrets:

My only regret is that I waited so long to get the Omni VI!!


I hope that some of you find all of this interesting and informative. 
Hope to see you in the NA QSO party contest tomorrow!

73 es Happy New Year - John, W4AU (ex-W3GOI)

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