[TenTec] Classic TenTec QSK, etc.

Steve Ellington steven4lq at gmail.com
Sun Jan 12 22:29:25 EST 2020

When I compared the 7300 and Corsair II, I was comparing them under a very
limited / narrow range of functionality.
There are just a few things that the old Corsair II can do better, limited
to low bands 80, 40, 30 meters, CW, QSK.
Other than those, the 7300 excels. The Corsair II would be a horrible
choice for any digital mode due to drift and no
computer interface and SSB isn't all that great. So don't misunderstand me
on this...The Corsair II was excellent at the time and still
runs rings around newer radios but only in a few areas.

The biggest topic these days is NOISE and with no antenna, RFG turned up
and AGC way up you would think the 7300 is horribly noisy.
However under typical band conditions you never hear that kind of
noise..It's all way below the ambient noise coming in on the antenna.
Naturally we
still wonder how an SDR radio can manage to make any noise...After all,
there are no conversion stages and no IF amplifiers, just a ADC which I
makes it's own racket but still below the band noise threshold.

As for Corsair vs Corsair II. There's a significant difference. The
original Corsair had a lot of annoying white noise when using narrow
filters. It's gone in the Corsair II. The Corsair was heir to the nagging
AGC thump on strong CW signals. That's gone in the Corsair II. AGC is quiet
smooth and actually the only audio derived AGC I've seen that actually
works without "riding" the RF Gain control. Too bad since the C-II was the
end of the road for TT's analog series.

QSK is pretty smooth but that varies with the particular radio. Some had
thumps and clicks in the headphones, mostly due to the design of the
sidetone circuit. I've managed to hack most of that out of mine. The front
end in them isn't all that tight. I've had to use a high-pass filter to
block AM BCB signals. I think the old Omni Series did better with it's
variable tuning front end. Lots of diodes can cause this.

As for the 7300. It's weakness is lack of front end selectivity and as
someone mentioned, Field Day can be a problem. We used my 7300 for FD this
year but it was necessary to use a band-pass filter in line with the
antenna. That totally cured the problem and this is common when you have
antennas 30 feet apart. The 7300's bandscope was a key factor in us getting
2nd place for our class in NC. Having that little gadget is invaluable once
you get used to using it.
Selectivity between close-in stations is like a brick wall on the 7300. The
Corsair II is pretty decent but even with it's 250 Hz filter plus the audio
filter it's not enough for FD or at least it leaves room for improvement.

Like I mentioned, I removed the 7300's amp control relay and bypassed it.
Now it's quiet enough... Not as quiet as the little reed relay in the
Corsair but bearable.

I can't remember the price for the Corsair II but with extra filters I
think it would be around $750 or so in 1986. If so, that's equal to about
$1,700 in today's dollars, about double the 7300's cost. Those filters are

Here's an interesting review of the Corsair II

On Sun, Jan 12, 2020 at 9:44 PM Bwana Bob via TenTec <tentec at contesting.com>

> Wait a minute...
> The Corsair receives better than a IC-7300?  My Corsair is a "keeper",
> but why would I want a 7300, even to replace my Paragon.  Maybe a  7300
> is better than a Paragon.  Even so, I would expect a "modern"  radio to
> perform better than a vintage one.
> 73,
> Bob WB2VUF
> On 1/11/2020 12:35 AM, Don Rasmussen via TenTec wrote:
> > I don't think you want to compare RGO to IC7300 or IC705, if you do then
> just buy one of those. They are greatly more feature rich for the dollar.
> But, if you already have one of those - I have IC7300, maybe an RGO can
> find a place in the shack. Steve N4LQ did a video comparing CW with IC7300
> and Corsair II. Corsair II won very big, IMO even when noise reduction was
> turned on for the Icom. But, this specific comparison is for the sound from
> the speaker, not frequency stability, memories, or modes! Corsair wins on
> quiet rx. I find that IC7300 is vastly closer to Corsair when I turn the
> AGC off. I would like to hear how RGO compares to Corsair and IC7300 on CW
> as Steve set things up - with equal speakers. My guess is RGO will have
> notably quiet audio from the samples I've heard. That could make it a nice
> niche machine. I posted about this because it seems like the project is
> moving ahead, as compared to others - like the Palstar transceiver project
> that faded before launch.
> > de Wb8yqj Don
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