[TenTec] Bring back the corsair 2

Steve Ellington steven4lq at gmail.com
Wed Nov 23 16:46:20 EST 2016 

Barry
You can erase my comment about the Corsair 2's noise. The Corsair 1 was the
noisy one.
As for the AGC. This was not a mod. TenTec totally redesigned the AGC
between the Corsair I and II.
The 1's system was the same as the Triton, Omni etc.

The AGC voltage in the Corsair II is derived before the audio filter thus
reducing the delay. Then the AGC voltage is rectified by a full-wave bridge
circuit as opposed to the half wave AGC rectifier used prior to the Corsair
II. This was accomplished by IC-2 which acts as a phase inverter to apply
the input signal to the rectifiers. Being a "bridge" rectifier, 4 diodes
are required instead of just one.  The bridge rectifier is not only faster
than the half wave but provides more voltage with which to quickly reduce
those strong signals.

On most TT rigs the AGC was really not a true AGC since the gain is not
actually varied. The Corsair, Omni ABCD and Triton's AGC used a shunt diode
to shunt the inputs of the 2 IF amplifiers as required. Other rigs actually
use the AGC voltage to vary the gain of the amplifiers. The thinking here
was that the IF amplifiers were designed to be linear at one particular
bias voltage. Varying the voltage would deviate from the ideal design. So
instead they simply reduced the amount of signal applied to the amplifiers.
The AGC voltage is used to forward bias a diode and shunt the input signal.
Actually it makes good sense.

Prior to the Corsair II, the AGC was developed AFTER the audio filter. This
was actually necessary since the audio filter was the primary means of
selectivity and the AGC needed to be part of that loop. Unfortunately the
loop was slow and strong signals caused severe AGC overshoot resulting in a
horrendous pop at the onset of a strong CW signal. Reducing the RF gain or
pre-selector tuning was necessary.

One very effective cure for the pop is to put 2 pair of back to back
schottky diodes across the audio output. I started out using IN4148's but
later found the Schottky's are much faster. I can now leave the RFG up on
my Omni C.
https://www.youtube.com/watch?v=sTOFnUFonCc

There were exceptions such as the Delta 580. That rig was very unique and
almost looks like someone else designed its AGC system.

Steve N4LQ


On Wed, Nov 23, 2016 at 4:05 PM, Barry N1EU <barry.n1eu at gmail.com> wrote:

> Steve, can you possibly provide more into on the Ten-Tec fix for the C2?  I
> can't remember ever hearing that before and I've researched it extensively
> over the years.  I'd really like to get that documented for the Ten-Tec
> Wiki.
>
> Glad you're enjoying the Corsair II!  I could be wrong, but I seem to
> remember you making some definitive posts back in the day handing the
> quietest rig trophy to the Omni C, but maybe that was in comparison to the
> Omni VI which I believe had you pulling your hair out  ;-)    When I had an
> Omni C in the shack it sure seemed drop dead quiet to me.
>
> 73, Barry N1EU
>
>
>
> On Wed, Nov 23, 2016 at 8:23 PM, Steve Ellington <steven4lq at gmail.com>
> wrote:
>
> > Hi Barry.
> > I used to think the Corsair II was noisier but I have a nice Omni C and
> the
> > Corsair 2 is much quieter. Maybe I had a dud?
> >  I have 3 of these C2's now!
> > TenTec finally fixed the popping AGC in the C2 by bypassing the audio
> > filter and using the AGC voltage doubler circuit.
> >
> >
> > On Wed, Nov 23, 2016 at 3:05 PM, Barry N1EU <barry.n1eu at gmail.com>
> wrote:
> >
> > > Warms my heart to see W9AC and N4LQ posting on the Ten-Tec reflector
> > > lately, like the good old days!!!
> > >
> > > Only want to add one comment Steve.  I'm almost certain you already
> know
> > > this, but I think there was a significant jump in noise from the Omni
> > ABCD
> > > to the Corsair series and then another jump up to the Omni V/VI series.
> > > You can mitigate much of the Corsair noise by replacing the AF op-amps
> > etc,
> > > as described here: http://corsair.wikidot.com/corsair-opamp .  I think
> > my
> > > Omni VI is as quiet as my Corsair, but both of them have been heavily
> > > tinkered with.
> > >
> > > Barry N1EU
> > >
> > > On Wed, Nov 23, 2016 at 6:59 PM, Steve Ellington <steven4lq at gmail.com>
> > > wrote:
> > >
> > > > I had a loaded K3s then bought an IC-7300 and the noise level was
> > > slightly
> > > > lower to the point that the K3s started gathering dust.
> > > > Recently I picked up a couple of Corsair II's having forgotten what
> > they
> > > > were like. After listening to the Corsair II for a while the noise
> > coming
> > > > from the IC-7300 sounds like Darth Vader's breathing. Just a few
> > minutes
> > > > ago I tried to have a QSO with a guy and I was having a terrible time
> > > > trying to copy his CW. I switched to the Corsair II and felt total
> > relief
> > > > flood by frazzled brain. I kicked in the 500 hz xtal filter. The
> noise
> > > > actually goes down instead of up as it does in DSP rigs. I then
> brought
> > > in
> > > > about 50% audio filtering and he sounded like a CPO...Remember those?
> > > >
> > > > The Corsair II was the last of long like of analog rigs from TenTec.
> > PLL
> > > > and DSP started creeping in and up came the noise.
> > > >
> > > > Here's a couple of videos I made to help get the point across. Again
> > let
> > > me
> > > > say that the 7300 is one of the quietest (modern) radios I've had and
> > boy
> > > > does it sound noisy next to the Corsair II!
> > > >
> > > > https://www.youtube.com/watch?v=oX8EWUcnvBU
> > > >
> > > > https://www.youtube.com/watch?v=8LBbiXXRex8
> > > >
> > > > It's frustrating. I don't want it to be this way. I want a receiver
> > > that's
> > > > better than the Corsair II. What to do?
> > > >
> > > > steve n4lq
> > > >
> > > > On Wed, Nov 23, 2016 at 1:32 PM, Steve Berg <wa9jml at frontier.com>
> > wrote:
> > > >
> > > > > There is no way that it would be profitable to recreate the Corsair
> > II
> > > > > these days.  I really love my Corsair II, and its external VFO.
> > But, I
> > > > > also realize that its days are numbered because many of the parts
> in
> > it
> > > > are
> > > > > no longer available.  And, while it was an outstanding DX and
> contest
> > > > radio
> > > > > when it was built, it is not suitable for contesting any more.
> Mine
> > > has
> > > > > done a great job for DXing from my rather poor location.
> > > > >
> > > > > I like it because after several years I have learned its quirks,
> and
> > > how
> > > > > to best use it under varying conditions.  Realizing its age, I
> bought
> > > an
> > > > > Omni VII during the fire sale so that I would have a decent and
> much
> > > > newer
> > > > > radio when the Corsair II finally breathes its last.  After several
> > > > months,
> > > > > I put the Omni VII on the shelf, and went back to the Corsair II.
> I
> > > > > eventually found a good home for the Omni with a newly minted
> ham.  I
> > > > don't
> > > > > miss it. It seemed to require a lot of menu usage for simple
> > > operations,
> > > > > and for which the Corsair II just requires a bit of adjustment of a
> > > knob
> > > > or
> > > > > two.  I was very impressed with the Eagle when I used one at the
> > > factory
> > > > > several years ago.  Would I buy one at $1700 to have a backup for
> the
> > > > > Corsair II?  Most likely yes, especially to help keep Ten Tec
> afloat.
> > > > Most
> > > > > of the Japanese radios make extensive use of menus, and I don't
> like
> > > > using
> > > > > those.  I have two Argonaut VI radios, and the receivers in those
> are
> > > > > simply incredible.  I would like to buy 2 more of them for use as
> > > VHF/UHF
> > > > > IF radios for transverters.  They are apparently similar to the
> > > receiver
> > > > in
> > > > > the Eagle, so that would be yet another reason to buy an Eagle.
> > Since
> > > I
> > > > > have little use for contesting, that does not enter into my
> > preferences
> > > > in
> > > > > rigs.
> > > > >
> > > > > I have also worked in economic development as a city administrator
> > and
> > > > was
> > > > > on the county economic development board out where I last worked in
> > > this
> > > > > field.  What Mike describes is what we referred to as elephant
> > hunting.
> > > > > And, I suspect that his comments about economic development being
> > taken
> > > > > over by the local Chambers of Commerce is sadly true.  What these
> > > people
> > > > do
> > > > > not understand is that by helping out smaller companies, there is a
> > > > > significant increase in a multiplier effect through the local
> > economy.
> > > > > And, the local governments also have to provide less in the way of
> > tax
> > > > > expenditures and other incentives.  Where I live now local
> > governments
> > > > give
> > > > > too many incentives to retail and warehousing, which do not pay
> > enough
> > > to
> > > > > support a family.  They are trying to capitalize on the local
> > > university
> > > > > students, but wind up shooting themselves in the foot rather
> > > > frequently.  I
> > > > > would love to see a federal suit challenging economic incentives on
> > the
> > > > > basis of the Fourteenth Amendment's Equal Protection Clause.  That
> > > would
> > > > > really start to level the playing field in local economic
> > development.
> > > > >
> > > > > Your Mileage May Vary...
> > > > >
> > > > >
> > > > > Steve WA9JML
> > > > >
> > > > >
> > > > >
> > > > > On 11/23/2016 10:33 AM, Ron Notarius W3WN wrote:
> > > > >
> > > > >> Yeah, like that's going to happen...
> > > > >>
> > > > >> Considering what Dishtronix has dealt with, prior to the Ten Tec
> > > > >> acquisition, in regards to overseas manufacturers, I have some
> > serious
> > > > >> doubts that Mike would seriously do this.  Even if there is
> > sufficient
> > > > >> market for the rig today, which I suspect there isn't.
> > > > >>
> > > > >> Now if you could design a Corsair III, including a DDS type dual
> > VFO,
> > > > and
> > > > >> could afford to build it domestically and sell it at a small
> profit
> > > for
> > > > >> circa US$600, you might have something.  Maybe.  But built in
> China?
> > > I
> > > > >> doubt it.
> > > > >>
> > > > >> 73, ron w3wn
> > > > >>
> > > > >> -----Original Message-----
> > > > >> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of
> > gary
> > > > >> mankoff
> > > > >> Sent: Wednesday, November 23, 2016 10:36 AM
> > > > >> To: tentec at contesting.com
> > > > >> Subject: [TenTec] Bring back the corsair 2
> > > > >>
> > > > >> We need a new corsair 2 ,just like the old one with the filters
> > > > installed
> > > > >> ,made in China.
> > > > >> This is the only way TT can compete.
> > > > >>
> > > > >> Sent from my iPad
> > > > >> _______________________________________________
> > > > >> TenTec mailing list
> > > > >> TenTec at contesting.com
> > > > >> http://lists.contesting.com/mailman/listinfo/tentec
> > > > >>
> > > > >>
> > > > >> ---
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> software.
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> > > > >>
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