[TenTec] Corsair vs Corsair II

[Jerry Haigwood]

The amplifier described below is also sometimes known as a "Norton Amp"
since Dr. David Norton patented it in 1975.  Because of the patents, it has
not been used all that much.  The amplifier is also known as a "Lossless
Transformer Feedback Amp."  A single BJT Norton Amp can have an IP3 greater
than +35 bdm and an IP2 of > +45 dbm.  A dual BJT Norton Amp can have IP2 >
+95 dbm!
Jerry W5JH
"building something without experimenting is just solder practice"




-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Barry N1EU
Sent: Tuesday, March 12, 2013 5:54 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Corsair vs Corsair II

On Tue, Mar 12, 2013 at 10:32 PM, GARY HUBER <glhuber at msn.com> wrote:

> Mike,
>
> You are welcome. I regret that I cannot locate the document where I 
> originally saw the reference to Corsair / Corsair-II having ANZAC 
> receiver design and later commentary on later TEN-TEC receiver design 
> being changed to avoid Copyright or similar legal issues.
>

Here you go, posted 2007 to this list by Jerry K0CQ.

73,
Barry N1EU

The bipolar RF (and first IF) stage uses transformer feedback with a three
winding transformer. Its a circuit developed for the output stages of cable
TV distribution amplifiers where acceptable intermod is 70 dB down and in
Ulrich Rohde's book on receiver design he sees nothing close to having its
performance. A double gate MOSFET doesn't come close. I've run Kenwood with
MOSFETs and those MOSFETS don't come close to the strong signal handling of
my Corsair II.

That circuit is covered by an Anzac patent or two and that may be why Tentec
went to the grounded gate JFET circuit in the Omni V and VI.
Those use four JFETS in parallel with individual source resistors to make
them balance better. I've not seem their performance compared directly to
the Anzac circuit, but the Omni V and VI seem to do quite well in the
intermod department.

Schottky ring mixers are hard to beat and the higher the LO power (so long
as the mixer is designed for it) the better the strong signal performance.
Its also important that at least two of the three ports of the ring mixer be
terminated over a wide range of frequencies, else NF, mixer loss, and
intermod can be a lot worse. The mixer output often sees a crystal filter
and that is the worst thing that can be done, one book on mixers says that
can cost 30 dB intermod range. The Corsair II, Omni V and VI use a broad
band IF stage with lots of dynamic range to provide that IF port broad band
load and it shows. It works.

Don't know about the Omni V and VI, but the "attenuator" switch on the
Corsair II actually removes the RF stage from the circuit. There is no
attenuator.
_______________________________________________
TenTec mailing list
TenTec at contesting.com
http://lists.contesting.com/mailman/listinfo/tentec