[TenTec] SO2R with Ten Tecs?

[Rob Atkinson, K5UJ]

I stand corrected and tnx to K0CQ for the clarification.  I read the manual 
for the Corsair II on this but did not understand it correctly.  I was 
reading the Omni VI manual on the same topic (2nd rx antenna connection) at 
the same time and got the two confused.  This past weekend I reread and 
experimented with the Omni VI and Corsair II I have.  The Omni accepts rf 
coming in from a second source at the rear panel rca jack and but does not 
transfer rf back out through that jack from the main antenna so239, to a 
second rx.  The Corsair II however *does* do that with its aux. ant. rca 
jack as Jerry writes below.  It's too bad they left this off the Omni but 
I'll bet the thinking was that since the Omni has vfo A and B it would not 
be needed.  The good news, as all you Corsair II owners must already know, 
is that with a second rx or transceiver (if the transceiver has an aux ant. 
input like the omni or you want to employ a coax switch--don't transmit!) 
you can operate split frequency with the Corsair II, by hooking up the other 
rig to the Corsair II's phono jack and flipping the back panel switch to 
trx.
I have these toys and very little time to play with them so you all are gg 
to have to be patient with me while I'm still figuring them out.  The 
confusion on my part over SO2R operation and the search for a fast rf switch 
was my misunderstanding of the term (SO2R is another novelty that has come 
up during my 18 year QRT).  I literally thought it meant one op/2 radios.  
In reality it's a misnomer--really means one op/two *stations* or 
single-multi--two rigs/two amps/two antennas, making a fast rf switch 
between two radios unnecessary, and explains why no one makes one.  I was 
making a simple concept more complicated than it had to be.  Whatever you 
do, don't quit the hobby for 18 years--way too much catching up to do.

Rob Atkinson
K5UJ
k5uj@hotmail.com

----Original Message Follows----
From: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Reply-To: geraldj@isunet.net
To: Joe L Blackwell <aa4nn@juno.com>, Joe L Blackwell <aa4nn@juno.com>
CC: tentec@contesting.com
Subject: Re: [TenTec] SO2R with Ten Tecs?
Date: Mon, 06 May 2002 22:25:58 -0500

There IS isolation IF and only IF you throw the RX/TRX switch on the
back panel that causes the isolation. If you leave that switch
connected, transmitter RF may show on the receiver input jack. Though
there's supposed to be PIN diode isolation even then.

Virtually NO receiver has an output for a second receiver. You can run
two receivers on one antenna with a simple power splitter, such as an HF
versions of a cable or TV two way splitter, looses 3 dB (and a hair)
which isn't usually a problem at HF. Most receivers tolerate being
connected with their inputs in parallel. Works better after a low gain
preamp. There have been commercial signal splitters for a gaggle of
receivers, often used on military ships. There was a relatively fancy
splitter in QEX using ferrite cores and a couple MAV11 MMICs.

You can build one with a preamp stage, followed by as many
cathode/emitter/source followers with their high input impedance to
drive each receiver. If there's enough gain in the preamp (a few dB more
than the loss in a splitter) you can use a resistive two way splitter
consisting of three 16 ohm resistors in a star connection. One resistor
to the input, one each resistor to the isolated output.

According to MY Corsair II manual, there's two diodes switched off by
removing the R voltage from the LFP-TR board, then the T voltage causes
a transistor to short the receiver input for further isolation. Getting
100 watts to the receiver input with or without the RX/TRX switch in the
RX position, means putting 100 watts of RF on the internal receiver
input. Which should be frying the internal receiver input via the low
level driver board.

Looking through the circuits, a second receiver on the auxiliary
receiver jack should receive just fine with the RX/TRX switch in the
closed position and neither that receiver nor the Corsair II receiver
should receive excess power from transmitting with the Corsair II.
Blowing a Beverage transformer would indicate failures in Corsair
circuits.

73, Jerry, K0CQ
--
Entire content copyright Dr. Gerald N. Johnson. Reproduction by
permission only.
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