[amsat-bb] Re: Diplexer

i8cvs domenico.i8cvs at tin.it
Sat Apr 9 10:34:38 PDT 2011

----- Original Message ----- 
From: "Anthony Monteiro" <aa2tx at comcast.net>
To: <amsat-bb at amsat.org>
Sent: Saturday, April 09, 2011 5:15 PM
Subject: [amsat-bb] Re: Diplexer

> A "duplexor" is a device that allows both transmitting and
> receiving over the same transmission line or antenna. It
> may or may not be a passive device and it may or may not
> be frequency selective.
> In WWII RADAR systems, a duplexor was used to allow
> the transmitter and receiver on the same frequency to
> share the same antenna. The duplexor was a waveguide
> device that had special gas-filled tubes to quickly
> switch the signal direction.
> 73,
> Tony AA2TX
Hi Tony, AA2TX

I have in my hands the Instruction Book for Radar Recognition 
Sets AN/UPX-6  of U.S. Navy  Department Bureau of Ships.

The UPX6 is a IFF transponder on board of aicrafts and was used
in WWII for  Identification of Friend or Foe.

The UPX-6  can transmit from 1010-1030 MHz and receive from
1090-1110 MHz and allows both transmitting and receiving over
the same transmission line and antenna via a circuit  made of coax
cable RG-58/CU that the manual calls a   "DUPLEXER" and not
a "duplexor".

This "duplexer" is working on the fact that a transmission line,
shorted at the far end a quarter wavelenght long for the incoming
signal,represent infinite impedance (an open circuit) at the sending
end of the line.

The UPX-6 was converted in the early 1980's to be used on 1296 MHz
and an interesting article written by W6NBI was published in Ham
Radio Magazine march 1981

I modified it and I got 40 watt output.......not too bad for that epoch
time !     

Best 73" de

i8CVS Domenico

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