[amsat-bb] Re: Diplexer

Sat Apr 9 19:53:29 PDT 2011

Andrew,
Both Duplexer and Diplexer allow for transmit and receive at the same time.

A duplexer, as used on a 2 meter repeater has an extremely narrow filter
allowing transmit on IE: 146.000 MHz and receive on 146.600 MHz. They
typically use cavity resonators, each cavity is 30" tall and 7-10" in
diameter and it takes 6 of them to make it work well. They must be tuned to
the repeater transmit and receive frequencies. 

A Diplexer is a small box with two filters allowing you to transmit on two
bands, receive on two bands, or transmit on one band and receive on the
other band at the same time. The diplexer keeps the bands separate to
prevent damage to the equipment on the other band.

Also there exists a Triplexer which is the same as a Diplexer but it
supports three bands. I have one here for 2M, 70cm, and 23cm. I use it on a
triband base antenna with a Kenwood TM 741A 

A Diplexer or Triplexer can be used to connect antenna connectors of radios
on different bands to a common coax, three antennas to a common coax or both
to use one run of coax for two or more bands. 

The Circulator mentioned for the radar is different from the Duplexer and
diplexer in that it allows the receiver and transmitter to be connected to
the antenna while the transmitter is operating. There are T/R and anti T/R
switches to prevent damage to the radar receiver during transmit and reflect
receive signals that reach the transmitter to the receiver. This is a pulse
echo system so receiver and Transmitter never function at the same time but
require a fast antenna switching time. A typical marine radar, switches from
Transmit to receive in 150 nS resulting in ~300 yards of "blindness"
measured from the antenna to the first target the radar can see. 

I hope this clarifies the differences.
Art,
KC6UQH

-----Original Message-----
From: Andrew Rich [mailto:vk4tec at tech-software.net] 
Sent: Saturday, April 09, 2011 1:39 PM
To: kc6uqh at cox.net; 'i8cvs'; 'Amsat - BBs'; 'Anthony Monteiro'
Subject: Re: [amsat-bb] Re: Diplexer

DU = TX RX
DI = RX
----- Original Message ----- 
From: "Art McBride" <kc6uqh at cox.net>
To: "'i8cvs'" <domenico.i8cvs at tin.it>; "'Amsat - BBs'" <amsat-bb at amsat.org>;

"'Anthony Monteiro'" <aa2tx at comcast.net>
Sent: Sunday, April 10, 2011 6:27 AM
Subject: [amsat-bb] Re: Diplexer

> As I understand it,
> A Duplexer allows for transmission and reception to take place in the same
> band using a single band antenna.
> A Diplexer allows for transmission and reception to take place on 
> different
> bands using a multi-band antenna.
>
> Art,
> KC6UQH
>
> -----Original Message-----
> From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
> Behalf Of i8cvs
> Sent: Saturday, April 09, 2011 10:35 AM
> To: Amsat - BBs; Anthony Monteiro
> Subject: [amsat-bb] Re: Diplexer
>
> ----- 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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