Question on vhf/uhf duplexers

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wb3cez
Posts: 39
Joined: Sun Mar 21, 2004 11:11 am

Question on vhf/uhf duplexers

Post by wb3cez » Thu Nov 08, 2012 12:04 am

For the first time, I have the need for a 144/440 duplexer for a new radio and need some information. After doing some research on the net, I have not found the answer to my question. The transceiver has one output only and is designed for use with a dual band antenna. However, I plan to use two separate antenna's. I have been told that duplexers are used with two separate inputs and directed to a single antenna. I wish to do just the opposite with one input directed to two separate antennas. Can duplexers work in this configuration? [/b]

k9yli
Posts: 223
Joined: Fri Aug 12, 2005 11:35 pm
Location: northwest wisconsin

Post by k9yli » Thu Nov 08, 2012 3:15 pm

I'm not an expert in this real, but I would just put a T connector in the coax and feed two appropriate antennas.
The antenna that matches the signal frequency will radiate most of the RF.

As the other antenna would be very inefficient at that frequency.

My precaution would be the length of the coax between splitter and antennas.
I would keep this length to be non-resanant on either frequency..

just try it.. if it doesnt work try some modifications...

w7ry
Posts: 28
Joined: Tue Jul 01, 2003 4:52 am

Re: Question on vhf/uhf duplexers

Post by w7ry » Mon Dec 17, 2012 2:46 am

wb3cez wrote:For the first time, I have the need for a 144/440 duplexer for a new radio and need some information. After doing some research on the net, I have not found the answer to my question. The transceiver has one output only and is designed for use with a dual band antenna. However, I plan to use two separate antenna's. I have been told that duplexers are used with two separate inputs and directed to a single antenna. I wish to do just the opposite with one input directed to two separate antennas. Can duplexers work in this configuration? [/b]

Yes they can. This is what they are designed for. They are more aptly called a splitter or combiner or cross band coupler. Manufactures take liberty with the word duplexer. A duplexer is actually used to transmit or receive on the same band at the same time. A duplexer is used for a repeater.

They do have some loss. About .2dB per port. But that isn't to bad.

73
Jim W7RY

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