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Fred McKenzie · December 6th 12, 09:22 PM posted to rec.radio.amateur.homebrew

In article ,
(David Griffith) wrote:

In order to connect a 2m/70cm radio and a 1.25m radio to a triband
antenna (2m/1.25m/70cm), one requires a triplexer and diplexer. I'd
like to cut down on the number and size of equipment to do this.

I asked Comet about making a single compact unit that takes 2m/70cm on
one port and 1.25m on the other. Mick Stwertnik told me that they
designed and specced it out, but the cost would be a prohibitive
$200-ish.

So I investigated making my own and found Jim Tonne's Diplexer program.
I asked him if he could extend the program to allow for designing
triplexers. He had some hackish solution that sort of worked, but he
doesn't know the math to do it correctly in the first place.

Where should I go from here?

David-

I take it your 2m/70cm radio has a single input with an internal
diplexer. I use a Comet CFX-324 triplexer, but my Kenwood TM-742 has
three separate inputs.

It seems to me that your radio's input might satisfy the need for a
2m/70cm diplexer. What would happen if you connected your triplexer's
2m and 70cm ports together with a co-ax T?

You might check SWR looking into the T, to see if it was close to 1 to 1
on both bands with the antenna and 1.25m ports terminated.

Rather than using the triplexer/diplexer combination, there might be
less loss if you use a separate antenna for 1.25m, with just a diplexer
for 2m/70cm.

Fred
K4DII