[TowerTalk] triplexers and stacking

Jim Thomson jim.thom at telus.net
Wed Mar 22 00:36:02 EDT 2017


Date: Tue, 21 Mar 2017 21:50:34 -0400
From: Mike DeChristopher <mfdechristopher at gmail.com>
To: towertalk at contesting.com
Subject: [TowerTalk] triplexers and stacking

I know some of you are using (or have used) a triplexer with your
tribander. Having very limited experience with triplexers and
tribanders, I'm hoping you can assist with a thought experiment we're
working through.


73,
Mike N1TA

## what I would like to know is... how the heck can you stuff 3 x amps, each running 1.5 kw
simultaneously, into just one coax, that in turn feeds just one balun, that feeds the tribander ?
A TH7 or mosely would go up like a roman candle, so a real tribander would be required.
Even then,  the poor balun would take a beating, along with the 213-U.   I would think you
would at least require some heavy duty coax  going up the tower, and then some flexible
heavy duty coax for the rotor loop,  like perhaps  LMR-600UF or  RG-393.  As far as the balun goes,
I dont know if RG-303 or  RG-400  would work...since both only have a 18 ga center conductor. 
What might work is  RG-304, which has a 14.5 gauge center conductor, and is aprx .280 OD on the
outer jacket, has a teflon dielectric. It’s a tiny bit bigger OD than RG-8X, so may well be able to wind on
a stack of 2.4 OD torroids.    RG-393 has a 11 ga center conductor and also teflon dielectric, but has
a .390 outer sheath, and is a bitch to wind on torroids, and keep the assy compact,  however, it can be done.
Trying to achieve high values of RS  from 20-10m is yet another trick, so the torroids dont heat up with
4.5 kw through them on the upper 3 bands.  With 393, you need 2 x CM chokes in series, stagger tuned. 
With 304 coax,  you could do it with a single stack, but 2 x CMs in series is not a big issue, provided that
304 can be wound tightly like 8X can. 

Jim  VE7RF



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