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Re: [TowerTalk] Tribanders on 12m/17m

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Tribanders on 12m/17m
From: Dan Zimmerman N3OX <n3ox@n3ox.net>
Date: Wed, 23 Sep 2009 18:14:48 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
>
> No problem with traps burning out...none on the  KT36XAs.


Yup, then you just need to deal with the feedline loss... but...

Most of the time no one actually needs 1500W ERP on 17m/12m to work DX .. so
that's a consideration if you don't usually care about 12/17 and just need
them in a DX emergency ;-)  So what if you lose 5dB  or 8dB or whatever in
the feedline?  You'll still put out a few hundred watts.

For permanent use you can do better if you don't have traps. When I put up
my 20m Moxon it replaced an antenna that I was using with a relay switched
feedpoint matching network on 20m and 17m.  I didn't want to lose 17m, so I
decided to put a feedpoint matching network on the 20 Moxon and just use it
as a 17m rotatable "sorta-doublet"

Then I took a closer look and figured out that if I switched a capacitor
into and out of the reflector it would give me a few dB gain and reasonable
F/B:

http://n3ox.net/projects/2017moxon/

It'd be an interesting add on to build a relay switched matching box for the
Force 12 and other similar trapless tribanders... couple new bands no
windload.  Of course, Force 12 says "WARC with tuner" on their website, but
I dunno... a simple dipole is gonna beat it in many installations once you
figure in the mismatched line loss.

73
Dan
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