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Re: [TowerTalk] elevated short vertical dipole orquarterwave monopole?

To: "Steve Katz" <>, "Michael Tope" <>,"Jim Lux" <>,"Guy Olinger, K2AV" <>,"TowerTalk" <>
Subject: Re: [TowerTalk] elevated short vertical dipole orquarterwave monopole?
From: "Tom Rauch" <>
Reply-to: Tom Rauch <>
Date: Fri, 3 Dec 2004 15:41:55 -0500
List-post: <>
> > ::Tom, you posted something recently somewhere about
LPDA mfrs
> > recommending running the feedline along one of the
excited booms and
> > stuff.  Yep, Tennadyne recommends this.  I've also seen
it recommended to
> > run the coax inside one of the excited booms, where an
LPDA's elements
> > didn't go through the booms, leaving them hollow.  In
lieu of this, which
> > seems wrong to me too, how do you recommend routing xmsn
line to an LPDA?
> > "Hanging down from the feedpoint for 1/2WL" isn't going
to cut it for most
> > of us, that would be a 33' rotor loop...73 de Steve

Assuming a 50 ohm feed:

If you run the coax along the hot boom, just run it along
the same boom that is attached to the shield. Ground the
coax to the boom where it exits and put a good choke balun
at the EXIT point.

We can't possibly expect to tape a cable to a hot boom and
then just exit to the tower without really screwing up the
system balance.

Some TV band logs with hot booms sometimes route the cable
through the shield's boom, but they exit the cable at an end
where the booms are shorted and boom voltage is near zero.
The cable can't exit the boom at a voltage point and not use
some sort of shield decoupling or isolation...or it will
have problems.

73 Tom


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