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[TowerTalk] LMR-400 with Rotators - A Dilemma

To: <towertalk@contesting.com>
Subject: [TowerTalk] LMR-400 with Rotators - A Dilemma
From: "Dr M J DiGirolamo" <DrD@2020.com>
Reply-to: DrD@2020.com
Date: Thu, 30 Nov 2006 04:14:32 -0500
List-post: <mailto:towertalk@contesting.com>
Dear Colleagues,

 I'm in the final stages of arranging antennas on top of this tower (project)
that you've been reading about since last May.   I have run against a dilemma
that I'm not sure is real or imaginary.

Situation:

   I have a 72' crankup tower with side-arm "cable loop guides" on each of the
tops of the 4 tower sections.  At the top is a 20 foot mast supporting several
antennas.   The lowest antenna is a HyGain TH-11DX to be mounted about 1 foot
above the thrust bearing.  Above are 4 antennas, including 432 and 1296MHz yagis
at the very top.

   My plan is to feed LMR-400 cable directly to all antennas 2M and below and
use LDF4-50A hardline to the top of the tower, joining it to a more flexible
LMR-400 jumper feeding the 432 and 1296 antennas, some 16 - 20 feet above.  This
makes a total of 5 feeds of LMR-400.  This combination was selected keep the
losses to a minimum.  The difficulty of working with hardline & LMR-400 with a
crankup tower has been carefully considered.  The conclusion is that lowering
the tower is a two man project.

Problems, questions, dilemma:

 1.  Is LMR-400 flexible enough to be used with a rotator?  My rotator has a 450
degree travel.

 2.  How do you physically arrange the LMR-400 to allow enough slack for the 450
degree rotation, once out of the top loop?  Remember, the HyGain TH-11DX HF beam
antenna is just about 1 foot above this upper loop.

 3.  How do you terminate/support the LDF4-50A to make the transition to LMR-400
cable?

 4.  Anyone have photos that might help with this or perhaps a webpage URL
showing details?

All thoughts and suggestions are all welcomed.

73,

Mike DiGirolamo, W4XN
W4XN@arrl.net
Charlottesville, VA

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