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RE: [BULK] - [TowerTalk] Using Belden 9913 on a crankup tower?

To: "''" <>,
Subject: RE: [BULK] - [TowerTalk] Using Belden 9913 on a crankup tower?
From: Steve Katz <>
Date: Wed, 5 May 2004 12:47:33 -0700
List-post: <>

> Could somebody tell me if Belden 9913(not 9913 flex)is usable on a crankup
> tower. What I am interested in, is if it is bendable enough when the tower
> is cranked down or will it bow out too much? Should I go to a more
> flexable cable for the run up the tower, or is it workable? This is for a
> 51 ft. crankup. Thanks for your help.
> ::I've been using 9913 since its introduction in about 1982 or so, and
> after trying it on several extendable towers, I'd opt for something else.
> The problem isn't the cable "bowing out," as you say, as much as it is the
> strain on the cable where it is supported against the tower or standoff
> arms.  When the tower's fully extended and the cable is nearly straight
> (vertical), no problem.  When the tower retracts and the cable begins
> forming loops, the upper support point for each loop stresses the cable a
> lot and causes premature failure at those locations.  On a very short
> extendable tower, this may not be a problem, but using a conventional
> 50-to-70 foot or higher tower with 20' sections, the weight of the
> cable(s) hanging from small support points causes the stress and begins
> dislocating the center conductor.  When the center conductor rests against
> the inside wall of the very thin poly tube inside the cable, the
> dielectric strength there isn't great and the cable can break down (flash
> over) at any one of these points.  There's an impedance bump at each of
> these points, too, which may not cause any problems in the HF-VHF region
> because the length of each discontinuity is small; but at UHF or higher,
> that could be a problem, too.  -WB2WIK/6

See:  for "Self Supporting Towers", "Wireless Weather 
Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions 
and ask for Sherman, W2FLA.

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