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Re: [TowerTalk] Rotator loops

To: "'Tower and HF antenna construction topics.'" <>
Subject: Re: [TowerTalk] Rotator loops
From: "Joe Subich, W4TV" <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Sat, 27 Feb 2010 10:07:24 -0500
List-post: <">>

> > I have also noticed that TV station remote trucks 
> > seem to use another solution for their rotating dishes - 
> > they wrap a few turns of coax loosely around the mast, so 
> > that a one-turn rotation only slightly loosens or tightens 
> > the wrap.  Seems like this would be a better, more 
> > durable practice for ham installations too.
> > 
> I agree.. they also do this to accommodate the big difference 
> in height as the mast extends, so the coax neatly stacks as it 
> comes down.

Having designed and built those trucks for a few years, there 
are two issues here: 

1) mast height is accommodated by the many turns of the "nycoil" 
   which stretches like a slinky as the mast is raised.  By the 
   way, the length of feedline is almost double the mast height. 

2) the antenna rotation is accommodated by a single loop.  The 
   "nycoil" is attached at the top of the mast for support.  The 
    mast does not rotate - only the antenna rotates. 


   ... Joe, W4TV 


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