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Re: [TowerTalk] Cushcraft A743/A744 DE Support Rope

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Cushcraft A743/A744 DE Support Rope
From: Bill Coleman <aa4lr@arrl.net>
Date: Sat, 28 Apr 2007 22:32:05 -0400
List-post: <mailto:towertalk@contesting.com>
On Apr 25, 2007, at 10:27 PM, Bill Coleman wrote:
>
> I put up my A743 40m add-on kit in October 2005. I was disappointed
> to come home and find that the DE support rope has broken, apparently
> right in the middle -- where the rope passes through the phenolic
> standoff.

Finally completed enough tower climbs to get a diagnosis on this. The  
line was frayed in two at the center.

Part of the problem was that I didn't quite install it correctly. The  
instructions call for the rope to pass to the opposite side of the  
phenolic tube before passing through it. This results in the support  
ropes crossing over each other.

When I installed the kit, the beam was already mounted on the tower.  
In the struggle to get the support post in place, I forgot about the  
cross-over.

Apparently, the cross-over limits the movement of the rope through  
the phenolic support. Without this crossover, the line tends to rub  
against the phenolic, and it eventually fails.

> So far, the DE has held together OK, the DE just droops a lot --
> about a foot or more on the ends below the reflector and director.
> Not sure how long the antenna will hold together with this much
> strain on the DE, so I plan to replace it soon.

I replaced the support rope with a sheathed nylon rope of 3/16".  
Getting it in place took some doing. I think the original rope had a  
lot more stretch. I measured out 23 feet, and used about six inches  
on each end to tie a bowline. The rope was almost straight across the  
droopy element.

With the crossover, I had to remove the support post and push it up  
vertically until I could put in the U-bolt. This was very difficult  
to do at the top of the tower, especially with the winds gusting to  
20 mph.

The support post was set to the minimum height, but the element is  
almost in perfect position. I'll give it a day to stretch and adjust  
it tomorrow. (Partly because I'm so exhausted from the tower work...)

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901

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