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Yagis, trolleys and trams - not shocking!

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Subject: Yagis, trolleys and trams - not shocking!
From: (
Date: Thu, 2 Jan 1997 12:02:40 -0500
In a message dated 97-01-01 09:01:31 EST, you write:

> The beam slid up the ropes smooth as silk, and Clint didn't even have to
>touch it till it toped the tower and started to level off. He reached out
>and grabed the boom and "ZAP" he was hit with a static discharge that could
>be heard on the ground. It made his hand and fingers numb for a few
>seconds, and surprised the heck out of all of us.
>LESSON 1: When sliding an antenna up a long parallel run of nylon rope,
>discharge it with a grounding wire before touching it.
>LESSON 2: When working at 92' never assume anything. Check and double check
>everything, the thing you least expect will jump up and bite you.

     Boy, that's a new one on me.  Just shows you that you can't always
anticipate everything.  

    The particular method that you describe is what I'll refer to as the
"trolley" method.  That is, the two ropes form the trolley 'tracks' and the
load (antenna) is slid up the ropes on top of the 'tracks'.  This technique
has several drawbacks, one of which you described.  As I see it, the problems
1) equalizing the tension on the trolley track ropes,
2) balancing the antenna on the track ropes,
3) the fact that the tracks get narrower at the top just at the time when you
need the most load stability,
4) the friction of the antenna on the ropes (your 10 meter antennas being on
the easy end of the scale weight-wise), 
5) and the aforementioned static surprise!

    Imagine the problem of using this method to install a long boom and/or
heavy antenna.  IMO Lesson 3 would be to avoid this method.

    The preferred method endorsed by most tower jocks on TowerTalk is to use
a "tram line".  A tram uses a single wire with the load slung UNDER it.  In
one fell swoop, you've eliminated most of the limitations and problems of the
trolley method.  Since a picture is worth a thousand words, if you're
interested in an illustrated discussion of this technique, it is available in
a (guess what?) reprint of a paper on yagi installation.  An SASE to TOWER
TECH, Box 572, Woodinville, WA, 98072, will get you a free copy.

73,  Steve  K7LXC

   TOWER TECH -- professional tower supplies and services for amateurs

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