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[TowerTalk] Antennas down FOLLOWUP

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Subject: [TowerTalk] Antennas down FOLLOWUP
From: (WL7M)
Date: Tue, 12 Feb 2002 08:53:18 -0900
May I second the observation about wind blowing UP the tower if you live on 
a hillside.  I live at 1300 feet overlooking the ocean on the gulf of 
Alaska.  We frequently observe 125 mph wind gusts from fall and winter 
storms coming out of the gulf.  My Mosley Pro57B has withstood these storms 
- without damage - but it is amazing to see the elements being blown UP 
when the winds hit.  I use Philystran cables to provide extra bracing in 
these conditions, and it pays off.


> > Closer investigation this morning leads to the following: 20M boom broke in
> >  UPWARDS direction! Likewise, the 15M & 10M booms were bent UP. Broken
> >  elements appear to have been broken sideways, based on the fact that I
> >  installed the clamps toward the ground. I suspect something other than
> >  ordinary wind and ice loading.
> >
>     This is pretty common if you live on or near sloping terrain where the
>wind is driven UP the hill and hits antennas from underneath. That's when 120
>degree boom trussing is used. You've got a venturi effect going on where the
>windspeed is higher at the top of the hill than the apparent windspeed so
>they hardware really gets slammed in those conditions.
>Steve    K7LXC
>Tower Tech

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