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Re: [TowerTalk] Horizontal tower movement at the top

To: "W7CE" <>, <>
Subject: Re: [TowerTalk] Horizontal tower movement at the top
From: "Roger (K8RI)" <>
Date: Tue, 8 May 2007 00:56:16 -0400
List-post: <>

> No joke!  It was a serious question and I was hoping for some serious 
> answers.  Specifically, how much movement is normal for the top of a 100' 
> Rohn 25G tower.

I don't know what would be normal, but mine is 97' with on top. The 144 and 440 
antennas are 30 feet above the top of the tower. I've been up  there in the 
same location you see in the photo, when the winds were gusting close to 30 
MPH.  I couldn't feel the tower move. OTOH being "up there" with 30 MPH 
gusts is...interesting. Sighting through a scope I can not see it move, but 
I've never checked it for movement with a transit.I'd guess it moves less 
than an inch even with winds considerably higher than that.

Roger (K8RI)

> 73,
> Clay  W7CE
>  ----- Original Message ----- 
>  From:
>  To: ;
>  Sent: Monday, May 07, 2007 2:12 PM
>  Subject: Re: [TowerTalk] Horizontal tower movement at the top
>  >You have got to be kidding! April Fool's Day was over a month ago!!
>  Bruce
>  From: "W7CE" <>
>  >To: <>
>  >Subject: [TowerTalk] Horizontal tower movement at the top
>  >Date: Sun, 6 May 2007 14:20:36 -0700
>  >
>  >Does anyone know how much horizontal movement is considered acceptable 
> at
>  >the top of 100' tall Rohn 25G, 45G and 65G towers?  I don't see any 
> mention
>  >of it in the Rohn catalog.  I know that the tops move, I just don't know
>  >how
>  >much is considered normal.
>  >
>  >I'm considering a rather unusual tower installation at my QTH.  Because 
> of
>  >large trees that occasionally lose branches during wind storms and 
> property
>  >line constraints, a guyed tower isn't practical.  For years I've had my 
> 3
>  >element yagi on top of a 95' Doug Fir tree and it has worked well there. 
> I
>  >watched it during our record setting wind storms last winter and the top 
> of
>  >the tree was only moving about 6-7" (less than the diameter of my Ham IV
>  >rotator).  This is a big tree with a 42" diameter base and an 8" 
> diameter
>  >stump at the 95' level where the antenna is mounted.  The problem with 
> this
>  >installation is getting up to the antenna to do maintenance, plus I'm
>  >planning on replacing it with a new SteppIR as soon as I figure out how 
> I'm
>  >going to mount it.  What I'm thinking about doing is installing 100' of
>  >tower as close to the tree as practical (less than 3') and attaching it 
> to
>  >the sides of the tree with angle iron at 20' intervals.  With this
>  >approach,
>  >I don't think the tower could ever come down unless the tree itself did
>  >also, which is unlikely based on our soil type and the excellent health 
> of
>  >the tree.  I would then mount the antenna on the top of the tower.  This
>  >would give me a much easier way to climb up to the top.  I can use 25G, 
> 45G
>  >or 65G for the installation, whichever would be best.  25G would be the
>  >easiest to install because of it's weight and I suspect that it is the 
> best
>  >choice.
>  >
>  >I'm looking for opinions on the viability of this solution.  Will the
>  >movement of the tree in the wind stress the tower too much or will it 
> about
>  >the same amount of movement that a guyed tower would normally experience 
> in
>  >a big wind?  Opinions?  Suggestions?  Am I thinking a little too far
>  >outside
>  >the box?
>  >
>  >73,
>  >Clay  W7CE
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