When a tree grows, it DOES NOT get longer along its trunk.
It grows from the TOP, adding new height.
Two branches on the same side of the tree one foot apart now will be one
foot apart next year, etc ... until the tree falls.
Keith Dutson wrote:
>I would not do what you are talking about. A living tree will tend to
>separate the tower sections over time.
>73, Keith NM5G
>[mailto:firstname.lastname@example.org] On Behalf Of W7CE
>Sent: Sunday, May 06, 2007 4:21 PM
>Subject: [TowerTalk] Horizontal tower movement at the top
>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
>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
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