[TowerTalk] Does Rohn Recommend This?

[Stan Griffiths]

>
>In talking with Chris, KD4DTS on a local UHF repeater, he related an 
>interesting tower installation:
>
>Apparently an enterprising ham decided that it was easier and cheaper to 
>dispense with all that fuss of pouring concrete for a base, guy anchors, 
>guys, guy tensioning, and heck with all those middle sections of tower 
>when there are perfectly good supports in his yard.
>
>He mounted his vertical antenna by lashing a top section of Rohn 25 in a 
>pine tree with wire ties.

There is hardly anything that Rohn recommends, but I would not let that stop
you from implementing good ideas.  Rohn is just very very careful about
everything they say to attempt to limit their liability.

This is certainly not the first, last, or only installation that uses
sections of Rohn tower lashed high in a tree.  VE7SBO has such an
installation.  There are some important precautions to use when doing this,
however.

For one thing, I wonder what kind of wire wraps are up to this job.  The
successful installations like this that I have heard of use large bolts
installed entirely through the center of the tree and fastened with nuts on
the opposite side to hold the tower in place.  Some use heavy steel straps
that are tightened around the tree.

A very important consideration is the tendency of the tree to rot at the top
where the tower section is installed.  Out west where fir trees are
sometimes used in this way, it is well known that the tree will rot above
the highest live branch.  What this generally means is you top the tree
leaving a couple of branches right at the cut.  You must install enough
tower so that the antennas will clear the branches and tree top by several
feet.  It might take more than one section to do this.

The reason you need so much clearance at the top is the fact that the top
branches will try to form a new tree top by growing straight up and through
your antennas.  This only takes a year or so and even with several feet of
clearance, you will need to periodically climb the tree and trim the
vertical branches to keep them out of your antennas.

This whole scene could work differently for other than Douglas Firs which
are the only trees I really know anything about.

Stan  w7ni@teleport.com


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