Tim,
Use either an eye lag that goes several inches into the trunk or and eye
bolt that goes through the trunk and is washered on the other side. The
tree will grow, so make sure you have a few inches sticking out of the
trunk.
When building tree houses and doing tree climbing, high strength forged
(closed eye) hot dipped galvanized bolts are used. These are an option,
however I simply use open eye stainless as the strength of the higher
grade material isn't needed.
Attach a pulley to the eye with Dacron rope. Run your antenna support
line through the pulley and down to the ground. At the ground level,
pound in a steel T post -- the kind used to support metal fencing.
Double over a bungee cord and attach it between the T post and the
antenna support line. This will keep the antenna under tension. The
bungee cord will eventually fail so you need to tie the antenna support
rope to the T post as well. Allow 3'-5' or so in the antenna support
rope so when the bungee cord breaks, the antenna will fall a bit. This
is essentially a fuse. It keeps the antenna support rope tight but if
it gets to the point where the bungee cord breaks, slack is let out.
It's enough to allow the tree to sway freely and independent of the
antenna, but not enough that the end of the antenna wire falls to the
ground.
My pulleys are installed at fairly significant heights that I don't want
to climb again anytime soon. Bolting provides for a fairly permanent
installation.
Please don't wrap around a tree. It doesn't even take six months for
the tree to begin growing around the wrap. It's OK for a Field Day
setup, but no longer. There is the very real possibility that wrapping
will damage the vascular tissue just below the bark and injure the tree
significantly.
I'm not a long time wire antenna user, but I've researched the subject
quite a bit and am satisfied with my current installations.
Use good pulleys. Check out a sailing shop and pick up some small
Harken pulleys. They'll run $12 - $25 each (depending on size) but they
are made of stainless and plastic.
-Jeff
W7WWA
On Fri, 2008-08-29 at 14:58 -0500, Tim N9PUZ wrote:
> I'm going to hang the center of a dipole from my tower. The question
> is really about attaching the two ends of the support ropes running
> through a pulley and down to provide for some movement in the wind.
>
> Our yard has several trees which are good candidates. For a more
> permanent installation like this (vs a Field Day type setup) what is a
> good technique for attaching to the tree trunk? Screw eye into the
> trunk itself? Some sort of belt type affair around the trunk?
>
> Thanks,
>
> Tim, N9PUZ
> _______________________________________________
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