In a message dated 9/6/02 5:00:39 PM Pacific Daylight Time,
> Does anyone out there have any experience with mounting a rotatable yagi
> to a tree? I've been told this is (or used to be) common in the Pacific
> Northwest. I'd be interested in hearing:
> 1) How to calculate a safe load
Calculate? How would you come up with a formula for the tree capacity?
I've installed 14-15 antennas in trees including HF yagis and 2L 40M
beams so I have a professional perspective but don't have any numbers to show
I usually top the tree when it's about 10 or so inches in diameter. How
strong is an 8x8 piece of wood? Pretty danged strong actually.
If you're talking about an HF beam, I wouldn't go any larger than about a
16' or so boom - the forces just get too big.
The other limiting factor is rotator capacity since I pipe mount the
rotator and then the antenna on top of it. I prefer the T2X since it has a
lot of mast mounting capacity and will twirl just about anything small to
moderate in size for a long time.
> 2) How to fabricate a suitable mount
I use a piece of galvanized pipe (1-1/2" ID = 1.9" OD) with a horizontal
piece welded to it (picture a cross). The horizontal ends are bolted to the
tree as is the vertical pipe. The rotator goes on top of the cross. I use
1/2" lag screws on the vertical pipe - 3-4 of them - and screw them right
into the tree. The antenna will blow away before the mount fails.
A BIG advantage for a tree installation is that it's UNREGULATED when it
comes to building departments! I charge a lot for them because they're dirty
and a lot of work.
TOWER TECH -
Professional tower (and tree) services for commercial and amateur