John wrote, " ...
> So, to first order at least, you can ignore the elements
> only compensate the boom if it is off center mounted to
> mast. Or better still, mount the boom in the center and
> some weight to one half to balance the boom. "
When I read John's outline of the force analysis it joggled
my memory. In April of 2002 I had read the three papers John
mentions. I discussed them with Lyle, K0LR, and we were
skeptical about the boom being the significant item. After a
bit of discussion and some pencil pushing we decided
"experiment trumps theory" (a wonderful phrase that brings
us back to Earth). We built a model of a beam with a single
through the boom element at one end and the pivot (mast)
going through the boom in the exact center (length and
width, not axial). It was a VERY windy day in Northern
Minnesota so we took the model out and tested it in the
wind. The result was counter intuitive - the horizontal
element at one end had no effect on which way the antenna
would point when it was allowed to rotate in the wind.
However, when we used a vertical element instead of a
horizontal element the model behaved like a normal weather
I took pictures of the experiment. I have them here in
Minnesota and will write a brief note about what is
happening and post them on my web site for interested folks
to examine. It may take one or two days to get the job done,
but I will advise the reflector when the information is in
Meanwhile, use John's summary (above) to guide you in
balancing with respect to torque (and static balance).
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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