In a message dated 8/19/2008 7:32:21 P.M. Pacific Daylight Time,
towertalk-request@contesting.com writes:
> I have a PST-61D with a large tribander and a shorty 40 above it on a 2
inch chrome-moly mast. Not long after I put it up this spring we
experienced some of the strongest clear weather winds I've ever seen
here in Arizona, with 90 mph gusts on several occasions and one that
topped out my wind gauge at over 100 mph. These are typically
mini-twisters caused by the wind swirling around the ridgelines on the
side of the mountain range I live on. They roar down the hillside like
a freight train and I've watched them rip branches off trees 200 feet
away from me while I stood in completely calm air. When one of these
little monsters hits the tower dead on, it is entirely possible for the
wind to be pushing on one end of the antenna boom while simultaneously
pulling on the other end. The torque on the system would be incredible
in such situations.
One way to help minimize wind induced mast torque when you've got more
than one antenna on the mast is to off-set them. That is, install one antenna
on one side of the mast and the next one on the other side. That way some of
the torque will be canceled out by opposite forces on the antennas. This was
illustrated by Dick Weber, K5IU, a PE when I think it was published in QEX
some years ago.
Cheers,
Steve K7LXC
TOWER TECH
**************It's only a deal if it's where you want to go. Find your travel
deal here.
(http://information.travel.aol.com/deals?ncid=aoltrv00050000000047)
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