The issue is not the weight of the antenna, but the surface
area it presents to the wind. Rohn's data on bracketed
towers is pretty sparse. They show one example with a
bracket at 66' on a 90' tower and rate the allowed load at
6.8 sq ft at 70 mph.
Rohn's 4-way-guyed foldover #25, which has 26' above the
guys, is rated for 6.2 sq ft at 70 mph.
Norm's Rotor Service has a nifty lookup tool for the square
feet of various antennas:
http://www.rotorservice.com/antenna%20wind%20load.htm
The TH6 shows as 8 sq. ft, which I think is too much for
your tower installation.
I would pick something in the 5 sq ft range, preferably not
a Mosley. If you lowered the tower to 16' above the bracket,
you could keep the TH-6, which might be your best bet in
terms of overall signal strength and safety.
Dave Hachadorian, K6LL
Yuma, AZ
----- Original Message -----
From: <K8qoe@aol.com>
To: <towertalk@contesting.com>
Sent: Tuesday, June 02, 2009 1:36 AM
Subject: [TowerTalk] Request for engineering help
Greetings
If there is a tower installation specialist
(and/or engineer) in
the house, I'd appreciate a call. I have a Rohn 25 tower up
50 feet, not
guyed but a house bracket at 23 feet. Three feet of the
tower are buried in a
cubic yard of concrete down two feet from ground level.
I have a Telex TH 6 (weight 75 lbs.) and three other
antennas I
will discard next week. Problem. I want to keep my TH-6 but
my climber says
he is troubled by so much weight on a non-guyed tower which
is 30 years old.
Is worried about tower fatigue. He wants me to replace the
Telex with a
smaller, less weight, Mosley.
Sooooooooooooooo is my tower guy's worries about
weight legit or
can I keep my TH-6 when I do my tower work in two weeks?
Call please.
Joe
Joseph Phillips, K8QOE
Ohio Section Manager
2800 Jupiter Drive
Fairfield, OH 45014
(513) 874-0006
jphillips@arrl.org
**************
An Excellent Credit Score is 750. See Yours in Just 2 Easy
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