[TowerTalk] Request for engineering help

[Dave Hachadorian]

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 at aol.com>
To: <towertalk at 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 at arrl.org



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