All:
I'll agree with Bill's recommendations, and not go more that 20 to 25 feet
above the top house bracket. This is also based on my similar experience
with a bracketed 40' 25G on the side of my house while in Iowa. The tower
was bracketed at only one spot - just at the 15' level (to include a 1 cubic
yard concrete base). It did fine with a load like an A3S, but it did sway
quite a bit. If you're in a high wind area, stay away from freestanding 30'
of this stuff. Be conservative, and only go 20', or maybe 25' of unguyed
25G above the bracket.
Oh, also make sure you do a great job of installing a nice concrete base -
it'll need it. 73.
Steve, NL7W
nl7w@arrl.net
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Bill Coleman
Sent: Friday, April 09, 2004 4:22 AM
To: towertalk@contesting.com
Subject: RE: [TowerTalk] 55 foot Rohn 25G proposed tower, source for HD
housebracket?
On Apr 6, 2004, at 9:36 PM, Bob A. Booey wrote:
> Dear List,
>
> I have about 59 feet of Rohn 25G which I want to put up. I will set 4
> or more feet of the first section in concrete putting the top down at
> 55 feet. I have a tall, estate type home, the eave is 21 feet above
> ground level. I figure I would heavy bracket the tower at the eave,
> using the HBUTVRO bracket, or something equivalent that is more easily
> found (suggestions appreciated).
The HB25 brackets are plenty strong for Rohn 25.
I have a similar installation. 48.5 feet of Rohn 25 with a pointy top,
buried 4 feet in concrete. Brackets at 17 and 25.5 feet. Tower has 5
feet of mast out the top, putting the antenna at 49.5 feet (15m).
I would recommend TWO brackets. In the Rohn catalog, all of the bracket
examples use at least two brackets. In addition to prevent bending of
the tower below the top bracket, it also offers some redundancy should
the top bracket fail.
> That would put the top at 34 feet above the bracket.
That's an awful lot of tower above the bracket. I only have 19 feet of
tower above the bracket. Consider that you'll have to climb up there to
install and service the antenna and rotator. Rohn 25 is only rated for
about 30 in free-standing service, and is probably no fun to climb.
When I climb up to the rotator level, my tower wiggles around more than
I'm comfortable with -- and that's still 4 feet below the tower top!
> I have a tapered top section (25AG I believe), and will use no
> protruding mast above the top and an A4S (5.5 sq. ft wind load) on
> top. Any possibility of can getting away without guy wires on such an
> installation? How much would an installation such as this be pushing
> it?
I think this is pushing it. You might do better to forego a section and
settle on 45 feet. That's still 24 feet above the bracket, which is a
lot.
Some of it depends where you live. What's the wind rating of your
county? Mine is 75 MPH in Gwinnett County, GA. By my calculations, my
tower with A3S can withstand 75 MPH winds with a 40% operating margin.
> Anyone have a Rohn HBUTVRO (or equivalent) HD house bracket for sale?
> Maybe HBU? Suggestions on where to get either one? Build one with
> angle stock from scratch?
I had no luck finding any used brackets other than some HB25A's, which
were too short for my installation. I ended up having to buy two
HB25B's new.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
_______________________________________________
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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_______________________________________________
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.
_______________________________________________
TowerTalk mailing list
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http://lists.contesting.com/mailman/listinfo/towertalk
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