Bob,
>From a "strength" perspective alone, if you are not in a high wind location,
you can probably get away with the installation you are proposing . . .
BUT . . .
There are some issues to consider. I often use 40 feet of Rohn 25G
house-bracketed at 21 feet as a temporary tower.
1. The bracket MUST be done correctly. If it's the only thing you are
depending on, it better be good. That means long bolts going through the wall
studs to a reinforcing stud or better, running across a couple of stud bays.
2. Climbing 30 feet above the last house bracket or guy level is not much fun
on 25G. You will love the swaying. It can be done, but for me it has a high
pucker factor. That's why my temp tower only goes to 40 feet.
3. You may encounter the CLANGING problem. Wires, cables and any other
hardware that is not securely attached may vibrate or hit the tower in the
wind. This will resonate inside the house. Most such noises can be eliminated
or greatly reduced by taking extra effort to fully secure everything to the
tower. You can get some clanging that is impossible to eliminate from a rotor
that has too much play in it.
4. You may also encounter the CREAKING problem. This one is much more
difficult to resolve. Again, this problem occurs when there is wind. It doesn't
take much to do it. As the antenna blows in the wind, there is going to be a
certain amount of twisting and swaying of the tower. These forces may cause
tower joints to move a bit - squeaking - and additional forces will be applied
to the housebracket, which efficiently conducts the sounds to the house. Can be
very annoying. Another annoying kind of sound that can be conducted to the
house is the vibration of the yagi elements in the wind.
My 25G house-bracketed tower lives on the corner of the house that is shared
with my daughter's bedroom. She hates the sounds the tower makes in the wind. I
only use the tower during some contest weekends. I leave the base and the
bottom two sections in place year round - up to and including the house
bracket. I add the extra sections, the rotor and the antenna just before the
contest and take them down in the days following the contest.
73,
Jim K1IR
To: <towertalk@contesting.com>
Subject: [TowerTalk] 55 foot Rohn 25G proposed tower, source for HD
housebracket?
From: "Bob A. Booey" <rentwist@comcast.net>
Date: Tue, 6 Apr 2004 21:36:18 -0400
List-post: <mailto:towertalk@contesting.com>
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). That
would put the top at 34 feet above the bracket. 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?
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?
73,
Bob, WA2T
_______________________________________________
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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