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[TowerTalk] Proposed Rohn 25g installation

Subject: [TowerTalk] Proposed Rohn 25g installation
Date: Sat, 30 Dec 2006 00:16:11 EST
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Hi All and Happy Holidays,
I'm in the process of trying to put together an installation of Rohn  25g 
somewhere between 39 to 49 feet high as the first of several towers for  my 
However, I have been unable to find enough sufficient  information in the 
Rohn published specs to put together what  I believe is a suitable engineering 
package to request a building  permit.
My proposed installation is as follows: Concrete base 3.5'x3.5'x3.5'  
reinforced with a rebar cage and utilizing a Rohn SBH25G  (short tilt tower 
section) encased in the concrete base, tower  bracketed to the house at the 21 
foot level, bracket (Rohn  HB25CG) bolted to the house with 4 threaded rods 
extending 6 -  8 feet into the attic, double bolted through multiple arrays of 
2  x 
4 wood joist stud supports, and extending the tower  another 18 to 28 feet 
above the bracket without any guys.  The  antennas (VHF/UHF yagis) will be 
mounted to a Glen Martin Hazer H-4  with a total windload of around 10 square 
the hazer only  extended during times of station operation.  
What are your thoughts concerning my proposed installation and what is  the 
best way to convert the data provided by Rohn?  The specs provided by  Rohn for 
bracketed towers don't cover anything bracketed below 30  feet and extending 
to 39 feet, or bracketed with one bracket.  I can use two brackets, but the 
lower bracket would not provide much  support, because I can only attach it to 
the 4 inch wall studs or use anchors  behind 3/4 inch plywood without 
performing modification to  the wall framing of the house.  I know using 
bracket  support devalues the tower load rating, but by how much?  The tower  
would probably never need to be climbed above 30 feet as the  hazer can be 
lowered down to 21 feet which allows the antenna system to  be worked on at or 
above the roof top level, and if  necessary the tower could also be tilted 
I previously performed a similar installation at a prior location  with the 
bracket at 18 feet, tower to 39 feet, with a windload of about  16-18 square 
(stacked Cushcraft X-7 with X740, under a 13B2 and a  A50-5S, H-4 Hazer, single 
12 foot Hy-gain mast, Yaesu SDX 800  rotor).  The installation was very secure 
without any  problems even during an ice storm with 3/4 inch ice loading, but 
 I installed it without obtaining any permits, therefore I don't  have any 
engineering calculations from the last  time.  
Thanks for any input.
Jim, AB4D    

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