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## Rohn 25G with house bracket.

 To: Rohn 25G with house bracket. w7ni@teleport.com (Stan Griffiths) Thu, 15 Aug 1996 15:49:02 -0700 (PDT)
 ```Hi Gene, Some of what I say you probably won't like. There are reasons, though, why there are no simple answers to your questions as you will see. >I'm new to tower construction, in fact this will be >my first tower. I'm considering 30 or 40 feet of Rohn >25G bracketed to my house at about 15'. I'm trying >to figure out what size antenna I could have on >such a tower. This is a very common problem and I believe you have come to the very best place with your questions. It still does mean you will get the answers you want . . . >The Rohn manual gives antenna wind loading information >on 25G self-supporting towers with and without ice. >But for the bracketed information they don't have >any ice numbers. Is there a standard formula to >apply to non-ice numbers to get the ice-numbers? >I'm in the Cleveland, OH area and we get freezing rain. You have noticed already that Rohn does not give you all the info you want. They don't give you much guidance for reading between the lines, either. The reason is simply that they are liable for every bit of information they publish. Less info published equals less risk for Rohn. I have not heard of any standard formula to get from non-ice numbers to ice numbers. >They also show a bracket elevation column with >two values: UPPER (FT) and LOWER (FT). Does this >mean that a single bracket must be placed between >these values or that two separate brackets must >be used and placed at these values. In the case of >a 40' tower the upper value is 30' and the lower is >15'. Again, Rohn's info does not help much. Most bracketed towers use a single bracket fairly low on the house, usually at the roof line of a single story house. If the tower is any higher than about 30 feet, a set of guys would be a good idea. For the installation you are planning, you can go about 10 feet above the top bracket without guys. >I'm sure this will be trivial for the experienced >tower gurus so lay the info on me. Well, such towers have been installed hundreds of times but much of the design is done by "gut feel" or years of observing other people's failures and avoiding their mistakes. What you need is the book that is about to be published by K7LXC. The very best advice I can offer you is to consult a structural engineer to look over your plan. This will cost you some money but it may also save your neck or at least your wallet. If you want to look at an article on how to do a first class job on a house bracketed tower, look at August 1996 QST, page 35. There you will see an excellent approach to making sure the tower will stay where it is supposed to, thanks to K1KP and N1CQ. I suspect you will get several comments from others that will help you. Stan w7ni@teleport.com ```
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