[TowerTalk] Footing size for Rohn 25 & 45

[Stan Griffiths]

>Does anyone know the required footing sizes for Rohn 25 and 45?  Also, 
>how high can you go with Rohn 45 without guys and just a house bracket at 
>8-10 feet?  If you have this information, I would greatly appreciated 
>it.  I would like to go up to 45 feet, if it is within specs.  
>
>Thanks.
>
>herbr@netcom.com

There is some info on this in the famous "Rohn book" that you can get from
K7LXC.

You will find that the answers are not clear and much more information than
you provided is required to make even a good guess.  For instance, what are
the highest winds you EVER expect to encounter at your location?  Also
important is the windloading specifications of the antennas you intend to
install on the tower.

There is also a Rohn brochure available that gives information about
bracketed and freestanding towers of the 25 and 45 size.  One problem with
this brochure is that Rohn does not even recognize a configuration using
only one house bracket.   All of their examples require two house brackets
and the shortest example is a 40 foot 25G that is bracketed at 15 AND 30
feet.  I know very few installations that can have a bracket at 30 feet.

If you decide that Rohn is too conservative (many do) and you want to do
something different than what thier limited suggestions offer, you will need
to do some engineering on your own, or hire a consultant to do it for you.
Not cheap!  Of course, you can also solicite advice on the "Tower Reflector"
and you will get dozens of opinions for free.  You will have to know which
ones to pay attention to and which ones to toss out which requires a fair
amount of expertise in itself.

There are several guys on this reflector who have been installing and using
towers for decades and they really know what they are doing through YEARS of
experience and probably a few failures.  Certainly, if they have not had
failures of their own, they have studied the failures of others in detail to
know what to avoid.  This whole tower design and installation business is
fraught with subtle dangers and serious design problems that are NOT
intuitively obvious.  You can't be too careful and my advice (which you can
toss out, if you want to) is to find a ham who has had several towers up for
at least a couple of decades and get him to coach you on this.

Good luck and be careful.

Stan  w7ni@teleport.com


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