[TowerTalk] 20 foot tower installation help

[Bill Coleman]

On Aug 16, 2007, at 12:18 AM, KC8DDQ at aol.com wrote:

> I'm getting ready to put up a 20 foot Rohn 25 tower. I was
> planning on pouring a 20"x20"x42" concrete base. I will be  
> anchoring a Rohn base
> plate to the concrete with four 36 inch 3/4" galvanized all thread  
> anchors
> set  in the concrete. The tower will be free standing.

This is not what the manufacturer recommends. See here:
http://www.radiancorp.com/ROHNNET/rohnnet2001/catalog/pdfs/25G/25G-1.pdf

Look at note #2 -- Fixed bases must be used, "Pinned" bases cannot be  
used.

Here's the diagram of the fixed base:
http://www.radiancorp.com/ROHNNET/rohnnet2001/catalog/pdfs/25G/25G-2.pdf

Look carefully at the dimensions -- note that the recommended base is  
FOUR FEET square, and four feet deep. Your 20"x20"x42" base is way  
too small.

Even the standard base is 24"x24"x48":
http://www.radiancorp.com/ROHNNET/rohnnet2001/catalog/pdfs/25G/25G-4.pdf

Your proposed base is too small for any conceivable use of Rohn 25G.

--

There was a recent mini-article in QST where a guy discussed the use  
of a 18" Sonotube to pour his tower foundation. The picture clearly  
shows Rohn tower sections. Unfortunately an 18" diameter base is too  
small. You'd have to use a 24" Sonotube for Rohn 25G.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901