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[TowerTalk] Re:

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Subject: [TowerTalk] Re:
From: (Bill Coleman AA4LR)
Date: Thu, 19 Aug 1999 14:30:28 -0400
On 8/18/99 17:22, Nat Davis at wrote:

>My question, at this point, is pretty simple. Where can I go to learn more
>about tower installation issues? 

The Rohn Catalog is the definitive resource.

>Is there a "how-to" book somewhere that
>talks about the stuff in layman's terms?

There was an article in QST a couple of years ago about a well-engineered 
bracketed tower installation.

>I borrowed my friend's Rohn manual
>but am really looking more for "text" than "tables!" I need to answer
>practical questions like: 

If you want absolute answers -- you'll need to hire a PE. 

>-- My house is wood frame construction. Will attaching the tower bracket to
>the studs in the exterior wall frame or to the eve overhang be "strong
>enough." (My area in the mountains of SW VA is a 70 MPH county.) 

Most likely not. When they built your house, I'm sure they didn't 
reinforce it with the tower in mind. You'll need to add reinforcing to 
distribute the tower-induced loads to the house frame. You'll also need 
to do better than just lag bolting the bracket to the studs. Carriage 
bolts, at the least, into very strong wood members.

>-- Is the 15'ish of tower above the bracket really "safe" without guys if I
>put a small tribander on it? How much antenna could I use (loading wise)
>since 30' height is not in the Rohn specs -- just take the 40' bracketed
>specs as being very conservative for 30 feet?? 

You'll note the the specs are pretty similar for all the bracketed Rohn 
installations if you look at the amount of tower above the top bracket. A 
small (5 sq feet) tribander will do nicely. 

You'll also note that all the Rohn bracketed installations call for TWO 
brackets. Although with only 15 feet between the base and your top 
bracket, it may not be worth it.

You might also look at the freestanding specs as well. Rohn 25 will 
almost hold a small antenna even without bracketing at 30 feet. Note that 
the base requirements are different.

>-- Or even more simple: is the performance of a beam at 30' worth the
>effort and $$ (compared to my dipole in a tree at a similar height)? 


I had an A3S at 35 feet before I moved. Sure, it isn't as good as a 
monobander at 100 feet, but it is a heck of a lot better than a crummy 
dipole! You might want to get enough mast to get to 35 feet. That's a 1/2 
wave on 20m.

Granted, any tribander will be more effective if you get it up higher 
than 30 feet. 

I have a theory about antenna installations. When you first go from 
single-element antennas to a tribander, you get a great leap in 
performance. No matter what you do from there, you never again get the 
same leap in performance. Not scientific, perhaps, but it seems to be 

Good luck.

Bill Coleman, AA4LR, PP-ASEL        Mail:
Quote: "Boot, you transistorized tormentor! Boot!"
            -- Archibald Asparagus, VeggieTales

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