[TowerTalk] Rohn tower installation specifications

[dotravel at aol.com]

Dave, unless you are attaching the tower to an unoccupied building one suggestion would be to use some from of sound insulation between the tower and the house brackets or between the brackets and the structure. 

I could not believe how much noise was transmitted into our house from my Tri-Ex 33 crank-up (converted to 41')   with TailTwister II, a tribander and 6m Yagi.

Every click, clunk and clack from the rotor, loud humming noises from the elements when the wind blows certain directions and even the noise from the tower sections moving slightly (in your case the mast rocking in a pointy top?) are clearly heard. I swear that I can even hear birds landing on the antennas.  I was prepared for a little noise but this was a LOT of noise.

Just prior to going crazy(er)  I added some 1/4" thick by 2" wide strips of neoprene between the tower legs and the house bracket and that got rid of about 70% of the noise. Your bracket may not be the same design as mine --- I just have a big triangular piece of flat bar that wrapped around all of the legs (one side was removeable) to isolate from direct contact so the task was easy.

Regards, John NA6L 


-----Original Message-----
From: Dave Cook <wa0ttn at netdave.com>
To: towertalk <towertalk at contesting.com>
Sent: Sun, Apr 1, 2012 12:24 pm
Subject: [TowerTalk] Rohn tower installation specifications


Hi guys, I'm in the process of relocating my 35' freestanding Rohn 25G tower
after 8.5 years on the air. I figured this time I'll bracket it to the
house, which is what I should have done in the first place. But I've run
across a few problems with the Rohn specifications:

 

1.       The tower will be bracketed to the house mid-way up and also near
the top of the tower with an eave bracket. The specifications for the
brackets "must support a minimum horizontal force of 815 pounds". I can't
find any calculations for how they came up with this number. And it seems
very excessive for a modest 35 foot tower bracketed in two places.

2.       The specs also state that the base must be a "fixed base", rather
than a pinned base. Again, in this case I don't understand why a pinned base
wouldn't be sufficient for a well-bracketed tower. Why would the base
experience any lateral loading?

3.       The specs also state that the base has to be the same 2x2x4 feet of
concrete that was spec'ed for self-supporting and guyed towers. In this case
I can understand somewhat having a solid chunk of concrete for the thing to
rest on, but the entire weight of the tower and antenna will be, by my
calculations just a little over 200 lbs. It doesn't seem to me that it needs
a 2000 lb chunk of concrete to keep that from sinking into the soil.

 

So in short, I'm just wondering if Rohn is simply CYA'ing themselves, or are
these specs really to be taken literally?

 

Thanks and 73,

-- Dave WA0TTN

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