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[TowerTalk] Antenna Masts, Again, and Again

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Subject: [TowerTalk] Antenna Masts, Again, and Again
From: (
Date: Thu, 29 May 1997 15:17:20 -0400 (EDT)
In a message dated 97-05-29 14:09:24 EDT, (Lee Buller)

> OK, I know this has been talked about ad nauseum on this reflector.  But, I
>  have to get my act together so I can get the tower crew in here in July.

    Okay, we'll all get naseous again together.
>  I am putting up a TH6 on 60 foot of Rohn 25G.  Pointy-Top which will
>  accomodate a 2" mast.  I have some brass shims too for the rotor already 
> made.

     What are the shims for? If there's no thrust bearing, there's not much
of a reason to have everything perfectly in line. With a real 2 inch OD mast,
it should be easy to center it with any popular rotator out there.
>  I want to also put up a 40 meter dipole like a KLM or Force 12 above the
>  TH6.  I am also want to put up a small two meter beam for SSB/CW tropo
>  from EM18.  I was going to put up a 6 meter beam, but I can do that on the
>  short tower of 40 feet.

     Harvey County is an 80 MPH wind zone. According to the MARC Program,
with your 40M dipole at 10 feet and the TH6DX six inches above the top of the
tower, you'll have 9110 inch pounds of  bending moment on the mast.
Recommended mast material should have a yield strength of 30,000 psi and
0.120 inch wall. Since 6061-T6 has a typical yield strength of 35,000 psi,
you should be in good shape. 

     BTW, the MARC (Mast, Antenna and Rotator Calculator) program is $9.95
>  Do I use drawn or extruded aluminmum?  

    You might not be able to find or afford extruded aluminum.  

73,  Steve  K7LXC

    TOWER TECH -- professional tower supplies for amateurs

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