There are hundreds of installations of 2L40's 10 to 14 ft
above tribanders on 2 inch O.D. 1/4 inch wall STEEL Masts
with yield strengths over 90,000 psi.
I've forgotten the yield strength of aluminum (~30,000 psi?)
but there is NO WAY a 2 inch o.d. 1/4 inch wall aluminum
mast will be strong enough to hold an HF Yagi more than
a few feet above the top of a tower.
Tom N4KG
p.s. Have you checked to be SURE your tower is rated
to handle that much wind load and the bending moment
created by a long mast above the top of the tower?
On Fri, 8 Nov 2002 22:18:02 -0500 "Ed Williams" <sunset392@cox.net>
writes:
> I will be installing a US Tower TX-489 and planning to install the
> following
> antennas
>
>
> 1. New KLM 10-30-7 LPA 1' above the tower (30' Boom & 8.25 sq ft)
> 2. Hy-gain Discoverer 7-2 40 Meter 2-element Beam ( 22.6' Boom &
> 6.0 sq ft)
> above that
> 3. Diamond 500HNA 144/440 vertical (17.8') on top
>
>
> I have a 6061-T6 2" x 24' aluminum mast and my question is what
> spacing is
> needed to insure no interaction between antennas and should the
> beams be
> rotated 90 degrees to each other or could I keep them in the same
> orientation.
>
> DE KN4KL ED
>
> _______________________________________________
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>
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