According to a chart in "Physical Design of Yagi Antennas" (Leeson, ARRL)
yeild strenths(lbin*sq) vary from 15klbs for 6063-T5 drawn alum. tube to
70klbs for 7075-T6 extruded alum. tube. compared to 4130 crommoly at 75klbs
and Structrual Steel A36 at 50klbs.
Use of alum. for masts has it place. I used some 7075 2.250 dia to support
a 4 ele KLM (40)and and TA36 the boom on the klm broke in high winds and the
mast did not bend.
If you a planning to put up antennas and have questions I highly recommend
the above book
Tom AC5TM
----- Original Message -----
From: <n4kg@juno.com>
To: <TOWERTALK@contesting.com>; <sunset392@cox.net>
Sent: Friday, November 08, 2002 11:17 PM
Subject: Re: [Towertalk] Antenna Spacing on New Tower
> 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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>
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