After being a ham for many years, a buddy of mine is ready to install his first
HF beam. He bought a Cushcraft MA5B mini-beam, a rotor and a used Rohn 50-foot
push-up pole.
The beam weighs 27 pounds and has 3.2 sq. ft. wind load. And last night he told
me he wants to install his 6-element 2-meter quad above the MA5B. The quad is
made of plastic spreaders and a wooden boom. Not much additional weight or wind
load but still enough to consider. And there's the rotor too.
So, we got into a discussion about how high he could safely extend the push-up
pole. He tells me the pole has pre-dilled holes and he thinks it allows 2 foot
of overlap between mast sections. I don't think 2 feet of mast overlap is
sufficient for what he wants to do. (My US Tower allows 4 feet of overlap
between sections.) He's not erecting a small, lightweight TV antenna which is
what I figure the mast was intended for.
The mast is house bracketed 15 feet up. He was under the impression he would be
able to safely extend the pole all the way up -- with guys, of course --
whereas I think he ought to plan on more overlap between telescoping sections
and therefore less height -- say something like 36-40 feet.
So, how high can he safely extend the pole and will he need two sets of guys
considering the house bracket at 15 feet?
73, N4KZ
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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