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EMT Mast For Cushcraft R5

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Subject: EMT Mast For Cushcraft R5
From: (Roger L. Elowitz)
Date: Sat, 5 Oct 1996 05:21:54 +0000
Hi Guys,

I have a Cushcraft R5 that I've mounted on an 1-3/4" EMT tubing. This mast
sits in a 9-ft South River tripod tower on my two-story home that has a
peaked roof. The mast is only about 2-1/2 feet inside the top of the tower.
That means that about 7-1/2 feet stick above the tower- supporting the R5. 

The above installation has been in place for about one full year WITH
EMT tubing cost all of $13 at an electrical supply store. The moment a
strong wind puts the slightest bend in it- I'll scrap it rather than risk
damaging the R5. However, after all the recent hurricanes here on the east
coast I rather doubt that I'll be replacing this mast any time soon.

But please don't get me wrong! I wouldn't dream of putting any serious
weight on this tube like a Ham-IV and TA-33 (3-el. Tri-band beam). Then
again, it's not just the weight that's operating here. It's the weight
acting through a sizeable distance accelerated by serious gusts. That can
make a powerful LEVER which will do all kinds of nasty things to EMT and
consequently turn the beam and mast into a novel pretzle design. This would
definitely be a case of "PENNY WISE AND DOLLAR FOOLISH!" 

The aluminum on the beam is a hell of a lot more expensive to replace than
the mast. I wouldn't chance it. But for an R5 or even an R7 or R7000- the
heavy walled stuff the guys have been recommending here on the reflector is
GROSS OVERKILL (for mounting a vertical antenna) in my humble estimation and
experience. Guess it's time to get some input from a mechanical engineer who
has some hard figures in front of him! Thanks for the chance to stick my two
cents in.

73's all de Roger, K2JAS


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