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
ABSOLUTELY NO GUYING AND WITH ABSOLUTELY NO BENDING OF THE TUBING. Now the
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
73's all de Roger, K2JAS
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