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Old October 9th 14, 08:04 PM posted to rec.radio.amateur.antenna
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Default A cheap wind-up and tilt-over tower?

In article ,
Ralph Mowery wrote:

If the ladder is very long and a beam is mounted to the top of it, when the
wind blows it will tend to twist the ladder. The narrow sections of that H
form are not designed for much twisting. A 3 element beam can cause a lot
of twist in a 40 or more MPH wind .


The twisting torque could also stress or break the junctions between
the ladder uprights and the steps. Once that starts to happen, the
ladder's structural integrity is going to go to hell... it could twist
more easily, or want to "rack".

For small light-weight beams with a very modest wind surface area, the
old-style telescoping "push-up" antenna masts aren't bad - they do
need to be guyed. You can get 'em with two, three, four, or (I think)
even more sections (about 10' each).

A friend of mine swears by the use of threaded electrical
conduit... not the light-weight "EMT" stuff, but the heavier
pre-threaded type (about three times the weight and three times the
cost of same-diameter EMT).

Rohn tower certainly has a lot going for it... and if I could figure
out a place to mount one at my house that wouldn't put the antenna too
close to the power lines or reaching over the property line into my
neighbors' airspace, my friend would gladly hand me two or three
sections of Rohn 25 for the asking. Sure would be nice... and it's a
lot more robust than any aluminum ladder would be.





 
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