On the other hand, if you guy the pole up ten feet or so, then the
lateral forces at the bottom are really trivial, and almost anything
from a ground rod to a T-post will do fine.
Enough time has passed so that I think I can tell a story - back in the
mid-70's, the State Department radio club had a shack in a room at the
top of an 8-story State Department Annex building. We weren't allowed
to pierce the roof, so we got 20 feet of Rohn 25 and secured it at the
base by "guys" that ran from the bottom of the base base horizontally to
cast-iron vent pipes on the roof. We put a Moseley CL-36 on it, and it
lasted until well after I had left State in 1979. I understand that a
derecho straight-line wind storm eventually blew it part-way off the
roof - I'm glad I wasn't around then to answer questions from the
building manager.
73, Pete N4ZR
Check out the new Reverse Beacon Network
web server at <http://beta.reversebeacon.net>.
For spots, please use your favorite
"retail" DX cluster.
On 2/16/2021 7:54 PM, Lux, Jim wrote:
On 2/16/21 4:18 PM, Michael Poteet wrote:
This is a request for opinions. I am thinking about putting up a wire
antenna. At my age (81) I have no interest in climbing towers, trees
or the
roof. Nor I am I interested in installing any support that requires a
concrete base or that weighs over 100 pounds.
I've noted there are at least a couple of telescoping masts (up to 50
feet)
that could be used to support simple wire antennas (when guyed
appropriately). One is carbon fiber, the other is aluminum. Is
there any
advantage of one of these over the other for "permanent" antenna
support?
Initial cost is not a factor.
I have one of the 40-ish foot carbon fiber collapsible poles. It's
fairly sturdy and easy to put up, but the top part *does* bend (it's
pretty small, think fishing rod tip).
The challenge is coming up with a way to support the bottom so it
stands vertically.
You don't want a big concrete base, which makes supporting a
challenge, to resist the overturning moment from wind loads and the
wire. With a 40 foot lever arm it doesn't take much force at the top
to have impressive forces at the bottom.
I've tried things like driving a 8 foot T-post about 5 feet in,
leaving 3 feet sticking up, and lashing a vertical to that. Aside
from the spectacular "trip hazard" of the T post, even with a tennis
ball on the top, it *will* bend or shift if the antenna is loaded.
And that's a fair amount of work to drive (my shoulders and back felt
it for days).
What kind of surface are you putting this mast up over? Grass? dirt?
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