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Click on image to enlarge
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My J-Pole antenna. This is the antenna I use for most of
my public service and emergency communications work. It takes only a few
minutes to set up or take down and can be stored/transported in a small
area, like the back seat of my little car. It was built using the plans
on the resource page: Copper pipe
J-Pole Plans |
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This is a close-up view of the SO-239 connector. It is
perhaps the trickiest part of building this antenna, as one has to be
very careful not to overheat it when soldering to the copper pipe. The
most durable way to attach it is to silver solder it , so a Teflon connector (silver plated if
possible; I couldn't find one) is desired.
The Teflon will withstand the higher heat for a short time, whereas the insulation
on the standard connectors will rapidly melt. After soldering, I put a layer of
Silicon Rubber caulk over it for additional protection. The wire is
placed so as to obtain the lowest VSWR in the center of the frequency
range, then silver soldered and taped. |
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A photo of the broken down antenna, with a yardstick as a
reference. This antenna has undergone several modifications in the years I have used it. Originally, the active portion was one
entire piece, making it over five feet in length. Additionally, the
base was made from PVC pipe.
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The first modification I made, was to break the active
section into two pieces to make it more manageable. I got the idea from a
recent QST article, where the author made a folding J-Pole using bungee
cord (like a tent pole). Knowing how easily the copper fittings he used
would bend, I felt threaded fittings would be more durable. You
should be able to see the joint in this picture and the next one. |
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The most recent modification I made was as a result of an
unfortunate incident at a public service communication assignment. I was
breaking down the antenna, and dropped one of the PVC base sections. It
hit the pavement and snapped in half at the T coupling. It's just
as well, as I have been getting a little concerned with the durability
of the threads on the PVC sections, and this gave me an excuse to
"upgrade." It also was a convincing reason to give my wife so
I could buy another ten foot section of 1/2 inch copper
pipe and some fittings. |
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