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Old November 30th 11, 02:28 AM posted to rec.radio.amateur.antenna
tom tom is offline
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Default Stub J-pole for six meters


All hands

Let me start over. I want a transportable, six meter, vertically
polarized antenna. The parts have to be readily assembled&
disassembled. I would like it to have a somewhat higher than normally
attempted radiation pattern for use between buildings, hills,
ridges... [I had thought that a J-pole might be a good compromise
instead of antennas with a more horizontal gain pattern.] It would be
really golden if the adding of additional parts would change the
pattern back towards the horizontal to use the antenna when it is
located above local horizon. Parts should be short enough to fit in
the foot well of the back seat of an ordinary sedan. It's a stretch
but If it did not need guying that would contribute to ease of
deployment especially in an urban operating location were the
anchoring possibilities for guy lines may be limited. [I'm trying to
devise an X frame tripod. It would be made out of fiberglass
structural channel in order to lower the weight of the tripod assembly
but that is not an antenna design problem.] I may need the antenna to
be elevated when operating near pedestrian traffic to reduce the risk
of RF contact or excessive exposure. Shielding the feed point from
physical damage; such as by having it inside a piece of Box channel
would be quite desirable. I'll leave it there and see what folks can
think of that might work.

--
Tom Horne, W3TDH


Regarding the higher than normal angle request, either

1) make it fairly short so as to approximate an isotropic radiator

2) make it a significant amount longer than a normal J pole so you get
lobes above the horizon. You will need to model this for each concrete
or natural canyon you expect to be in.

And then think a lot more. Possibly a different solution is better.
Different band to start with. I don't know, just trying to stir up your
thinking.

tom
K0TAR


 
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