Thread: J pole question
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Old May 8th 06, 01:56 PM posted to rec.radio.amateur.antenna
Jon Kåre Hellan
 
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Default J pole question

writes:
If it's what I think it is the design is a coaxial feed section with
a 1/2wl radiator. The difference being a coax fed rather than a
balanced line feed. In either case it relies on an unterminated 1/4wl
section reflecting a high impedence to match the end impedence of
a 1/2wl section. That being something in the range of 3000-5000
ohms (at resonance).


Here's a very simple end fed vertical dipole:

http://www.la2t.org/otfgallery/album...plukk/1002.jpg

http://f3wm.free.fr/radio/pocket.html

It's simply a piece of coax. The braid is stripped off the last 1/4
wavelength. Another 1/4 wavelength from the end, there is a choke to isolate
a 1/4 wavelength of braid from the rest of the cable. Presto, dipole!

Support it with a fishing rod, hang it from a tree, whatever.

73 de LA4RT Jon