wrote
oups.com...

Jack Painter wrote:
wrote
Can anyone tell me where I can find plans for building a great
jpole
that is dual band and has a low swr?

Also, do you have to ground or use a balun with a jpole? I have
seen
some plans that say you dont on their design.


I use the design found at : http://www.hamuniverse.com/jpole.html
Standard 1/2" copper pipe with acid-free solder, no balun, no choke,
and
approximately 70' of Belden 9913 feedline. Grounded roof top mast
uses #4
bare copper lightning down conductors in two directions, coax is
shield
grounded at ground level, then to an I.C.E lightning surge arrestor,
then to
a 25w marine vhf transceiver. The J-Pole is bench centered on 156.800
Mhz
and allows 18-23w output (at the transceiver) across the vhf-marine
band.
Very experienced antenna builders on this group have explained that
my
results without a balun/choke at the feedpoint is a combination of
luck
concerning feedline length and operating bandwidth. Accordingly, your
results would most likely vary, but the design is a confirmed
performer.

73,
Jack Painter
Virginia Beach, Virginia

How do you "adjust" this antenna for optimum swr? Would it change the
results using "qwick connect" fittings instead of welding/soldering?

Are the end caps that are soldered on included in calculating the
length?


Yes the caps are part of the electrical length. Tuning is accomplished by
adjusting the tuning bar (dimension "C" up or down between the two vertical
elements. Very little adjustment is required from the design dimensions for
"bench" swr. Of course that would need to be tested as installed is you want
to know the actual output in watts at the antenna. Mine required no field
adjustment.

73,
Jack Painter
Virginia Beach, Virginia