Modeing shows that radiating current can occur on a J-Pole feedline due
to mutual coupling from the antenna. The amount depends heavily on the
length and orientation of the feedline. The main effect of the current
on the pattern is to distort the main lobe, reducing the amount of
signal directed horizontally. I suspect that the widely varying reports
on the effectiveness of a J-Pole are due, in part, at least, to
different feedline lengths and orientations and therefore different
amounts of feedline radiation.

If there is significant current on the feedline, it might take a couple
of current (choke) baluns, placed about a quarter wave apart, to reduce
it to a small value.

Most people don't realize that ground plane antennas are subject to the
same phenomenon.

Roy Lewallen, W7EL

Larry wrote:
ml wrote:

second

I have a arrow 2/440 j pole works great---- it dosn't have any
radials hanging off naturally, so since basically just the center
conductor is connected would you suspect my coax shield is 'part of
the antenna' radiating alot of stuff??
(course the shield does attach to the bottom mounting plate of the
antenna but i wasn't counting that


In the typical J-pole antenna, the shield connects to the long element
and the center to the stub. I don't know your antenna in particular,
but I would suspect this is the case and don't believe it is considered
a radiating element.