jimbo wrote:
Dan Richardson wrote:

I'm wondering if you are using a common mode choke? Also what type of
mast are you using to support the antenna?


I have tried with and without a coax loop, 5 turns about 6 inches in
diameter. I couldn't see any difference. I use a 1/8 inch diameter rope
to hang the J-Pole from a joist in the basement or from a roof rafter in
the attic.

A single choke blocks conducted common mode current. But a J pole (and
ground plane, for that matter) can also have considerable common mode
current due to coupling between the antenna and feedline, which can
distort the pattern and reduce the gain at the horizon. This can
actually be made worse by a choke in some cases. Two chokes, about a
quarter wave apart, are necessary to reliably reduce the coupled
current. The amount of conducted and coupled current you have without
chokes depend on the feedline length and orientation, so it can be small
in some installations and large in others. I suspect that's one reason
why people report such widely varying degrees of success with this antenna.

Roy Lewallen, W7EL