In article ,
Sal salmonella@food poisoning.org wrote:

How would you change the feed method? I've had generally good performance
from my J-poles but I'll gladly improve what I do, if you have some ideas.

One of the older ARRL guides or antenna books shows a balanced method
of feeding a J-pole. A standard half-wave coaxial balun is used. The
two balanced outputs of the balun are tapped onto the two sides of the
J-pole matching section, some distance above the usual "50-ohms-or-
thereabouts" attachment point.

My understanding is that the impedances "seen" on the two sides of the
matching section won't be identical; the short side ends at an
open-circuit point and the other side "ends" at the beginning of the
half-wave section, where the impedance is high but not quite an open
circuit. Hence, you won't achieve complete balance this way - there
will probably be some current flow on the outside of the halfwave coax
balun section.