"Caveat Lector" wrote

Here is some antenna theory to read to answer your questions
URL:
http://k9erg.tripod.com/theory.htm

Nice site. Except for the inaccurate advice warning of disastrous effects
from operating a J-Pole w/o a BalUn. I use neither a BalUn nor any
coiled-feedline as a choke. If my feedline is radiating, it's the most
efficient feedline radiator ever made, getting loud and clear 100 mile
coverage on VHF Marine between other high sites, and surface contacts
between 20-30 nautical miles depending on height of vessels antenna.
Another misconception about J-Poles is from at least one web-site offering
plans, in which the offerer warned against grounding the antenna. Dangerous
and wrong of course, as the antenna and its mast should be grounded and
performs very well as such. The stub-capped tops of a copper-pipe J-Pole
antenna at the highest point of a structure will indeed be an air terminal
for lightning that was going to strike that immediate area anyway. Maybe my
lightning down conductors heading 180 degrees from the J-Pole to series of
ground rods are the SECRET G.
--
Users considering a static and lightning-grounded (and un-choked) J-Pole
should make sure the British did not already invent/patent this form of
improvement to the J-Pole radiation pattern. ;-)
--

73,
Jack