Jimmie:

A half-wave radiator (the J is such) is an excellent ant and it can be run
without ground plane...

However, the J with the added bulk of the quarter-wave matching section
makes no sense, when a gamma match can be used with a slight gain in
efficiency... I worked out such a design and use it on 10 meters... a 1:1
current balun at the ant is necessary, or ferrite beads over the shield of
the coax--I found an inductive reactance of the balun/beads of about 2000
ohms at the operating freq is ideal and halts all line currents.... the
lenght of the gamma rod will be approx. 1/3 longer when used on a 1/2 wave
then when used on a 1/4.... I use no counterpoise, but a 1/4 lenght of wire
can be hooked at ground and the ant worked against it... I find it
unnecessary with the balun and ant properly tuned and matched...

You will not see this ant on the web... take my word for it, it is a decent
antenna... better yet, try it, if you are unhappy, just remove the gamma
and stick on the 1/4 wave matching section and you have the J...

Warmest regards,
John

"Jimmie" wrote in message
. com...
For A while now I have been pondering practical ways to build a 20 meter J
antenna mostly for the grins and giggles of doing it. Recently I came by a
couple of lengths of triangluklar tower. I was thinkinking about erecting
these an placing a metal pole down the middle shorting the two together at
about 16 ft from the top. The radiator would consist of a 30+ ft
fiberglass whip. Any thoughts on this design would be appreciated. Other
ideas for a J have been dismissed because they would require guys. I need
something that would be freestanding.