Well, I said that wrong, I figure the length of the gamma rod will run right
around 6 ft for 20 meters, this should get you close enough to tune from,
the cap reactance needed in series with the rod will need to be of a value
to cancel that of the inductive reactance intoduced by the gamma rod... I
think that is clearer...

Warmest regards,
John

"John Smith" wrote in message
...
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.