Hello Harbin

The bottom of the J-Pole antenna is a 1/4 wave length to transform the high impedance of the 1/2 wave length above into a lower impedance (close to 50 ohms). The impedance of that 1/4WL sould be Z = SQUARE ( Z coax X Z antenna) .... in that case Z antenna is the impedance of the 1/2 WL (usually several hundreds ohms)
That's why the space between elements as well as there diameter is important.

You certainly know the Topfkreis ... which is the same antenna ... 1/2 WL + 1/4 WL ... but with another technical realisation.

Hoping it helps.

Regards

Jean-Marc
F4DRH
www.barbaxoops.com




"Harbin" a écrit dans le message de news: ...
Howdy:
In a j-pole the 1/4 wave element, and the bottom 1/4 of the 3/4
element should act as a transmission line, right? So... shouldn't these
elements be as very close to each other to cancel one another out, closer
than what I see on most j-poles? Or is this space have something to do
with the impedance of the antenna?

--
SeeYaa Harbin Osteen KG6URO

This is YOUR futu
http://halturnershow.com/aztlan_caps.wmv
http://media.putfile.com/La-Gran-Marcha
The Mexican Solution:
http://www.centerforsecuritypolicy.o...s&code=06-D_18

-