[Antennas] RE: J POLE QUESTION

Fri, 12 Jul 2002 00:04:05 -0400

>  THe Jpole is just a vertical Zepp antenna.

   ??? A "J" pole doesn't have to be vertical.
   I think the open ended stub is dissimilar to the feed
system of the Zepp, or we would be calling them Zepps.

>  The bottom 1/4 wave section will cancel the field
> providing balanced currents are on the wires, then,
> only the top 1/2 wave will radiate omni directional.

   True.

>  If the currents are not balanced then the Jpole will
> not resonate!

   Not true, any current imbalance, stub or feed line,
will simply cause another source of radiation.

>  I suspect that the 1/4 wave section acts like a current balun by itself.  

   The stub is a (broadly) tuned impedance transformer,
useable and operating in either directions with great range.

> Anyone have experience with not being able to resonate a Jpole 

> until they added a balun ?

   The dipole's resonance is reasonably independent of the feed system,
the sleeve balun only greatly reduces the feed line current and thus
the coaxial feed line's ability to radiate and perturbing the dipole's
pattern.
   I have built a lot of "J" poles.

        73 (= Best Regards) de: Ron [email protected]
     100% LINUX, since July, 1997   SENT Time and Date are UTC
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