[Antennas] Design your own "J" Pole antenna.

Fri, 12 Jul 2002 10:11:54 -0500

Greetings,

Another way to match the J is to use a loop on the end of the coax. If you
are matching a copper pipe 2 meter J then make a loop which will be about 4
inches high. The loop is just coax stripped down to the center conductor
insulator and soldered back to the shield in a loop at the end of the center
conductor. There is no direct connection to the J. Tape the loop against the
bottom of the matching stub with the end of the loop (where the center
conductor is soldered to the shield) about even between the elements. Then
tape the rest of it to the elements until no more loop, the rest of the loop
just goes between the elements.Also wrap the connection point with tape. A
lot easier done than said.

es 73 de Pete WA5JCI   EM21jv

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----- Original Message -----
From: "Lefczik, Larry D" <[email protected]>
To: <[email protected]>
Sent: Friday, July 12, 2002 9:45 AM
Subject: RE: [Antennas] Design your own "J" Pole antenna.

> Read a very in-depth article "From a J to a Zepp" by Gary O'Neil N3GO a
few
> years ago.  If you can find a copy of that article, and read it a few
times,
> you will gain a good understanding of the Zepp antenna.
>
> One way to view the Zepp (J-Pole) is as a 1/2 wave element which has a
> characteristic impedance of around 5000 Ohms.  The 1/4 wave matching stub
is
> shorted at the end.  Somewhere between the shorted (0 Ohms) end and the
> element (5000 Ohms) end, you find a 50 Ohm point to match your feed line.
>
> Yes, this is a very over simplified analogy, but it may help someone
> visualize what happens.  (It took me a long time to figure out how I could
> connect a transmitter to a dead short (DC) and make an antenna radiate,
> especially when I made a 440 MHz J-Pole.)
>
> N3GO also studied the differences in construction material such as copper
> pipe, 450 Ohm ladder line, and 300 Ohm Twin-Lead.  The 300 Ohm Twin-Lead
> seemed to be the best material.
>
> This is HAM radio, Build a few and experiment, Let us know what you find.
> 300 Ohm twin lead is cheap at Home Depot, so is copper tubing.  Don't get
me
> wrong, the discussion here has been very interesting and your questions
are
> good, but, you learn allot by cutting wire.
>
> 73 de WA2EHZ
> - - -
>
> Your moderator for this list is:
> Larry Wilson KE1HZ [email protected]
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