Talk:J-pole antenna

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This article claims that a Slim JIM and a J-Pole are one and the same. This is simply not true. - AB2MH Ryan 01:14, 8 October 2006 (UTC)

I think the section talking about the quarter wave section isolating the antenna is also incorrect. The quarter wave section is a transmission line, and acts as a transmission line impedance transformer. When I have time, I'll fix this and add a reference. I'd also like to add material about the Super J (with phasing section), but not with the article in its current inaccurate state, --ssd 20:31, 14 July 2007 (UTC)

On doing some research, I found Cebik's pages on this (linked now). He seems to say both that the Slim Jim is a variant of the J-pole, which, in turn, is a varient of the end-fed Zeppelin antenna. --ssd 18:52, 21 July 2007 (UTC)

I have rearranged and clarified this article somewhat. I think this is about as much as you can say about a J-pole without going into construction details or its history. The diagram here is nice; I could add pictures, but the j-pole is large and difficult to photograph clearly. --ssd 22:17, 21 July 2007 (UTC)

The J Pole or Zepp Antenna is a voltage fed antenna that was invented by the Germans (citation needed). It was first used on the Zepplin Ballon Air Ships (citation needed) hence the name Zepp Antenna. It consisted of a quarter wave and a half wave length/s of the same peice of ribbon or open feed line. The first quarter was the matching stub and the half wave section with one side of the feedline removed was the end fed radiator. It was simply left to trail from the air ship at altitude. This Zepp Antenna later became known as a J Pole and or Slim Jim. Indeed - the stub is both an impedence match and a transfomer. Somewhere between the lower end - closed circuit, and the top of the stub - open circuit an exact 50 ohm match can be found to suit 50 ohm unbalanced feed lines. The voltage and current above the feed point, on the stub, have equal and opposite voltage an current and cancel each other out leaving the end fed half wave or dipole to radiate. I have built many of these for friends, clubs and emergency services and have found they can be extended to a five eight or three quarter wave end fed (although they becomes dogs to tune and need to be kept clear of any metal objects - unless, placed near a vertical metal mast in which case they then become directional). They can be stacked for greater gain with two end fed three quarters in phase producing up to 6-7DBd. A phasing stub needs to be inserted betwen radiators to return the voltage and current to phase at the start of each new three quater length.

In any event the main page should be edited to indicate the history and it's origional name ZEPP not J Pole. 73 Tidalenergy 00:16, 8 October 2007 (UTC)