Comments on: If a J-Pole Antenna is Good for 2m, Would it be 3X as Good for 6m? http://kb6nu.com/if-a-j-pole-antenna-is-good-for-2m-would-it-be-3x-as-good-for-6m/ My personal adventures in amateur radio Thu, 11 Mar 2010 13:10:45 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: Eric WY7USA http://kb6nu.com/if-a-j-pole-antenna-is-good-for-2m-would-it-be-3x-as-good-for-6m/comment-page-1/#comment-299793 Eric WY7USA Fri, 15 Aug 2008 02:14:58 +0000 http://kb6nu.com/if-a-j-pole-antenna-is-good-for-2m-would-it-be-3x-as-good-for-6m/#comment-299793 What’s up with the feedpoint? Why do the two designs differ as to where to place the feed point? Basically a j-pole is an endfed antenna. the radiator is the 1/2 wavelength piece that extends over the 1/4 wave matching stub (the two parallel sections). You can find any impedance you like on the matching stub. At the bottom you will find a low impedance (zero ohm short circuit) and at the top a high impedance (in theory infinite ohms, in reality about 4000-5000 ohms). The location where you will find a 50 ohm match depends on the impedance of the radiator section. And that impedance depends on the dimensions of it. What’s up with the feedpoint? Why do the two designs differ as to where to place the feed point?

Basically a j-pole is an endfed antenna. the radiator is the 1/2 wavelength piece that extends over the 1/4 wave matching stub (the two parallel sections).

You can find any impedance you like on the matching stub. At the bottom you will find a low impedance (zero ohm short circuit) and at the top a high impedance (in theory infinite ohms, in reality about 4000-5000 ohms). The location where you will find a 50 ohm match depends on the impedance of the radiator section. And that impedance depends on the dimensions of it.

]]> By: Bill http://kb6nu.com/if-a-j-pole-antenna-is-good-for-2m-would-it-be-3x-as-good-for-6m/comment-page-1/#comment-299671 Bill Fri, 08 Aug 2008 16:56:40 +0000 http://kb6nu.com/if-a-j-pole-antenna-is-good-for-2m-would-it-be-3x-as-good-for-6m/#comment-299671 Here's a 6 meter J-pole built from 450 ladder line. I hope to have one in my trees in the near future. http://www.astromag.co.uk/j-pole/ 73 Bill Here’s a 6 meter J-pole built from 450 ladder line. I hope to have one in my trees in the near future.

http://www.astromag.co.uk/j-pole/

73
Bill

]]> By: Alan http://kb6nu.com/if-a-j-pole-antenna-is-good-for-2m-would-it-be-3x-as-good-for-6m/comment-page-1/#comment-299642 Alan Thu, 07 Aug 2008 17:32:16 +0000 http://kb6nu.com/if-a-j-pole-antenna-is-good-for-2m-would-it-be-3x-as-good-for-6m/#comment-299642 Hmm... given that beam antennas are relatively small at VHF and above, I've never bothered with a J-pole. As a very new ham I built a 6m 4-ele quad out of wood and was very pleased with it (dimensions are available all over the 'net). It was ugly as sin and I had to turn it by hand (on a pole, a mere 10' above my back deck), but it worked wonderfully. I've moved up to a commercial quad now. There are times on 6m when I'm sure a J-pole will work for DX contacts, but a small beam is easy to make and well worth it. Hmm… given that beam antennas are relatively small at VHF and above, I’ve never bothered with a J-pole. As a very new ham I built a 6m 4-ele quad out of wood and was very pleased with it (dimensions are available all over the ‘net). It was ugly as sin and I had to turn it by hand (on a pole, a mere 10′ above my back deck), but it worked wonderfully. I’ve moved up to a commercial quad now.

There are times on 6m when I’m sure a J-pole will work for DX contacts, but a small beam is easy to make and well worth it.

]]>