Antenna question

2-meter J-pole antenna for the 145.585MHz audio retransmission of NASA TV

This is a 2-meter J-pole antenna for the 145.585MHz audio retransmission of NASA TV. Probably the best VHF antenna, it was built by American Legion Post 380. They constructed and sold many of these in past years, but unfortunately no more. Not only are the Legion J-pole antennae effective radiators, but the SWR is virtually 1.0 with no reflections. Recently, this antenna was raised from 25 feet to 40 feet AGL.

Anyone know where to get the plans they used for this antenna?

Joe, KJ9M

 

AC0VC

March 19, 2012 - 9:08pm

Try this site for information about the J-Pole in question.

Indorf

April 4, 2012 - 7:45am

The j pole is an antenna that is a half wave fed by a quarte wave, in a "J" configuration. There are many j-pole calculators on the net. Look at the Super J if you really want to be effective. But just type in j-pole in google and start browsing. BTW I have a super J on 2 meters "440", six meters, and 20 meters (used the tower as part of the antenna) just remember this formula.......234/frequency in MHZ = 1/4 wave. the long section of the J is 3/4 wave long,part of the first 1/4 of the long section is to feed the 1/2 wave above it. and the short is 1/4. the top of the short one should be where the 1/2 wave starts in essence the hook of the J is the feeding section. split the coax, attach the shield to one side and the center conductor to the short side. Move the attachment point up or down to tune the antenna. Good luck, if you need more info, e-mail me at kc5uta@yahoo.com and I will send you some real good plans.....Dave

KC2FCB

April 12, 2012 - 5:13pm

If you are a member of ARRL, go to the website and research in QST articles. Also ARRL publishes numerous ANTENNA HANDBOOKS which describe what and how. ENJOY

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