Re: J-pole antenna.

One expert in J-poles is Dr. Edison Fong of USC Berkley (I think). He teaches graduate level electronics and has his students make (and sell) a very good J-pole dual band antenna. Cost in the neighborhood of $20-29...don't remember. Profit goes to his students for additional projects.

He has published several very good articles on J-poles. Most j-poles made by folks are not very good. it is a complex antenna and the materials are integral to the tuning. There is a great deal of variability in those materials. If not compensated for, the results are poor.

I was talking with him yesterday in reference to my seminar and he told me about the research he has done in his quest for a good J-pole.

I suggest you google his name and track down the article. I think most are in QST (an amateur journal) but available on the net.

If you are interested in obtaining one, you can either "bid" on e-bay, but I don't know how it is posted, or contact him at his email edison_fong at hotmail dot com

He makes several versions. One that is designed to fit inside of a certain RF transparent PVC pipe (not all pipes will work) for self supporting applications and another that rolls up.

Electrically they are somewhat different. He will also tune to specific frequencies if needed. I have two, one on the amateur frequencies and one on MURS-GMRS.

In the article, pay particular attention to the gain figures. it is not a gain antenna, although it will certainly out perform a rubber flex antenna.

If you get one, I suggest also getting the extension coax. Really, you can not beat the price and each one is tested by is grad students.

If you want a J-pole I obviously recommend his.

I have spent the last few days writing a section about antennas and antenna gain vs coax length. How high a mast is high enough and what are the trade off's between height, coax loss and antenna gain. It is a complex subject.

Probably more than you wanted to know....

Nomad
aka Ron, N1AHH
http://tinyurl/GDC-/welcome