Hybrid Moxon for 20m - HomeBrew Forum at eHam.net

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eHam.net Forum : HomeBrew : Hybrid Moxon for 20m

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Hybrid Moxon for 20m	Reply
by M1PAH on June 25, 2009	Mail this to a friend!
I hope someone out there will be able to help. I have built a hybrid moxon for 20m based on a design by N5GLR I found on http://www.moxonantennaproject.com/n5glrmoxon.htm The dimensions are a follows The director is 2 x 10ft lengths of rg58 both shorted at the ends and fed via the centre conductor The reflector is a 21 ft long length of rt58 shorted at both ends Both the dir and ref are 14ft long and folded with a gap between dir and ref of 23" the boom is 9ft. My antenna is resonant at around 14.190 and the 2:1 bandwidth is from 14.161 - 14 262. What I would like to do is optimize it for max forward gain. I have the Mmana-gal software but can't work out how to use it for what I need. Is there anyone out there who might have used this type of antenna or has the know-how and software to give my some dimensions for an optimized version? Any help would be greatfully received Regards Dave M1PAH

RE: Hybrid Moxon for 20m	Reply
by W5FYI on June 25, 2009	Mail this to a friend!
L.B. Cebik, W4RNL(SK), wrote extensively on Moxon antennas (aerials), including his studies on maximizing gain, etc. He also was an expert on NEC modeling techniques, and included comprehensive tutorials on his web site. Although he is gone, his works remain at www.cebik.com. You'll have to register (it's free), but then you can read more than you've ever cared to know about all kinds of antennas--a virtual on-line antenna encyclopedia! Give it a try. FYI

RE: Hybrid Moxon for 20m	Reply
by M1PAH on June 25, 2009	Mail this to a friend!
Thanks for that will have a look Dave

RE: Hybrid Moxon for 20m	Reply
by N3OX on June 25, 2009	Mail this to a friend!
"Is there anyone out there who might have used this type of antenna or has the know-how and software to give my some dimensions for an optimized version? " Yes. Throw out the coax "Moxon", which is really just a lossy loaded dipole. Read this for more info: http://www.karinya.net/g3txq/coax_antennas/ Plus, if the reflector were to actually operate as a lossy, loaded reflector, the shield would have to be split in the middle. In short, the "theory" behind the coax Moxon is time wasting nonsense. Here's an estimate of the pattern of a Coax "Moxon" in blue plotted against an actual Moxon in black: http://n3ox.net/files/coaxmoxon.jpg Then download AC6LA's Moxgen from here: http://www.ac6la.com/ Use it to calculate the dimesions of a wire Moxon. Build it to within, say, 6mm of those dimensions. Then it's as good as it gets (which is pretty good). If you need more gain, you can probably eke out more from a different sort of two element yagi, but it will be much wider side to side and a Moxon is already good in terms of gain and F/B across the whole band. But I expect replacing your lossy coax dipole with a real Moxon is really going to perk up 20m for you. 73 Dan

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