GMRS Moxon Antenna

[WSBN727]

Built a prototype GMRS Moxon with 4 elements using 12 gage solid wire, paint stir sticks and ZIP ties.  It works but not as much gain as a 4 element Yagi it appears.   
Can anybody help with best  spacing for the 3rd and 4th director elements?  I find nothing as far as calculators etc.  I’m really only seeing  3+ element moxons directions and they are for 2m 6m ….. and up I would like to play around with adding more elements and fine tuning.  SWR is excellent 1.01 simplex to 1.3 for repeaters.  Fun antenna build and easy.

[SteveShannon]

I thought that by definition a Moxon is only two elements. There are other antennas that claim to be three and four element Moxons, but a Moxon is just a specialized Yagi.  Single band Yagis work by having a single reflector, a single radiator, and multiple directors. In most cases the directors are all 5% shorter than the radiator. Sometimes the directors taper so each is shorter than the previous director.  Have you tried making your directors shorter?

[labreja]

Sorry I can't help, but that's really cool!

[BoxCar]

As a Moxon is a variation of the Yagi, the driven element should be between the director elements and the reflector. the reflector is around 5% larger than the driven element and the directors 5% shorter as they go toward the front of the antenna. I'm not certain of the spacing between the elements.

[WSBN727]

16 minutes ago, SteveShannon said:

I thought that by definition a Moxon is only two elements. There are other antennas that claim to be three and four element Moxons, but a Moxon is just a specialized Yagi.  Single band Yagis work by having a single reflector, a single radiator, and multiple directors. In most cases the directors are all 5% shorter than the radiator. Sometimes the directors taper so each is shorter than the previous director.  Have you tried making your directors shorter?

Yes they are a little shorter.  Just took off roughly 5% or so.

[kidphc]

If you are chasing gain. Try quad antennas, they usually have a narrow cone when compared to a yagi.

When I say narrower I mean, less spread vertically as well as the pattern was more focused from what I in antenna software and theories.

I just ran into issues when trying to DIY due to the spreaders. I just wasn't very happy with the materials






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[SteveShannon]

I think that this paragraph is pretty succinct:

The Moxon rectangle is a 2-element array using dual coupling between elements to produce its nearly cardioidal pattern. Because it depends upon both the mutual coupling between parallel portions of the elements and the coupling between element ends, it is not amenable to the addition of further elements for increased gain. In other words, a Moxon rectangle is not expandable by the addition of director in the manner of a standard Yagi.

But the author, SK W4RNL, goes on to describe how to stack the rectangles:

http://on5au.be/content/a10/moxon/moxstack.html