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Author Topic: VK2ABQ verses Moxon Rectangle  (Read 23213 times)
M3GXX
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Posts: 13




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« on: April 03, 2007, 11:35:13 AM »

I am considering building a mini beam for 20 Meters and I was wondering which was the best the Moxon Rectangle or the VK2ABQ antenna?

My garden is 70ft long by 35ft wide but goes from a East at the top to West at the bottom, not great for using a wire antenna as I have.

The main useage is for 20M digi modes and voice.

Any suggestions from fellow amateurs would be great

Ian
M3GXX
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AB3EI
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Posts: 28




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« Reply #1 on: April 04, 2007, 04:23:09 AM »

Well, since Moxon based his design on the VK2ABQ, the difference is not large.  According to Cebik, "Moxon lengthened the front and rear elements and shortened the side tails. The resulting rectangle requires very little more turning radius than the square, but improves the gain of the antenna considerably."

Visit http://www.cebik.com/mu/mu2a.html for more information.

Of course, you might consider a two-element Yagi. The Yagi will outperform either Moxon or its predecessor in terms of gain and does not require significantly more space to install.  

Cheers,

Bob AB3EI
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M3GXX
Member

Posts: 13




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« Reply #2 on: April 04, 2007, 10:29:33 AM »

I would love a 2 or 3 element yagi and I have the space for it in my garden, but then I'd have to pay about £150 for an application for planning permission then I could still get refused even thou there is a amateur within spitting distance of me with a 3 ele tri-bander.

We should get planning permission for any antenna that is either greater than 3 meters in length or 3 meters above the ridge of your house, depending on what area of the UK you live in, or if the local authority class it, or not as most amateur antenna's, as "de-minius", they like you to pay out for planning permission for anything that isn't a TV antenna or a satalite dish or even if you want 2 dishes up!!

I will be getting a TGM 3 element beam when I can afford it, and then see if the neighbours complaint to the local authorty, but if I start smallish and work up hopefully they wont say a thing and especially when they can see the 3 element tri-bander 33ft up in the air Hi Hi

Regards
Ian
M3GXX
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KE4DRN
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Posts: 3734




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« Reply #3 on: April 04, 2007, 01:38:19 PM »

hi ian,

the moxon is direct fed so no need to match it as with
the yagi.

take a look here to see what others have done

http://www.moxonantennaproject.com/design.htm

you already have the cebik.com site.

I'm working on my 20M moxon using aluminum tubing.

73 james
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AB3EI
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Posts: 28




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« Reply #4 on: April 10, 2007, 04:36:21 AM »

Ian,

I'm confused.  Why would a 2L yagi be more noticeable than a Moxon?  They're about the same size, have the same visual "footprint".  Yes, you can build a Moxon with wire, bu that's just the elements.  You still need some sort of support structure to keep the wires in place; that support structure will be as visible as a 2L yagi.

Anyway, I don't see the distinction.  Maybe there's another factor I'm missing! =)

73 de AB3EI
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M3GXX
Member

Posts: 13




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« Reply #5 on: April 10, 2007, 09:03:00 AM »

Hi AB3EI,

Yeah I get your point, but after doing some measurenents in my garden I would not be able to fit either the Moxon or a 2 ele beam.

If I wanted any beam over 22-23ft wide and wanted to direct it in any direction apart from North or South I would exceeding my boundary of my property, as my garden is only 25ft wide, I am fine in the North/South direction as my garden is 95ft long. Also due to my licence I am only allowed to run 10 watts, although I have had several contacts in the US and Canada and all over europe, its a lot harder on voice than on the data modes and I do prefer voice.

So unless I can either build an beam thats small enough to be able to fit into my garden and be able to be rotated without exceeding my boundary I think I will have to just have to try and save and buy something like a TGM 3 ele,approx £440, but that may take some time due to not being able to work for medical reasons and another child due un June!

I have looked into the Hex beam a bit but the Gain and F/B gain doesn't seem as good as a 2 ele beam or the Moxon, but it may well be the only alterative till I can afford a comerical beam like the TGM 3 ele.

Regards
Ian
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WB6BYU
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Posts: 13481




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« Reply #6 on: April 10, 2007, 05:38:39 PM »

You appear to have enough room for a 20m quad - it is only 1/4 wave
on a side.  Even in a diamond configuration hanging from a top rope
you can still make it fit.  If you make the loops taller and narrower they
will give a bit more gain for horizontal polarization.  Taken to an
extreme you get JA1HWO's "skydoor antenna", which you can read about
here:

http://www.page.sannet.ne.jp/ja1hwo/

though you might want some help from babel.altavista.com or Google
to translate it.  (Just search for "skydoor antenna".)  For 20m it would
be 3.2m wide and 9m tall.  I've designed VHF versions of quads using
skinny loops - they certainly would fit within the width of your garden.
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NA7U
Member

Posts: 72


WWW

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« Reply #7 on: March 22, 2011, 11:49:20 AM »

M3GXX,

As to your original question, the VK2ABQ vs. Moxon (which is sort of a misnomer because there is a middle design that G6XN, Les Moxon, came up with...):

VK2ABQ is simpler to construct as it is a square, although the spacing between the ends of the elements is more critical than in the Moxon. The VK2ABQ is also easier to multiband if you want to add higher bands than 20M. The Moxon does have more gain and I believe better F/B.

My suggestion is that you look into a 20M EDZ, which will give you as much or more gain than either of the above in two directions. There are ways to shorten it so it would fit. You could remove the short window line matching stub and run window line all the way to the station and have a fine multi-band antenna. Not rotatable, however, and that sounds like that may be a consideration (?)

Last resort you could put up one or more (at different orientations) shortened dipoles (see K7MEM site). Shortening dipoles up to a point really has minimal impact on their efficiency.

Good luck!!  Smiley
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MW1CFN
Member

Posts: 31




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« Reply #8 on: September 02, 2013, 08:33:52 AM »

Quote
...an application for planning permission then I could still get refused even thou there is a amateur within spitting distance of me with a 3 ele tri-bander.

For the benefit of others who worry about this sort of thing, whilst planning is always the subjective and therefore rather wildcard assessment of a human officer, if the existing installation really is that close to you and the neighbourhood character is much the same and there are no special circumstances affecting your property (listed, conservation area, etc), then the local authority would have difficulty in refusing an application for a very similar installation.  If they did refuse, I would expect a well-made appeal to the Planning Inspectorate to be successful.

But always remember the four year rule: if you have had anything up for four years, then the authority, to quote the law "shall not take enforcement action".

Disregard any empty threats from piqued planning officers about 'difficulty selling your house' without a planning certificate.  Rather than bang your head against brick walls and involving bureaucratic local authorities, buy yourself a £50 insurance for any prospective buyer via your solicitor against any enforcement action (which is essentially impossible after four years anyway).

I've never seen a house not sell when one of those insurances is provided, and it's a hell of a lot cheaper than the planning fee!  In fact, the last house I had without a similar, building regs certificate (though the work had been done to those standards) sold for more than the asking price!  Why bother with paper pushers who forget what they tell you, find ever-more supposed 'problems' for you to expensively sort out and then give you grief, when you can just pay £50 and not have any of it?



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KA4NMA
Member

Posts: 355




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« Reply #9 on: September 06, 2013, 08:42:45 PM »

Would a phased vertical system fit your garden? Or one of the many different versions of collinear antenna's (endfire, broadside, sterba curtain, etc)?

Randy ka4nma
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G4AON
Member

Posts: 543




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« Reply #10 on: September 08, 2013, 10:34:59 AM »

So unless I can either build an beam thats small enough to be able to fit into my garden and be able to be rotated without exceeding my boundary I think I will have to just have to try and save and buy something like a TGM 3 ele,approx £440, but that may take some time due to not being able to work for medical reasons and another child due un June!

I have looked into the Hex beam a bit but the Gain and F/B gain doesn't seem as good as a 2 ele beam or the Moxon, but it may well be the only alterative till I can afford a comerical beam like the TGM 3 ele.
The TGM MQ-34SR claims to have similar gain to a mono band full size 20m yagi with an 18 foot boom, everyone should rush out and buy one (I don't think so)...

Ian, don't be fooled by performance claims for small size, multi-band yagis. You won't find them advertising their antennas with gain figures in QST, because they can't back up the claimed performance.

Realistic gain figures are produced by Optibeam and even their OB11-3, with 11 interlaced full size elements on an 18 foot boom doesn't match the claimed performance of the TGM yagi.

Free space gain figures calculated with eZnec, for some reasonably sized antennas are:

2 ele quad (8 foot boom, multi-band 20 - 10m), up to 5.2 dBd
5 band Spiderbeam, up to 4.9 dBd
5 band Hexbeam, up to 3 dBd

I haven't a set of dimensions for a Moxon, but it is similar to a Hexbeam from memory.

73 Dave
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G3TXQ
Member

Posts: 1530




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« Reply #11 on: September 08, 2013, 11:29:46 AM »

K4KIO has step-by-step instructions on how to build your own 5 band hexbeam, if you decide to go that route:
http://www.leoshoemaker.com/hexbeambyk4kio/broadhexgeneral.html

If you are content with it being a single band antenna the construction becomes much simpler - no need for the centre post etc.

If you try it, you might be very disappointed if you then swapped it for the TGM!

Steve G3TXQ
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