So much gain, even HM's Coastguard came to check it out


His Majesty’s Coastguard inspecting the 10m Moxon on Dunkery Beacon G/SC-001

With conditions on 10m being so good, I’ve been trying to make a decent ‘portable’ Moxon after seeing this thead. This is the second attempt to get it to work, the first being a complete flop - literally - and required the wisdom and advice of @VE6IXD on getting it to stay vertical.

At my QTH there wasn’t much wind… so today was the day to try it, along with a gentle introduction for M7OCZ to the world SOTA who i brought along for the trip. Well at the summit of Dunkery we had reasonable strong winds, about 30mph but thankfully not gusting too much today.

I managed to get everything assembled and working but the winds were strong enough to make the antenna rotate by itself… so you start beaming to New York and end up working Cardiff. I fixed this by attaching a guys to the Moxon pointing roughly at about 300 Degrees. Operating was also made difficult as i’m an idiot and just assumed the coax would be long enough… hence i needed to operated with the radio on my knee.


That wasn’t Fun-knee

So what did I think ?
Better reports into US generally. I found that picking stations out of the QRN and noise much much easier. Had a great pair of s2s with @KF7NP in Arizona on w7a/MN-095 and @W1DMH in Canada on ve2/qc-020. I am convinced those would have been tough without the gain the moxon provided, especially the RX. The most telling was @F4WBN who is in my 10m skip zone and i have worked allot with a vertical. His report was allot stronger today even out the side of the moxon.

The coastguard really did come and take a look. Looks like there were on a training mission and trying to find a spot to land, which they did fairly close to the summit.

This report was a toss up between an ‘antenna build’ or an ‘activations report’. So here is the “build”

The antenna is a 3d printed design, which I hope to improve on, mainly its portability - reducing the weight of the tent poles. I’m now happy with the setup and ease of deployment:

  • Sotabeams Tactical 7000HDS with ring and guys. You need a stiff mast, you don’t need the top sections.
  • 3D printed hub, with interference fit for the tent poles
  • 8.5mm fibreglass tent poles. But these are chunky and I need a lightweight solution. Watch this space (and if anyone has any ideas…)
  • I used the sotabeams heavyweight wire, but next time i’d use the lightweight stuff.
  • Stabilising ring and corner guys for the moxon. Clips onto hooks printed in the wire corners. This worked really well at keeping the moxon the correct shape and stable in the wind.
  • 3d Printed coax T and strain relief

If anyone would like help on the design or the 3D models for this design, please let me know. I may even be convinced to print a few if anyone is intrested. I will publish the models on printables dot com.

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Very interesting. I think a M0XON is a good SOTA antenna but there are practical issues as you describe well. I don’t have a 3D printer but I’ve discovered there are companies which will print from a file so I might be able to build one.

I don’t have an answer to the pole issue. The top sections of telescopic poles would work but that seems an expensive way to do it. PVC pipe might work but it isnt very stiff.

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Hi Tim,
Glad to hear the Moxon is working for you. I guess I forgot to mention that I always have a stool so I can sit and use the radio in my lap! It avoids the Fun-knee contortions!
I am envious of the trans-Atlantic S2S contacts. Good stuff.
Ian

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You want something that is elastic that pushes out the corners of the moxon i think. Lightweight Backpackers tents pole would Perfect - apart from the fact they are conductors made from aluminium. The cheap Chinese fishing rods found on aliexpress may be worth a punt but I am not sure. I’m also looking at polyester fiberglass rods. They look light and flexible, i may order a sample to see…

The rods I used today are 8.5mm chunky tent poles stolen from the family tent !

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It looks well-built and seems like a great idea. Thanks for the report! I am still just hung up on my SOTABEAMS Bandhopper that I have cut away everything except the 20M portion of the antenna. A monoband Dipole is just hard to beat. Awesome activation and thanks for the pics.

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You are absolutely right, a dipole is simple, easy to deploy and super reliable! This antenna is not as simple, more weight, more to go wrong and more faffing ! Something I intend to use on days like the transatlantic s2s days, but not when I need speed or reliability.

We could invent an sota antenna top trumps game for a sota get together. Now that’s a random thought….

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I really need to do more experimenting with antennas, I kind of found my groove with what works and have no really ventured out of that realm. Hope to catch you on the bands sometime!

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Would a vertically polarised Moxon be easier to build/deploy ?
In that case you’d have the elements in the same plane as the pole

Rick

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I’ve got the bits to make a vertical Moxon but haven’t got around to it yet. The problem is if you feed it conventionally I think the coax will interfere with the antenna unless you could lead it away horizontally for a few metres which might mean having a second mast.

My plan is to feed it off-centre with a balun in the bottom corner. Just need to get my act together and build it!

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That sounds like an excellent idea !

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Maybe you could just put up two poles and aim for a verticle yagi with that configuration, 1 pole radiator, 1 pole reflector ? You could use guys to keep them equidistant ? just thinking…

[later…] but then you are constrained by the beam direction :cold_face:

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Su

Yes I have tried that (once) and it does work, but it’s hard to swing around !
I think it’s easier just to take my mini amplifier as I did today and run 30W into my flowerpot vertical, but I realize that’s not possible for you at the moment.

Rick

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bamboo canes?

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Going on my ‘mk1 Moxon’ experience which was a flop, you need something that gives these poles (which are under huge leverage) some sort of horizontal stability. Prehap’s a guy at 45 degrees further up the mast - basically what I did for the moxon corners ?

Or make everything superlight …

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2mm diameter 3m long fibreglass/polyester rods are available for £3.75 each. I’d guess you need to add VAT and P&P of course. They weigh 6g/m, so not very much.

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Looks fun! If you can share the printables link that would be great. Tempted to try this in the back garden.

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Hi !
I put the design on printables dot com tonight:

10M Lightweight Moxon

Let me know how you get on and if you need any help, hopefully my instructions and models make sense. I used freecad, and the cad files are included to make adjustments (mainly for interference fits to mast and tent poles)

Hope you can make the most of conditions on 10m !

Thanks
Tim M7TSU/P

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