M1PAF'S 20 Meter Vertical Moxon

 

Thanks to this site and Pete Mills in particular I decided to build a Moxon to take on our trips to the Scottish Islands. Wire dimensions were as Pete's EZNEC model. Mark 1 used a couple of fishing pole as supports but the bent far too much in the wind so I decided to engineer a more substantial arrangement that is easier to put up.

   

The beam is supported by two cross arms mounted to a push up GRP mast and the pictures below show the mounting arrangements. To eliminate as much metal as possible from within the beam I used a form of GRP plate called TUFNOL to fabricate the mountings, with hydraulic pipe clamps used for the tube clamps. These are also plastic only leaving two bolts and a plate that are metallic.

At the end of the cross arms I bolted in eye bolts so that the wire element can be quickly clipped into place. The wire is supported at each corner by a dog bone insulator with a cable tie either side of it to hold the insulator in place while the antenna is being erected. The dog bones are attached to a short length of Kevlar line with a snap link at the far end.

   

The push up mast I use was supplied without any provision for guying so again I made some guying rings out of TUFNOL. These are used with Kevlar guys and one up the whole thing is very stable and has stood up to some high winds with no problem.

This is the antenna erected and you can clearly see the upper cross arm. The lower one isn't as visible but it's the same idea. This arrangement works much better than I imagined - it keeps the wire in tension in all dimensions and can be put up by one person easily. It also packs up into a convenient size as the cross arms are each 3 sections of 1 metre long.

The sections for the cross arms came from a company called spiderbeam http://www.spiderbeam.net and I can recommend their stuff (no association).

The antenna worked exceptionally well adjacent to the ocean and as a result we managed over 4500 QSO's in 6 days with Japan and Asia contacts coming very easily with our 100W.

If anyone would like more information I can be contacted via details on qrz.com.

Thanks to all again,

Paul M1PAF

 

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