10 m (28 MHz) Moxon Antenna

BACKGROUND: 

A little bit of gain can make a big difference in an HF radio antenna, and one of the simplest and smallest gain antennas is the Moxon Beam.   Now you can easily build yourself a portable one for the 10 m band with some 3d printed parts and poles from Aliexpress. 

The resulting antenna weighs just 3 lbs including the mast, and packs down to a small 22" x 4" bundle - small enough to toss in a carry-on bag for a flight, even. 

So, print up the parts and follow the instructions below to build and tune your new 10 m Moxon.

Want to see it in action? Check this out: 

BILL OF MATERIALS:

Some links are Amazon affiliate links which gives me a small kick-back when you order through them, but costs you nothing more. 

TOOLS:

• 3d Printer capable of printing PETG
• Soldering iron https://www.digikey.com/en/products/detail/american-hakko-products-inc/FX888DX-010BY/24390014 Hakko is my preferred option. High quality, simple, and reliable. 
• Heat Gun.
• Razor Blade.
• Wire cutters.

ASSEMBLY: 

1.) Print all the things.

I've included the GCode I use on a Prusa i3 Mk ii if you want to just download and hit “print.”

The pole tips should be printed with supports between the two “hooks” that create the loop.  Use a razor blade or tweezers to carefully cut those away. 

2.) Prep the spreaders.

Unscrew the base cap and trash the two thinnest sections.  You should end up with 7 sections and an extended pole that's just under 7 ft long. 

Epoxy the pole tips onto the ends of the poles. 

To prevent loss of the pole caps, I drill a small hole in the caps, tie a piece of cord to them, and secure them to the pole with heat shrink so they're permanently tethered. 

3.) Prep the Mast.

Slip the guy ring onto the mast.  Attach the hub to the mast with the 8mm bolt. 

CAUTION: The threaded sections of the mast can be hard to loosen up if you tighten them too much.  Be gentle with the section threads. 

Do not attach wire to the ground (center) lug. 

4.) Prep the Feed Line.

Cut the BNC connector off of one end of the coax cable. 

Wrap 6 or so turns of RG316 through the toroid.  Use heat shrink, tape, or a zip tie to secure the coax onto the toroid. 

Solder a female banana plug to the center conductor and shield of the coax.  Secure the banana plugs with tape or heat shrink to prevent failure. 

(Shown with RG-174 instead of RG-316)

5.) Prep the radiating wire.

The dimensions below show my final radiator dimensions.  Consider starting with wires cut slightly longer.  It's easier to remove wire than to add wire. 

Cut a two pieces of wire just over 94" long each.  Solder a male banana plug to one end of each wire. 

Measure 72" from the banana plug and mark where you will attach a small loop of cord for the corner of the antenna, and attach point to the spreader bar.  

At the corner, tie on some cord to create a 1" loop.  If you are not able to tie it secure enough to prevent movement, use super glue and/or heat shrink to hold it in place. 

At the end of the 94" wire without the banana plug, tie on a piece of cord.  The nail knot https://castandspear.com/nail-knot/ is very useful for this purpose.  Use that cord to make an 8" gap with the other end of the cord tied to a wire cut to just over 202" long.

29.5" from the end of the wire, tie in another 1" loop of cord for the corner. 

29.5" from the opposite end of the 202" wire, tie another 1" loop of cord for the 3rd corner. 

Attach a piece of cord to the end of the wire, use the cord to create an 8" gap, and tie the second 94" long wire to the end of that cord. 

You should end up with a piece of wire like that shown in the image above with small loops of cord secured at the corners. 

Wind it all up on a K6ARK antenna winder. https://www.printables.com/model/383037-k6ark-wire-antenna-winder-ul-wireframe-model

6.) Assemble the antenna. 

Extend the lowest 3 sections of the mast and guy it out.  Unscrew all of the pole section ends BEFORE inserting the spreaders into the hub. 

Not sure how?  Try these vidoes:

Extend the spreaders and insert them into the 3d printed hub. 

Unwind your coax. 

Insert the male banana plug at the end of the wire into one of the female banana plugs on the end of the coax. Unwind the wire from winder and connect the corner loop to one of the spreader poles.  Continue unwinding and connect the next corner loop to the next pole, and the next corner loop to the next pole, and the last corner loop to the last pole. 

Take the banana plug on the end of the wire and pull it taut to the feed point, bending all of the spreader poles upward, and plug it in to the female banana plug at the feed point. 

Use a velcro strap to secure the coax to the top of the pole so the full weight of the coax does not pull down on the antenna feed point. 

Trim wires or make adjustments to do some final tuning, and you're ready to operate!

Have fun, and please post your best contacts with this antenna in some build comments. 

Thanks, and 73.