Summer Fun – A Moxon Antenna for 6 metres

Six Meters is a great Amateur Radio band, and there are quite a few active operators,  but just about everyone I’ve talked to recently says something along the lines of “ Six Meters sounds great I’d love to be on it”,  or “I’d love to get on Six Meters but I don’t have an antenna” It seems it’s seen as more of a “summer only”  band in times of slow solar activity. Indeed, ‘ol Sol isn’t going to let you talk to England via the F2 layer with the current number of sunspots.

Even without big sunspot numbers,  Six meters is a lot of fun via Summer Sporadic “E” layer propagation. VK wide and VK-ZL paths are often a daily occurrence, and VK-Pacific regions, VK-Hawaii, VK-West Coast NA/SA are all a possibility. 

The fact that just about all modern Transceivers now include Six Meters as standard, and the demise of channel 0 and the accompanying TVI issues that went along with that, ( thanks digital TV!) means that “6” is now more useable than ever. 

Another plus with 6 metres is that getting a decent antenna up for the band isn’t difficult. For Sporadic E contacts, although a simple vertical or even a dipole will get you on the band, having a bit of gain and direction will often turn what would be a marginal contact on a vertical into a solid contact. This gain and direction is even more important when using weak signal modes like WSPR, FT8 and JT.

i have been on 6 metres off and on over the years with various antenna I’ve put together, from verticals to beams. This year I decided to put up something better than the 40M dipole tuned up on 6.

I’ve  always been aware of the Moxon antenna . I have often contemplated constructing one to use portable for the 20 metre band vertically polarised near salt water. It’s smaller size, small footprint 2 element design seemed ideal to sit on top of one my push-up masts at home.

One of the good things about building a Moxon is that at 50 MHz, it’s not a very big antenna at all and, is easily managed by one person. Lightweight construction methods and wire elements will work a treat.

Fortunately, there is a good deal of info on the internet about the antenna. There was a very good page called “ The Moxon Antenna Project” , but unfortunately it appears to be down at the moment. There was good information, and many build examples on that page, I hope it gets put back up soon. If working with aluminium tubing is your thing,  then DK7ZB has a dedicated section for the Moxon on his website.

Step one is to find a Moxon program, either a stand alone downloadable app or one of several online calculators…I went with this one

 

It really is as simple as putting in the frequency you want to build the antenna for, and letting the program do the work. you’ll be presented with a nice table with all the dimensions. Stick to them to the millimetre if you can, and I”ll bet you’ll be rewarded with a working antenna first pop. Pay special attention to the gap between the two sets of folded elements (measurement “C” in the table above), this dimension is critical to the correct operation of this antenna.

Ok, so on paper, we have all the information on the dimensions of the antenna, now we have to translate those lengths into an actual antenna. I found the best place to start was just googling “Moxon Antenna” and looking at a lot of the images and videos available on line. Everything you thought of (or didn’t), will come up and you’ll soon be inspired. Aluminium, wire, wood, steel, nylon, plastic, fiberglass and PVC are just some of the materials people have used in the construction of this antenna.

 

I decided to go with a Nylon chopping board from BigW for the baseplate. This is only going to be in the air for the summer, so longevity isn’t a priority. I used smaller short squidpole tubing from Haverfords as my spreaders. The spreaders had a 150mm length of wooden dowel inserted for strength, and were clamped to the chopping board with conduit clamps from the local plumbing supply house. The right angle bracket is a pergola fixing from Bunnings, drilled to accomodate the U bolts I used to suit my mounting mast. Simple!

 

I mounted a BNC socket through the chopping board and bought out the cable and sealed it with liquid electrical tape. I put a balun at this point also (yeah you should use one). I used an FT140-43 Toroid and wrapped 8 turns through it. I ended up hot gluing the balun assy to the nylon surface, seemed to be quite sturdy.

At this stage, I temporarily mounted the antenna after fitting the wire elements. Click on the pictures to enlarge them, you’ll see the pink brickies cord I used as element spacers. the second picture shows the short piece of 16mm PVC water pipe I used to guide the coax to the feed point. I used a two terminal piece of chocolate block electrical connector, hidden inside the far end of the pvc pipe to transition the coax to the elements feed point. I sealed up the ends with bluetack to keep any water or creepy crawlies out. Unfortunately I forgot to get a photo of this arrangement.

The wires were stretched out and attached with cable ties slipped over the end of the squid pole spreaders and secured with PVC electrical tape.

I used a super strong PVC jacketed, 7 strand copper clad steel, kevlar reinforced antenna wire that I had left over spare from a previous project, but you could use just about anything that can take a bit of tension. 1mm enamelled copper wire for the elements would work well and would be more than strong enough. Just tension everything so that its sits nice and taut across the spreaders.

The Moxon calculator must have got it right the first time, as I couldn’t measure any VSWR on my FT-817 at the design frequency of 50.110 Mhz . The antenna seemed to be working, a quick test with some local operators, Adrian VK5AW,  Rob VK5TRM, and Mal VK5MJ showed it was both getting out and had directivity. Conveniently, I was able to hear a couple of Six metre beacons from QLD as well. Turning the antenna to test the front to back ratio demonstrated a deep null in the pattern with the antenna driven element 180 degrees to the source, exactly as expected.

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I decided to mount the antenna above my 8 ele 2/70 Quad, so it is about 13 metres above ground level. I’s rotated with an armstrong rotator, the mast for both antenna is strapped to the palm tree!

The antenna seems to be performing well, It’s only been up for around 10 days and I’ve already had several solid SSB and FT8 Sporadic E contacts so far this summer, exactly the reason I built it in the first place. I leave it on the 6M WSPR frequency all day and have spotted stations as far out as 3D2 Fiji and FK1 Vanuatu. So it hears great as well. It’s also small and light enough to pack it in the car and see if you can get some contacts from a park or summit on Six too.

So if you’re sick of hearing about Six metres and wish you could get on the band, then this simple antenna should be on your to-do list this weekend!

See you on Six

73

Andy, VK5LA

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One thought on “Summer Fun – A Moxon Antenna for 6 metres

  1. Hi Andy, I built a 6 m moxon sometime back, I used 10mm fiberglass rod ( electric fence spacers) & the spacer insulators & retainers for the wire elements were from Sotabeams. I have used it a number of times portable & it performs well! If interested I can post some photos after Christmas. At home I use a homebrew 3 element yagi up about 10 m. Les, VK5KLV.

    Liked by 1 person

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