Moxon Antenna. RCHacker #49

DIY build and simulation of the Moxon antenna with 4nec2 software. Not a bad choice for long range FPV work on 433Mhz. Also it is simple and cheap to build.

Moxon design software.

Simulation software.

Interesting articles by VE2AZX

My designs files on github.

[Blaze]

Kind of like a yagi ? No the Moxon is a Yagi ! To be more precise a Moxon is a 2 element yagi that uses capacitive end coupling instead of lossy inductors as a means of reducing its size while maintaining an acceptable input impedance.

By using capacitive end loading the moxon achieves a much greater radiation efficiency as compared to other designs which use lossy matching networks and inductors to reduce the size of the antenna. The bottom line is the moxon is a very highly efficient short boom 2 element reduced size yagi.

If you're a ham this is important because a mono band Moxon yagi will easily outperform a trapped triband yagi at a fraction of the cost and weight.   

By the way nice work on that little moxon. 

[izzzzzz]

you can tune the driven and the reflector by hanging a wire from one of the corners on each element, then trim the wire to tune. Use field strength meters or VNA to fine tune.

[Rchacker]

Cheers. My obsession with RF is putting other projects on hold, but once done I will have all the range I will ever need.

[iamhak]

Built the Moxon and turnstyle tonight. Much better. getting about 850m on the ground so far. Will put it in the quad and do some range checks.
Thanks again :)

[Cyberdactyl]

Awesome Mark. Found this over at Flitetest. I always look forward to your videos.

[Quadromax]

Great vid Mark! Built this antenna and used it on my 9XR TX (Orange LRS tx) and turnstyle on my wing (Orange LRS RX). Noticed that separation between reflector and tx really makes sense. Got 1.5 miles and over 50% RSSI left;-)

[Rchacker]

I know it is not statistically significant but I have now had two FRSky D8RII+ receivers fail in exactly the same way. (drastically reduced range). So I am now moving to openLRS. There is a learning curve, but worth it for more features, better range. I get a lot of help requests with what sounds like bad units from HK, So I would get them from DTFUHF.

Stick your crosshair out the back of your quad on a bbq skewer.

[Rchacker]

It is all to do with the wire lengths, the generator programs calculates everything for 50 ohms, so if you are good with your measurements you are probably alright.
IBCrazy did a tutorial on rcgroups for making your own SWR meter, but measuring the impedance directly requires more specialised equipment.

[iamhak]

I have been having terrible range issues with Orange LRS. Have tried the v and sander styles. Looking forward to building this to see if it fixes the issue,
Thanks so much for all your tutorials :) They are appreciated.

[DIRTYDOO]

I made a moxon for 435 mhz for the orange tx and i love it in combo whit a turnstyle on de plane very stable connection thanx for the tips cudent have done it whit out you vid

[wattage]

I can absolutely confirm this antenna is a monster for long range. Previously with my Nagoya N77 at 3.5 miles I was getting RSSI readings of 60-70%. With the Moxon I threw together last night, at 5.3 miles I was still getting solid, unwavering 100%. My only reason for turning around was concern for my battery.

I had it angled on its side for vertical polarisation and the RX antenna was a home made dipole.

Thanks so much for this video, the Moxon is an incredible antenna!

[Rchacker]

That is really good to know. Of course I still need to test it but it looks like I have more range than I will ever need.
Now to work on the video system.

[Rchacker]

Not something I have taken into account and really hard for me to test, perhaps I can try cutting some of the foam away at a later date. The wire I am using has enamel coating but I like that as it protects the rf front end from static. Relative to air enamel has a dielectric constant of 5.1 but it is a very thin coating. Silicone RTV 3.6, Poylstyrene 2.5 (this might be the value for solid, the polystyrene I am using is mostly air).
Surprisingly balsa has one of the lowest values at 1.4.

[Rchacker]

I use the spreadsheet based editor. Not the easiest but the most powerful as you can incorporate equations into your design.

[Rchacker]

Have not tested in practice yet but it should be much better.

[Rchacker]

If you had 3 of them with a diversity setup it would work great, but only 2 antenna diversity systems are available at the moment.
OpenLRSng however may be heading in that direction.
Until then you are better off with an omni directional antenna like the turnstile or vee on the receiver.

[nellodude]

Great way of tuning an antenna. Thanks for sharing it with us.
How do you make sure the feed point is 50 ohms?

[thijss]

Thanks for this video! I will try to design some custom antenna's for my rc link (2.4Ghz FrSky) and i will definitely take a look at your experimental designs.

As an electronics guy rf is like black magic to me and i would like to learn more about it, antenna design will definitely help me explore that world.

[Rchacker]

It is best to power off any other modules and remove close antennas.

[Rchacker]

Not sure about the sander style they are just a monopole. They seem to work best as a pair on a diversity receiver which makes it more like a vee. Using just one is a mistake.

The units do perform, but run a bad antenna or none at all they could get damaged.