Yagi WiFi Antenna for 2.4GHz band

I wanted a traditional yagi (or Yagi-Uda) antenna for my wifi, so I designed this.

I think 5 elements is the sweet spot for Yagis. You should get around 10 dB of gain (or directivity as I prefer to call it) and still have a nice compact antenna that's easy to build. You can buy (or build) larger Yagis but the extra performance is often marginal and they're harder to align.

The antenna measurements were designed using the calculator at 3g-aerial.biz.

Any wire around 1 to 2mm should work fine for the elements. I used some stripped out mains cable (twin+earth) which has a conductor diameter of 1.8mm. The channels for the dipole are just over 2mm, the other holes are 1.8mm. If your wire is a bit smaller then you can use some glue to secure them. Alternatively you can ease out the holes with a drill bit if your wire is a bit bigger.

Assembly
You'll need some coaxial cable with a suitable plug. I used RG316 coax - buy some coax with the SMA connectors already attached. SMA connectors come in two types:

• regular SMA connectors with the pin in the plug and the hole in the socket
• Reverse Polarity (or RP) SMA connectors, which have the pin and hole reversed.

RP is the more common type for wifi - check the device you're connecting to in order to determine what you need.

Element lengths:
Reflector element: 59.5mm
Dipole (the one connected to the coax - see notes below): 56.5mm (total length tip to tip once installed)
Director 1 (next to dipole): 52.7mm
Director 2: 51.9mm
Director 3: 51.2mm

You need to cut the elements fairly accurately (within 1mm if you can). I designed a jig for accurately cutting wire which you can find here - https://www.thingiverse.com/thing:6826737 but a ruler will be fine.

The dipole is made in two halves. Cut them slightly long and trim them to length when they're soldered and fitted in the antenna body.

Solder the coax to the dipole elements: one half to the outer braid, and one half to the inner conductor. Try to solder the coax to the ends or the top of the dipole elements (see picture) it will make it easier to fit them in the antenna body. Remember to feed the coax through the hole in the antenna body before soldering!!

The coax braid is very fine - be careful about stray strands causing a short. Use a continuity tester to make sure there's no connection between the two halves of the dipole.

The dipole elements and coax are a tight fit in the antenna body - I made the hole slightly bigger in the uploaded model. You may need a spot of glue to hold it in place.

The other elements can either be held by friction or a spot of glue depending on what size you're using.

I've designed some basic mounting hardware which is simple but functional. I used the end mount and wall mount, which I screwed to the internal wall of an outbuilding. I haven't printed the bottom mount - it's intended to be glued to the bottom of the antenna and fixed to a pole or other stand.

The end of the antenna is tapered to a square so it can fit either way (vertically or horizontally polarised) in the end mount.

Performance
I used the antenna with an ESP32 board to collect data in an outbuilding. The walls and the position of the access point make wifi a challenge. The yagi in the picture performed very well - much better than a basic rubber duck which couldn't make a reliable connection.

Alignment: I found the antenna worked best when it was pointed slightly off axis (maybe 30 or 40 degrees) ie not directly at the access point. It may be that wall reflections come in to play at the microwave frequencies. Be prepared to experiment.