Best DIY antenna design for increasing the range of a 2.4 GHz router

Question

I am new to antenna design and this field in general. I am looking to design a WiFi antenna (less than 15 cm x 15 cm) that can effectively increase the range of a 2.4 GHz WiFi router.

It should be extremely directional as I am only trying to increase the range in one direction (this is for a project, not for any practical use).

So far from my research, the most attractive option is a Yagi-Uda antenna, as it is relatively small and not too complicated, and it also has a high directivity. However, my first build was relatively unsuccessful. I used the design from a YouTube video.

The antenna looks like this. It is a disk Yagi and the results in the video were extremely promising.

However, my application of it is slightly different, and I was also not able to build it the exact same way, as the dimensions were not clear. It called for use of copper, and I bought copper colored aluminum, which in hindsight was a mistake, but I did not know how much it would affect the performance. It seemed to make soldering more difficult, but I can't tell if it affected the actual range.

Additionally, the disks I cut were by no means perfect and had imperfections. In order to attach the antenna to my router, I cut and soldered on an SMA male cable and connected it to the RP-SMA female under the unscrewed built in antenna on the router (with a few adaptors of course).

The antenna performed sub-optimally, only really increasing the range by around 4 meters (measured using continuous recording of the RSI value). Additionally, I very quickly put together a parabolic antenna out of tinfoil molded into a cup shape, and I just touched the bare wire on the SMA Male in order to connect it, and to my surprise this performed better than the Yagi, going up to about 6 meters away.

My question is, what is the best antenna to do this, and if it is one of the ones that I chose, what modifications should I make in order to improve it?

Additionally, any resources on proper dimensioning for the Yagi antenna (boom length, director spacing, etc.) would be greatly appreciated.

Answer 1

The best DIY antenna design is one that uses materials you can obtain, and can be assembled with your level of skill -- not necessarily the design with the most exciting YouTube video.

A more basic Yagi with straight wire elements and a non conductive boom may be better for you. The spacing of the elements, their length, and even their diameter are all critical to make a long multi-element Yagi work at the design frequency.

Searching the web, you'll find easier-to-construct designs where the boom is wood and the elements are cut from 14 gauge wire (easily pulled from cable designed for house wiring). You could also use a small diameter rigid plastic tubing for the boom. But the wire element spacings and lengths are critical, so be precise as you work.

If the boom in this design is too long, you can use an online calculator like the one here to do a custom design for any boom length. You can get a 7-element Yagi within a 15 cm boom length. Read the texts and you'll learn even more while you're building it.