Just what is a cantenna? Though the name is not original, the common use is a functional merger of can and antenna. A Yagi-type directional waveguide antenna, it is used to increase the range of wireless networks.
A number of years ago, a guy named Andrew Clap from Portland, OR was looking at a Seattle website (http://www.seattlewireless.net/DirectionalYagi) and wanted to make his own using whatever parts he could afford. That was the birth of the Pringles Can antenna. The main disadvantage of the Pringles can however is the cardboard design. The cardboard just does not last very long and is not very tolerant of our North West weather.
So what is a good cantenna made from? A can needs to be a good conductor and hold up to the elements. The diameter of the can is important as well. There is a calculator on some of the website links that are mentioned at the end of this blog, but for a 2.4GHz wireless network, the diameter should be between 70mm and 100mm. Though not set in stone, that is what works best before performance drops significantly.
How is a cantenna made? Here’s what I did, and what was used:
Materials
- 85.5mm coffee cans X2
- N Female connector with a radiator (www.jefatach.com/product/cnfbst)
- Foil tape
- Dremmel tool with metal cutting disc and boring bit
- Whatever you want to use to “decorate” the cantenna
How it was assembled:
I have to admit, I first sent my husband out to get two coffee cans. I gave him the specific dimensions and the brand that I wanted (they make different sizes, and I wanted the right size) and he set off in the middle of the night to grab my coffee cans. The next morning, I opened the cans, poured out the coffee (which I donated to my mother, as I make lousy coffee), and got to work on slicing and dicing.
I had to slice off both ends of one can, and the flanged area of the other, as it sloped inward and I wanted the sides to be same. I then made slits in one can and fit it over the other, using foil tape to secure them together. Using the calculator on the Jefa Tech website, I measured the 1/4 Guide Wavelength from the closed end of the can and drilled a hole just wide enough to house the radiator assembly. Since the edge of the can was very sharp after slicing the end off, I used a thin strip of foil tape to cover the edge, as I’ve been known to be sliced and diced myself at times.
That done, next came the fun part. 
I started with a base coat of black Rust Oleum spray paint. It was tricky since it was sooooo hot when this was all done. The paint dried almost too quickly, but it worked. I knew from the start what I wanted to put on my cantenna. The hard part was figuring out how to do it. I’d done screening in High School, but that was a long time ago and I’ve gotten a bit rusty with an exacto knife. I opened a picture I had of Tux, the Linux mascot, in GIMP photo editor. In there I filtered the picture to black and white, then outlined it. I printed out multiple copies and cut out each copy according to the color being applied. Gold for the feet and beak, silver where the black would usually be, and black where it would usually be white. It took two coats of each application.
I wanted a brushed metal look to the can, so I outlined the black area of Tux with a Sharpie, and using Q-tips dipped in spray paint of silver and gold, I “brushed” the cans. After it all dried, the radiator was added for the final piece.
The final signal strength as tested Friday June 5th was -80 dB. Not too bad from what I’ve seen so far. I had wanted to add the funnel to it, but didn’t have the time. I might just add it anyway and test it over the summer.
Now then, the links! I found many good websites about cantennas but one stood out for me in terms how well documented their testing was. http://flakey.info/antenna/waveguide Don’t let the name bother you, they are only as flakey as the rest of us!
Some other good links are:
http://www.youtube.com/watch?v=KN_1oe3z7EQ
http://www.turnpoint.net/wireless/cantennahowto.html
http://support.jefatech.com/cantenna
Some final thoughts for this project:
I can hardly wait to try “Tux” out wardriving this summer. I’ve long sniffed networks, but have not used an antenna to do so. The places we usually go are the more out-of-the way places such as the Oregon Coast. We’ve mapped quite a few networks down there that are open (public access, though a few are private – we don’t use those). My daughter wants to build one this summer, so it looks like we’ll have a whole family of penguins to test. On one of the websites I went to, they used a J&B whiskey container for their cantenna and they got excellent results. So I have a feeling all this summer I am now going to be looking for the “perfect” can! Can’s will never look the same to me again.
