How to make a home-made wi-fi cantenna

I was intrigued by the fact that some people had managed to extend the range of their wireless networks by building their own wireless antennas, called cantennas because they are generally made from cans. So, I decided to try and make my own. And, of course, I attempted to make it using only regular things and the cheapest components.


In this article I’m going to attempt to document the creation of my cantenna so other people out there can try and make their own. Hopefully this will be a simple, easy-to-follow guide and I’m going to try and make the science (not much) of it as simple as possible. The intention for me was probably a bit ambitious, but what I want to do is use my cantenna to extend the reach of my wi-fi lan to reach from my house to the beach, so I could some work in the sunshine.
Well, you might be wondering what you need to make such a thing.
Here are the ingredients I used:
1. One cardboard tube. I found one at work that was sent to a picture desk containing photos. This seemed ideal. It had a useful diameter and was quite long.
2. Some ordinary kitchen-type tin foil, long enough to cover the inside of the cardboard tube.
3. One N-type square chassis socket (Maplin: FJ80, £1.694 exl.).
4. N Male to BNC Adaptor (Maplin: FJ82, £2.545 exl.).
5. BNC plug 50 ohm (Maplin: FHH17, £1.694 exl.).
6. 50 ohm cable (Maplin: XS51, £0.417/m exl.).
4. One piece of stiff copper wire, or just a copper paper clip.
5. A stanley knife.
6. A sturdy sewing needle and a length of thread.
Image showing cut down the side of the tube

Image 1
First off I sliced the tube straight down the side so that I could pry it open (as seen in image 1).
Then I covered the inside with glue, using glue stick, while keeping the tube open by wedging my screwdriver inside. I then carefully covered the inside with tinfoil. Shiny side inwards. Be sure to make the foil as smooth as possible as creases and bumps may interfere with the reflection of the waves. I used a pringles tin to slide into the tube to try to flatten the foil as much as possible (as seen in image 2).
Image showing pringles tin to smooth the tin foil

Image 2
Then I had a look at Flakey.info’s Circular Waveguide Antenna to get the measurements I needed for where to place the transmitter in the tube. There’s a very good JavaScript calculator on this page that is based on the waveguide theory.
To make the transmitter piece of the cantenna, what is needed is to solder the paper clip to the N-type connector. The paper clip might need some bending depending on the height calculated by the calculator. I just doubled the paper clip over to get the right height (as seen in image 3).
Image showing doubled over paper clip soldered to N-type connector

Image 3
I marked off the spot and then used the stanley knife to cut a square hole slightly smaller than the diameter of the N-type connector. I made it smaller so that the connector will need some squeezing in and won’t slip out easily. It seemed too difficult to try and find some small screws to fasten the connector, so all I did was a bit of needlework. I sewed the connector to the tube using just an ordinary sewing needle and some thread. Try to make sure that the connector makes as much contact with the tin foil as possible.
Now, all that’s left to do to the tube place a foil covered cap on the one end and tape it up. I made sure that some excess foil was sticking out of the slit and then taped it up tightly so that the seam was joined as well as possible (as seen in image 4).
Image showing excess foil and tube ready to be taped up

Image 4
Now, for the cable. Connect the BNC plug to the end of the cable. Try follow instructions if they’re supplied, or just connect it as it seems it should be done. It might be a good idea to solder the wired onto the connector. Then just screw the BNC to N-type connector to the N-type connector on the tube and the slot it into the BNC connector on the end of the cable (as seen in image 5).
Image showing cable connected to cantenna

Image 5
The connector on the other end of the cable depends on the type of connection on your router/acces point. I have a Netger DG824M and it uses a very-hard-to-find “Reverse Female SMA Connector”.
And once that’s done you have a created your very own cantenna!
I have not done very thorough testing with the cantenna, but just tested it in my street and got at least 100m till the signal started dropping. So I was quite impressed. (see images 6 & 7).

Image showing cantenna balanced on rubbish bin pointing down the street Image showing Gary walking down the street with the laptop testing the connection
Image 6 showing cantenna balanced on rubbish bin pointing down the street Image 7 showing Gary walking down the street with the laptop testing the connection
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