If you want Wi-Fi by the campfire or down at the dock this weekend, you can make a cantenna for as low as $23 (it will be more if you need some of the tools or common supplies). You can either connect the canntena to your computer or your router. Either method will allow you to connect to your network from a long distance. I used my cantenna last weekend to pick up my network (over 700 meters away) while sitting in a boat in the middle of the lake.
The FCC controls the radio frequencies of the electromagnetic spectrum, so if you point the cantenna in the wrong direction, you might be disrupting all kinds of signals. Avoid using it by airports or any other places heavy on radio frequencies. I think it is illegal in some places and I have heard of people getting arrested for using one.
Cantennas are a unidirectional (line-of-sight) antennas, meaning the signal only exists in the direction the cantenna is pointed. This is different than antennas you might see on a wireless router, which create a sort of “bubble” of Wi-Fi in all directions. Since the signal is more concentrated with a cantenna, it can travel farther. So if you are in a wide open area, you could be affecting something far away and not even know it.
You might already have a bunch of these items on hand, which will help lower the cost. The three components you are not likely to have are the N-connector, the pigtail cable, and the USB adapter (in bold). That is where the $23 comes from. You may need to spend more if you don’t have some of the other stuff listed below.
- A computer
- A clean, empty tin can with a reflective interior (I used this one, but you can also try this one. It seems that cans that contain about 46 fluid ounces is about the right size for this project)
- USB network adapter with removable antenna or a wireless router with removable antennas
- Female, chassis-mount N-connector ($7)
- A “pigtail”: N-male to RP-SMA-male cable (for most USB dongles) ($6) or a RP-TNC-to-N-male cable (for routers) ($10)
- 12-gauge copper (you can also use any scrap wiring you might have as long as it is about 2mm thick and fits into the N-connector)
- Any USB network adapter ($10) with a removable antenna or a router with a removable antenna
- Soldering iron with a thin tip (a large tip creates too much heat and can melt the connector)
- Solder (or a kit with both)
- Flux (optional, but makes it a bit easier to solder, especially if this is your first time)
- Digital calipers (not required, but helps for more precision)
- Dremel rotary tool with a cutting bit and a grinding bit
- Can opener
- Tape measure
Begin Constructing The Cantenna
Cut The Copper Element To Size
Using the digital calipers, cut a piece of 12-gauge copper that is about 31mm long. This is a critical component as it receives the wireless signal and sends it to the cable that will be connected to your computer (or router).
Prepare The Can
Remove one of the lids using the can opener and then rinse out the can.
Measure And Mark The Cut Lines
Next, you need to determine where the copper element needs to be placed on your can. If you used the same can that I did, you can just follow the instructions below.
If you used a different can, you will probably want to read this article and find your own measurements. You will need to calculate the wavelength of the frequency you will be using (this tutorial is for 2.4GHz). The image below can be used as a general guideline.
Use the sharpie to make a dot about 63.5cm (2.5in) from the bottom of the can (the end that still has a lid).
Then, center the dot by placing the N-connector over it and tracing around the connector so you know where to cut the hole. Also mark where the screws will go to make sure you don’t cut the hole too big.
Cut The Hole
Use the rotary tool to cut a hole and grind down the edges. You can cut the hole using other tools, but just don’t cut yourself. You will also have to try and avoid creating a bunch of jagged edges. In addition to being sharp, if there are fragments hanging down into the can, it can affect the signal quality.
Attach The N-Connector
This is the tricky part, especially if you have never soldered before. Put the copper element into the hole in the N-connector and solder it in. I would recommend using a soldering iron with the thinnest tip you can find. Also, if too much heat is generated, you can melt the plastic housing, effectively ruining the connector.
Put Everything Together
Now that everything is built, all you need to do is connect everything and plug it in.