Build A Wi-Fi Cantenna

By Dhruv Mohindra | Published 01 Jun 2007 14:33 IST
Build A Wi-Fi Cantenna
Build A Wi-Fi Cantenna
Boost your WiFi network using, strangely enough, a can!

Often believed to mean "Wireless Fidelity," where the word "Wi-Fi" comes from remains a mystery. Still, most people agree it's much better than using the name "IEEE 802.11b Direct Sequence."

The "Can"tenna
A cantenna is a home-made antenna built from commonly found, empty tin cans. Why would your network need a cantenna, rather than an (inbuilt) antenna? Consider:
  • They increase the range to a greater extent
  • Provide high gain comparable to those of commercial antennas
  • Can help spot Wi-Fi hotspots as you travel
  • Commercial antennas are expensive

In other words, if you wish to have a wire-free network across distances of several metres, a cantenna is indispensable. It allows direct communication, at the same time maintaining good speed. In fact, you can enjoy a game of Counter Strike over the network across several buildings. Apart from these, it will aid in your being interpreted as the geek, at least in your group of friends! 

What you need is what you get!
Building the cantenna is easy, provided you get the right material. Here, we will be putting together the classic Pringles cantenna. If you've ever enjoyed Pringles potato chips and have experienced the immense misery that accompanies seeing the empty can's metallic bottom, don't get upset. In fact, the chips should be consumed as quickly as possible so that the cantenna can be built right away! Likewise, you may need to visit a radio shack for some special goods and the number of trips are proportional to how carefully you read the next few lines.

The N-type female connector

The N-type connector from the back

RP-SMA male connector components

Visit your favourite supermarket and purchase a can of Pringles. The four items that follow can easily be found at a radio and electronics shop, while the next few can be obtained from a hardware store.

You will also need
  •  A wire cutter
  •  Something to drill a hole or two
  •  Soldering skills

Building It

This procedure shall not take more than half an hour if you've already gathered the tools.

Step 1 Let's start with the can itself. The precondition is that you have consumed all the contents and properly rinsed the can.

Hole in one!

If you're using the Pringles can, measure 3 3/8 inches from the bottom. Drill a hole such that the N type female connector can easily slide in. Now put away the can for a while.

The next step is to prepare the cable. This special cable is called a pigtail. Ready-made pigtails can be expensive, so we'll construct our own. The RG cable that you acquired earlier has two ends (naturally)-one of them should be soldered to the N type female connector.

A pigtail from scratch

The inner conductor of the coaxial cable will go into the respective protruding metal of the connector while the shield should be soldered to its body. Similarly, solder the other end and then crimp it to the SMA male connector. For the same, first solder the small male pin to the inner conductor of the cable and then insert this into the minute hole though the connector. The pigtail is now ready.

3  Take a piece of Gauge 12 copper wire. Solder it to the top of the N type connector.

The soldered copper wire

Step 4   Now mount the assembly on the can. Let the SMA connector end pass through the hole first. The N type will form a lock and will appear as shown.

The top view

Step 5  Mark a point on the copper wire such that the arrangement extends approximately to the centre of the can's diameter. Gently pull out the cable and chop off the extra wire above this point.

Step 6  Put back the cable, and if required, use a few nuts and bolts to secure the assembly. This completes the construction of the reflector.

Step 7  For the collector bit, attach a nut at one end of the metal rod. Now hold it such that the nut points towards the ground.

Step 8  Add the lid and slide it to the bottom such that it hugs the nut. Next, place three washers one after the other such that the last one reaches the mid-point of the rod. If the washers don't fit the rod perfectly, try using some household aluminium foil. If there is a large diameter difference, don't lament-get four pieces of a pipe with a larger diameter than the inner rod and washers. Begin by inserting a washer, then a pipe, then a washer, and so on. The pipe would hold all the washers in place since its diameter is greater.

Taming the collector 

The final collector

Coming back, insert a roundish insulating material (plastic will do) and let two more washers occupy their respective places on the rod.

The collector can now be mounted. Put the lid back in place with the rod hanging inside the Pringles container. Make sure the rod doesn't touch the copper filament that was previously soldered to the N-type connector.  

Step 10  It's time to test your hack now! Go find a wireless card and a wire-free network or two.

Putting It All Together
If you have a desktop computer with a PCI or USB WLAN card, you're probably already testing your newfound passion! Unfortunately, if you are the lucky owner of a laptop with an inbuilt Wi-Fi system, life isn't that easy. You will have to open a small cover, generally found on the lower surface of the laptop. This will expose a couple of cables running up to the inbuilt antenna. Think twice before pulling them out and inserting your own-make sure you don't end up voiding your warranty in the process. However, if you know what you are doing and do it correctly, there should not be any problems.

Testing Times
Yagi antennas (like the one you just made) are highly directional, and this signifies greater range (remember the highly directional laser light?). Also, noise is kept down for neighbours who share the same channel as you.

To establish a connection with someone, start by aiming slightly towards the left or right of their receiver, and slowly rotate the assembly to find the best gain possible. Elevating the antenna can sometimes help.

If the antenna is to be placed amidst open surroundings, some weatherising needs doing-paint the external surface to ward off rust, or enclose the whole assembly in a PVC pipe.

Wrapping It Up
We have discussed the basic antenna, and it is from here that the true hacks emerge. You have learnt how to construct a relatively tough-to-build antenna, and a tin-can setup should follow similar but easier steps. So put your creative shoes on-and don't forget to aim at the right building!

Dhruv Mohindra
Dhruv Mohindra

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