How to Build a Tin Can WiFi Antenna (cantenna)

Here are some ways on how to build your own tin can WIFI antenna. I got this article from this site http://www.turnpoint.net/wireless/cantennahowto.html. And I would like to thanks the owner of the site and the writer of this article for sharing his ideas in building a tin can wifi antenna. Hope you enjoy building your own CANTENNA.... Good Luck!

How to build a tin can wifi antenna (for 802.11 b/g wlan or other 2.4GHz applications):

Steps:

1. Collect the parts
2. Drill or punch holes in your can to mount the probe
3. Assemble the probe and mount in can

Collect the parts:

1. N-Female chassis mount connector
2. Four small nuts and bolts
3. Thick wire
4. Can

 

Connector

A N type Female Chassis-mount connector. One side is N-female for connecting the cable from your wireless equipment, and the other side has a small brass stub for soldering on wire.

Nuts & Bolts

You'll need them just long enough to go through the connector and the can.

Wire

You'll need about 1.25" of 12 guage copper wire. This wire will stick into the brass stub in the N-connector.

A Can

Look for a can between about 3" and 3 2/3" in diameter. The size doesn't have to be exact. Some experienced a can that was 3.87" in diameter. Others have reported good results with big 39oz. coffee cans that are 6" in diameter. The pringles can is really too small for good performance, however. Try to get as long a can as possible. The old fashioned fruit juice cans should work well.

Drill or punch holes in your can to mount the probe

The N-connector assembly will mount in the side of your can. You need to put holes in the right place to mount the connector. The placement of the hole and connect is very important. It's location is derived from formulas that use the frequency that the antenna will operate at and the can diameter. To make life easy on you, here's a calculator to figure it out for you. Or if this calculator is not functional, please click this www.turnpoint.net calculator.

Can Diameter

Cuttoff Frequency in MHz for TE11 mode	MHz
Cuttoff Frequency in Mhz for TM01 mode	MHz
Guide Wavelength in Inches	inches
1/4 Guide Wavelength	inches
3/4 Guide Wavelength	inches

Enter the diameter of your can above and click on the calculate button. 802.11b and 802.11g WiFi networking equipment operates at a range of frequencies from 2.412 GHz to 2.462 GHz. Ideally, with your can size, the TE11 cut-off frequency should be lower than 2.412 and the TM01 cut-off should be higher than 2.462. It would be good, also, if your can is longer than the 3/4 Guide Wavelength. If your can is a little off in length or diameter, don't despair, experimentation is fun!

You want to mark the location on the can where you will put the hole for the connector. The 1/4 Guide Wavelength number tells you how far up from the bottom metal end of the can to put the center of the hole. Open only one end of your can, eat the contents, and give it a good washing. You'll probably want to remove the label too. Use a ruler to measure up from the closed end 1/4 Guide Wavelength and mark the can with a dot.

If you've got a drill, select a bit that matches the size of the center of your connector. You may want to start with a small bit and work the hole larger and larger. You could even start with a hammer and nail, then use drill bits. If you don't have a drill, start with a nail hole and use a file to get the hole to the required size. If you're using a bolt on connector, make four more holes for the bolts - you can use the connector as a drilling guide.

Assemble the probe and mount in can

Now you'll need that bit of wire. You'll need a soldering iron or a friend with one as well. Cut the wire so that when it is stuck in the connector, the total length of both the brass tube and wire sticking out past the connector is 1.21". Get as close to this length as you can.

When you've got your wire correctly sized, solder it into the connector keeping it as straight and upright as you can. When it's cooled, bolt or screw the assembly into your can. Put the heads of the bolts inside the can and the nuts on the outside to minimize the obstructions in your antenna.

Your Done!

Connect your antenna to your wireless card or access point

To use your cantenna, you'll need a special cable commonly called a "Pig Tail". The pig tail connects your wireless card or access point to you antenna. One end of the cable will have a "N" Male connector (just right for connecting your cantenna), while the other end will have a connector appropriate to your card or access point.

You'll want to have a wireless NIC or access point with an external antenna connector. Otherwise, you may have to hack into the one you have to hook up

the cable. Some doesn't recommend this unless you're good with a soldering iron and electronics.

Hook up your cable, point the antenna at a friend's, and see how far you can stretch you network.

This antenna has linear polarization. That means that how you rotate the antenna

will affect the strength of your signal. Usually, you will want to put the connection straight down, but experimentwith rotating the can while watching the signal strength on your PC to get the best performance.