802.11 Cantennas Done Up Homebrew Style
April 12, 2002
Creativity is alive and thriving in the free WLAN movement. Here's a report on some cool ways to catch the waves (the radiowaves that is).
As wireless carriers spend billions for the hardware and software needed for modern mobile networks -- Marc Duggan uses a juice can and some Legos to connect to a free 802.11b network in Waterloo, Canada.
Like the enthusiasts decades earlier that created the first personal computers from the most basic components, fans of the unlicensed 2.4GHz frequency are converting items found at your local grocery store into inexpensive WiFi antennas. What started as a cheap alternative to commercial gear has flourished with designs distributed over the Internet, contests and something akin to cult-like adoration for a network administrator who put homebrew 802.11 antennas on the map using a simple can of chips -- the edible variety.
In the summer of 2001, Rob Flickenger, a network administrator, published plans for converting a used Pringles container into a directional antenna costing $5 a piece with a 10 mile range. From there, free 802.11 networks shared plans for broadcasting with coffee, soup, pasta -- even 40-ounce beef stew 'cantennas.'
Recently, Gregory Rehm held the first 802.11b Homebrew Antenna Shootout. The competition matched a commercial antenna against several home-grown designs. Rehm says he found himself searching his cupboard and sizing up the canned food aisle at the grocery store for future antennas.
Rehm reports that the 40-ounce beef stew can employing a waveguide antenna design took top honors, with the 26.5-ounce pasta can and a coffee can trailing. What conclusion can one draw from the shootout?"If you can eat a big can of stew, you can make a high performance antenna," Rehm writes at his Web site.
Most of these designs involved physically aiming your antenna. To direct your homemade antenna's signal, you have to either hold the device in your hands or rig it to a simple tripod. What if you don't go in for such labor-intensive methods and have some Legos handy?
The multicolored interconnecting blocks of plastic have traveled far from their origins as a simple toy. When Legos introduced its MindStorms kit complete with motors, programming language and remote control, they drew the attention of robotics designers, computer programmers and Canadian Duggan searching for a way to automate his juice can 802.11b cantenna.
Duggan attached his directional antenna to a base of Legos mounted on a tripod. By including gears, motors and a remote control unit, he was able to scan the Waterloo skies for the nearest free 802.11 signal from his easy chair or laptop. "I'm really lazy," admits Duggan. Here are the details.
If soup cans are too low tech for you, a hybrid solution might come from the buy-out of satellite television provider Primestar by DirectTV. An electric engineering professor in Washington State has published a way to create a directional 802.11 antenna using discarded Primestar dishes. This is how it's done.
Homebrew 802.11 devices will not outperform most commercial products. You can forget about a potato chip container or soup can following today's move toward Non Line-of-Sight wireless connections - one tree branch and you're toast. So, what draws people to tinker with their Airport AP or WLAN card? The same drive for freedom that powered people like homebrew computer fan Steve Wozniak is at the heart of the free wireless movement today.