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Published on The O'Reilly Network (http://www.oreillynet.com/) http://www.oreillynet.com/cs/user/wlg/448 Antenna on the Cheap (er, Chip) by Rob Flickenger Jul. 5, 2001 Like many would-be 802.11b hackers, I'm increasingly obsessed with pushing more bits further and faster for less cost (I believe the unofficial goal of our community wireless project is to provide infinite bandwidth everywhere for free. Of course, there are problems with approaching infinity, but it's still fun to try!) The work that Andrew Clapp and others have done is helping to demystify the ancient black magick of Resonance (i.e. antenna building). And so, over last weekend, some friends and I decided to give it a go for ourselves. (standard disclaimer): Anything you do with your gear is YOUR RESPONSIBILITY. This is a stupid idea that will probably ruin your radio, set your house on fire, bring the FCC to your door, ruin your crops, and send famine and pestilence across the land. And as the operator, it is YOUR RESPONSIBILITY to not take the word of some raving lunatic on the web with funny colored hair, and find things out for yourself. Your mileage will vary. I'm probably lying. You have been warned. Anyway, our first run was a direct rip-off of Andrew Clapp's terrific original design (knowing next to nothing about antenna construction, it's helpful to start off with a working known good.) By using PVC, all-thread, washers, some cheap copper tubing, a Pringles can, and some scrap cardboard, we were able to make a prototype shotgun yagi in a matter of hours. Having a couple of other excited alpha geeks around can help move construction projects along very quickly. Once this was up and running, we looked at the design, and of course speculated about ways to optimize it. While a directional antenna showing between 12 and 15db gain is impressive, it's also pretty large, physically. We realized that, if we were careful, we could fit a full wavelength inside the Pringles can itself (at a reduced total gain), but make the entire antenna much more compact. In about 45 minutes, we had the collector rod built, the locknuts on, and the whole thing in place. The result: A Pringles can that pulls about 12db! Parts list: All-thread, 5 5/8" long, 1/8" OD $1.00 two nylon lock nuts $0.10 five 1" washers, 1/8" ID $0.10 6" aluminum tubing, 1/4" ID $0.75 A connector to match your radio pigtail (we used a female N connector) $3.00 1 1/2" piece of 12 gauge solid copper wire (we used ground wire from house electrical wiring) $0.00 A tall Pringles can (any flavor, Ridges are optional.) $1.50 Scrap plastic disc, 3" across (like another Pringles can lid) $0.00 Total: $6.45 Of course, buying in bulk helps alot. You probably won't be able to find a 6" piece of all-thread; buy the standard size (usually one or two feet) and a 10-pack of washers and nuts while you're at it. Then, you'll have enough for two, for about $10. Tools required: Ruler Scissors Pipe cutter (or hacksaw or dremel tool, in a pinch) Heavy duty cutters (or dremel again, to cut the all-thread) Something sharp to pierce the plastic (like an awl or a drill bit) Hot glue gun Soldering Iron Construction time: about an hour Front collector construction: Mark and cut four pieces of tubing, about 1.2" (1 15/64"). Where did I get this number? First figure out the wavelength at the bottom of the frequency range we're using (2.412 GHz, or channel 1). This will be t