Donatello
Newbie
Mar 10, 2008, 9:51 AM
Post #1 of 4
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How to build a WiFi antenna from junk and get online from almost anywhere
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This is legal to build and own!
It might not be legal in your area to use it to 'wardrive'.
Anyway, I have a park near my house and sometimes use a PSP or other device in the park. The problem is, that it is rather far from my house... not too far, but far enough so that my WiFi 802.11 connection does not work.
So there is a way to make a cool combination wave-guide/Yagi antenna out of junk that will reach about 6 wireless networks from the park! I can hit the Starbucks up the street if it's not foggy. (Fog or rain attenuates the signal... more on that later.)
You will need:
- A Pringles Can
- A WiFi Dongle adapter
- A USB extension
- Threaded Rod
- Washers
The one pictured here is made with a different type of dongle adapter - one that has an external antenna. But I was able to get one to work by inserting the entire dongle in a Pringles Can! I was also able to make one with 1/2 of one of those mylar metallized ballons (make a parabola) - but it's big and a Pringles can is less noticeable in the park.
See here:
That shows one taken apart. The Pringles can is metallized on the inside and so acts as a waveguide.
For added boost, there is a Yagi insert that goes inside. That's the threaded rod with the washers on it. You don't really have to do that part... the Pringles can waveguide works fine without it. Besides, the one in the picture (it's not mine) looks like the washers are not spaced properly for WiFi, it looks like he was trying to tap into higher frequencies.
Remember learning how to do division in Math Class? Well, you need to do a little to figure out washer configuration for a Yagi-Uda antenna....
You need to know only basic arithmetic to figure out how far away to place the washers on this contraption. It's easy.
Microwaves travel at the speed of light: 300,000 Kilometers/second.
The waves we want to capture are about 2.4 GigaHertz (WiFi).
So that means we need to know how to do division.
I learned division in 2nd grade. So did you.
So we know all we need to know to design a Yagi Antenna because you need to calculate how far away the washers must be spaced. That's it.
300,000 Kilometers = 300,000,000 meters
300,000,000 meters = 30,000,000,000 centimeters
That's how many centimeters light travels in a second.
WiFi is about 2.4GHz, which means that every second there are 2.4 billion waves. We want our washers spaced to match this number.
2.4 GHz = 2.4 Billion waves
2.4billion = 2,400,000,000
So now all we need to do is divide 30 Billion by 2.4 billion and we know how many centimeters apart to place the washers! EASY!
30/2.4= 12.5 centimeters.
So each washer must be about 12.5 centimeters away from the one next to it!
That wasn't so hard now, was it?
The "driven element" needs to be about 1/4 of a wavelength from the back of the can...
The last little bit of math - honest - and it's done... so...
12.5/4 = 3.125
So the driven element in our little antenna needs to be 3 1/8 centimeters from the back of the can.
That's it.
This will enable you to tap into the wireless connection at the Starbucks up the street or from far away. If you have your own network, you can build two of these types of antennas and blast your Wi-fi connection halfway across town! One of the antennas will hook up to your network at home, and you will go across town and point the other antenna at it creating a kind of microwave beam between the two antennas. They need to be pointed right at each other!
You can get REALLY FAR this way. Perfectly safe from Wardrivers if you have secured your home wireless network.
Bwahahahaha... this is one of the coolest projects and all your friends will think you are an evil genius.
Come to think of it... I am an evil genius... or at least that's what my mom always says. (She was saying it long before that ugly incident with the neighbor's stupid cat and the MASER I built from those two old microwave ovens and a smoke detector. NOTE: Don't put steel wool on a cat and fire a 2000 watt MASER at it. NOT EVEN A LITTLE BIT.)
NOTE: This does not work as well in the rain. WiFi are very weak Microwaves, in fact, the same exact frequency that your microwave oven uses. It's the resonant frequency of water... which is why microwave ovens heat water so well. So when rain falls, it actually tries to cook the raindrops thereby attenuating the transmission. That's what is going on at all those cellphone towers... they are ever-so-very slightly cooking every raindrop.
But don't worry... your microwave oven is about 1000 watts, and this little device is less than 1 watt. Still, don't put it up to your head if you don't have to! :-D
Bwahahahahahahaha 
After you are done building a WiFi antenna and sucking in networks all over town, go and check the search engine I built. I need a couple of beta testers to give it a run.
http://www.cheatsearch.org
I put up another beta of the thing for people who decide to beta test it. The algorithm is slightly different... which one is better? (www.cheatsearch.org/beta.html)
Thanks!
Looking for beta testers to test a cheat search engine that searches only for cheats. www.Cheatsearch.org
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