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(http://forum.free-games.com.au/forum/Ga … _P1013983/)
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.
Skulle det inte teoretiskt gå att omvandla detta till 2100-bandet genom att Räkna om formlen såhär...
14.28/4 = 3.57
Det jag fortfarande inte greppar om är hur stora brickorna skall vara. Tittar man på en Yagi riktantenn så är spröten olika långa beroende på vilken frekvens de försöker fånga..