Fun with WiFi
WiFi Antenna with a direct TV Dish
Here is the problem; I live about 100 meters from a community center. I would like to be able to use my network from with in the center. I don't want to spend a lot of money nor use a Cantenna over there. Currently I receive no signal in the center from my house. I moved the router to the back steps to test signal.
I was able to get a signal in the community center by putting the router out side on the step however the connection was still poor. To make it worst, in the center I had to put my laptop in the window.
The Solution
I was able to get my hands on a Direct TV Dish. Lots of people are throwing these things out to replace them with HD dishes. I wanted to test the feasibility of converting the dish to shoot a signal to the community center. The dish is nice because it already has an arm for the focal point. Some double stick tape and a few C Clamps later I had the router mounted to the dish, and the dish mounted to the step.
The result was great! I was able to get a full signal
sitting at a table inside the club house.
I was very surprised at the difference because I didn't think it was going to work.
Before I hooked up the dish I received a SNR of 4 dB. With the dish I was able to get 22db from the community center. I am going to start constructing a 2.4 GHz Satellite antenna of my own.
I have seen a few others on the internet.
http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/
http://www.wwc.edu/~frohro/Airport/Primestar/Primestar.html
http://www.cs.cornell.edu/w8/%7Eeckstrom/802.11a/primestar/
http://www.trevormarshall.com/biquad.htm
http://www.turnpoint.net/wireless/cantennahowto.html
Today I am going to order the parts that I am going to use for this project. As I start building I will post my progress here.
5-20-2006
The new Plan
The dish got me thinking. My Linksys router has two antennas that I can remove. I can make two antennas, one to send and one to recieve. The connectors that are used are called RP-TNC male / Female. These are not regular TNC connectors. Why they used wacky hard to find connectors i will never know. My guess is they don't want some nut making antennas in his garage.
I stated building a Waveguide Antenna to connect to the right
antenna. First I needed the right cylinder, My wife bought me a
good bottle of wine from Argentina, that came in a great tin, 90mm. Next I
raided the cabinet and found a bread crumb can with a 90 mm microwave friendly
lid.
Next I started by figuring out where the element should be located. The formula to figure this out is (1/Lo)2 = (1/Lc)2 + (1/Lg) 2.
Lo is the wavelength of the hf signal in open air or
Lo/mm = 300 / (f/GHz).
Lc is the wavelength of the low cut frequency which depends on tube dia
only Lc = 1,706 x D
Lg is standing wavelength inside the tube, it is function of both Lo and
Lc
Martu Palomaki web page helped me. He explains the theory well. Theory of the Waveguide Antenna
Because my diamiter is 90mm and I want 2.4 GHz. The result is....
Lo = 125 mm Lo/4 = 31 mm
Lg = 215 mm Lg/4 = 54 mm
At 54mm I drilled the hole for my surface mount female N connector.
Next I started on the element. I used a brass welding rod and soldered the element to the N connector, I then sanded it down to 31mm.
I then mounted the element and Tada, Waveguide is now ready for Defcon in Las Vegas.
Here it is mounted on my tripod.
Next I started making the Bi Quad dish. Of as I call it .... the
Chairtenna
Next I started with LMR 400 cable. This is not RJ 58 or 9. This is a thick cable made for RF transmission. Some people say using 58 or 9 will distory your equipment... I have no clue I am just having fun.
Next I made and mounted the BiQuad to a direct TV Dish.
Ladies and Gentleman, I give you the
CHAIRTENNA!
Next I did a flash upgrade to my router, set the Waveguide to "send" and the Chairtenna to "recieve." I get a great Wifi connection at the club house. No one knows how my WiFi can get there but thiers can't. Shhh... it is our little secret.
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