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Wednesday, May 18, 2005

Dish Testing

[click photo for gallery]

I've been playing with WiFi lately and one of the things I want to know how to do is improve the range of network. Well there are a few ways to do this. You can get an amplifier... which will make the signal stronger through electronics (like a guitar amp makes a guitar louder.) But amplifiers for WiFi are damn expensive. You can also buy antenna's which will improve range... but they're also expensive. Antennas can also be made... but they're pretty tricky... I've tried a couple and they haven't been effective. Finally, there is a solution that is by far the easiest and cheapest... using a parabolic reflector to focus the signal at a plain old WiFi adaptor. Like a satellite dish. In fact. We used a satellite dish.

(Skip to the next paragraph if you're not a techie.) It started when I picked up a very nice little USB WiFi adaptor, the DWL 122. USB adaptors are ideal for using with reflectors because they can be easily mounted, and the only line you have running any long distance is USB... which has no loss. If instead you used an external antenna connected to a WiFi card or some such, the loss from the coax cable and plugs can be very great (so I've learned from the 2600 radio guys :D ).

So anyhow Jon and I tested out using a satellite dish to extend the range a WiFi connection. Using an iBook on one end, and an Airport base station in the back of a tricycle for the other point, we check the signal of the connection at various distances. First we tried without the dish, then we tried using the dish. And the results were quite suprising! The dish made the long distance connections far stronger... heres a graph of the results.

Now the satellite dish we used (I know there's no good picture of it, sorry :P ) its quite large and not very portable. Could be good for mounting on a roof for a link between buildings, but its not practical for wardriving or the like. So in search of smaller dishes I came across this site on using inexpensive chinese cookware as parabolic reflectors. They seemed to be getting good results from using these things so off to china town it was and I picked up a skimmer thing and made a neat little dish from it. I haven't tested it yet, but next time Jon's around we'll set up the tricycle again.

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5 pillowblog: Dish Testing [click photo for gallery] I've been playing with WiFi lately and one of the things I want to know how to do is improve the range of netw...


Michael Fuller said...

Good work man. That tricycle is mildly less ridiculous looking than a baby carriage, hehe. First a baby carriage, then a tricycle.... so next is a bicycle, then a car right? Then an airplane?

pillowcase said...

well fyi the tricycle dosent to much. it just is an access point. i coulda just walked down the street with the airport :P

a tricycle of war would require all the carriage had... maybe more :D

Anonymous said...

STRONGLY suggest you test using NetStumbler, even if (gasp!) you have to borrow a PC laptop. % results graphs are too vague, & NS gives the most revealing plots when around when testing & tweaking. Additionally use the largest mesh scoop you can find, normally a #12 (300mm or 12")- yours looks only ~8 inches & will have gain 10-12dB rather than the 12-15dB of the #12. See a aestheically pleasing "boutique" version (mounted on a flexible stalk lamp stand)=> http://www.usbwifi.orcon.net.nz/btique.jpg Stan in NZ

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