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Saturday, June 4, 2011

Low-cost 100 yard WiFi LAN

I work about 100 yards from where I live, and I wanted to keep from paying for another internet connection if possible. I used stock Linksys WRT-54G wifi routers, loaded them with OpenWRT, and built two waveguide antennae.
I followed a procedure very close to the Cantenna HOWTO page, except that I used 4-inch black drain pipe from the hardware store ($10 for 10 feet) to make several. This pipe is almost exactly the optimal size for 2.4 Ghz, and it works like a charm. The only difficulty is that since a waveguide antenna needs to be metal, I had to line the inside of the pipe with aluminum foil.
It all works nicely, and I have had a consistent 1-2 Mbit connection for the last two years.
For the mounting hardware, I used electrical conduit from the hardware store. The antenna attached to the tree is attached using a switchplate. The router is housed in an upside-down plastic can spray-painted brown. If you're not looking for it, you'll never see it.
The large gray antenna is a 18-db store-bought omni-directional antenna that I'm not currently using. My homemade antennae work much better for a point-to-point link. Also, the power supply in the second photo is dangling down after maintenance, it is normally tucked into the can.
I tested my setup with and without the antennae, and saw about a 20 dB signal strength increase due to the antennae. That's not great, but the noise rejection is what's really important for a short distance like this. Because of the noise rejection I get a very reliable connection, even good enough for VoIP.

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