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Boost your WiFi reception with a homemade antenna dish

I found a very interesting article on MetaFilter earlier on how to boost your WiFi reception - or, how to make a WiFi antenna out of a cheap USB WiFi dongle, an extension cable, and Chinese cooking utensils.
During my last holiday, I discovered that I could log in to a free WiFi hotspot from my balcony if I positioned myself in a certain way. Unfortunately, the source was a fair distance away and more than a centimeter or two of movement was enough to cause my connection to drop. However, it has come to my attention that it is possible to build a homemade WiFi antenna which could eliminate this problem.

However, a word of warning from a MetaFilter poster beforehand:

“Cantennas” are technically illegal in the U.S. under Part 15 FCC rules, and in some states, including where I live, arrests have been made for use of such devices, where they are considered evidence of intent for unauthorized network intrusion. Using highly directional antennas to leach WiFi access from fixed locations also makes it much easier to accurately triangulate your location as an infringing user; I’ve had a couple of idiot neighbors try to grab access from my WiFi signal, and I’ve really appreciated the reliable directional signals they provided while trying to do so, as it made it much easier to locate them, and play reverse head games with them.

WiFi “works” precisely because it is a very short range service. Using directional antennas, “power boosters” or other mechanisms to intentionally circumvent the Part 15 range limits entirely for your own convenience is boorish at best, and can disrupt legitimate users operating gear in the intended manner. Don’t be a jerk.

Having said that, it is an interesting concept and makes good reading material, and can be useful for genuine purposes such as getting a signal in your camping site’s free WiFi by placing the receiver above the hight of the other caravans. The best site for this, I have found, is http://www.usbwifi.orcon.net.nz/.

Basically, you need something to substitute for a parabolic antenna dish (kitchen gear such as a colander is great), a USB WiFi dongle (very cheap, can be picked up off eBay for £10 + P&P), a USB extension cable (very cheap worldwide), some tools and a bit of know-how.

First, you drill a hole in the center of your dish for the extension lead to go through. The distance from the center that the dongle goes is important to focus the signal. If we take the circumference of your dish as ‘c’, the depth of your dish as ‘d’, and the focus as ‘f’, the equation is f = d² / 16c. The dongle can be held in place using firelighters and sticky tape or similar. A more detailed explanation is available here.

Apparently it really works and can give a maximum range of 2-3 miles. That’s pretty impressive if you ask me.