This thing is the closest you can get to having a massive parabolic dish without having a massive parabolic dish.
Here is the detailed construction of a 16dB gain QUAD BIQUAD antenna. This is sort of a rare breed, something you don't see too often, but it's killer. It's a bit more difficult to make than a standard one-element biquad, but it's worth it. This thing is almost as directional as my 18" parabolic dish. Remember...the power (your signal) doubles every 3dB...this one's nearly 16dB ; )
With this you can get Linksys, Netgear, or D-link Access Points from over 2 MILES away.