there are shematic all over the net for making high gain amps. as long as it isnt for resale and no more than 5 are made, and it is as close to the fcc standard as possible, you dont need a lisence.
Saw this on HardOCP: http://www.stanford.edu/~jstockdl/tmp/usbwifi.orcon.net.nz/ I had a cantenna made from a large tin of dog food, saw about 6-9dB gain IIRC. It was very directional too. Would like to try the link above though
