This page details the construction of a biquad antenna. The biquad antenna is easy to build, and provides a reliable 11dBi gain, with a fairly wide beamwidth.
A tin can waveguide antenna, or Cantenna, may be just the ticket. This design can be built for under $5 U.S. and reuses a food, juice, or other tin can.
A small antenna to boost the signal of a laptop wireless card, that can be stuck to the back of the laptop screen.
ein paar hintergund informationen über ausbreitung von antennen signalen
The W1GHZ Online Microwave Antenna Book
alles möglich über wifi-devices and antennen tuning