Scientists Shintaro Uda and Hidetsugu Yagi invented the Yagi antenna in 1926. It was successfully used in 1928 wireless radar and has been effective for radio, television and other radio frequency antenna designs ever since. The Yagi antenna is a simple dipole design, i.e., the antenna elements extend to both sides of the mast. In a classic Yagi design, the antenna elements are the driver, the reflector and the director. For the do-it-yourselfer, all you need to know is that it works as a simple, effective homemade antenna for free WiFi.
A design that can be portable, too
Start with an empty potato chip can, such the kind containing Pringles or Lays Stax. The can will act as your receptor.
Clean a potato chip can with soap and water.
Measure one inch up the exterior closed side of the can. Mark this point with a pencil.
Make an opening in the can at the marked point. Use a nail first, then a punch so as not to dent the can’s exterior. The final size of the opening depends on the type of N-connector you are using.
Cut a ½-inch length of 12-gauge wire. This is will be your antenna element.
Solder the length of wire to the solder end of an N-connector.
Secure the N-connector to the potato chip can with the wire length inside the can. If you are using screws and bolts, attach the screws from inside the can.
Attach the male end of a 75-ohm coaxial cable to the N-connector that is outside the can. Connect a pigtail (reducing cable) to the other end of the coaxial cable.
Connect the pigtail to a WiFi card. The external connection on the WiFi card must match the pigtail end.
Adjust your new antenna manually for strongest reception. The wire element in the can should point up or down