This article will show you how to put together the ultimate homebrew antenna -- a working Yagi antenna for 2.4 GHz Wi-Fi out of litle more than paperclips stuck together. This model is commonly called the Frisko antenna , after the French Frisko brand of ice cream cups whose wooden spoons were used in the first prototypes.
The current designs of most external Wi-Fi cards put the antenna in a lawed position, with the antenna very close to the computer. This means that the pattern of emissions is often blocked by computer itself. Not only that, the small packaging of wireless cards prevents an optimal design for the internal antenna to pick up wireless network devices more than a couple of 100 feet away.
This is one of the reasons that attaching even a small external antenna can greatly improve signal strength, especially if it is oriented properly.
Dipole Antenna you will build in this article is folded dipole . The Dipole antenna is just the the simplest antenna. The dipole is a half wave antenna that consists of two opposing radiating elements. It's made up of two quarter-wavelength poles that are not connected to each other and fed in the middle by the transmission line. A standard dipole is open on each end, but it can also be folded over on itself.
The Antenna design shows a simple dipole made from steel paperclips . Each arms of the dipole is 31 mm in length, or 1/4 of a wavelength for Wi-i channel 6. The center conductor is soldered to right arm, while the shield is soldered to the left arm. It doesn't matter to which side you solder.
The dipole antenna is unique in that it can be mounted vertically or horizontally. When standing vertically, the dipole antenna is omnidirectional. When horizontal, this antenna will radiate outward in two directions off the sides (and slightly upwards), like turning a donut on its edge.
(source ; Wi-Fi Toy Extreme Tech)
