Building the Bandwidth Expander

Overview

Sometimes, when you have a location out on the fringes (or even beyond the fringes) of your access point's reach, it takes a gain antenna to connect at the maximum bit rate, or sometimes to connect at all. This project shows you how to build a gain antenna out of a tin can, a coaxial connector, and not much else.

Gain antennas have a sort of spotted reputation in the Wi-Fi business. Some people think that if you're fooling with gain antennas, you're up to no good. Certainly the FCC frowns on them, but they're not illegal, and they can be extremely useful in a number of ways.

As I've said in Chapter 8, gain antennas aren't magic. They're basically lenses for radio waves. They take the radio-frequency energy from your access point or client adapter and focus it so that it travels mostly in a single direction rather than in all directions at once. Just as a focused beam of light from a flashlight travels farther than the light radiating in all directions from a lit match, your omnidirectional (all-directions-at-once) radio signal will become a beam, and it will go much farther in a single direction than it does coming out of an omnidirectional antenna. Similarly (though not as obviously) they focus the weak radio signals coming into the antenna from a distant access point or client adapter and make them easier to read.

You can buy some very effective microwave antennas for Wi-Fi use from commercial vendors (see the subtopic 'Choosing a Commercial Antenna' in Chapter 8) but for a lot of applications you can simply make your own out of appropriate-sized tin cans. In order to do this project you don't have to be a participant on Discovery Channel's Monster Garage but you do need to be reasonably adept with hand tools such as:

• Electric drill

• Combination square and scribe

• Soldering iron

Before you even think about building your own gain antenna, you need to read Chapter 8, particularly the subtopic 'How Antennas Work.' Once you understand the theory behind what you're doing, you can look around and see what other materials may be available to you. Antennas have been made from dryer vent pipe, 3" and 4" copper drain pipe, and even rolls of sheet metal curved into a tube and soldered or riveted together.

The type of antenna you can build from tin cans is called a waveguide antenna. The other popular build-it-yourself antenna is called a Yagi antenna, and while it's not prohibitively difficult to build your own Yagi, it's certainly a lot more fussy metalwork, and I'm not sure the results are better commensurate with the extra effort required to make one.

Yes, once again, you can make a Pringle's can antenna, but virtually any waveguide antenna made of a real tin can (rather than silver-colored cardboard) will plow a potato chip can into the proverbial soil.