AirPort Antennas from MacWireless -- Want to increase the range of your AirPort or AirPort Extreme network? The Mac-savvy wireless company MacWireless is now selling a number of directional and omni-directional antennas that connect to graphite and snow AirPort Base Stations (MacWireless points at the necessary surgical instructions for these two, which weren't designed to have antennas added) and AirPort Extreme Base Stations with antenna connectors. Prices range from $70 to $150 and gain levels vary between models. To stick with antennas that are Apple-certified and fit in with the look of the AirPort Extreme Base Station, look at the Dr. Bott ExtendAIR Omni and ExtendAIR Direct, which MacWireless also carries and which Macworld just reviewed. If you're interested in increasing your signal strength outside or in extreme environments, you might also check out MacWireless's various outdoor mounting boxes and Power over Ethernet products.
For those unfamiliar with antennas used for wireless networking, you can learn more about it in my book, The Wireless Networking Starter Kit, but, briefly, an omnidirectional antenna is essentially a stick which radiates in a 360-degree pattern, so you'd position it in the middle of the area you want to serve. A directional antenna focuses radio waves in a specific direction, so it's best placed on the edge of an area you want covered. [ACE]