From Small Dog Electronics
Boost Wireless Network Strength and Speed: Quicky Jr. II By Matt Klein
Many of us live and work in areas with many available wireless networks, or cannot get a full strength signal from our networks for whatever reason. While AirPort reception on modern desktop and portable Macs is excellent, and getting better with each generation, sometimes we just need better reception.
There are solutions that include disassembling your computer and stringing an antenna through the Express Card slot or performing other modifications, but my favorite tool for this job is the QuickerTek Quicky Jr. II.
This little antenna simply plugs into any available USB port and gives you up to three times the range than you?d get with the built-in wireless hardware. A stronger signal means faster transfer speeds, lower latency, and a more satisfying user experience?particularly if you use Time Machine to back up wirelessly, or stream uncompressed audio to an AirPort Express (like I do every day).
The AirPort signal strength menu bar item has five ?bars,? and indicates signal strength logarithmically. So, if all the bars are black, you have a signal ten times more powerful than when only four bars are black. You can imagine then just how much signal strength matters for speed. Our customers report also that using the Quicky Jr II in areas congested with wireless networks helps your speeds regardless of signal strength.
Quicky comes with easy to install software, and is compatible with Mac OS X Tiger, Leopard, and Snow Leopard. It supports 802.11 b, g, and n, and all encryption types except WPA Enterprise."
Also, Radio Labs has a product that claims a few miles of signal strength. One plugs a whip antenna into the USB slot of a computer. The antenna can be up to 30 feet from the Windows, OS X, or Linux computer.