Building Wireless Community Networks, Second Edition

Antenna Characteristicsand Placement

While I am not a radio frequency (RF) engineer, I have had a lot of practical experience setting up 802.11b networks. There isn’t nearly enough room here for a full examination of the nuances of radio frequency communications. For more authoritative sources, be sure to check out the great resources in the Appendixes. Radio is an entire field of study unto itself.

Antenna selection has a tremendous impact on the range and usability of your wireless network. Ironically, the design of almost every external 802.11b card puts the antenna in the worst possible orientation: sideways and very close to the laptop (or desktop). In this position, the radiation pattern is almost straight up and down! Not only does this drive half of your signal into the table, it leaves your poor, underpowered radio susceptible to interference from the computer itself. Fortunately, laptop manufacturers have responded to this problem, and are now following Apple’s lead in building antennas into their screens and cases.

You will see a tremendous difference in signal strength by attaching a small omnidirectional external antenna to your client card and orienting it properly. Which way is proper? That depends on your environment. If you are having trouble pulling in a signal, try every possible position with your signal strength meter open. I’ve put mine on top of my monitor, below the desk, sideways, on the table behind me, and even slung over my shoulder. The best orientation ...