Very nice article on Antennas and 802.11

http://www.byte.com/documents/s=1422/byt20010926s0002/1001_marshall.html Antennas Enhance WLAN Security By Trevor Marshall October 1, 2001 Antennas are most often used to increase the range of WLAN (wireless LAN) systems, but proper antenna selection can also enhance the security of your WLAN. A properly chosen and positioned antenna can reduce the signal leaking out of your workspace, and make interception extremely difficult. In this article, I analyze the signal of different antenna designs, and how the positioning of the user's antenna makes a difference in signal reception. <snip>