Electromagnetic Spectrum: Data Communications, Radio

http://telecom.tbi.net/transmission.htm

NTIA (National Telecommunications and Information Administration) U.S. Frequency Allocation Chart (very detailed!)

http://www.ntia.doc.gov/osmhome/allochrt.html

FCC (Federal Communications Commission) home page

http://www.fcc.gov/

History of Wire and Broadcast Communications by FCC

http://www.fcc.gov/cib/evol.html

FCC Radio Spectrum Chart links

http://www.fcc.gov/oet/faqs/freqchart.html

U.S. Department of Defense joint spectrum chart

http://www.jsc.mil/images/speccht.jpg

Andrew Bateman radio design course: "Transmitter & Receiver Architectures"

http://www.avren.com/Courses/TX_RX_Architectures_plain.htm

WTB (Wireless Telecommunications Bureau) directory of wireless communication services

http://www.fcc.gov/wtb/services.html