Packet radio is a form of packet switching technology used to transmit digital data via radio or wireless communications links. It uses the same concepts of data transmission via Datagram that are fundamental to communications via the Internet, as opposed to the older techniques used by dedicated or switched circuits.
Amateur radio operators began experimenting with packet radio in 1978, when after obtaining authorization from the Canadian government, Robert Rouleau, VE2PY and The Western Quebec VHF/UHF Amateur Radio Club in Montreal, Canada began experimenting with transmitting ASCII encoded data over VHF amateur radio frequencies using homebuilt equipment. In 1980, Doug Lockhart, VE7APU and the Vancouver Area Digital Communications Group (VADCG) in Vancouver, Canada began producing standardized equipment (Terminal Node Controllers) in quantity for use in amateur radio packet radio networks. In 2003, Rouleau was inducted into CQ Amateur Radio magazine's hall of fame for his work on the Montreal Protocol in 1978.
Not long after this activity began in Canada, amateurs in the US became interested in packet radio, and in 1980, the FCC granted authorization for US amateurs to transmit ASCII codes via amateur radio. The first known amateur packet radio activity in the US occurred in San Francisco in December of 1980 when a packet repeater was put into operation on 2 meters by Hank Magnuski, KA6M and the Pacific Packet Radio Society (PPRS). In keeping with the dominance of DARPA and ARPANET at this time, the nascent amateur packet radio network was dubbed the AMPRNet, in DARPA style and Magnuski had obtained IP address allocations in the 220.127.116.11 network for amateur radio use worldwide.
Many groups of amateur radio operators interested in packet radio soon formed throughout the country including the Pacific Packet Radio Society (PPRS) in California, the Tucson Amateur Packet Radio Corporation (TAPR) in Arizona and the Amateur Radio Research and Development Corporation (AMRAD) in Washington, DC.
By 1983, TAPR was offering the first TNC available in kit form. Packet radio started becoming more and more popular across North America and by 1984 the first packet based bulletin board systems began to appear. Packet radio proved its value for emergency operations following the crash of an Aeromexico airliner in a neighborhood in Cerritos, California the weekend of Labor Day 1986. Volunteers linked several key sites to pass text traffic via packet radio while keeping the voice frequencies clear.
For an objective description of early developments in amateur packet radio, refer to the article "Packet Radio in the Amateur Service".
The most common use of packet radio today is in amateur radio, to construct wireless computer networks. Its name is a reference to the use of packet switching between network nodes. Packet radio networks use the AX.25 data link layer protocol, derived from the X.25 protocol suite and adapted for amateur radio use.