Packet radio
Packet Radio (PR in the following) is a data transmission mode used in
Amateur Radio, which is based on protocols similar to those on the
internet, in particular AX.25, which is a subform of the X.25 protocol, just with limited length of data blocks, the so-called packets.
PR networks allow regional, national and even intercontinental
delivery of e-mail and other data transfer, but restricted to radio
amateurs. TCP/IP is also in use on packet radio, allowing the use of all
the high-level protocols like HTTP or FTP known from the internet.
Each PR station consists of at least one transceiver with antenna
and a modem.
In more traditional setups a TNC (Terminal Node Controller) is also present. These PR stations also have a terminal (which may be emulated by a
computer), to allow operator interaction with the TNC, but automatic
PR stations do not need a terminal.
Today however one often finds PR stations where the modem is directly interfaced with the computer which has its own protocol implementation instead of relying on the TNC.
