HF Digital Modes
Radioteletype is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers (PCs) running software to emulate teleprinters, connected by radio rather than a wired link.
"Phase Shift Keying, 31 Baud" is a digital radio modulation mode, used primarily in the amateur radio field to conduct real-time keyboard-to-keyboard informal text chat between amateur radio operators.
PACTOR is a radio modulation mode used by amateur radio operators, marine radio stations, and radio stations in isolated areas to send and receive digital information via radio.
Winlink, also known as the Winlink 2000 Network, is a worldwide radio messaging system that mixes internet technology and appropriate amateur radio radio frequency (RF) technologies.
Notes: Winlink 2000 Network
The Hellschreiber or Feldhellschreiber is a facsimile-based teleprinter invented by Rudolf Hell. Compared to contemporary teleprinters that were based on typewriter systems, the Hellschreiber was much simpler and more robust, with only two moving parts.
Multiple frequency-shift keying (MFSK) is a variation of frequency-shift keying (FSK) that uses more than two frequencies.  MFSK is a form of M-ary orthogonal modulation, where each symbol consists of one element from an alphabet of orthogonal waveforms. M, the size of the alphabet, is usually a power of two so that each symbol represents log2M bits.
Olivia MFSK is an amateur radioteletype protocol designed to work in difficult (low signal-to-noise ratio plus multipath propagation) conditions on shortwave bands.
DominoEX is a family of offset incremental multi-frequency shift keyed modes with low symbol rate. A single carrier of constant amplitude is stepped between 18 tone frequencies in a constant phase manner.
Notes: MFSK or "polytone" modes
ALE (Automatic link establishment) is a protocol developed by the USA military and used mainly as an automatic signalling system between radios. It is used extensively for military and government communications worldwide and by radio amateurs.
Digital Voice and Image
Revised: David March 13, 2012, at 03:24 PM EST