PSK31 or "Phase Shift Keying, 31 Baud" is a popular computer-soundcard-generated radioteletype mode, used primarily by amateur radio operators to conduct real-time keyboard-to-keyboard chat, most often using frequencies in the high frequency amateur radio bands (near-shortwave). PSK31 is distinguished from other digital modes in that it is specifically tuned to have a data rate close to typing speed, and has an extremely narrow bandwidth, allowing many conversations in the same bandwidth as a single voice channel. This narrow bandwidth also concentrates the RF energy in a very narrow bandwidth, allowing relatively low-power equipment (25 watts) to communicate globally using the same skywave propagation used by shortwave radio stations.

PSK31 or "Phase Shift Keying, 31 Baud" is a popular computer-soundcard-generated radioteletype mode, used primarily by amateur radio operators to conduct real-time keyboard-to-keyboard chat, most often using frequencies in the high frequency amateur radio bands (near-shortwave). PSK31 is distinguished from other digital modes in that it is specifically tuned to have a data rate close to typing speed, and has an extremely narrow bandwidth, allowing many conversations in the same bandwidth as a single voice channel. This narrow bandwidth also concentrates the RF energy in a very narrow bandwidth, allowing relatively low-power equipment (25 watts) to communicate globally using the same skywave propagation used by shortwave radio stations.