PSK31 or “Phase Shift Keying, 31 Baud”, also BPSK31 and QPSK31, is a popular computer-sound card-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 makes better use of the RF energy in a very narrow space thus allowing relatively low-power equipment (5 watts) to communicate globally using the same skywave propagation used by shortwave radio stations.

PSK31 programs for ham radio PSK31 digital mode emissions

• HamScope
  HamScope is a freeware windows multi-mode communications package for amateur radio that supports: PSK31 BPSK and QPSK RTTY ASCII MFSK16 PACKET CW. Support radio control interface for several ICOM, TenTec, Kenwood, and Yaesu transceivers. Compatible with DXbase LOGic 7 RYLogit TRX-Manager YPLOG. By KD5HIO Glen
• MixW V3
  PSK31, RTTY, SSTV, MFSK, MT63 Olivia Hellschreiber SSTV and other modes, Log, DXCluster, telnet access, log backup, Rotor, CAT and whatever you dream in a single program
• MultiPSK
  Windows freeware multimode program by F6CTE it supports BPSK31 QPSK31 PSK63 PSK63F PSK10 PSKFEC31 PSKAM CW CCW THROB 4 bauds THROBX RTTY SITOR-AMTOR-NAVTEX FELD HELL PSK JT65 HELL HF FAX SSTV FILTERS
• DigiPan 2.0
  DigiPan provides a panoramic display of the frequency spectrum in the form of an active dial scale extending the full width of the computer screen. DigiPan is the result of a joint effort between myself and Nick Fedoseev, UT2UZ, the author of MIXW32, and is intended to make PSK31 operation easier and more enjoyable for everyone. You can download digipan 2.0 for windows form here.
• PSK31 Deluxe
  PSK31 Deluxe is a PSK31 and PSK63 program for novices and power users. It has been replaced by Digital Master 780 and is now a legacy product. The last version of PSK31 Deluxe was shipped with the HRD 4.0 SP4 kit and is no more availabe and supported.
• Digital Master 780
  Digital Master 780 is a windows multi-mode program which uses Ham Radio Deluxe for radio control. It is part of HRD package and support PSK, QPSK, Contestia, CW, DominoEx, Hell, MFSK, MT63, OLIVIA, RTTY, RTTYM, THROB and SSTV. Free version was made available with HRD 5.
• Zakanaka
  A digital mode decoding and terminal program that uses no terminal unit, terminal node controller, or multimode hardware. It does all its decoding using the sound card inside the computer, and it can interface with a radio using a COM port. Zakanaka is an extremely cost-effective way of operating PSK31 and RTTY