PSK31 or "Phase Shift Keying, 31 Baud" is a digital, used primarily in the amateur radio field to conduct real-time informal text chat between amateur radio operators. Colloquial usage of the term PSK31 in amateur radio most often implies the use of binary phase shift keying which is the mode BPSK31. By not assigning the X in XPSK31, BPSK31 is implied. History PSK31 was developed by English amateur radio operator Peter Martinez (G3PLX) and introduced to the wider amateur radio community in De… (More on Psk31)