PSK31 or "Phase Shift Keying, 31 Baud"'s a digital, used primarily in the amateur radio field to conduct real-time informal text chat between amateur radio operators. History PSK31 was developed by English amateur radio operator Peter Martinez (G3PLX) and introduced to the wider amateur radio community in December 1998. Martinez initially called his creation "varicode", because it uses variable length encodings (Huffman codes) to represent characters. PSK31 was enthusiastically received, and… (More on Psk31)