PSK31 is a popular digital communication mode used in amateur radio and other radio communication applications. Introduced by Peter Martinez, G3PLX, in 1998, PSK31 stands for Phase Shift Keying, 31 Baud. It utilizes phase modulation to transmit data over radio frequencies, with a symbol rate of 31.25 baud (or roughly 31.25 symbols per second). PSK31 operates in the high-frequency (HF) bands, typically within the narrow bandwidth of approximately 31 Hz, allowing for efficient use of radio spectrum and reliable communication under weak signal conditions. PSK31 is characterized by its robustness, narrow bandwidth, and relatively simple implementation, making it well-suited for low-power and portable operations, as well as for digital modes contests and casual communications among amateur radio operators. PSK31 software is available for various operating systems, enabling users to decode and encode PSK31 signals using personal computers or dedicated digital mode interfaces connected to transceivers. s://en.wikipedia.org/wiki/PSK31