A) Phase Shift Keying
PSK31 is one of our favorite modes. It is very narrow and works in all kinds of conditions with modest power and antennas. Free amateur radio software like Ham Radio Deluxe have also made it very easy to get started with PSK31.
Phase-shift keying (PSK) is a form of digital modulation that transmits data by changing, or modulating, the phase of a signal.
|Terminal Node Controller (TNC) used with computer for PSK communication|