PSK31 was developed in the 1990s as an improvement over RTTY and is encoded to contain redundant information which allows a degree of automatic error correction on reception. The overall signal is very narrow using two carriers spaced 31.25 Hz apart which can be clearly seen when no data is being carried.

Spectrum showing a number of PSK31 signals

Decoding PSK 31

The following image shows the PSK31 communication program bundled with the ‘fldigi’ software, whilst the following image shows the out from ‘supersweeper’ which is part of the ‘Hamdradio deluxe’ suite and can simultaneously decode numerous PSK31 channels at the same time.

PSK_31 communication software

Supersweeper software simultaneously decoding several PSK31 signals