22 July 2010

Phase Shift Keying (PSK)

PSK31 is a digital mode designed by Peter Martinez G3PLX for live keyboard QSO's (the same type operation as RTTY).

The PSK31 mode uses a transmission speed of 31.25 baud using varicode caracter coding what provides a speed of 50 words per minute (very few people can type faster than this). The varicode character set has varying data lengths for each character with the most commonly used letters having the shortest data length.

Instead of using FSK (Frequency Shift Keying) or on/off keying uses BPSK (Binary Phase Shift Keying) or QPSK (Quad Phase Shift Keying). The mode uses advanced DSP and narrow band techniques. A BPSK-31 signal, when properly driven occupies about 31 Hz bandwidth! Other common formats are PSK63 and PSK125, obviously the higher the data rate, the wider the bandwidth and the less reliable under noisy or poor conditions.

Click HERE to visit the DigiPan "Digital Panoramic Tuning" web site and download the Digipan software for PSK operation.

EPC PSK signals are commonplace around 7.035 MHz, 14.070 MHz and 28.120 MHz. Even when band conditions are very poor. One of the main advantages of PSK31 is that the mode is very effective when signals are extremely weak (even with QRM)! Because of the narrowband DSP technology used, most software will allow the user to monitor two or more QSO's simultaneously without having to change frequency on the rig.