FreeDV is an application for Windows and Linux that allows any HF SSB radio to be used for digital voice mode with a bandwidth of just 1.1 kHz

Speech is compressed down to 1400 bit/s then modulated onto a 1100 Hz wide QPSK signal which is sent to the Mic input of a SSB radio.

On receive, the signal is received by the SSB radio, then demodulated and decoded by FreeDV.

Features

Codec 2 voice coder and FDMDV modem
50 baud 14 QPSK voice data
1 Centre BPSK carrier with 2x power for fast and robust synchronisation.
1.125 kHz spectrum bandwidth (half SSB) with 75 Hz carrier spacing
1400 bit/s data rate with 1375 bit/s open source Codec 2 voice coding and 25 bit/s text for call sign ID
No interleaving in time or FEC philosophy resulting in low latency, fast synchronization and quick recovery from fades.
44.1 or 48kHz sample rate sound card compatible

Watch FreeDV, the new HF digital audio program for Radio Amateurs.