FreeDV Ham Radio digital voice software

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.


  • 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.