May 26, 2018
Narrow band digital voice
FreeDV is a Digital Voice mode for HF radio. FreeDV allows any SSB radio to be used for low bit rate digital voice. Speech is compressed down to 700-1600 bit/s then modulated onto a 1.25 kHz wide signal comprised of 16 QPSK carriers which is sent to the Mic input of a SSB radio. The signal is received by an SSB radio, then demodulated and decoded by FreeDV. FreeDV 700B rivals SSB in it’s low SNR performance. At high SNRs FreeDV 1600 sounds like FM, with no annoying analog HF radio noise.