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.
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 Center 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
It's Open Source, and using Codec2. See http://freedv.org/
(Source : Southgate Amateur Radio News)
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