ARLA/CLUSTER: FreeDV Ham Radio digital voice software

[João Gonçalves Costa]

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 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

In this video watch when it's switched to analog SSB. The SSB bandwidth is about 3 times that of the digital audio. Also note the diagonal black streaks across the waterfall display. That's fading, probably from two reflections arriving out of phase. The ID on the bottom is coming in during the silent periods between words.

It's Open Source, and using Codec2. See http://freedv.org/

Watch FreeDV, the new HF digital audio program for Radio Amateurs.
http://www.youtube.com/embed/Pfyn0NEcNHs?rel=0

Digital Voice Google Group
https://groups.google.com/forum/?fromgroups#!forum/digitalvoice

FreeDV
http://freedv.org/

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