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<p class="MsoNormal"><span lang="EN-US">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
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">On receive, the signal is received by the SSB radio, then demodulated and decoded by FreeDV.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Features:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">• Codec 2 voice coder and FDMDV modem<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">• 50 baud 14 QPSK voice data<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">• 1 Center BPSK carrier with 2x power for fast and robust synchronisation.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">• 1.125 kHz spectrum bandwidth (half SSB) with 75 Hz carrier spacing<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">• 1400 bit/s data rate with 1375 bit/s open source Codec 2 voice coding and 25 bit/s text for call sign ID<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">• No interleaving in time or FEC philosophy resulting in low latency, fast synchronization and quick recovery from fades.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">• 44.1 or 48kHz sample rate sound card compatible
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">It's Open Source, and using Codec2. See http://freedv.org/<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Watch FreeDV, the new HF digital audio program for Radio Amateurs.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><a href="http://www.youtube.com/embed/Pfyn0NEcNHs?rel=0">http://www.youtube.com/embed/Pfyn0NEcNHs?rel=0</a>
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Digital Voice Google Group<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><a href="https://groups.google.com/forum/?fromgroups#!forum/digitalvoice">https://groups.google.com/forum/?fromgroups#!forum/digitalvoice</a>
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal">FreeDV<o:p></o:p></p>
<p class="MsoNormal"><a href="http://freedv.org/">http://freedv.org/</a> <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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