Provided by: freedv_1.1-1_amd64 
NAME
freedv - Digital Voice for HF
DESCRIPTION
FreeDV is a GUI application that allows any SSB radio to be used for low bit rate digital voice.
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.
FreeDV was built by an international team of Radio Amateurs working together on coding, design, user
interface and testing. FreeDV is open source software, released under the GNU Public License version 2.1.
The FDMDV modem and Codec 2 Speech codec used in FreeDV are also open source.
New Upgrade as of March 2013
The new version 0.96 provides a 1600 bit-per-second mode that communicates at much lower signal levels
than previously. Communications should be readable down to 2 dB SNR, and long distance contacts are
reported using 1 to 2 watts power. A compatibility mode for communication with the older 0.91 version is
included.
Why FreeDV?
Amateur Radio is transitioning from analog to digital, much as it transitioned from AM to SSB in the
1950s and 1960s. How would you feel if one or two companies owned the patents for SSB, then forced you to
use their technology, made it illegal to experiment with or even understand the technology, and insisted
you stay locked to it for the next 100 years?? That is exactly what was happening with digital voice. But
now, hams are in control of their technology again.
FreeDV is unique as it uses 100 percent Open Source Software, including the audio codec. No secrets,
nothing proprietary FreeDV represents a path for 21st century Amateur Radio where Hams are free to
experiment and innovate, rather than a future locked into a single manufacturers closed technology.
Demo Video
Watch this video of a FreeDV QSO.
http://freedv.org/tiki-index.php?page=video
Here is what you need:
A SSB receiver or transceiver
FreeDV software
A computer with one (receive only) or two sound cards.
Cables to connect your computer to your SSB radio.
Test your Transmitter Frequency Response
When you play this 10 second 1 kHz to 2 kHz sweep .wav file(external link) through your transmitter, the
power level should remain constant. If not, look for filtering and processing to turn off.
Connecting Your Radio
If you are lucky enough to have a "9600" input and output on your radio, this is the best connection for
every digital mode, even 1200 packet, and your audio box should be configured for 9600 or "no pre-
emphasis/de-emphasis" if it has that setting. If the radio's configuration menu has a 1200/9600 setting,
leave it permanently on 9600.
The "9600" and "1200" settings are misnamed. "9600" should really be called "direct connection", and
"1200" should be called "processed". The audio processing in your radio does not help any digital mode.
Configuring Your Radio
Turn off as much processing as possible. In general noise blankers, DSP band limit filtering, and narrow
bandpass filters are likely to hurt rather than help. Compression, DSP noise and carrier elimination, and
voice processing are definitely wrong for Digital modes. FreeDV's FDM modem does its own DSP, and in
general this is true for other digital programs as well. The only things that we would expect to hurt the
signal are intrusion of the opposite sideband, images of out-of-passband signals, and intermodulation
distortion. You can see the effect of different settings in the S/N display of FreeDV.
Drive your transmitter and amplifier so that it emits 10%% to 20%% of its rated power continuously. There
is a 12 dB peak-to-average power ratio in the FDM modem, and peak clipping in your amplifier will reduce
the received S/N. Modern transmitters and amplifiers are only as linear, and only have as much headroom,
as is necessary for voice SSB. Ask manufacturers and reviewers to start rating linearity and headroom for
digital modes.
SEE ALSO
http://freedv.org/