xenial (1) freedv.1.gz

Provided by: freedv_1.1-1_amd64 bug

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/