ARLA/CLUSTER: FreeDV: Digital Voice for HF - Communications should be readable down to 2 dB S/N, and long-distance contacts are reported using 1-2 watts power.

João Costa > CT1FBF ct1fbf gmail.com
Quarta-Feira, 30 de Outubro de 2013 - 13:18:21 WET 

Introduction
FreeDV is a GUI application for Windows, Linux and MacOS (BSD and Android
in development) that allows any SSB radio to be used for low bit rate
digital voice.

Speech is compressed down to 1600 bit/s then modulated onto a 1.25 kHz wide
16QPSK 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. Communications should be readable down to 2 dB S/N, and
long-distance contacts are reported using 1-2 watts power.

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 version 0.96.5August 15, 2013: Repairs T/R switching
(including both serial control line switching and hamlib serial commands)
and a conflict in the use of the space bar between the options panel and
T/R switching.
Why FreeDV?Amateur Radio is transitioning from analog to digital, much as
it transitioned from AM to SSB in the 1950's and 1960's. 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's exactly what *was* happening with digital voice. But now, hams are
in control of their technology again!

FreeDV is unique as it uses 100% 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 VideoWatch this video <http://freedv.org/tiki-index.php?page=video> of
a FreeDV QSO.
Here is what you need:

   - A SSB receiver or transceiver
   - FreeDV software, download links are below.
   - A Windows or Linux PC with one (receive only) or two sound cards.
   - Cables to connect your PC to your SSB radio.

Test your Transmitter Frequency ResponseWhen you play this 10 second 1 kHz
to 2 kHz sweep .wav
file<http://rowetel.com/downloads/codec2/1k_2k_sweep.wav>[image:
(external link)] through your transmitter, the power level should remain
constant. If not, look for filtering and processing to turn off.
Connecting Your RadioIf 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 "pre-emphasis". The
pre-emphasis that comes with the 1200 setting doesn't help any digital
mode. The 9600 connection is the most direct and unprocessed path to the
modulator and demodulator of your radio.

Those who don't have a special connection for digital modes can use the
normal audio inputs and outputs of your radio. The same cables and hardware
that you use for other digital modes that are based on PC programs will
work with FreeDV, but you will need a second sound interface for the
microphone and speaker connections to the FreeDV program. A USB headset of
the sort used by gamers is all you need for the second sound interface.
Configuring Your RadioTurn off as much processing as possible. In general
noise blankers, DSP band limit filtering and narrow bandpass filters are
more likely to hurt than help, while compression, DSP noise or carrier
elimination, and voice processing are *definitely* wrong for Digital modes.
FreeDV's HF modem does its own DSP, and in general this is true for other
digital programs as well.

You can see the received effect of different settings in the S/N (signal to
noise ratio) display of FreeDV. A higher S/N is better.

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
our HF 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, thus we suggest you
maintain amplifier headroom by operating well below your full power output.
FreeDV is more efficient than SSB voice, and will achieve similar range to
an SSB signal driven at higher levels, and better audio quality. We
encourage you to ask manufacturers and reviewers to start rating
transmitter and amplifier linearity and headroom for *digital* modes, not
just SSB voice.
Download

   - Windows Installer
(NEW!)<http://files.freedv.org/FreeDV-0.96.5-win32.exe>[image:
   (external link)].
   - Windows binary files <http://files.freedv.org/freedv-windows.zip>[image:
   (external link)].
   - Macintosh OSX <http://files.freedv.org/OSX>[image: (external link)].
   - Debian package repository, Wheezy x86 and
amd64<http://files.freedv.org/debian>[image:
   (external link)].
   - Red Hat Enterprise Linux repository set-up
RPM<http://files.freedv.org/freedv-repo-1.0-1.el.noarch.rpm>[image:
   (external link)].
   - Red Hat Enterprise Linux 6 repositories, i686 and
x86_64<http://files.freedv.org/el>[image:
   (external link)].
   - Fedora repository set-up
RPM<http://files.freedv.org/freedv-repo-1.0-1.fedora.noarch.rpm>[image:
   (external link)].
   - Fedora repositories, Fedora 17, 18, 19, i686 and
x86_64<http://files.freedv.org/fedora>[image:
   (external link)].
   - Android <http://blog.jms.id.au/2013/02/freedv-on-android>[image:
   (external link)] under development.

You can also build from source
code<http://freetel.svn.sourceforge.net/svnroot/freetel>[image:
(external link)], project files are in the fdmdv2 and codec2-dev folders.
Information on how to set up read-only access to Subversion is
here<http://sourceforge.net/scm/?type=svn&group_id=217466>[image:
(external link)].
Quick Start GuideSeveral start-up guides are available

   - Microsoft Windows Users Quick
Start<http://freedv.org/tiki-index.php?page=Microsoft+Windows+Quick+Start+Guide>
   - Video Guide for Microsoft Windows
Users<http://freedv.org/tiki-index.php?page=Video+Microsoft+Windows+Quick+Start+Guide>
   - Video Quick Guide to
Microphones<http://www.youtube.com/watch?v=7pSj7IZfGKI>[image:
   (external link)]

Useful FrequenciesUSA, 14.236 MHz
Login to FreeDV QSO Finder for list of frequencies

Support
Please post your questions to the "Digital Voice" Google group:
digitalvoice  googlegroups.com

Design & Key Features
Design:

   - Codec 2 voice codec and FDMDV modem
   - 50 baud 16 QPSK voice data
   - 1 Center BPSK carrier with 2x power for fast and robust
   synchronisation.
   - 1.25 kHz spectrum bandwidth (half SSB) with 75 Hz carrier spacing
   - 1400 bit/s data rate with 1375 bit/s voice coding, 25 bit/s text for
   call sign ID, 200 bit/s FEC.
   - No interleaving in time, resulting in low latency, fast
   synchronization and quick recovery from fades.
   - 44.1 or 48kHz sample rate sound card compatible

Key Features:

   - Cross platform, runs on Linux, Windows, MacOS, BSD, and a Java version
   runs on Android.
   - Open source, patent free Codec and Modem that anyone can experiment
   with and modify
   - Waterfall, spectrum, scatter and audio oscilliscope displays.
   - Adjustable squelch
   - Fast/slow SNR estimation
   - Microphone and Speaker signal audio Equaliser
   - Control of Transmitter PTT via RS232 levels
   - Works with one (receive only) or two (transmit and receive) sound
   cards, for example a built in sound card and USB headphones.

Credits
FreeDV was coded from scratch by David Witten (GUI, architecture) and David
Rowe (Codec 2, modem implementation, integration).

The FreeDV design and user interface is based on FDMDV, which was developed
by Francesco Lanza, HB9TLK. Francesco received advice on modem design from
Peter Martinez G3PLX, who has also advised David on the FDMDV modem used in
FreeDV.

Mel Whitten, K0PFX has contibuted greatly to the design, testing and
promotion of several Digital Voice systems, including FDMDV. This practical
experience has led to the current design – a fast sync, no FEC, low latency
system that gives a “SSB†type feel for operators. Mel and a team of alpha
testers (Gerry, N4DVR; Jim, K3DCC; Rick, WA6NUT; Tony, K2MO) provided
feedback on usability and design of FreeDV.

Bruce Perens has been a thought leader on open source, patent free voice
codecs for Amateur Radio. He has inspired, promoted and encouraged the
development of Codec 2 and FreeDV.

As development continues, a great many people are pitching in whom we have
not credited on this web site, but we appreciate all of their work.
Developer Resources
There is a free, if somewhat old, wxWidgets book that you can download
here<http://www.phptr.com/content/images/0131473816/downloads/0131473816_book.pdf>[image:
(external link)].

Links
Google DigitalVoice group <http://groups.google.com/group/digitalvoice>[image:
(external link)]
FDMDV Digital Voice Resource Page <http://n1su.com/fdmdv/>[image: (external
link)]
Codec 2 Voice Codec <http://rowetel.com/codec2.html>[image: (external link)]
FDMDV Modem <http://rowetel.com/blog/?page_id=2458>[image: (external link)]
Why Open Source Digital Voice Is Important <http://codec2.org/>[image:
(external link)]
FreeDV Specification<http://freedv.org/tiki-index.php?page=FreeDV+Specification>
Notes for users of Tigertronics rig
interfaces<http://freedv.org/tiki-index.php?page=Tigertronics>
K7VE's FreeDV QSO Finder <http://qso.k7ve.org/>[image: (external link)]
David Rowe interviewed about
CODEC2<http://www.youtube.com/watch?v=Nzf4XCCwHoI>[image:
(external link)]
HamRadioNow.tv Episode 81 Bruce Parens and Mel Whitten interview at Dayton
Hamvention 2013 <http://arvideonews.com/hrn/>[image: (external link)]

FAQ
Q1: Is there any way to save the screen settings when you drag the tabs to
multiple windows on the main screen?
A1: No, as we can't work out how to support saving and restoring this
information with wxWidgets.

More Info: http://freedv.org/tiki-index.php
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