ARLA/CLUSTER: Próxima actividade de teste através da estação CQ0UARB

[Miguel Andrade (CT1ETL)]

Caros colegas,

O desafio que vos lançámos (e cujo anúncio será renovado dentro de dias,
como é habitual) consiste num teste em comunicações de voz (telefonia)
através do uso de uma das novas aplicações em formato digital para o Serviço
de Amador.
Caso não compareçam estações equipadas/interessadas em participar neste
teste, mantemos, como habitualmente o apelo para o envio de imagem em
televisão de varrimento lento no modo tradicional.

No entanto, para quem estiver interessado em aceitar o repto deste mês,
convidamos-vos a instalarem o programa FreeDV, o qual podem adquirir de
forma gratuita em - http://freedv.org/tiki-index.php.

Nada nos garante que vá funcionar em FM e em particular através de uma
estação repetidora de UHF, mas caso queiram explorar a sua instalação
aconselho vivamente o visionamento deste vídeo -
http://www.youtube.com/watch?v=zijJ556cs08.

Quem não estiver devidamente equipado para a emissão e recepção, poderá
apenas participar em recepção.
Uma vez que as comunicações serão intervaladas e mantidas também em formato
analógico ao longo de todo o teste ninguém será alheado do teste.

Aguardamos pela vossa participação e entusiasmo, pois embora este mês o mote
não seja a transmissão de imagens, será sem dúvida mais uma experiência para
fugir à rotina e explorarmos novas modalidades. 
Até mesmo o maior fracasso no objectivo proposto valerá a pena pelo desafio.
Na pior das hipóteses terminaremos a noite a trocar imagens, como é
habitual.
 
Deixo-vos com uma cópia da mensagem enviada pelo João Costa, em Outubro
passado, sobre este assunto.


73 de Miguel Andrade ( CT1ETL )
IM58js - 38º44'57" N/009º11'26" W
CQ Zone 14 ********* ITU Zone 37
endereço em/adress in www.qrz.com/db/CT1ETL
  

________________________________________
De: cluster-bounces  radio-amador.net
[mailto:cluster-bounces  radio-amador.net] Em nome de João Costa > CT1FBF
Enviada: quarta-feira, 30 de Outubro de 2013 13:18
Para: Cluster-ARLA
Assunto: 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.

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 0.96.5
August 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 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, 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 Response
When you play this 10 second 1 kHz to 2 kHz sweep .wav file 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 "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 Radio
Turn 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!). 
• Windows binary files. 
• Macintosh OSX. 
• Debian package repository, Wheezy x86 and amd64. 
• Red Hat Enterprise Linux repository set-up RPM. 
• Red Hat Enterprise Linux 6 repositories, i686 and x86_64. 
• Fedora repository set-up RPM. 
• Fedora repositories, Fedora 17, 18, 19, i686 and x86_64. 
• Android under development. 
You can also build from source code, project files are in the fdmdv2 and
codec2-dev folders. Information on how to set up read-only access to
Subversion is here.

Quick Start Guide
Several start-up guides are available
• Microsoft Windows Users Quick Start 
• Video Guide for Microsoft Windows Users 
• Video Quick Guide to Microphones 
Useful Frequencies
USA, 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.
Links
Google DigitalVoice group
FDMDV Digital Voice Resource Page
Codec 2 Voice Codec
FDMDV Modem
Why Open Source Digital Voice Is Important
FreeDV Specification
Notes for users of Tigertronics rig interfaces
K7VE's FreeDV QSO Finder
David Rowe interviewed about CODEC2
HamRadioNow.tv Episode 81 Bruce Parens and Mel Whitten interview at Dayton
Hamvention 2013
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