Fldigi, the Fast Light Digital modem application, is a free and open-source program which allows an ordinary computer's sound card to be used as a simple two-way data modem. The software is mostly used by amateur radio operators who connect the microphone and headphone connections of an amateur radio SSB transceiver or an FM two way radio to the computer's headphone and microphone connections, respectively.
This interconnection creates a "soundcard defined radio" whose available bandwidth is limited by the soundcard's samplerate and the external radio's bandwidth.
Such communications are normally done on the shortwave amateur radio bands in modes such as PSK31, MFSK, RTTY, Olivia, and CW (morse code). Increasingly, the software is also being used for data on VHF and UHF frequencies.
Using this software, it is possible for amateur radio operators to communicate worldwide while using only a few watts of RF power.
Fldigi software is also used for amateur radio emergency communications when other communication systems fail due to natural disaster or power outage. Transfer of files, emails, and FEMA ICS forms are possible using inexpensive radio hardware.
Maps, Directions, and Place Reviews
Supported digital modes
Portability
Operating Systems
Fldigi is based on the lightweight portable graphics library FLTK and the C/C++ language. Because of this, the software can run on many different operating systems such as:
- Microsoft Windows (2000 or newer)
- OSX
- macOS
- Linux,
- FreeBSD,
- OpenBSD,
- Solaris.
Additionally, Fldigi is designed to compile and run on any POSIX compliant operating system that uses an X11 compatible window system / graphical user interface.
Architectures
The Fldigi software is written in highly portable C/C++ and can be used on many CPU architectures, including:
- amd64
- i386
- armhf/armel
- ia64
- mips
- mipsel
- powerpc
- s390
- s390x
- sparc
- Raspberry Pi .
Sound Systems
Multiple sound systems are supported by Fldigi, allowing the program to abstract the soundcard hardware across differing hardware and operating systems.
- Open Sound System (OSS)
- Portaudio
- Pulseaudio
- Read / Write to WAV files (file I/O)
Features
- NBEMS: The narrowband emergency messaging system
- Support for transmitting and receiving in all languages by using UTF-8 character encoding (some modes)
- Connection to external programs via TCP/IP port 7322
- Ability to be used as A KISS modem (via TCP/IP port 7342)
- DTMF encode / decode
- Soundcard oscillator frequency/skew correction
- Measure soundcard oscillator's skew to atomic clock: WWV or WWVH
- Measure frequency skew to atomic clock: WWV or WWVH
- Transmit a WWV-like time signal as a calibration reference
- Control of external transmit / receive radio hardware by using GPIO pins. (For embedded hardware)
- Decoding of morse code (CW) by self-organizing map artificial neural network (trained artificial intelligence)
The Fldigi Suite
The "Fldigi Suite" consists of the Fldigi modem and all extension programs released by the same development group. These extensions add more capabilities to Fldigi such as verified file transfer and message passing. Interconnecion between these programs and the Fldigi modem is made over TCP/IP port 7322.
Flamp
Flamp implements the Amateur Multicast Protocol by Dave Freese, W1HKJ and is a tool for connectionless transferring of files to multiple users simultaneously without requiring any existing infrastructure. The program breaks a given file into multiple smaller pieces, checksums each piece, then transmits each piece one or more times. When all parts are correctly received the sent file is re-assembled and can be saved by receiving stations. This program is useful for multicasting files over lossy connections such as those found on high frequency or during emergency communications.
Flarq
Flarq implements the ARQ specification developed by Paul Schmidt, K9PS to transfer emails, text files, images, and binary files over radio. This protocol is unicast and connection-based. The software seamlessly integrates with existing email clients such as Microsoft Outlook, Mozilla Thunderbird, and Sylpheed.
Flmsg
Flmsg allows users to send, receive, edit, and create pre-formatted forms. Such a system speeds the flow of information during emergency communications. The software has a number of forms built-in including FEMA ICS forms, MARS reports & messages, Hospital ICS forms, Red Cross messages, IARU and NTS messages.
Flwrap
Flwrap is a tool for the sending of files using a simplified drag and drop interface. Data compression is available also, which reduces data transfer times.
Flnet
Fllog
Flwkey
RSID
To identify the mode being transmitted a signal called an RSID, or Reed-Solomon Identifier, can be transmitted before the data. Using this identifier the receiving software can automatically switch to the proper mode for decoding. The assigning of these identifiers to new modes is coordinated to ensure inter-operation between programs. Currently 7 soundcard-digital-modem programs support this standard.
- PocketDigi
- FDMDV
- DM780
- Multipsk
- Fldigi
- AndFlmsg
- TIVAR
RSID operates by sending a short burst of a specific modulation before the data signal, which can be used to automatically identify over 272 digital modes. This burst consists of a 10.766 baud 16-tone MFSK modulation where 15 tones/symbols are sent. The burst occupies 172 Hz of bandwidth and lasts for 1.4 seconds.
Community-provided extensions
Fldigi allows external programs to attach and send / receive data by connecting to port 7322/ARQ or 7342/KISS. When used this way, Fldigi and the computer's soundcard are acting as a "softmodem" allowing text or data sent on one computer to be transferred using the wireless radio link in-between. Programs which have a history of use with Fldigi as the underlying modem include:
- D-Rats - easy to use chatrooms, email, and file transfer over-radio.
- PSKmail - send and receive on-internet e-mail over a remote radio connection.
- Fldigiattach - attach Fldigi as modem for Linux AX.25 and TCP/IP connections.
- UIChat - Java-based amateur radio chat program.
- LinkUP - Program for unattended operation and person to person chat.
- Linux - Fldigi can be used in Linux as a KISS (TNC) modem for AX.25 and TCP/IP connections.
Awards and recognitions
- At the 2014 Dayton Hamvention the project lead, Dave Freese (W1HKJ), was recognized with the Technical Excellence Award "for his development and distribution of the Fast Light Digital Modem Application (fldigi) family of programs for use in amateur and emergency communications."
- Fldigi was selected as Sourceforge's June 2017 Staff 'Project of the Month'
- Fldigi was one of Sourceforge's 'Projects of the Week' for Oct 17, 2016
Notable users
AirChat
In 2014 the group Anonymous released a communications tool named AirChat, which used Fldigi as the underlying modem. This provided a low speed yet reliable data connection using only moderate radio hardware. The AirChat software allows for anonymous transmissions of both encrypted and unencrypted messages over unencrypted channels.
Shortwave broadcasters
Following the successful tests by the Voice of America's VOA Radiogram program, international and government shortwave broadcasters began testing and experimenting with digital data over shortwave broadcast channels using the Fldigi software. These tests led to regular weekly digital broadcasts by the broadcasters listed below.
- VOA Radiogram, service terminated in 2017 and continuing as Shortwave Radiogram.
- In June of 2017, following the demise of VOA Radiogram, Shortwave Radiogram began broadcasting digital data-streams using Fldigi via WRMI in Miami and Space Line [1] in Bulgaria.
- Radio Havana Cuba
- Radio Moscow
- Radio Australia
- Radio Miami International
- Italian Broadcasting Corporation
- WBCQ (SW)
- Mighty KBC
MARS
The Fldigi suite of programs has become popular within the U.S. Army and U.S Air Force Military Auxiliary Radio System.
PSK Mail
Fldigi is used as the underlying modem for the PSKmail project . PSK Mail allows users to retrieve and send normal emails over radio.
Disaster relief services
The software is also utilized by some organizations for both routine and disaster/emergency relief services.
- Multiple state and county Emergency operations centers
- W1AW (ARRL)
- Amateur Radio Emergency Services (ARES)
- Radio Amateur Civil Emergency Service (RACES)
- Civil Air Patrol
- Skywarn
Decodeable broadcasts
The broadcasts listed below are transmitted on a regular schedule and can be decoded using Fldigi.
- SITOR text forecasts and storm warnings
- WEFAX visual weather fax
- SYNOP surface synoptic observations
- NAVTEX warnings, forecasts, and safety information broadcasts
- VOA Radiogram Broadcasts
- W1AW Broadcasts
Source of the article : Wikipedia
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