Fldigi
Fldigi 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 "sound card defined radio" whose available bandwidth is limited by the sound card's sample rate 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. 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.
Supported digital modes
| Mode Name | Speeds Supported | Custom Modes |
| Morse Code / CW | 5 - 50 words-per-minute | Yes |
| PSK | 31, 63, 63F, 125, 250, 500, 1000 | No |
| FSQ | 2, 3, 4.5, 6 | No |
| 0.5, 1.0, 2.0 | No | |
| Contestia | 4/125, 4/250, 8/250, 4/500, 8/500, 16/500, 8/1000, 16/1000, 32/1000, 64/1000 | Yes |
| DominoEX | Micro, 4, 5, 8, 11, 16, 22, 44, 88 | No |
| Hellschreiber | Feld Hell, Slow Hell, Feld Hell X5, Feld Hell X9, FSK Hell, FSK Hell-105, Hell 80 | No |
| MFSK | 4, 8, 11, 16, 22, 31, 32, 64, 64L, 128, 128L | No |
| MT63 | 500S, 1000S, 2000S, 500L, 1000L, 2000L | No |
| Navtex | Navtex | No |
| Olivia | 4/250, 8/250, 4/500, 8/500, 16/500, 8/1000, 16/1000, 32/1000, 64/2000 | Yes |
| QPSK | 31, 63, 125, 250, 500 | No |
| 8PSK | 125, 250, 500, 1000, 125FL, 250FL, 125F, 250F, 500F, 1000F, 1200F | No |
| PSKR | 125R, 250R, 500R, 1000R | No |
| RTTY | 45.45/170, 50/170, 75/170, 75/850 | Yes |
| SYNOP | SYNOP | No |
| THOR | Micro, 4, 5, 8, 11, 16, 22, 25x4, 50x1, 50x2 100 | No |
| SITORB | SitorB | No |
| Throb / ThrobX | 1, 2, 4 / X1, X2, X4 | No |
| WEFAX | IOC576, IOC288 | No |
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
- OSX
- macOS
- Linux,
- FreeBSD,
- OpenBSD,
- NetBSD,
- Solaris.
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
- Open Sound System
- Portaudio
- Pulseaudio
- Read / Write to WAV files
Features
- : The narrowband emergency messaging system
- Support for transmitting and receiving in all languages by using UTF-8 character encoding
- Connection to external programs via TCP/IP port 7322
- Ability to be used as a KISS modem via TCP/IP port 7342
- Dual tone multi-frequency encoding and decoding
- Automatic switching of mode and frequency by use of Reed Solomon Identifier signal identification
- Inbuilt macro language and processor for programmable automated control
- Sound card oscillator frequency/skew correction
- Measure sound card oscillator's skew to atomic clock: WWV or WWVH
- Measure RF receiver 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.
- Simultaneous decoding of multiple morse code signals.
- Decoding of morse code by self-organizing map artificial neural network
The Fldigi Suite
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.
https://sourceforge.net/projects/fldigi/files/flamp/ Flamp
http://www.w1hkj.com/FlarqHelpFiles/ Flarq
https://sourceforge.net/projects/fldigi/files/flmsg/ Flmsg
https://sourceforge.net/projects/fldigi/files/flwrap/ Flwrap
https://sourceforge.net/projects/fldigi/files/flnet/ FLNet
https://sourceforge.net/projects/fldigi/files/fllog/ FLLog
https://sourceforge.net/projects/fldigi/files/flwkey/ FLWkey
Flcluster
Flaa
Flrig
FLRig is a component of the FLDigi suite of applications that enables computer aided control of various radios using a serial or USB connection.Using FLRig in combination with FLDigi, events such as frequency, power level, receiver gain and audio gain may be adjusted from the computer automatically or by user intervention.
Test Tools
LinSim
CompText
CompTTY
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 sound card-digital-modem programs support this standard.
- PocketDigi
- FDMDV
- DM780
- Multipsk
- Fldigi
- AndFlmsg
- TIVAR
Software Architecture
For simple keyboard-to-keyboard communication Fldigi can be operated using just the main window. For more complex uses or file transfer external programs can be attached to the internal TCP/UDP ports 7322, 7342, and 7362.The image below helps to illustrate the interconnections and signal-flow within the Fldigi architecture.
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 sound card 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.
- - send and receive on-internet e-mail over a remote radio connection.
- - attach Fldigi as modem for Linux AX.25 and TCP/IP connections.
- - Java-based amateur radio chat program.
- - Program for unattended operation and person to person chat.
- Linux - Fldigi can be used in Linux as a KISS modem for AX.25 and TCP/IP connections.
Awards and recognitions
- At the 2014 Dayton Hamvention the project lead, Dave Freese, was recognized with the Technical Excellence Award "for his development and distribution of the Fast Light Digital Modem Application 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
- Fldigi was selected as Sourceforge's December 2017 Community Choice 'Project of the Month'
Notable users
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
- Amateur Radio Emergency Services
- Radio Amateur Civil Emergency Service
- Civil Air Patrol
- SATERN, the Salvation Army Team Emergency Radio Network
- SKYWARN a program of the United States' National Weather Service whose mission is to collect reports of localized severe weather.
Shortwave broadcasters
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 2017, following the demise of VOA Radiogram, began broadcasting digital data-streams using Fldigi via WRMI in Miami and Space Line in Bulgaria.
- Radio Havana Cuba
- Radio Moscow
- Radio Australia
- Radio Miami International
- Italian Broadcasting Corporation
- WBCQ
- Mighty KBC
MARS">Military Auxiliary Radio System">MARS
[Department of Homeland Security]
Fldigi is being used in-testing as part of the DHS Shares program, which utilizes "existing HF radio resources of government, critical infrastructure, and disaster response organizations to coordinate and transmit emergency messages"http://pskmail.org PSK Mail
Fldigi is used as the underlying modem for the project. PSK Mail allows users to retrieve and send normal emails over radio.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.Decodeable broadcasts
The broadcasts listed below are transmitted on a regular schedule and can be decoded using Fldigi.- VOA Radiogram Broadcasts
- W1AW Broadcasts