Open Source Amateur Digital Voice
FreeDV is a Digital Voice mode for HF radio. You can run FreeDV using a free GUI application for Windows, Linux and OSX that allows any SSB radio to be used for low bit rate digital voice.
Alternatively you can buy a SM1000 FreeDV adapter that allows you to run FreeDV (1600 and 700D modes) on any HF radio without a PC or sound card. If you are a hardware or software developer, you can integrate FreeDV into your project using the LGPL licensed FreeDV API.
FreeDV is being developed 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 Lesser Public License version 2.1. The modems and Codec 2 speech codec used in FreeDV are also open source.
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 speech 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.
FreeDV 700D can outperform SSB at low SNRs.
FreeDV 2020 is built around leading edge neural net speech coding (LPCNet), putting Ham radio at the forefront of digital radio innovation. It provides 8 kHz wide audio bandwidth, while using just 1600 Hz of RF bandwidth.
Urban HF noise is a growing problem for SSB communications. Hams around the world are using the advanced FEC and modem technology in FreeDV to overcome urban HF noise in channels where SSB is unusable.
Here is what you need:
- A SSB receiver or transceiver
- FreeDV software, download links are below.
- A Windows, Linux or OSX PC with one (receive only) or two sound cards.
- Cables to connect your PC to your SSB radio.
- A SM1000 Digital Voice Adaptor
- Cables to connect the SM1000 to your SSB radio
Connecting Your Radio
If you don’t have a built in sound card for digital modes you 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 to an average power of about 20% of its PEP power. There is a 8-12 dB peak-to-average power ratio in our HF modem. Over-driving will reduce the received S/N. More is not better for DV!
- FreeDV 1.4.1 Beta Windows 32-bit Installer
- FreeDV 1.4.1 Beta Windows 64-bit Installer
- Now in the main Fedora and Fedora EPEL 6 & 7 repositories!
- FreeDV-1.4.1 OSX DMG
- Now in the Debian Unstable repositories!
- FreeDV GUI Source Code
- Codec 2 Source Code
- FreeDV GUI Source Code Archive 1
- FreeDV GUI Source Code Archive 2 (Pre 1.4)
- Codec2 Source Code Archive 1
- Codec2 Source Code Archive 2 (Pre 0.9.2)
- LPCNet (Experimental FreeDV version) Source Code Archive
Several guides are available
- FreeDV User Manual – How to get started, notes on advanced and new features in the latest versions of FreeDV.
- VK5SA FreeDV Quick Start Guide
- SM1000 Manual – How to set up, use and reflash the SM1000.
- VK5DM guide to building SM1000 patch leads
Who can I Talk To?
Login to the K7VE FreeDV QSO Finder to find other Hams using FreeDV.
|Argentina||7.045 MHz LSB||Mon, Wed, Fri 1800 UTC||Radio Club Coronel Pringles, listen on the LU4EEC KiwiSDR|
|Netherlands||3.720 MHz in USB||Every Sunday 1000 UTC||Net|
|UK||3.643MHz LSB||Sundays mornings at 09:00 Local||RSGB broadcast by Matt G6WPJ|
|UK||3.697 MHz LSB 700D||1600 Local||Casual QSOs|
|USA||14.236 MHz USB||Anytime||Casual QSOs|
- Please post your questions to the Digital Voice Google group.
- Developers please subscribe to the Codec 2 Mailing List.
For casual chat there is a #freedv IRC channel on freenode.net
- Cross platform, runs on Linux, Windows and OSX.
- Open source, patent free Codec and Modem that anyone can experiment with and modify
- Waterfall, spectrum, scatter and audio oscilloscope 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.
FreeDV is being maintained and extended by David Rowe, VK5DGR. Richard Shaw KF5OIM maintains the Cmake build system, Windows and Fedora packaging. Walter, K5WH is leading Windows testing in the USA. Debian packaging thanks to A. Maitland Bottoms (AA4HS) and the Debian Hamradio Maintainers. Mooneer Salem K6AQ and David Tiller, K4DET, have been kindly building OSX images for the project.
As development continues, many people are helping whom we have not credited on this web site, but we appreciate all of their work.
In 2012 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 contributed 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.
- Google DigitalVoice group
- Codec 2 Voice Codec
- K7VE’s FreeDV QSO Finder
- Radio Club Coronel Pringles in Argentina is very active with FreeDV and other digital modes. You can listen to their FreeDV transmissions on 7.045 MHZ LSB Monday, Wednesday, and Friday evenings at 1800 UTC on the LU4EEC KiwiSDR.
- FreeDV 1600 Specification
- Notes for users of Tigertronics rig interfaces
- David Rowe interviewed about CODEC2
Adding FreeDV To Your Hardware Product or Software Project
If you are a hardware or software developer, you can integrate FreeDV into your project using the LGPL licensed FreeDV API.
No license fees are required to use FreeDV. Including it in your project is a simple as compiling a library of C code. FreeDV does not require an operating system, it runs happily “bare metal” on small machines such as micro-controllers. It does require a hardware Floating Point Unit (FPU).
The FreeDV stack is gcc compilable C software that runs in about 1% of the CPU resources on a modern PC. FreeDV 1600 and 700D has even been ported to a “bare metal” STM32F4 micro-controller (168MHz, FPU, 128k RAM, 500k flash).
FreeDV requires a floating point processor. While it might be possible to create a fixed-point implementation, there is little incentive to do so since floating point processors capable of running FreeDV are now available under $5.
How much have you spent on Ham radio gear this year? How did it compare to FreeDV? FreeDV represents an open and free future for digital voice over Ham Radio. You can help by donating via PayPal or Patreon.
The FreeDV developers have donated 1000’s of hours of highly skilled engineering time. Your donation will reduce the out of pocket costs of the developers for hardware, travel, and FreeDV promotion at Ham events.