Introduction

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.

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.

News

Check the GitHub Releases Page for the latest information on software releases.

October 2023FreeDV 1.9.4 – Bug fixes and experimental OmniRig support
September 2023FreeDV 1.9.2 – FreeDV Reporter usability improvements and bugfixes
August 2023FreeDV 1.9.1 – TX monitoring support, various bugfixes
July 2023FreeDV 1.8.12 – Frequency change request support for FreeDV Reporter, various bugfixes
June 2023FreeDV 1.8.11 – FreeDV Reporter support, Hamlib improvements
April 2023FreeDV 1.8.9 – Quick Record, callsign history
March 2023FreeDV 1.8.8.1 – PSK Reporter and serial port usability improvements
ARDC awards grant to FreeDV
January 2023FreeDV 1.8.7 – “Easy Setup” to simplify first-time setup
FreeDV is now on Discord

Why FreeDV?

Amateur Radio is transitioning from analog to digital, much as it transitioned from AM to SSB in the 1950s and 1960s. 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 manufacturer’s closed technology.

Controlled testing suggests FreeDV is comparable to and, in some cases, works better than SSB on low SNR channels.

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.

FreeDV 1600 and 2020 is being used over the QO-100 satellite and for experimental combinations of Internet and HF radio to overcome poor propagation.

Here is what you need:

  • An SSB receiver or transceiver
  • Either:
    • FreeDV software (download links are below, available for Linux, macOS and Windows),
    • An SM1000 Digital Voice Adaptor, or
    • An ezDV device
  • If using a PC and the FreeDV software:
    • A sound device associated with your radio. This is typically the USB sound device created by a modern radio (when plugged in) or a purpose-built audio interface (such as SignaLink or RIGBlaster).
    • A sound device to listen to the decoded output and/or to transmit. This is usually a USB/Bluetooth headset or the sound card built into your PC.
    • Note: two separate hardware devices are required if you want to transmit.
  • If using a SM1000 or ezDV device:
    • Cables to connect your device to your SSB radio (optional for ezDV depending on the radio model).

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 an 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!

Download

Source Code

Documentation

Several guides are available:

Who can I Talk To?

Login to FreeDV Reporter (source) to find other Hams using FreeDV.

WorldwideAnyThird weekend of every month (12AM Pacific Saturday to 11:59 PM Sunday)FreeDV Activity Day
Argentina7.045 MHz LSBMon, Wed, Fri 1800 UTCRadio Club Coronel Pringles, listen on the LU4EEC KiwiSDR
Australia7.177 MHzAnytimeCasual QSOs
Netherlands3.625 MHz LSB 700DEvery Sunday 1000 UTCNet
UK3.640 MHz (primary)
3.643 MHz (secondary)
LSB 700D
Sundays mornings at 09:00 LocalRSGB broadcast by Matt G6WPJ
UK5.3685 MHz USB,
3.693 or 3.697 MHz LSB
(as conditions permit)
700D
1600 LocalDaily Net
USA14.236 MHz USBAnytimeCasual QSOs

Getting Help

If you need assistance with FreeDV, you can try the following:

Key Features

  • 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.

Credits

FreeDV is being maintained and extended by Mooneer Salam K6AQ and David Rowe, VK5DGR. Richard Shaw KF5OIM maintains the Cmake build system 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.

As development continues, many people are helping whom we have not credited on this website, but we appreciate all of their work.

History

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 the 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.

Links

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 as 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 microcontroller (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 for under $5.