Free DV – open source digital voice codec for HF

Want to try this out soon – need to interface my TS-520 to my laptop:

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.

FreeDV is a GUI application for Windows and Linux that allows any SSB radio to be used for low bit rate digital voice.

Speech is compressed down to 1400 bit/s then modulated onto a 1100 Hz wide QPSK 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.

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.

See a demo of a freeDv QSO:

More info at:



About va3paw
Ham radio enthusiast, software developer

3 Responses to Free DV – open source digital voice codec for HF

  1. GIlbert W. Finley says:

    Hi: I have been active here on FreeDV for a couple of years now and haven’t heard another VE3, I would especially like contacts on both 75 and 40 so far the only contacts have been on 14.236. I work Florida regularly and K0PFX too.73 Gil VE3DFU Sarnia

  2. jose says:

    hello, I’m LU5 DKI and I’m experimenting with free dv with 2 local friends with 2 local radio amateurs in 80 meters, with interfaces homemade, we would like to exchange ideas to get started in this form of communication, my email is LU5 DKI speedy., thank you very much

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