The large VHF / UHF digital voice communication modes all require the same AMBE vocoder chip from dvsinc. This surface mount chip can be aquired standalone for a relatively high price or all of the required encode / decode electronics can be preinstalled in the form of various boards such as the DV Mega.

Every single product which transmits and receives most mainstream digital voice modes requires one of these chips from the specific manufacturer.

This introduces limitations, however. In the case of attempting to run a virtual private server providing an analog to digital DMR bridge using the DMRGateway software , I couldn't procede any farther until I plugged a USB fob with the vocoder chip which is completely impossible on a virtual server. Even if I had a physical computer with USB, price is a large limiting factor in this as well.

So basically, at this point, after several hours of research and attempting software packages, there is no way I have found to decode / encode digital voice through the means of software only.

Due to the fact that amateur radio requires unencrypted and usually led by an open-source community, I am wondering if anybody has even heard if this has been done before, if someone is working on it, or if there are any alternative open-source digital voice modes for VHF and above not requiring a separate vocoder chip?

Small Update: Alinco looks like they use an open source GMSK modem using the ITU V.32 protocol. I couldn't really find any other information on this, however.

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    $\begingroup$ Some experiments have been done with codec2 on VHF. I've never tried it personally though, nor have I heard of anyone who has. The amateur radio hobby seems to be divided between people who get on the air a lot with whatever equipment the manufacturers give them, and experimenters that build new radios and technology but rarely get on the air. So I'm not sure anything will ever come of it :-) $\endgroup$ Commented Sep 19, 2016 at 20:51
  • $\begingroup$ Codec2 uses FSK. This MAY work over VHF, but the problem is you have to modulate over SSB or it will underperform FM if you try to send it over FM modulation. GMSK modems, however, tend to perform well over FM modulation, and DSTAR users can build a node with a DVboard and an FM transceiver discriminator/flat audio. I would really love to see something like codec2 which uses GMSK. $\endgroup$
    – Skyler 440
    Commented Sep 19, 2016 at 22:46
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    $\begingroup$ I'm pretty sure the link above describes a GMSK modem sending Codec 2 encoded voice, though he does say running it through an FM radio didn't perform very well. The D-STAR modem isn't patented and has open-source implementations, and also a data-only mode. You could theoretically run Codec 2 over D-STAR, though I'd guess D-STAR's data rate is well in excess of what's required by Codec 2. $\endgroup$ Commented Sep 20, 2016 at 12:12
  • $\begingroup$ MD380EMU and OP25, both available on GITHUB now accomplish this task or encode & decode ! $\endgroup$
    – Skyler 440
    Commented Apr 9, 2019 at 17:53

1 Answer 1


Here is a link to a presentation by Bruce Perens K6BP two years ago: http://algoram.com/dcc2014/AMBE_Exposed.pdf. Start at "Can Hams Use Software AMBE?" I am not aware of any significant changes since then. There exists a software solution (mbelib), but it is patent encumbered. So much so that the authors are anonymous.

You are probably aware of the open voice codec "Codec2" by David Rowe: http://www.rowetel.com/?page_id=452. But it doesn't appear to fit your use case.

  • $\begingroup$ Thanks for the answer, and nice links. I am well aware of Codec2, but it does not seem to work over FM unlike DSTAR because of the FSK characteristics. mail-archive.com/[email protected]/… $\endgroup$
    – Skyler 440
    Commented Sep 19, 2016 at 22:52
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    $\begingroup$ Codec2 really is a codec. It is often used with FSK, but that is not necessary. Also, FSK is just the discrete form of FM, do I don't see your point. $\endgroup$ Commented Oct 5, 2016 at 1:38

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