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The page isn’t immediately clear for non-hams. Voice digital mode radio is dominated by closed-source protocols. This is an attempt to open it up (M17), along with a reference implementation (TR-9). Some additional links:


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    Thank you for sharing, I have several questions if I may:

    • It is not clear, exactly, why the title says ‘DMR’. DMR is a specific protocol (just like D-Star or Fusion), but M17 does not appear to be compatible with any of them. M17 appears to be closer to dPMR, yet another protocol (because FDMA [1]) Is that correct, that M17 is not compatible with DMR (which is basically Motorola’s spec) ?

    • all 3 existing protocol use voice compression/decompression that is implemented in Proprietary and patented AMBE+2 chip and algorithm. No devices compatible with any of the 3 protocols can be manufactured without that codec, and the chip (as well as it is implementation if used to build the chip) must be licensed from DVS Inc. M17 chose, thankfully, to use open source code ( http://www.rowetel.com/wordpress/?page_id=452 ), but not clear if a chip for it already exists with similar dimensions and power requirements as the one for AMBE+2. Is there such a thing ? (I know that FreeDV uses this, but the size of the box hosting the Codec2 is pretty large [2] )

    • D-Star also works on HF frequencies (longer waves more distant communication). not clear what M17 does in this regard. I am assuming it would, but wanted to check if you know.

    • DMR uses TDMA method , meaning that 2 people can talk on same 12.5 kHz of bandwidth, As they were on 1 channel (because TDMA delays (shifts) the signal with 30ms delay ). Same works with data, or a mix data on 1 channel and voice on another. This means (at least in my understanding, which may be wrong) 50% less repeaters, to support same number of channels as the other tech.
      What would be comparable bandwidth efficiency for M17 compared to DMR(TDMA) as projected on voice quality and data speed ? (eg, voice on 12.5 kHz would sound more natural than on 6.5 kHz bandwith)

    [1] https://blog.retevis.com/index.php/dmr-versus-dpmr-comparison/ [2] http://www.rowetel.com/?page_id=3902 [3] M17 portable radio prototype http://www.rowetel.com/?p=7324

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      I’ll number the answers if that’s ok with you, just for future reference. I’ll start by saying that I don’t generally use any kind of Digital Mobile Radio myself.

      1. I put the term “DMR” in here. As I said, I don’t use any kind of digital audio radio but I’ve seen DMR confusingly used as shorthand for both the standard and the general concept encompassing D*Star and others. I was referring to the concept, sorry for being wrong here. If mods could remove that DMR reference in the title might help avoid similar confusion.

      2. I don’t know, I’m not the project author. Probably best to ask them as there may be other considerations (e.g. size, power consumption) that come into play.

      3. Looking at some of the TR-9 code I’ve seen references to 100-439.425Mhz, so I’d assume UHF/VHF operation but again, you may be better off asking the project. In theory HF might be possible but most local digital amateur signals I hear are (bearing in mind I don’t use one so it could just be my area) on 2m or 70cm bands.

      4. I don’t know, you’d have to talk to the project. This is just something I saw that looked interesting enough to look into further and I thought I’d share it.

      I think the questions you’re asking are good questions to ask. If you do get in touch it would be very helpful if you could comment with any info on the answers here.