DMR to Echolink gateway

Discussion in 'Echolink/IRLP Tech Board' started by W4RRN, Mar 20, 2017.

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  1. W4RRN

    W4RRN XML Subscriber QRZ Page

    Hello All,

    I am considering to get a dmr radio and hotspot. I was just wondering if there was a dmr to echolink gateway out there.

    73's,
    Warren
    KN4AQG
     
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    You can make one. Linux is your friend.

    I recommend the RPi3 Model B.

    They work great for Allstar too.

    Have Fun.
     
  3. AH6LE

    AH6LE Ham Member QRZ Page

    I am not aware of any opensource analog/dmr bridge.....
     
  4. K0RGR

    K0RGR Premium Subscriber QRZ Page

    There are some DMR repeaters with Echolink. There are some potential issues - an incoming transmission from Echolink to DMR has no way of knowing if the time slot is clear. The author of Echolink has a rule that Echolink is not to be linked to any other VoIP radio network. It's also got another potential problem - if you have Echolink on your DMR repeater, and then use it to link to something else that is also on DMR, you can cause a huge feedback loop that ties up the talk group(s) involved and all the repeaters and users attached thereto. This happens with some frequency on Brandmeister and also on the D-star Reflectors - last time I tried to listen to D-star Reflect 01C, someone did this. I moved over to Ref 30C, and eventually, the same thing happened there.

    So, I would advise you to follow the rules Echolink has put in place.

    Wireless Holdings has a product in development that should help to eliminate the feedback loop issue. It will allow repeater owners to have a DMR, D-star, FUSION, and analog repeater in the same rack, and link them all to each other.
     
    F4VSE and KD8ZJP like this.
  5. KI6E

    KI6E Platinum Subscriber Platinum Subscriber QRZ Page

    They could also solve this at the backhaul if they wanted to. Brandmeister and Echolink could create software to link the networks at the backhaul servers.
     
  6. W4EAE

    W4EAE Premium Subscriber QRZ Page

    For a lot of reasons, an Echolink to DMR bridge would be undesirable; not least of which is sound quality. DMR uses a digital codec (AMBE), but so does Echolink (GSM). Both are rather low audio quality codecs, and it is never a great idea to transcode from one highly compressed codec to another. The issue is the type of compression artifacts created by GSM are very different from the compression artifacts created by AMBE; so in the end you have nearly double the distortion of sound.

    Transcoding something like D-Star to DMR does not produce the same level of losses in quality as the codecs are two different versions AMBE and are very similar. Transcode D-Star to DMR and back to D-Star though, and it becomes a mess. This is why ad hoc linking is a bad idea, particularly on a much used reflector. Even if there are no loops, the signal you hear might be transcoded four or five times from one end to the other in certain situations; rendering is virtually unreadable.

    If you want to play with transcoding digital to analogue, a fun project that couldn't really hurt anything is a DMR, D-Star, or C4FM to (local) FM node. You can build this with a Pi, a single AMBE chip, an FM radio, and some code from Github.
     

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