DMR, D-Star, System Fusion

By Adrian, Sat 21 October 2017, in category Amateur radio

amateur radio, D-Star, DMR, YSF

DMR, D-Star, System Fusion

Several people asked whether QRadioLink can have support for decoding other amateur radio digital modes, which are very common these days on amateur radio bands.

DMR is an international standard standing for Digital Mobile Radio, developed by the European Telecommunications Standards Institute (ETSI) in standard TS 102 361. There are plenty of manufacturers using this standard, and the price of terminals can be very cheap. DMR uses 4FSK modulation.

D-Star is a dedicated standard for amateur radio digital voice, with fewer manufacturers of radios and somewhat higher prices. The modulation type is GMSK.

System Fusion is another amateur radio standard developed by Yaesu and a relative new-comer on the market. The modulation used by System Fusion is C4FM, a variant of 4FSK.

All these modes have several things in common: they work with an FM radio and they use a proprietary voice codec called AMBE. Implementing receive only support for them would be almost trivial, thanks to Clayton Smith's gr-dsd. I've done it before with Gqrx (see my fork for digital modes ) and I could do it again. However I see no point in adding decode only support in QRadioLink. One should be able to also transmit these modes, not just receive them. In addition, the fact that they use a proprietary audio codec means I can't distribute the complete code without entering a legal grey area which I'd rather avoid.

As far as I know, the most complete implementation of these radio protocols is Jonathan Naylor's MMDVMHost. One could possibly use it for SDR purposes with some non-trivial changes. However, I believe that the moment to add support for modes which use a proprietary codec has not come yet. People are welcome though to try and add support for DMR, D-Star and YSF, but I will probably not merge any pull requests at the moment.