DMR, C4FM and D-STAR compared
Amateur radio arrived at digital voice three times over, from three directions, and the results do not talk to each other. A DMR radio cannot work a D-STAR repeater. Choosing between them is mostly a question of what is already on the air where you live.
DMR
Borrowed from commercial land mobile radio, which is why the equipment is comparatively cheap. DMR splits each channel into two time slots, so one repeater carries two conversations at once. Access is organised around talkgroups — numbered rooms you join — and a colour code, which does the same job as a CTCSS tone in keeping other systems out.
Programming a DMR radio means building a codeplug, which is genuinely more work than tuning an analogue set. In return it is the most widely deployed digital mode worldwide, largely through the BrandMeister network.
C4FM
Yaesu's System Fusion, developed for amateur use rather than adapted to it, and the easiest of the three to live with. A Fusion repeater accepts analogue FM as well as digital and switches automatically, so nobody is locked out. Rooms are reached through Wires-X, and a DG-ID number can restrict access in the way a colour code does on DMR.
D-STAR
The oldest of the three, developed with the Japanese national society and long associated with Icom. It carries a callsign in every transmission, routes by callsign rather than by room, and has a low-rate data channel alongside the voice. Its footprint is smaller than it was, but it remains strong in parts of Europe and Japan.
Choosing
| DMR | C4FM | D-STAR | |
|---|---|---|---|
| Origin | Commercial | Amateur (Yaesu) | Amateur (JARL / Icom) |
| Analogue fallback | No | Yes, automatic | No |
| Access parameter | Colour code | DG-ID | Callsign |
| Setup effort | High (codeplug) | Low | Medium |
The honest advice is to ignore the specifications and look at what is on the air within reach of your antenna. A mode with no local repeater is a mode you will not use, however good it is.