Icom hardware, module letters, and why Near Repeater Search is not roaming. Working notes, v1.1, 10 September 2026.
D-STAR has no talkgroups, no timeslots and no trunking, and its repeater hardware comes from one manufacturer. Its answer on roaming is the most interesting of the four that say no.
The same four questions are asked of every mode, in the same order, so the seven parts stay comparable:
MMDVMHost on a Raspberry Pi, an MMDVM modem board (STM32-DVM, ZUM MMDVM, or Micro-Node Teensy), and one or two radios with a 9600 baud port or a discriminator tap. Pi-Star is the usual image. Linking is done by ircDDBGateway, a separate daemon from MMDVMHost. Before MMDVM there was G4KLX's DStarRepeater and the OpenDV package, still around but largely superseded.
Icom, and only Icom. Current generation is the ID-RP2010V (2m), ID-RP4010V (70cm) and ID-RP1200VD (23cm), each with the controller built in. The older generation needed a separate ID-RP2C controller driving ID-RP2000V or ID-RP4000V RF modules, plus the ID-RP2V, ID-RP2D and the ID-RP2L 10 GHz link. That older line is end of life.
The current Icom boxes do D-STAR only, FM only, or mixed, but only one at a time.
D-STAR has no trunking. Not unused, not out of reach: the mode simply does not have it. Of the six modes, three have trunking (DMR, NXDN and P25) and three do not (D-STAR, C4FM and M17). D-STAR is in the second group, so the question of why amateurs skip trunking never arises here. Part 7 covers that argument for the modes where it applies.
| Mode | Channel bandwidth | Modulation | Bit rate |
|---|---|---|---|
| D-STAR (DV) | 6 kHz occupied, 6.25 kHz spacing | GMSK | 4800 bps total: 2400 voice, 1200 FEC, 1200 data |
D-STAR chose to narrow the RF. There are two completely different ways to be spectrum efficient and the modes divide over them. D-STAR and NXDN genuinely occupy 6.25 kHz of spectrum. DMR and P25 Phase 2 occupy the full 12.5 kHz and divide the time instead, carrying two conversations in it. That single choice is why D-STAR has no timeslots, and why a D-STAR-locked multi-mode repeater carries one user where a DMR-locked one carries two.
D-STAR's two bandwidth numbers are different quantities and get conflated. JARL's own standard says 6 kHz or less occupied, and Icom publishes emission designator 6K00F7W. The familiar 6.25 kHz is the channel spacing. Both belong in the table, labelled separately. Quoting one as though it were the other is the usual error.
Every mode has a routing field, which decides where your audio goes, and all of them except D-STAR also have an access field, which works like CTCSS and decides whether the repeater listens to you at all. The two get confused constantly in the other five modes. D-STAR is the one whose access entry is "none".
| Mode | Access field | Routing field | Range |
|---|---|---|---|
| D-STAR | none | Module letter, and URCALL | A to Z |
D-STAR has no talkgroups at all. You pick a module letter on a reflector, A through Z, and that is the room. The other mechanism is URCALL, where column 8 is the qualifier: L links, U unlinks. Callsign routing to an individual is the third thing URCALL does.
D-STAR shares that shape with M17 and with nothing else. Four of the six put routing in a number the user dials, DMR's talkgroup and C4FM's DG-ID among them. D-STAR and M17 both use a letter attached to a reflector name instead.
Roaming needs two halves: a network half, meaning several sites linked so that being on any of them puts you in the same conversation, and a radio half, meaning something the radio can measure and logic in the radio to move by itself. D-STAR has no network half, and only part of the radio half: a list, with the operator choosing from it.
This is settled from Icom's own manual rather than by inference. Icom's DR mode has a Near Repeater Search that looks like roaming until you read what it does:
The transceiver searches for the nearest repeaters by using your location and the repeater's entered position data. The nearest repeaters in your transceiver's repeater list are displayed as selectable options.
It shows up to twenty, ranked by distance, and the operator picks one. The radio never switches by itself. Note also what Icom's own wording says it ranks on: your location and the repeater's entered position data. Distance, not signal strength.
So D-STAR sits in a middle category: not roaming, but not nothing. GPS assisted lookup with a human making the choice. Of the four modes that answer no, C4FM has the network half and not the radio half, D-STAR has a list and an operator, and P25 and M17 have neither half at all.
D-STAR is single channel, so a D-STAR-locked repeater carries one user. The multi-mode gotcha is worth repeating here, with D-STAR as the example:
Key up in D-STAR while the repeater is locked in DMR and your transmission is simply ignored. The repeater may look busy and you will hear nothing, or depending on setup you get a "repeater not available" message. Nothing is broken. You arrived during somebody else's mode hang. Wait out the timer and try again.
The mode hang timers, and why the machine sends CW every ten minutes, are in part 7.