The capabilities nobody uses — and one that borrowed a number from DMR.
D-STAR was designed by the JARL in the late 1990s and put on the market by Icom in 2001. It is the oldest amateur digital voice mode still in service, and by a wide margin the most feature-rich. Most of those features have never been used by most of the people who own the radios.
This page is an inventory of what is actually in there.
Everything on this page rests on one design decision. A D-STAR DV transmission is 4800 bits per second, and it is split:
| Portion | Rate | Carrying |
|---|---|---|
| Voice | 3600 bps | AMBE-encoded audio, including error correction |
| Data | 1200 bps | Callsign fields, plus a general-purpose data stream |
The data runs at the same time as your voice, always, whether you use it or not. Around 950 bps of it is usable payload. That quiet, permanently-open side channel is what makes GPS, text messages, D-RATS, and everything else possible — and it is the single biggest architectural difference between D-STAR and the modes that came after it.
The everyday mode. Voice plus the simultaneous slow data described above. This is what you are using unless you have gone out of your way not to be.
When 950 bps is not enough, DV Fast Data gets you 3480 bps — about 3.5 times faster. It does this by throwing away the voice: data frames are put where the voice frames would go.
Two consequences worth knowing. DV Fast Data is not simultaneous with voice — you are sending data instead of talking, not while talking. And Icom states plainly that it is not compatible with DV mode low-speed data. It is a separate thing, not a faster version of the same thing. It is what makes picture transfer bearable.
The forgotten giant. DD mode is a 128 kbps data pipe — not voice at all, essentially Ethernet over radio. You can connect a PC and browse the web through a D-STAR repeater.
The catch is brutal: DD is 1.2 GHz only, and in practice ID-1 only — a radio Icom discontinued years ago. Almost nobody has the hardware, and almost no repeaters support it. It is the most capable and most orphaned feature in amateur digital voice.
The radio connects to the internet and transmits no RF whatsoever. Icom’s manual is explicit: in Terminal mode the transceiver does not transmit or receive RF signals through the antenna. You press PTT, you talk, and your audio goes out over Wi-Fi, 3G, or LTE. The antenna does nothing.
The point is coverage. No repeater in range, travelling, in a hotel — Terminal mode puts you on the network anyway.
The same internet connection, but now the radio does transmit, acting as a gateway for other D-STAR radios. Your ID-4100 sits on the desk on the LAN; you walk around the house with an ID-52 talking through it. The ID-4100 can run 50 watts as an access point, which makes it a rather muscular hotspot. You need two callsigns: one for the access point, one for the remote radio.
| Radio | What it needs |
|---|---|
| ID-31/51 PLUS2, ID-4100 | A PC or Android device running RS-MS3W / RS-MS3A, usually via an OPC-2350LU cable |
| IC-705, IC-9700, IC-905 | Internal Gateway — plug into LAN. No PC or phone needed at all. |
The catch the sales literature buries: Terminal and Access Point modes work only via Icom callsign routing. They do not support linking to reflectors — not REF, not XRF, not DCS, not XLX. You can be heard on a distant gateway, but for someone to reply they must capture your callsign and route back to you. If you want reflector access from the internet, a hotspot does the job better and cheaper.
The most substantial thing anyone ever built on D-STAR. D-RATS, written by Dan Smith, KK7DS, turns that 950 bps side channel into a real data terminal:
This is why D-STAR got real traction in emcomm. A damage assessment or a resource request can be passed as written text on a form, over the same repeater carrying the voice net, with no transcription errors and a permanent record. Nothing in DMR or Fusion does this.
APRS position data carried inside the D-STAR data stream. Your GPS position rides along with your voice, gets picked off by the gateway, and lands on aprs.fi. You are beaconing without ever keying an APRS radio.
Photos from a phone (RS-MS1A / RS-MS1I) or a PC (ST-4001), sent over DV or — far more sensibly — DV Fast Data. The IC-705, IC-905, IC-9700, and ID-52 PLUS can do it from the radio itself.
A 20-character message that appears on the receiving station’s display. Modest, but it has been there since 2001, and it costs nothing.
Not an official Icom feature, but the data channel is exposed as a serial port on radios like the TH-D74 and IC-9700, and people run packet over it by treating it as a byte stream. Turning on DV Fast Data takes it from roughly 950 bps to 3480 bps. Firmly in the tinkerer’s corner, and a good example of what an open data channel invites.
D-STAR’s signature trick. Put a person’s callsign in the UR field and the network finds whichever repeater they were last heard on and delivers your audio there. No talkgroups, no reflectors, no linking. You call a person.
It has existed since 2001 and has been chronically underused — though the flood of Pi-Star hotspots has given it a second life, since every hotspot runs ircDDBGateway and can route.
A gotcha: there are two different ircDDB routing systems in use — ircddb.net and the QuadNet Array — and they do not talk to each other. If callsign routing mysteriously fails, check which one your hotspot is pointed at.
A group-calling layer on top of callsign routing. You register with a StarNet group, and anything sent to that group is delivered to everyone in it — a talkgroup, essentially, built out of callsign routing rather than reflectors. QuadNet’s Smart Groups are the modern incarnation.
Here is the joke at the heart of D-STAR.
The whole identity argument for D-STAR is that your callsign is your ID — no numbers, no lookup tables, no duplicates. Then European developers built CCS, the Call Connection Service, as a simpler alternative to Icom’s G2 routing. It let you reach a station by entering a number on the DTMF keypad, like dialling a telephone. It turned out to be wildly popular, because dialling a number while mobile is a great deal easier than fiddling with a callsign field.
When they rebuilt it as CCS7, they needed a bigger number space. And rather than invent one, they made a decision of pure pragmatism:
Your CCS7 ID is your DMR ID. The seven-digit number issued by RadioID.net — the one built for the mode that D-STAR partisans say uses meaningless numbers instead of proper callsigns — is now also your D-STAR routing number. If you have a DMR ID, you already have a CCS7 ID and need do nothing. If you have several, the lowest one is it.
CCS7 is supported in G4KLX’s ircDDBGateway, and a CCS7 ID is required to reach the DCS reflector network on several European servers. The servers are named CCS701 through CCS7xx by region.
There is a lesson in it. The mode with the most elegant identity scheme in amateur radio ended up bolting on a numeric one, because a number is easier to punch into a keypad at seventy miles an hour. Engineering elegance loses to the human thumb every time.
Four separate reflector systems can be reached from D-STAR, and a modern gateway speaks all of them:
| Network | Prefix | Notes |
|---|---|---|
| D-Plus | REF | The original Icom-era reflector network |
| DExtra | XRF | Open-source alternative |
| DCS | DCS | Digital Call Server; CCS7 ID required on some servers |
| XLX | XLX | Multiprotocol; speaks D-Plus, DExtra and DCS at once, and bridges to other modes |
XLX is the one doing the interesting work now — it will happily transcode D-STAR to DMR and Fusion, which is how a 2001-vintage mode ends up talking to a Brandmeister talkgroup.
Look at that list again. Simultaneous data with every transmission. A 128 kbps data mode. Structured emergency forms. Position reporting for free. Picture transfer. Direct person-to-person calling across the planet. Keyboard chat. Internet operation with no repeater and no hotspot.
Now count how many D-STAR operators you know who use any of it beyond plain voice on a reflector.
The reasons are not mysterious. The features arrived piecemeal across twenty-five years and four generations of radio. They need software that is often abandoned, hardware that is often discontinued, a PC or a phone tethered to the rig, and a registration step that half of new users never finish. Meanwhile DMR turned up with none of it and a $25 handheld, and that was that.
But the capability is still sitting there, in a radio a great many hams already own. It is worth knowing what you have.