Also known as: D-STAR, DSTAR
D-STAR (Digital Smart Technologies for Amateur Radio) is an amateur-radio digital voice and data standard developed by the Japan Amateur Radio League (JARL) and widely implemented by Icom. It uses GMSK modulation and an AMBE-family vocoder for its digital-voice (DV) mode, and is best known for internet-linked repeaters that route calls by amateur callsign anywhere in the world.1 D-STAR was the first of the three mainstream amateur digital-voice systems — ahead of Yaesu’s System Fusion and the open M17 — and it established the pattern the others followed: a narrow digital channel plus an internet backbone.
Overview
D-STAR has two air interfaces. The everyday one is DV (Digital Voice): a 4800 bps GMSK stream in a 6.25 kHz channel that multiplexes digital speech with a slow “D-STAR data” side channel of roughly 900–1200 bps — enough for GPS position beacons, short text, and callsign routing without interrupting the voice. A second interface, DD (Digital Data), runs 128 kbps in a 150 kHz channel on the 23 cm (1.2 GHz) band and behaves like a slow Ethernet link; it is rarely deployed compared with DV. The system’s headline feature is not the radio link at all but the gateway network: every DV frame carries four callsign fields (the caller “MY”, the destination “UR”, and up to two repeater fields “RPT1/RPT2”), and gateway software uses them to route a call over the internet to a distant repeater or a reflector — a conference server that many repeaters connect to at once.
Technical characteristics
| Property | Value |
|---|---|
| Access | FDMA |
| Modulation | GMSK, 4800 bps (BT ≈ 0.5) |
| Channel spacing | 6.25 kHz (DV), 150 kHz (DD) |
| Vocoder | AMBE (DVSI AMBE 2020), 2400 bps voice + 1200 bps FEC |
| Voice/data split | ~3600 bps voice+FEC, remainder sync + slow data |
| DD mode | 128 kbps digital data, 23 cm band |
| FEC | Convolutional coding + interleaving on the header |
| Routing | Callsign (G2) routing; DPlus / DExtra / DCS reflectors |
How the DV frame works
A DV transmission opens with a header that carries the flags and the four callsigns. Because losing the header means losing the routing, it is heavily protected — scrambled, convolutionally coded, and interleaved — then GMSK-modulated ahead of the voice. The voice that follows is produced by the DVSI AMBE 2020 vocoder at 2400 bps, wrapped with 1200 bps of forward error correction to survive fading, for roughly 3600 bps of the 4800 bps budget. The remaining capacity carries frame sync and the slow-data sub-stream. Because the vocoder is a proprietary DVSI product, D-STAR (like DMR and YSF) cannot be fully re-encoded in open software without a licensed AMBE chip or library — one of the motivations behind M17’s royalty-free Codec 2 choice.
History
JARL specified D-STAR around 2001 under a Japanese government-funded research program to modernise amateur radio, publishing it as an open protocol so any manufacturer could implement it.2 In practice Icom built essentially all of the commercial radios and repeaters, giving the standard a single-vendor feel even though the specification itself is public. The vocoder is the one closed piece. D-STAR reached the market in the mid-2000s and, being first, seeded the amateur digital-voice ecosystem — including the low-cost hotspot movement (Raspberry-Pi boards such as DVMega and openSPOT) that later carried DMR and Fusion as well.
Deployment
D-STAR is used by amateur operators worldwide through DV repeaters, personal hotspots, and networked reflectors. Reflector systems (DPlus, DExtra, DCS, and the newer XLX multiprotocol reflectors) act as the internet backbone, and gateways bridge RF repeaters into it. Coverage is strongest in Japan, North America, and Western Europe. It competes for the same operators as amateur DMR and System Fusion; many hotspots and reflectors now bridge all three, so the practical distinction is often just which handheld a given operator owns.
Decoding it with GopherTrunk
GopherTrunk is a receiver, and D-STAR’s GMSK air interface is within reach of its DSP front end; the link-layer header (callsigns, flags, and slow-data such as GPS) is decodable because it is plain FEC-protected framing. The voice payload is AMBE, which is a licensed proprietary vocoder, so GopherTrunk can recover and log the frame metadata but does not reproduce speech without an external AMBE facility — the same honest limit that applies to DMR and YSF audio. See Status for GopherTrunk’s current D-STAR link-layer coverage.
Sources
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D-STAR — Wikipedia, for the JARL-developed amateur digital-voice standard, its GMSK modulation, AMBE vocoder, DV/DD modes, and reflector networking. ↩
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JARL D-STAR — Japan Amateur Radio League, the originating body’s overview of the D-STAR system, its open specification, and DV/DD structure. ↩