Before this:NXDNFrom voice to bits: vocoders
dPMR, D-STAR & System Fusion
Key takeaways A round-up of the lighter digital modes you’ll meet that are mostly not trunked. dPMR is an ETSI 6.25 kHz 4FSK FDMA standard, close to NXDN, used for light commercial radio. D-STAR is an amateur mode (Icom) using GMSK at 4800 bps with a single DV voice stream plus slow data. Yaesu System Fusion is amateur C4FM that can mix digital and analog via AMS. These are mostly conventional, but you’ll still hear them — and GopherTrunk can decode their voice. The open M17 mode rounds out the picture.
The systems earlier in this module were full trunked networks. These last few are different: they’re mostly conventional digital modes — fixed channels and repeaters — that you’ll nonetheless run across on the air. None usually has a control channel to follow, but each carries digital voice GopherTrunk can decode.
dPMR — NXDN’s close cousin
dPMR (digital Private Mobile Radio) is an ETSI standard that uses 6.25 kHz FDMA with 4FSK modulation. If that sounds almost identical to NXDN, it is — the two share the same narrowband 4FSK footprint and are easy to confuse on the waterfall. They’re separate standards, but their on-air fingerprints are nearly the same width and shape.
dPMR is used mostly for conventional, light commercial radio — small business fleets and similar — rather than big trunked networks. Treat it as the European sibling of NXDN that you identify the same way: very narrow, 4FSK, confirmed by the decoder.
D-STAR — the amateur GMSK mode
D-STAR (Digital Smart Technologies for Amateur Radio) is a ham-radio mode developed with Icom. Its traits:
- GMSK modulation — Gaussian Minimum Shift Keying — at 4800 bps. This is a different scheme from the 4FSK of NXDN/dPMR and the C4FM of Fusion.
- A single voice stream (called DV, digital voice) plus a slow data channel riding alongside for things like callsigns and short messages.
- Strong support for internet-linked repeater networks, which made it popular for long-distance amateur contacts.
It is an amateur mode, so you won’t find public-safety trunking here — just ham operators on repeaters and simplex.
Yaesu System Fusion — C4FM that mixes modes
Yaesu System Fusion is Yaesu’s amateur digital mode, built on C4FM — the same four-level FSK family you met in digital modulation for trunking. Its standout feature is AMS, Automatic Mode Select: a Fusion repeater can automatically handle both digital and analog signals, switching as needed. That lets a single repeater serve digital Fusion users and traditional analog FM users without anyone choosing a mode by hand — a pragmatic bridge for clubs moving to digital gradually.
Not trunked, but still on the air
The common thread is that none of these is normally a trunked system. There’s usually no control channel granting voice channels — they’re conventional modes on fixed frequencies and repeaters. You meet them not by hunting a control channel but by tuning the channel directly. The good news is that GopherTrunk can decode the voice they carry once you’re on the right frequency, even though there’s no trunking to track.
One more worth knowing: M17 is a fully open, community-developed digital voice mode — free of the patent-encumbered vocoders the others rely on. GopherTrunk supports it, and it’s a refreshing contrast to the proprietary codecs elsewhere in this path.
Recap
- dPMR is an ETSI 6.25 kHz 4FSK FDMA standard, nearly a twin of NXDN, for light commercial use.
- D-STAR is an amateur mode using GMSK at 4800 bps with a single DV voice stream plus slow data.
- Yaesu System Fusion is amateur C4FM, and its AMS feature mixes digital and analog on one repeater.
- These are mostly conventional — no control channel — but GopherTrunk decodes their voice.
- The open M17 mode is a patent-free alternative worth knowing.
That wraps the survey of other digital systems. The next module gets hands-on, starting with identifying the system you’re actually looking at.
You can also revisit the broader catalogue of non-trunked transmissions in other signals.
Frequently asked questions
What is dPMR?
dPMR (digital Private Mobile Radio) is an ETSI narrowband standard using 6.25 kHz FDMA with 4FSK modulation. It is very close to NXDN in footprint and is used mostly for conventional, light commercial radio. It is not usually a trunked system, but you’ll meet it on business and utility channels.
What is D-STAR?
D-STAR is a digital amateur-radio mode developed with Icom. It uses GMSK modulation at 4800 bps carrying a single voice stream (DV) plus slow data. It is a ham mode rather than a trunked public-safety system, popular for repeaters and internet-linked networks.
What is Yaesu System Fusion?
System Fusion is Yaesu’s amateur digital mode, built on C4FM 4FSK. Its Automatic Mode Select (AMS) feature lets a repeater handle both digital and analog signals automatically, so a Fusion repeater can pass either. Like D-STAR, it is an amateur mode, not a trunked system.
Are these modes trunked?
Mostly no. dPMR, D-STAR, and System Fusion are predominantly conventional — fixed channels and repeaters rather than control-channel trunking. You’ll still meet them on the air, and GopherTrunk can decode their voice even though there’s usually no control channel to follow.