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DMR (Digital Mobile Radio) is a digital voice and data standard originally developed by ETSI (European Telecommunications Standards Institute) for commercial two-way radio. Amateur radio operators adopted DMR around 2012, and it has since become the most widely used digital voice mode in the hobby. DMR's combination of affordable radios, two simultaneous conversations per channel (TDMA), talkgroup-based routing, and extensive worldwide repeater networks has made it a dominant force on VHF and UHF.
DMR uses TDMA (Time Division Multiple Access) to divide a single 12.5 kHz channel into two time slots. Each time slot carries an independent voice or data stream, meaning a single DMR repeater can handle two simultaneous conversations on one frequency pair — effectively doubling the capacity compared to analogue FM.
Voice is digitised using the AMBE+2 (Advanced Multi-Band Excitation) vocoder, which compresses speech into a 3,600 bits per second data stream. The AMBE+2 codec is proprietary, developed by DVSI (Digital Voice Systems, Inc.), and requires a licensed chip or software implementation. This is one of the criticisms of DMR (and D-STAR and System Fusion, which also use AMBE variants) — the voice codec is not open-source. The M17 project was created partly in response to this.
The most distinctive feature of amateur DMR is the talkgroup system. A talkgroup is essentially a virtual channel — a group of users who want to talk to each other. When you transmit on a talkgroup, everyone monitoring that talkgroup on connected repeaters hears you.
Talkgroups can be local (just one repeater), regional, national, or worldwide. For example:
Each repeater's administrator configures which talkgroups are available on each time slot. A typical setup might have a local talkgroup and a regional talkgroup on Time Slot 2, with national and international talkgroups on Time Slot 1.
Amateur DMR repeaters are interconnected through network infrastructure. The major networks include:
Brandmeister — The largest worldwide amateur DMR network. Brandmeister supports dynamic talkgroup activation (you can connect to any talkgroup on the fly by briefly keying up on it), hotspot support, and bridging to other digital voice modes. Most new amateur DMR users end up on Brandmeister.
TGIF — A community-oriented network with a focus on simplicity. Originally stood for "Thank God It's Friday" from the weekly nets that inspired it.
DMR-MARC — One of the original amateur DMR networks. Uses a more static talkgroup configuration model.
FreeDMR — An open-source network infrastructure project.
Different repeaters may be connected to different networks, and talkgroups are not always consistent between networks (the same number may mean different things). Check your local repeater's information to know which network it uses.
A codeplug is DMR's equivalent of a memory channel list, but more complex. It defines:
Programming a codeplug from scratch is tedious. Most operators start with a pre-built codeplug for their area and radio model, available from local DMR groups, repeater websites, or tools like the Brandmeister Codeplug Generator. Codeplug programming software is specific to each radio manufacturer.
If you don't have a local DMR repeater, or you want to access the network from home without tying up a repeater, a hotspot is the solution. A hotspot is a low-power personal "repeater" (typically a Raspberry Pi with a MMDVM hat or a standalone device like the openSPOT or Pi-Star) that connects to the DMR network over the internet. You talk to the hotspot with your DMR radio at very low power, and it relays your audio to the network.
Popular hotspot platforms include:
Hotspots have become enormously popular because they give you access to the entire worldwide DMR network from your desk with just a handheld radio.
Wait for the "bonk" — When a DMR transmission ends, most radios make a characteristic sound (sometimes called the "bonk" or "kerchunk"). Wait for this before transmitting to avoid doubling.
Keep talkgroup selection appropriate — Don't ragchew on a worldwide talkgroup when a regional or local one would do. Worldwide talkgroups tie up repeaters across multiple countries.
Don't "kerchunk" excessively — A brief key-up to activate a dynamic talkgroup is fine, but repeatedly keying up without identifying is poor practice.
Identify as you would on any mode — FCC and other regulatory requirements for station identification still apply on DMR.
| Feature | DMR | D-STAR | System Fusion | M17 |
|---|---|---|---|---|
| Standard | ETSI (open standard) | JARL (proprietary) | Yaesu (proprietary) | Community (open-source) |
| Voice codec | AMBE+2 (proprietary) | AMBE (proprietary) | AMBE+2 (proprietary) | Codec2 (open-source) |
| Time slots | 2 (TDMA) | 1 | 1 | 1 |
| Routing | Talkgroups | Reflectors / callsign routing | Rooms / WIRES-X | Reflectors |
| Radio cost | Low–Medium | Medium–High | Medium–High | Low (DIY) to Medium |
| Network size | Very large | Large | Medium | Growing |
DMR's main advantages are affordable radios, dual time slots, and the largest network. Its main drawbacks are the complexity of codeplug programming and the proprietary voice codec.