DMR in plain terms
DMR stands for Digital Mobile Radio. It is an open digital voice standard published by ETSI, originally developed for commercial and professional radio users. Amateur radio operators adopted it because inexpensive radios became available and because it can be linked worldwide over the internet. On the ham bands it is mostly used on VHF and UHF, in the same places where you would otherwise find analog FM.
How DMR works
Two ideas define DMR:
- Digital voice: your voice is converted to data by a vocoder, sent as a digital signal, and turned back into audio at the receiving radio.
- Two time slots (TDMA): a standard 12.5 kHz channel is divided into two alternating time slots, so two separate conversations can share one frequency. They are usually called TS1 and TS2.
Because the data includes error correction, audio often stays clear until the signal gets weak, then breaks up or drops, rather than gradually fading into noise as FM does.
DMR IDs, color codes and talkgroups
A DMR ID is a unique number that identifies your radio on the network. Hams usually request one through a registration database such as RadioID.net, which asks for proof of an amateur license. You program the ID into your radio, and it is sent with each transmission.
Other terms you will meet:
- Color code: a number, typically 0 to 15, that a repeater uses to decide which signals to accept. If your color code does not match the repeater’s, it will not respond.
- Talkgroup: a virtual room that groups conversations, for example a regional or special-interest group. You choose which talkgroups your radio listens to and transmits on.
- Timeslot: the repeater uses slot 1 or slot 2 for a given talkgroup, and your radio needs the right one.
- Codeplug: the configuration file that holds channels, contacts, talkgroups and settings. Setting up a codeplug is often the hardest part for beginners; many clubs share tested starter files.
Networks and hotspots
DMR repeaters are often connected to internet-based networks such as Brandmeister or TGIF, among others. These let a talkgroup reach many repeaters at once. If there is no repeater near you, a personal hotspot, a small low-power device linked to the internet, can connect your radio to the network from home. Check the rules for your license and country before setting one up, and follow the network’s own policies.
Can DMR radios talk to analog?
Not directly in digital mode. Many DMR radios can also operate in analog FM, so one handheld can work both kinds of repeater. But a DMR transmission heard on an analog FM radio is typically just noise, and an analog signal is not decoded as DMR. Some repeaters can operate in mixed mode, accepting either type of signal, but that depends on the repeater.
DMR vs DRM
The names are easy to confuse. DMR is Digital Mobile Radio, described here. DRM is Digital Radio Mondiale, a digital system for broadcasting on the long, medium and short wave bands (see the shortwave frequency range). They are unrelated technologies.
Is analog being phased out?
Analog FM is still very widely used by hams, and there is no worldwide date by which it must end. In some commercial and public safety fields, digital has been replacing analog over time. In amateur radio, digital voice grows alongside analog, and local repeater communities differ. Check what is active in your area before buying a radio.
What you need to get started
- A valid amateur license appropriate for the bands you use.
- A DMR-capable radio.
- A DMR ID registered in your name.
- A codeplug with local repeater frequencies, color codes, timeslots and talkgroups.
- Optionally, a hotspot for home use.
Pros and cons
Pros: efficient use of spectrum, good audio quality, global talkgroups, and data features such as text messages.
Cons: more complicated setup than analog, limited compatibility between different digital voice systems, and audio quality that depends on the vocoder in use.
To see how DMR fits among other signals you might hear, read about identifying digital modes by sound and waterfall. For another method of linking repeaters over the internet, see what IRLP is in ham radio.