DMR Radio Systems

DMR is the most widely deployed professional digital radio standard in industry, and for most Turkish sites moving off analogue it is the default answer. It is defined by ETSI TS 102 361, which means the air interface is public and multi-vendor rather than proprietary.

A DMR channel is 12.5 kHz wide, like an analogue narrowband channel. The difference is what happens inside it: the channel is divided in time into two alternating slots of 30 milliseconds each. Two conversations run in parallel on one frequency, one per slot.

That single fact drives most of the economics. One repeater and one licensed frequency pair now carry the traffic that previously needed two.

The second difference is at the receiver. An analogue receiver amplifies whatever arrives, noise included, so speech degrades gradually into hiss as the user walks away from the repeater. A DMR receiver decodes a bit stream and applies error correction, so speech stays clean and then, at the very edge, breaks up. Usable range for a given power is measurably longer, and the boundary is far sharper.

Tier II is where most projects belong. Users select a channel; if that channel is busy they wait. That is acceptable while the number of simultaneous conversations stays well below the number of slots available. When it does not, the answer is DMR Tier III trunking or XPT.

• Text messaging — a status update that does not occupy the voice channel
• GPS position reporting — location on a dispatch map, at an interval you set
• Individual and group calls — a conversation that does not interrupt everyone
• Radio check — confirm a radio is powered and in coverage without the user answering
• Remote disable — a lost or stolen radio is rendered inert from the dispatch position
• Lone worker and man-down — automatic alarm on inactivity or on the radio going horizontal

Man-down and lone worker are frequently the reason a site moves to digital in the first place. They are a safety control, not a convenience feature, and they are what an occupational-safety auditor asks about.

Choosing a radio model is the last step, not the first. The order that works:

1. Requirement analysis — how many users, in how many groups, working across what area 2. Site survey and coverage analysis — terrain, structures, antenna positions available 3. System design — number of repeaters, slot plan, group and talkgroup structure 4. Frequency planning and BTK licence application 5. Installation, programming and commissioning 6. Coverage verification measurement and handover documentation

Skipping step 2 is the most expensive mistake in radio projects, because the shortfall only becomes visible after the equipment is bought and installed.

Sites are linked over IP where a corporate network already reaches them, over microwave links where it does not, and by simulcast where a single channel must be radiated from several sites at once. Enclosed volumes — tunnels, basements, underground car parks — need dedicated indoor coverage rather than more transmit power.

A DMR system is infrastructure, and it is judged over years rather than at handover. TechnoRF covers firmware versions, programming changes as the organisation reorganises, antenna and feeder checks, power and battery replacement, fault response and coverage re-verification after building work.

Every project is handed over documented: architecture diagram, channel and talkgroup plan, radio-to-user mapping by serial number, coverage report, licence file and maintenance schedule. That documentation is what allows the system to be extended by someone else in five years. See company profile for the full process, or get in touch.