DMR 099

Why DMR?

Overview

The first question I usually get is, "Why should I get into DMR?" This turns out to be an easy answer in the commercial world, however it can be a bit of a challenge in the amateur realm. The answers are pretty similar for both. Here's the short answer: DMR is a standards based RF modulation protocol making it easy for lots of manufacturers to build equipment for. What this means to you is choice usually to the tune of cost. Equipment can vary from $50 - $10,000. The DMR standard puts most of the radios on a very even playing field. Each radio must contain some minimum features and comply to certain specifications in order to meet the DMR standard. In this section I'll explain why DMR is a great mode for both amateur and commercial radio operations.

Some Caveats

Just to get it out there upfront, here is a quick list of some items that cause inconsistencies not only in the amateur experience, but in DMR in general.

  • DMR is a commercial protocol aimed at a commercial users, NOT amateurs.

  • While DMR is standards based with three (3) tiers, not all of the features and functions are defined in the standard. GPS as an example is not defined in T2.

  • Not all DMR systems are equal therefore cause an inconsistent experience. Some are commercial off the shelf implementations, some are open source, and some are in between.

From our Mission Statement, we want people to have a consistent DMR experience. Besides the nonstandard features, the DMR systems are typically the limiting factor. I'll dive more into this in the systems section. Commercial systems are not as flexible as the BrandMeister Network, so please be aware that some of the features listed are not applicable to all "systems."

50,000 Foot View

In short, DMR uses Time Division Multiple Access (TDMA), so for the cost of a single frequency or channel, it provides two talk paths. This means that a single repeater can have two conversations concurrently without interfering with each other. Why is this a thing, or maybe said, why is this important? Using amateur radio as an example, a single repeater is typically shared by many users. Those using the repeater may have different reasons for using that repeater. Those could range from Emergency Communications, to Special Event Support, to Rag Chew (just general conversation), to Nets, and for Club Business. Typically repeaters are not linked to other repeaters so their area of influence (or coverage area) is a draw for the user base. The better the coverage, the more users.

In this example, if the Emergency Communications group is using the repeater, other groups like the Event Support Group could use the repeater, but might cause some confusion. Typically when contention occurs, one of the groups will find another repeater or communication path to support their effort. DMR solves this use case quickly by supporting two concurrent conversations. There is a hidden benefit that I'll go into more detail later. Quickly, DMR can actually support many concurrent conversations, but is limited to the two timeslots at the same time.

I'll give a common example for commercial use. School districts have used radios for a long time to support operations. Each school has been operating either a duplex (repeated) or simplex channel. This worked great when you look at just a single school and its operation. Many schools though are on a campus, where three or four schools happen to share the same property and are in close physical proximity. If there is a security issue at one, this old way of doing business would force a radio call from someone at one school to the office where they would then call via phone to the other schools to advise of the security issue. Using DMR, each school can use 1 timeslot for just the school and the other for all the schools to communicate with each other.

Linking repeaters, which makes a system, make it that much more functional. Now wide area communications can be had with ease. Add in support for other features like GPS and you've got a robust communications system that allows for more than just voice.

Summary

DMR being a standards based protocol makes the cost of entry low, giving Technician Class Amateurs worldwide operations quickly and affordable. DMR using TDMA technology means that a single repeater can support two concurrent conversations for the price of one. DMR being digital means that it can be linked to a system giving the users many features and functions not available in traditional analog radio. And finally, most "amateur" grade DMR radios are capable of both dual band (VHF/UHF) and dual mode (analog/DMR) operation. Meaning, if you find one of these radios, you'll be set for most of your amateur needs as a Technician Call Operator.

Continue on to learn more about DMR. Hopefully, I've peaked your interest without going to deep into the technology.