DMR stands for Digital Mobile Radio and uses the Motorola TRBO protocol for communications. Like other digital modes such as D-Star, C4FM and APCO P25, the TRBO protocol converts your voice into a digital form and sends it out via RF (with other bits of information included) and allows you to communicate to other DMR radios and also DMR repeaters, which are networked together around the world via the internet.
What makes DMR stand out from some of the other digital modes is that it utilizes TDMA (Time-Division Multiple Access) to divide a single frequency into 2 distinct “channels” or time slots. By doing this, you can have two conversations going on at the SAME TIME, using one frequency.
Imagine using one frequency while radio A is talking to radio B on time slot 1, and radio C is talking to radio D on time slot 2 … SIMULTANEOUSLY. Pretty neat, huh?
Here is a nice graphic from Retevis to help visualize and understand what is going on…
Although the graphic above relates to how a DMR repeater works, this same principal applies to using a simplex frequency as well.
To make matters a little more fun and complicated, each radio must have a unique Radio ID for digital identification between radios and you can also use Talkgroups to separate traffic and target specific groups of DMR users.
Looking for a GREAT basic explanation of DMR, what it is, how it works and why it is so beneficial? Check out the Miklor DMR Basic Tutorial.
Below, is a very short description of DMR, with local repeater and talkgroup information.
DMR Tier I products are for license-free use in the 446 MHz band in the European Union.
This part of the standard provides for consumer applications and low-power commercial applications, using a maximum of 0.5 watt RF power. With a limited number of channels and no use of repeaters, no use of telephone interconnects, fixed/integrated antennas, and a talk timer of 180 seconds, Tier I DMR devices are best suited for personal use, recreation, small retail and other settings that do not require wide area coverage or advanced features.
DMR Tier II covers licensed conventional radio systems, mobiles and hand portables operating in PMR frequency bands from 66-960MHz. The ETSI DMR Tier II standard is targeted at those users who need spectral efficiency, advanced voice features and integrated IP data services in licensed bands for high-power communications. ETSI DMR Tier II specifies two slot TDMA in 12.5 kHz channels.
DMR Tier II is based on the following ETSI standards.
- ETSI TS 102 361-1 Air interface
- ETSI TS 102 361-2 Voice and generic services and facilities
- ETSI TS 102 361-3 Data protocol
DMR Tier III covers trunking operation in frequency bands 66-960MHz. The Tier III standard specifies two slot TDMA in 12.5kHz channels. Tier III supports voice and short messaging handling similar to MPT 1327 with built-in 128 character status messaging and short messaging with up to 288 bits of data in a variety of formats. It also supports packet data service in a variety of formats, including support for IPv4 and IPv6.
What Is A DMR Radio ID?
A Radio ID is a unique number assigned to you (and your callsign) by the RadioID.net Team. Like a telephone number or IP address, your Radio ID identifies you as a unique radio user on the various DMR networks and repeaters around the world. Because DMR is digital, we have so much more that we can do with the RF flowing to and from our radios. For example, because of Radio IDs we can see and display the callsign of the person talking to us on the radio face by the use of the RadioID.net Database. Every time you PTT your DMR radio, your Radio ID gets transmitted to the DMR network and everyone can see who you are. Pretty cool, right? BUT DON’T FORGET.. YOU MUST STILL ID BY VOICE TO BE LEGAL! Even though your callsign shows up in the network logs and on other users radios does not mean you are identifying yourself a licensed ham. You must ID like you do on analog.
So why else is this so cool? Identifying every radio and repeater uniquely with an ID enables the very essence of DMR networking to function. i.e making private calls to each other, organizing specific talkgroups for countries, states, regions, cities, clubs, special interest groups etc.
In short, a Radio ID enables you to talk to and hear only the people and traffic that you want to.
It’s totally free to get your Radio ID and you NEED ONE if you are going to have a DMR radio and use it. Is it the law? No. But you aren’t going to enjoy using DMR unless you have one, so do yourself a favor and get registered with RadioID.net as soon as you buy a DMR Radio.
Talk Groups (TG) are a way for groups of users to share a time slot, without distracting and disrupting other users of the time slot. It should be noted that only one Talk Group can be using a time slot at a time. If your radio is not programmed to listen to a Talk Group, you will not hear that Talk Group’s traffic.
The DMR-MARC Mototrbo™ network supports a number of Talk Groups on TS1 including World Wide (TG1, PTT), North America (TG3), and World Wide English (TG13). TS2 is for local, state, and regional Talk Groups. The DCI/TRBO network uses TG3163 for North America and TG3161 for World Wide, and TG3 for World Wide English on TS2.
The Brandmeister network is very similar to DMR-MARC, but the talk groups and reflectors are organized some what differently. For example, Talkgroup 3129 on the MARC network might not be the same as Talkgroup 3129 on the Brandmeister network.
The Brandmeister network is the most popular at the moment with most users.
The DMR standard also supports private calls (one-to-one), encryption, and data. Private calls are not allowed by most of the amateur networks and many consider private calls not amateur friendly; private calls tie up a large number of repeater time slots across the network. Encryption is not legal on amateur radio in the USA but is allowed in Canada! Data and text messaging is supported on some networks.
For simplex traffic, the accepted standard in the amateur community is to use TG99 on TS1 with CC1.
What is a Static Talkgroup?
A static talkgroup is one that is permanently activated on a particular timeslot by the repeater sysop. This type of static assignment passes ALL traffic from the DMR network over the air on the timeslot it is assigned to.
For example, if a statewide talkgroup is assigned to the local repeater on timeslot 1, anytime someone keys that talkgroup on the network, regardless of where they are, the audio will be retransmitted locally.
In simple terms, this networks many repeaters together full-time for that particular talkgroup.
What is a Dynamic Talkgroup?
Dynamic talkgroups assignments are used for temporary activation on a timeslot on a particular repeater. This type of talkgroup functions for a set amount of time AFTER a local repeater user activates it by transmitting on a repeater using that talkgroup in their radio. When the timer expires and no local user has keyed up again for a set amount of time… the timeslot and the talkgroup and release and the repeater is again open only to the talkgroups that remain static.
For example, if you are traveling in British Columbia and wish to talk to a friend back home in Ontario, you could key up the Ontario talkgroup on a B.C. repeater that allows dynamic talkgroups and make a call on repeaters at home that have the Ontario talkgroup set as static. When you are done with your conversation, the dynamic timer will expire and the B.C. repeater will go back to normal.
The following DMR repeaters are available in the Durham Region area:
VE3OBI – Courtice – 442.1375 – CC1
VE3SBX – Ajax – 442.3625 – CC3
VE3LBN – Oshawa – 443.9875 – CC3
VA3WIK – Toronto – 442.1875 – CC4
VE3NUS – Toronto – 444.2875 – CC1
9 = Local/Region
91 = Worldwide
93 = North America
99 = Simplex
302 = Canada
310 = TAC-310
311 = TAC-311
3023 = Ontario
VA3XPR – Toronto – 441.9375 – CC1 (Now encrypted)
1 = World Wide
2 = Local 1
3 = North America
8 = Golden Horseshoe Area
9 = Local 2
13 = WW English
113 = UAE 1
123 = UAE 2
302 = Canada
310 = TAC310
3023 = Ontario
3022 = Quebec
3024 = Manitoba
3026 = Alberta
3029 = New Brunswick
3027 = British Columbia
9998 = Parrot
9999 = Audio Test
Presently, a number of Toronto area DMR-MARC repeaters have been disabled due to jamming/interference.