What is DMR?

Digital Mobile Radio is, as the name implies, digital.

Originally developed in Europe, DMR is used worldwide. You have probably heard of MOTOTRBO, Motorola’s implementation of DMR. Like D-STAR, we can do stuff with DMR just not possible in the analog world.

The big difference between D-STAR and DMR are the markets they were designed for. D-STAR is from the Amateur world, and focuses on the user controlling what connections are possible over the D-STAR network. D-STAR encourages user experimentation and customization as well.

DMR is from the commercial world where the user just wants to “Push-To-Talk”. The focus is on ease of use as the radio is simply a means of communication. How and where the network connects is left to the system manager.
BrandMeister is changing DMR into a more “Ham-Centric” mode. Much like D-STAR, the BrandMeister network lets the used decide how a repeater is connected to the network.

Just as FM and D-STAR require more than just entering a frequency, DMR has its own unique set of parameters to program. Don’t panic, they do make sense, especially if you remember DMR is designed for the commercial market, and we have adapted it for Amateur use.
To put things simply, there are several “Big Ideas” with DMR: Radio IDColor CodeTimeslot, and Talkgroups.

  • Radio ID (Subscriber ID): DMR is digital, and networked, so each radio has a unique ID number to identify it on the network. In the D-STAR world this corresponds to the “MYCALL” parameter. To obtain a radio ID, go to: http://www.radioid.net It may take up to 24 hours for them to assign you an ID number, and you should receive it through your email. Please do not transmit with your DMR radio until you have received a Subscriber ID and have this programmed into your radio. Using ad-hoc Subscriber ID numbers will cause conflicts with other users on the network.
  • Color Code: This is the DMR version of PL, there are no colors associated with this, only numbers typically 1-16. Why they call it “color code” is beyond me. Typically most DMR ham repeaters will use CC: 1.
  • Timeslot: DMR uses magic known as “Time Division Multiple Access” (TDMA). In Simple English, this means the repeater can support two simultaneous conversations by alternating between two timeslots. About 30ms is given to timeslot 1, then the transmitter flips to timeslot 2 for 30ms, then back to timeslot 1, and then to timeslot 2; you get the idea. Since you transmit on just one timeslot, your radio’s battery last longer as it is really only transmitting about half the time you have the PTT keyed. In other words, the repeater’s Time is Divided such that Multiple hams can have Access (TDMA).
  • Talkgroups: DMR is designed for the commercial market where radio users typically have something in common, such as Security, Engineering, Parade Operations, etc. It isn’t very efficient to have separate repeater pairs for each group, so DMR uses “Talkgroups” to group together users who want to talk to each other. On DMR repeaters we have several Talkgroups that allow you to talk to geographically increasing areas: local, regional, statewide, all the way up to worldwide. Talkgroups are also either “Always On” (Static for BrandMeister) or “User Activated” (Dynamic for BrandMeister). “Always On” means just that, network traffic to this talkgroup is always on. UA (User Activated or “PTT” for us Old Skool DMR Guys) talkgroups have a timer associated with them, typically 10 minutes. The practical side of this is that after 10 minutes of local inactivity on a User Activated talkgroup, it is dropped from the network connection. To start listening to a User Activated talkgroup, key up, and you probably want to talk at least once every 10 minutes as well in order to keep the network feed.

Our system is connected with the Brandmeister server, and can access the Brandmeister talk groups. Our repeater ID is 311427, if you’re on another repeater or a DMR hotspot, using this ID entered in as a talk group will get you into our repeater from anywhere. If you wish to have a QSO on our local system, but live outside of the coverage area, a hotspot could be valuable.

A couple of the talk groups with the most action to try out would be:

  • TG 311427 – Would be used for local QSO’s on the local repeater, can also connect remotely using a hotspot if you’re out of range.
  • TG 91 -Is the World Wide talk group, this will have the most action on it, and you can make contacts all around the world.
  • TG 92- Europe
  • TG 93 -North America
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