DMR

DMR - Talkgroups and Timeslots

DMR has the drawback of a steep learning curve. Many amateur radio operators, new to DMR, find the system and terminology to be overwhelming at first. What is a codeplug? A talkgroup? Colorcode? Timeslot? Without the inherent knowledge of the system being used, DMR appears to be very complex.

Terminology - 

Codeplug - A codeplug is a file that contains the programming (frequencies, channels, groups, etc.) for the radio. Its basically the only way to program most DMR radios because they do NOT or are too complex to program from the front panel. Most radios have their own programming software.

Colorcode - It's similar to picking a tone for tone squelch on FM. Usually set to 1. CC1 or Colorcode 1.

Timeslot - DMR is a digital mode that splits its frequency usage in two by sending its 2 data streams, one after another, back to back, in 30ms bursts. Timeslot 1 and Timeslot 2. This allows for 2 users, interwoven, on the same frequency at the same time. The bits of data are sent in packets. The loss of ability to read the bit stream is the BER or bit error rate and the overall loss of decodeable packets is your packet loss percentage

Talkgroups - A talkgroups is like a virtual repeater. You will hear everyone in the group and everyone in the group will hear you. When you connect to a group you are actually connecting your hotspot or repeater to that group, linking it to the virtual repeater.

Static - Always on

Dynamic - On call 

The System - 

Brandmeister is a word you will hear a lot. It is a group of hams that have set up the servers and software to be a DMR internet relay network. We use these servers to link up our repeaters and hotspots so they can route the data packets to and from the various places the packets need to go. The packet pathfinding is accomplished with a number system. 0 to 999999999. For the Brandmeister System, all DMR ID's, Repeater ID's and Talkgroups share this numerical system. The Brandmeister Network, by default, passes all traffic dynamically, from number to number.

Because of this dynamic nature, there must be control points to access the data. Because repeaters and hotspots are the physical radios of the virtual repeaters or talkgroups, they are the control point of the data flow. Repeater sysops use both "white" and "black" lists to control the flow of traffic as well as static groups on certain timeslots. A "whitelist" is a list of numbers that a repeater or hotspot will allow to be keyed up dynamically and a "blacklist" is the opposite. Numbers to ignore. If there is no white or black list any number can be keyed up on either timeslot dynamically. One or more static groups can be set for either or both timeslots and most if not all repeaters and hotspots have one or more static groups set up per timeslot to link that repeater or hotspot to the system.

Because there is no current agreement on the most efficient configuration, many repeaters have vastly different configurations of Talkgroups and Timeslots, leading to added confusion by new users trying to "figure it out" and program their new DMR radio.

Conclusion - 

DMR is growing quickly in popularity and hopefully some understanding of the system will allow newer users to enjoy the experience of joining the DMR community.

73! de WH6DYI

Published on  April 15th, 2019