Category Archives: DMR

DMR and Talkgroups in EI

Quite often I get asked about DMR Radio and how to program Talkgroups (TGs) and Timeslots (Slots).

First, what it a timeslot? Your transmitted signal is broken into 30ms digital packets. Each slot is 27.5ms of data, 2.5ms of a gap, the result being your transmitter switches on and off very rapidly. Doing this allows your signals to share the same channel at the same time as someone else. One on Time Slot 1 and one on Time Slot 2.

Group A are using Slot 1 while Group B are using Slot 2 simultaneously. They don’t interfere with, nor can the be heard by one another.

A DMR talkgroup is a method of organising radio traffic such that the the DMR users can choose to hear the same thing and not be bothered by other radio traffic on a DMR network.

Talkgroups can exist for many purposes. On the Brandmeister network World Wide is TG91, Jamboree on the Air (JOTA) is TG907, a link to the Southern Ireland Repeater Group voice network is on TG27240. Just about any group of DMR users could have a talkgroup assigned to them that they can all monitor and take part in, without having to talk to each other one by one.

Given the demand for Talkgroups however, and how quickly their use can fade, no one is all that keen on allocating a Talkgroup number for everything. A good way to start out is to use one persons DMR ID as the Talkgroup ID and try it out. If the special interest group is still running after 6 months or so, then everyone can be fairly confident that it won’t be waste to allocate an ID to it.

Now what does this mean regarding programming them? Well, based on the current guidelines, I have updated my own DMR page with an example of three different repeaters, and how a memory bank (Zone) could be programmed in line with the guidelines. If it still isn’t making sense to you. Drop me an email ( details on HamQTH and QRZ). 73

EI7CDD DMR Repeater, Retevis RT8 and GPS functionality

Last week, I gave a short talk on DMR and Brandmeister at the South Eastern Amateur Radio Group club meeting. There were quite a few members present and there were plenty questions.  The full presentation is available from here, but what is new (since the IRTS AGM presentation) is this image taken from Xastir.


This is a track formed by a numberof GPS position information beacons from my Retevis RT8 Radio, the data bursts are received at the EI7CDD DMR Repeater, and then forwarded to the worldwide APRS Internet Service backbone before appearing on the map.

What is interesting to me is that the RT8 was just thrown on the dash of a van, no special effort was made to optimise its position, the terrain is by no means flat, undulating would be the best description, and yet, the RT8 was still able to hit the EI7CDD repeater from up to 20k away.