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

Geek vanity

I’ve been on an enforced go-slow recently and now that I’m more mobile I started looking for things to do. Several of my transceivers have the ability to add custom ‘bootup’ screens. So I thought how hard could it be?

Like most things, it is easy once you know how. K9WX figured it out already in short, use a 120×48 pixel, 1 bit bitmap, 120×48 created in Microsoft Paint.

The result isn’t very imaginative, but I get a chuckle out of it and that’s all that matters.


Southern Ireland Repeater Network

I was asked to do a presentation on the Southern Ireland Repeater Network for the Irish Radio Transmitters Society AGM weekend that should have taken place in April. Unfortunately, due to the ongoing pandemic, it didn’t happen. Currently, the repeater network is maintained by the Southern Ireland Repeater Group.

As the AGM was cancelled, I kicked the can down the road a bit, but finally last Monday evening I presented the slides to my local club (SEARG). Given it was originally supposed to be a presentation to a national audience, the slides are now available from here.

Predicted coverage map of the Southern Ireland analogue voice repeater network