Digital Mobile Radio or DMR, is a system to transmit audio as a digital stream to other transceivers or more usually to and from repeaters. The general term used is Digital Voice or DV and DMR is not the first DV mode that amateurs have used. There’s APCO/P25 that is used in conjunction with emergency services and of course the well-known D-Star and Fusion. These last two modes are only used by amateurs and that’s a big difference. While using what is a 2006 European ETSI standard, DMR was never designed for use by amateurs as D-Star and Fusion were. Equipment for DMR is cheaper because of the numbers of units created for commercial use, but it is also complex to program and has many features that while needed in commercial installations can cause confusion in the amateur world.
That is not to say that configuring D-Star or Fusion rigs has always been easy but with DMR in the commercial world the programming of the HTs is done by specialists, never by the users, so the challenge is greater for an amateur to configure a DMR rig than say a D-Star one.
What’s so special about digital voice anyway? Well DV is supposed to give better audio quality at lower signal levels. DV can be routed over networks such as the Internet to other repeaters on the other side of the world. Some limited computer data can be transmitted even when voice traffic is being used at the same time. What makes DV good is not always the HT or the Repeater but more often what can happen in the networks behind the repeaters. Whether Fusion, D-Star or DMR, there exists virtual audio conference rooms where you can talk to multiple other people from around the world – gathering places if you like. D-star calls these reflectors, DMR calls these Talk Groups and Fusion actually calls them rooms.
Which of the main three DV standards is “the Best” – answer “it depends” and the major thing it depends upon is what repeaters or other access points to the Digital Voice system you have in your area. D-Star used to have by far the largest coverage but that is changing and some areas have lots of Yaesu Fusion repeaters while DMR repeaters in some areas are “popping up like mushrooms”. If you are in an area, as I am, in Germany, where DMR is becoming the major player as regards repeaters, it makes sense to go with DMR. If you only have Fusion or D-Star digital repeaters in your area you should look at whether you want to get equipment on those networks. I am glad to say that over the last 6 months more and more gateways are being put in between the networks so someone accessing through a D-Star repeater can talk to a group on the DMR or Fusion network and vice versa. The encoding of the digital voice and its transmission is totally different in the three systems hence it is unlikely that we will ever have simplex DV contacts between HTs on each of the DV standards but if the HTs all switch back to analogue FM they can talk to each other.
Motorola started the DMR DV standard with their TRBO “turbo” systems. These are managed in the main part using “C-Bridge” units to connect internationally and the Infrastructure is managed by the DMR-MARC group *The Motorola Amateur radio Club). Each region in the world has a master and peer structure between the repeaters, with at least one master server. In Germany that master server was DMR-DL and each new Motorola DMR repeater would connect to that to form part of the larger network. DMR-DL expanded over time and eventually also connected back to the DMR-MARC network in the US. Then along came a Chinese company – Hytera and their repeaters wouldn’t talk to Motorola repeaters or the C-bridges, so a small Hytera network started up in Germany. At this point, another group decided they needed to bridge the two networks and this work was, what was later to become DMRPlus. After a while, the people running the main server for the DMR-DL network could not support it any more for personal reasons and slowly it appeared that DMR-DL would close. So many of the Motorola servers that were attached to the DMR-DL (DMR-MARC)’s master server in Germany switched over to DMRPlus network which by now could support both Motorola and Hytera repeaters through IPCS2 units (IPCS – IP Site connection server). DMR-DL did indeed close down for a while however some other amateurs managed to get it going again but by then most of the Motorola DMR repeaters had switched to DMRPlus or the newer Brandmeister network.
From an amateur point of view, the Motorola DMR-MARC and Hytera DMRplus repeaters are similar, however, they both have their own independent back-end networks with their own talk group “audio conference rooms”.
DMRPlus is an amateur-only interface between networks supporting Motorola on one side and networks supporting Hytera on the other side and grew to be able to support these plus the MVDVM and other hot spot units.
Out of a UK, only “Phoenix” network a new world-wide network called Brandmeister has appeared in the last couple of years. Both of these new networks wanted a more open architecture and the big change that the Brandmeister connected repeaters brought over the DMR-MARC and DMRplus connected ones was the fact that the user could choose which talk group they wanted to connect to from their radio and the Brandmeister network would route them there. In the case of the earlier standards, the repeater owner sets up a list of talk groups that can be accessed via the Time Slot 1 channel and another list for Time Slot 2. In comparison to the number of possible Talk groups on Brandmeister, these lists limit the number of talk groups that can be accessed from a DMR or DMRplus repeater but usually contain the most common regional & national talk groups.
These different capabilities are on the repeater and network side. Nowadays you don’t need a different HT for each of the DMR standards. All current DMR HTs sold to the amateur market will work with all three DMR networks.
E & O E.