Some Essential Terminology for Using DMR and the Networks
The MCC - Mobile Country Code
Everything in the world of DMR has to accept the use of the MCC code. Every country has one, and was derived primarily for the Mobile Phone Networks.
It seemed logical for the DMR community starting out, that to adopt this internationally recognised system was advantageous.
All the codes can be viewed here @ https://en.wikipedia.org/wiki/Mobile_network_codes_in_ITU_region_2xx_(Europe)#UK .
This table indicates 234 and 235 are the MCC codes for the UK.
User Identification
All users of the DMR Protocol are obliged to be registered via Radioid.net, in order that their data connections become valid. This is not about personal security, it’s about protocol and the ability for data to traverse accepted pathways. Only one ID is required by each user, and it can be used for multiple digital modes.
The Identifications are formatted in such a way that the systems know what the terminals are, whether they are repeaters or users, as in 6 digits or 7 digits.
A terminal is a radio or connection device of any sort, that sends and receives data, to and from the network.
Servers.
Dependent on which network, there will be upwards of 1 server providing a dedicated operating system that will form pathways for the voice data packets depending upon the service provider.
There is a complicated systems of inter-relational databases that determine the availability of a path, that check whether it has been fixed or not by a known repeater/hotspot, the validity of the path, and the authority for the path provided by the system, and a database to insure a user can in fact legitimately use the system, and a database of connected subscribers of all types.
The server or servers will be constructed in such a way that there will be a system of Talk Groups made available, to which the users can subscribe.
BrandMeister
The most prolific and active of these networks is the BrandMeister (trans:FireChief) network, about which you can read here - https://wiki.brandmeister.network/index.php/United_Kingdom.
The BrandMeister network consists of a worldwide network of 46-48 servers, that at the time of writing has 6697 repeaters, and 18319 hotspots connected. Connections between the servers are ‘fast-forwarded’ so that they each contain virtually identical data.
An overview of the activity can be seen at brandmeister.network, together with any project news.
A computer user can monitor selected talk groups at hose.brandmeister.network. Additionally brandmeister.network gives you access to a multitude of services.
There are various menus and searches available from the left hand side. Most users of the Network have personal access to their own profile on which to manage a hotspot or a repeater.
While DMR users will be aware of the principles of the two time slots available, the BrandMeister only records the information according to their use and control by a system operator in a repeater, or a user on his terminal. Only the path to a Talk Group is relevant for the individual server.
You could unwisely transmit TG 2350 on Time Slot 1 of a repeater, while it is already fixed on Time Slot 2. This effectively makes use of both Time Slots simultaneously. BrandMeister just carries the data, it doesn't concern itself with Time Slots.
In the UK - Talk Groups 1-90 do not pass over the network, except Talk Group 75 that is used to cluster repeaters together in the Salop Cluster (Shropshire). This can also be accessed by using TG 23575. Talk Group 91 with Sub Groups 901, 902 and 903 to which to QSY. The UK in general has opted to use TG 2350 as the calling group as opposed to 235 the MCC Talk Group. Talk Groups do not need to be named, as no one person has complete knowledge of designations. Use the number, it is so much simpler.
The full table of common Talk Groups can be found in the UK Wiki.
Some UK repeater keepers have chosen to connect to the Irish BrandMeister server 2721, but this has no effect on the operation, other than perhaps a difference in latency of the Data Connectivity.
The general principles on the BrandMeister network are that if I was in Australia or any other Country, accessing a BrandMeister repeater there, I can transmit into the UK using TalkGroup 2350, provided that a time slot on a repeater was available. Some BM servers such as in the USA however restrict access to users other than US ID’s. However I do not believe this to be a universal restriction.
IPSC2
Formerly and more commonly known as the Phoenix Network, the UK part of the IPSC2 has three main servers, and one linked server all interlinked. The IPSC2 Network as a whole have a large number of partially connected groups that provide links to the international Talk Groups. But the UK Talk Groups are only interlinked between the four servers in the UK. So if I wished to communicate to some colleague in France for example, I would have to link a repeater or hotspot to IPSC2-France3 and call on the respective talk groups there.
As it stands currently, all MMDVM Repeaters in the UK are connected to the ‘A’ server, Hotspot Users are generally connected to the ‘F’ server, and Motorola and Hytera Repeaters are connected to the ‘K’ server, and the so-called FreeDMR network that has some other differences has its own server. All four are interlinked that allows the 235, 80, 81, 82, 83, 84, and regional talk groups to pass between them.
As an overview I see a DMR communciation system that has been fractured for sometime for probably several reasons, that I shall not discuss. There are several networks with BrandMeister and IPSC2 being the most populated. There are currently 84 UK Repeaters on BrandMeister and 70 on IPSC2, however there are a small number like mine - GB7HT - that are on both. There are 9 repeaters on FreeStar (FreeDMR).
About me
I have been licensed since 1977 and have all mode capability from my QTH in the North East of England, specialising in software presently.
I have been asked to provide some insight into DMR specifically from the broad aspect as a community of communities. There is plenty of information on specifics found elsewhere.
I do this from my experience as a long-time communicator from the professional world.
I joined DMR just as BrandMeister was developing, and my first entry was via the short-lived DV4Mini stick. But it was interesting. Then I built the first of three repeaters.
At the time I was living in France and DMR hadn’t really taken off there at that point. The MD380 then emerged onto the market and the rest is history.
The first repeater F5ZLR was constructed from an unused D-Star repeater, using the two Motorola GM350’s, an Arduino Dué with a Zum Hat and clock board, all driven by a Raspberry Pi 2b with the excellent MMDVM suite of programs developed by Jonathan G4KLX.
There was no way at that time for the outside world to see what was going on at the repeater as there was no real readable dashboard, although I had installed one of the web-based dashboards that simply reads and displays the condition of the Pi.
I commanded the repeater at distance through a complicated network of 3 routers, by ssh therefore headless. The later arrival of Pi-Star made it visible to the general amateur populace, as well as a good administrative platform. It did what I require of it.
This first repeater was on the BrandMeister Network, which in France is the most active of the networks today. IPSC3 has by comparison very few repeaters.
Sadly due to my return from France and the building upon which the antenna was mounted being demolished, this repeater is now off until a new sysop can find a site.
After the first repeater, I built a second DMR unit F5ZLW out of a Tait 800 Mk1 series UHF repeater.
This time I used a ZumRadio Pi-Hat that mounted directly onto a raspberry Pi. Still in France at the time, I chose to have both French and UK TalkGroups on it, on BrandMeister, as well as one of the IPSC2 Networks, using the DMR-Gateway MMDVM software.
I never tried IPSC2 France and IPSC2 UK together as they both share the same port although different IP addresses.
This repeater I brought to England with me, and re-registered it as GB7HT, still with both Networks available.
You can find the basis of a code plug on qrz.com/db/gb7ht. The repeater uses the Talk Group Re-write options in the DMR-Gateway. You can view this repeater at http://gb7ht.ddns.net:8080 on a Pi-Star dashboard.
I have since been deeply involved in Raspberry Pi and SVXLink, about which I shall write in due course.
Chris G4NAB