DMR – Digital Mobile Radio.

As it stands the whole concept is a professional application of a dual slot time-division multiplex radio system, that has been adapted for use in an amateur field where there are differing opinions and attitudes. The highly technical aspect of it is not the issue here, but the technique. 

From a communications standpoint there are several points to consider in the area of technique.


Firstly that this is not HF and any attribution of techniques of communicating in the HF fashion in voice mode is without merit. There is no point in calling CQ for example. The Q-Codes have no relevance on phone, it has just become habitual. “HI – Aitch-ie” is laughter in CW, why not just laugh a bit instead. Do you really need to spell your name, unless it is really difficult. Old habits die hard as they say, but the time to change has been and gone.

Neither is it like operating in the FM or SSB fashion on VHF or UHF, as the principals do not correlate. Longer breaks between transmission are essential to avoid disruption. Rapid operating is not effective, as the audio in DMR is not of that so called ‘BBC quality’. Receive – Wait 2-3 seconds – Then transmit slowly, clearly and distinctly. Do not rush your transmission or repeat it twice in quick succession, it is can be just as unintelligible – twice. How many times has it been heard “I’m sorry I didn’t get that, I wasn’t listening”? If you make a transmission, LISTEN for replies.

The simplest of explanations of DMR (or other digital modes) is that it is more like telephone direct dialling, with the added advantages of calling groups of people rather than just individuals. However this very idea creates diverse opinions of how the system can or should be used.

Because of these diverse opinions, we should look at one of the most open of networks carrying DMR at the present time, and that is the BrandMeister Network. BrandMeister has a worldwide network of 45 servers all working together with software providing virtually instantaneous communication with global potential.

The structure is not under review here as it already has proved itself over many years and is in constant development. Access is free, however financially supported by many individuals. No one is paid, for as in most pastimes, time and often material is donated. Consequently no system is infallible but what there is here is second to none.

The rules are also not under review, for as in most organisations, the rules are in place for the protection of the network, and for the users. Any changes that are made should not impinge on the participants, but they, the users must be prepared to learn how to get the best from it.

The uses of the network, the protocols if you will, are determined by the users, be they guardians of repeaters on the network, or the individual users. Full details are available on and on each of the national pages from the drop-down menu. Users need to read and learn about the networks and their radio, preferably before transmitting.

The Global Policy.

It can be seen by any user that it is possibly to communicate on a global level with individuals or groups of individuals depending on how the participants wish to view the network from their own point of view.

The Language Policy.

Clearly there are international users who may wish to communicate in another language other than their own, or those that lack the ability to do so.

The National Policy.

Interestingly the ability to generate national traffic is not necessarily at the forefront in some repeater keepers’ minds. But the ability to be able to communicate that widely is built-in. Whilst National TalkGroups are available, not every sysop wishes their users to have them full-time. Dynamic TalkGroups that are user-activated are available.

The Regional and Local Policy.

Always the concern for local affairs is paramount. Diffusion at a local level is considered important for radio clubs. Thus Local or Regional TalkGroups are also available, but again may not always be presented full-time.

The “I want to be Independent” Policy.

The difficulties arise in a number of areas mainly due to lack of comprehension as to what is possible, rather than the wish to participate in experimentation with another networking tool such as HBLink3* elsewhere.

The fracturing of DMR is the case in point, where little groups of people are looking at independent networks of their own, forgetting the wider perspective of the potential of the existing network. They have seen that they believe to lack control over certain aspects, driving them to decry the rationale that everything they really want is already available.

The introduction of HBLink3 servers onto the active BrandMeister Network is a cause for concern, for it is powerful software and capable of enormous disruption. Hence the rules in place on BrandMeister that permit only certain open-bridges. There are indications that some of these independent networks have so little activity that they are asking to bridge back to BrandMeister, when in fact they should consider that direct connection is preferable as a service to their users.

The “How to Connect to Satisfy Everyone” Policy.

No-one likes to listen to nothing, but contrariwise no-one likes to hear irrelevant content. But this is the difference between the world of Amateur Radio and the Professional World. Amateurs do not want to be left out of anything, but want the choice of to what to listen. The professionals have generally only one channel to monitor without need of such choices.

Repeater keepers are the main support to the network, by connecting their devices to the server of their choice, they offer the availability of two channels and the many routes for the users.

In the repeater keeper’s mind he has to balance the use of the repeater with the costs involved in administering or maintaining it. The repeater keeper is ultimately really an individual who does what suits him in the end although generally tempered with common sense, but if this is a committee then it can get complicated.

Questions that arise are:

Does the sysop provide a full time listening opportunity to Local/Regional/National/Global or a mix? 

Does the sysop leave the repeater open for use (or abuse) of the users without some guidance on how best to drive it? 

Does he connect to a group of repeaters or a smaller network, or leave it as a completely stand-alone device.

  1. The questions can be easy, or they be difficult. The duty cycle of a repeater can be a cause for concern to the keeper, so if he wants to control the use, then it is often dependant on what groups are connected. Nonetheless BrandMeister provides timer-control to the sysop so that he can regulate the activity if required. Naturally some experimentation may be necessary to determine the paths to be active or those that should not. No-one will listen to or monitor a quiet repeater that has no traffic. Naturally the sysop should consider a draft document of the repeater operating conditions. BrandMeister provides this space on the dashboard too.
  2. An open repeater without rules can induce anarchy, particularly if the same group call is active on both time slots, or certain world-wide group calls are constantly activated for no reason other than because someone can.
  3. The format of available TalkGroups on BrandMeister means that any hotspot user or any repeater user can activate any group call from 91 upwards on either slot. So either Global, National, Regional or Local access is possible.
  4. The simple way for a regional group of repeaters is to engage in a cluster, and for the consensus to utilise one of the repeaters’ DMRId numbers as a group call, then there is no need to invoke special procedures. Thus this one group call number can serve to be a fixed group call on one time slot universally between the repeaters that are involved in the group. Thus users can be assured of some continuity as they move around the region covered. Again the information can be dispersed on the BrandMeister Dashboard of the repeater(s) concerned.
  5. A lone repeater, effectively talking to a network of one is just a project. Nothing can be shown to be advantageous in not providing connectivity with a network or another repeater, it’s just a local conversation café.
  6. Naming of TalkGroups is kept to a minimum. The important part of a TalkGroup is its number. Names have only been attributed to significant groups at National level. 
  7. Repeater keepers choosing to sever connectivity from a wider network to become an independent network are doing themselves and their users a disservice. Ultimately the users will make the decision for the keepers and vote with their feet and join the most active of memberships. It is only natural.

So in summation, a network provides a service, whether locally, regionally, nationally or globally. How the choice is made is entirely in the hands of the users and repeater keepers, however it has to be accepted in the case of repeaters, it is often the individual sysop that chooses and not the assembly of users, so the sysop or the committee of the repeater should review their local policy from time to time in the light of what is current and available.

In the event of another network of size being available, it is not impossible for the repeater to have more than one network connection, with the subsequent enhancements for the users to choose. DMR-Gateway is already in use in many cases on MMDVM Repeaters.

However the final point to be made here is that in all cases of DMR it will always be first come first served on the time slot in use at the time.

*For HBLInk3 read my other blog on the subject.

These are the opinions of the author.

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