With digital radio changing so quickly, below is a bit of an update in regards to DMR radio networks.
DMR stands for Digital Mobile Radio and is an internation standard for digital radios since about 2005. It can contain voice and data. It was created as a standard so it remained low cost and could be used and made by any country.
DMR was designs with three tires where tire 3 is usually for trunked radio networks, however this didn’t start until about 2012. DMR is used between 30MHz and 1GHz
DMR uses 12.5 channel spacing but had two voice channels per frequency. This is done by having the two voice channels on two different time slots. In very basic terms, the radio will listen to 30ms of each time slot and only play the selected one. This means you will miss every second 30 millisecond, but as this is so short, you wouldn’t notice any of the voice missing unless the signal is weak.
Within each time slot, you can have talk groups. So, if you are not on the right frequency, time slot and talk group, you may not hear anything or be heard.
DMR Conventional
This can be either DMR Duplex (as in a base repeater) or DMR Simplex ( where uses talk direct to each other without a repeater). Radios can be lower in transmission power, and best suited to individuals or companies in outdoor recreation, small business, or other applications that do not require a lot of radio users and wide-area coverage. However a repeater can be used to widen the range of a DMR network.
DMR Capacity Plus
This is a single site network, is one with no central control channel. All radios on this system scan each frequency at that site continually. There is a maximum 6 frequencies / 12 channels (tier 1 and 2). This could be a Motorola Solutions Cap+ network, PA People Cap+ network and so on. There can be up to 1600 users per site.
Occasionally you will come across a 1 frequency Cap+ site with no second frequency. However single frequency DMR Capacity Plus systems are often preferred to standard conventional because of the following reasons:
- Capacity. You can easily have 4-6 talk groups on a single repeater.
- System wide All Call. You can easily contact every radio when doing a capacity plus all-call if their radio is on and in range.
- System wide Private Call. You can easily connect to your private call recipient if their radio is on and in range.
- System wide radio ping and disable. A radio ping can ping a users radio to see if it is on and in range.
- With Conventional DMR you must be on the right slot and correct talk group in order to do any of the above.
DMR Connect Plus
This is a multi-site Trunked linked by IP and has a centralised control channel. An example of this is the Orion Network commenced in Australia in 2010 with Connect Plus. Also they started the Orion CapMax Tier 3 in 2019, the longer term aim is to move all Connect Plus users over to CapMax Tier 3 and eventually shut down the Connect Plus network. This has already happened in Queensland.
An example is the Orion Con+ on DSD (Site 1-XX).
DMR Capacity Max Tier 3
This is a multi-site Trunked with a centralised control channel with advanced radio features (integrated data applications such as GPS services, text messaging, data services and dispatch console capability). Examples include the Orion CapMax on DSD (Site H2-XXX).
Please let me know what your thoughts about this are. Did it help you? Is there something else you want to know?
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