WHAT IS DMR?
DMR stands for Digital Mobile Radio and is an international standard that has been defined for two-way radios. The DMR standard allows equipment developed by different manufacturers to operate together on the same network for all the functions defined within the standard.
The aim of the DMR standard was to create a digital radio system with low complexity and low cost that still allows for equipment from different manufacturers to work together, allowing users to shop around rather than being locked into a proprietary system which would be costly to replace and maintain.
The European Telecommunications Standards Institute (ETSI) is responsible for the creation and maintenance of the DMR standard. The standard was first ratified in 2005 and has subsequently been updated and revised several times, most recently in November 2018.
What is DMR?
Is all DMR equipment compatible?
Yes, and no; while basic functionality will work between systems (such as voice transmission) if your chosen manufacturer has performed interoperability testing, you might be using features outside those defined by the DMR standard. Before deciding what equipment to purchase, you should check what features you are currently using and find out if any are unique to your current equipment.
What frequency does DMR equipment work on?
Digital Mobile Radio works between the frequencies of 30 MHz (Megahertz) and 1000 MHz, also known as 1 GHz (Gigahertz). This range of DMR frequencies is divided into two categories:
- Very High Frequency (VHF) - Range between 30 MHz and 300 MHz
- Ultra High Frequency (UHF) - Range between 300 MHz and 1 GHz.
From these ranges, most DMR equipment falls into the 136 - 174 MHz and 403 - 527 MHz parts of the spectrum. Each country has its own organisation tasked with allocating licences, but some DMR frequencies are allocated as licence-free (for DMR Tier I) while others require a licence to operate.
Do I need a licence for DMR equipment?
The short answer is “it depends”. If you have a small number of users and basic communication requirements you may be happy to use DMR Tier I (see what are DMR tiers?) radios which do not require a license and are simple to use. It should be noted that Tier I equipment has a shorter range and are susceptible to interference from other users. If you require a more complex system you will need to apply for a licence from the frequency licencing body in your country.
DMR licencing is a complex topic, but with Motorola Solutions’ extensive partner network, we can pair you with a local expert to help you find the solution that is right for you.
How does DMR compare to TETRA?
DMR and TETRA are both standards created by the European Telecommunications Standards Institute (ETSI) to address different types of user. DMR is targeted at the commercial markets while TETRA is targeted at public safety. This is demonstrated best by the difference in interoperability testing for the two systems.
DMR system interoperability is tested by manufacturers working together on a one-to-one basis. For comparison, TETRA products must be tested by an independent third-party featuring multiple vendors. DMR tests only include 6 mandatory interoperability features, whereas TETRA testing requires 49 mandatory features to be tested.
The higher number of tests for TETRA equipment allows public safety bodies such as the police and fire services to make separate purchase decisions without worrying about compatibility between their systems during an emergency. However, the more stringent TETRA standard does not allow manufacturers to be flexible in the way they implement new and exciting features in the way that the DMR standard does.
Motorola Solutions can help you to pick the right radio technology for your requirements. Contact us today using the button below.
What is the range of DMR?
The answer to this question depends on the equipment you are using and the infrastructure you have installed around it. As an example, the International Space Station, orbiting at an altitude of 408 km uses DMR to communicate with the earth, but there are very few obstructions between the station and the antennas on the ground so the signal is easily received. In comparison, a DMR Tier I radio operating inside a building may only work for around 100 metres.
DMR radio systems can have any range you wish them to have if the correct infrastructure is installed; DMR Repeaters can extend signals over a large area, but pockets of connectivity can be created by distributing data between repeaters through other means such as microwave links or the internet.
Motorola Solutions extensive partner network means can we can pair you with a local expert to help you find the right system solution for your unique requirements. Contact us today to start your journey.
What is a DMR Repeater?
DMR radios are able to communicate with each other directly without a centralised system, but this is not always an ideal situation. Signals between radios connecting directly to each other can be hampered by obstructions in the line-of-sight between them such as trees, buildings, and hills.
A DMR repeater added to the system allows radios to send their communications via a central point which repeats the message to the rest of the system. By installing a repeater high up (often on top of a building) the calls to the repeater are less affected by the obstructions. It also allows radios located far away from the repeater in opposite directions to communicate with each other, effectively increasing the range of the system.
Repeater stations can be connected together by either retransmitting received signals (parroting) or by sending received signals to other repeaters on the system via other methods (internet, unidirectional transmitter, etc). With these methods, the range of the system is only limited by the amount of infrastructure you install.
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