DMR Simplex Frequencies Explained
Although most DMR contacts today use repeaters or hotspots, DMR simplex frequencies remain an important operating option. Simplex allows two DMR radios to communicate directly on the same frequency and time slot, without relying on repeaters, networks, or the Internet.
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:
- 1. Very High Frequency (VHF) – Range between 30 MHz and 300 MHz
- 2. 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 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.
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.
Talkpod 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.
Benefits of DMR Technology
As DMR is a fully public, open standard backed by a huge variety of suppliers. Through this users have both the security of supply and the advantages of continuous, competitive development. Open standards encourage wide ranging supplier participation; there are many examples of the successes of technologies developed in this way. The DMR standard scores highly against legacy analogue systems and other digital approaches.
