What is Digital Mobile Radio
Digital Mobile Radio (DMR) is a land-mobile radio network standard developed by the European Telecommunications Standards Institute (ETSI). DMR is used by professional land-mobile radio networks worldwide and by thousands of amateur radio operators world wide.
A wide variety of DMR mobile, base and portable equipment is available from numerous manufacturers.
DMR uses Time Division Multiple Access (TDMA) to provide two 30 ms “slots” per 12.5 kHz radio channel. Each slot can carry independent voice conversations – this means that each DMR repeater provides two simultaneous voice channels. Each slot can also have an almost unlimited number of “talk groups”– these function as discrete channels within that slot. Users on one talk group will not hear those on another.
DMR provides better noise rejection and weak signal performance than analogue systems by using advanced Forward Error Correction (FEC) and codecs to remove noise and reconstruct signals that would otherwise be lost.
For more information https://vkdmr.com/
DMR Repeaters and Talk Groups
One of the great advantages of DMR is that repeaters are designed to be linked together directly via IP. This allows interconnection of repeaters in the next suburb, or on the other side of the world…
They are more than 500 interconnected DMR repeaters, across 44 countries, including Australia and New Zealand. There are more than 60,000 registered amateur DMR users.
The St George Amateur Radio Society hosts a DMR repeater VK2RLE, located in southern Sydney operating 438.425 MHz with minus 5 MHz input offset.
More information about the other DMR repeaters in Sydney, NSW and Australia wide can be found here https://vkdmr.com/the-dmr-network/
Time Slots and Talk Groups
Each DMR repeater has two slots, Time Slot 1 & 2. Each slot has a number of talk groups which need to be programmed into your DMR radio.
More information about time slots and talk groups used on Australian DMR repeaters can be found here https://vkdmr.com/using-dmr/
Unlike other amateur digital radio systems, DMR transceivers are available from a number of manufacturers, in both mobile/base and handheld formats, either mono band or dual band VHF and UHF with features ranging from the very simple to comprehensive. Prices start from about $150 AUD.
Transceivers for the amateur DMR radio system must be DMR Tier 2 compatible. Before purchasing, research into which transceiver would best suit your needs is recommended. Information and reviews of DMR transceivers can be found here https://radiosification.blogspot.com/2017/11/comparison-of-dmr-radios.html and http://www.miklor.com/COM/Review_DMR_Radios.php
DMR related Facebook groups are The VK DMR Network and Australian DMR HAM Radio User
Disclaimer: DMR transceiver information links are provided by The St George Amateur Radio Society (SGARS) in good faith, however SGARS does not accept an responsibility for the information provided.
DMR Radio Programming and ID Registration
DMR transceivers must be programmed with repeater frequencies, talk groups and time slots, receive and scan groups etc which is contained within a configuration file, commonly known as a "code plug". Programming cables and software are generally available from the DMR transceiver manufactures.
Writing a configuration file from scratch can be a challenging experience for a newcomer to DMR, hence The St George Amateur Radio Society (SGARS) has setup a database of DMR configuration files provided by SGARS members. These code plugs include configuration data for DMR repeaters in the Sydney, NSW and ACT area. DMR configuration files can be downloaded from here.
Disclaimer: DMR transceiver configuration files are provided by The St George Amateur Radio Society (SGARS) and it's members in good faith, however SGARS and it's members do not accept an responsibility for the configuration data contained in the file.
To access the DMR network each amateur radio operator must have an unique user ID, which must be included in the configuration file. DMR user ID numbers are managed centrally, and may be obtained here.