Digital mobile radio (DMR) is a digital radio standard for voice and data transmission in non-public radio networks. It was created by the European Telecommunications Standards Institute (ETSI), and is designed to be low-cost and easy to use. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25 kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. DMR and P25 II both use two-slot TDMA in a 12.5 kHz channel, while NXDN uses discrete 6.25 kHz channels using frequency division and TETRA uses a four-slot TDMA in a 25 kHz channel.
DMR was designed with three tiers. DMR tiers I (Unlicensed) and II (Conventional Licensed) were first published in 2005, and DMR III (Trunked version) was published in 2012, with manufacturers producing products within a few years of each publication.
Amateur radio use
DMR is used on the amateur radio VHF and UHF bands, started by DMR-MARC around 2010. The FCC officially approved the use of DMR by amateurs in 2014. In amateur spaces, Coordinated DMR Identification Numbers are assigned and managed by RadioID Inc. Their coordinated database can be uploaded to DMR radios in order to display the name, call sign, and location of other operators. Internet-linked systems such as DV Scotland Phoenix Network, BrandMeister Network, TGIF, FreeDMR and several others (including several previously closed clusters which now connect to larger networks to facilitate wide-area accessibility), allow users to communicate with other users around the world via connected repeaters, or DMR "hotspots" often based on the Raspberry Pi single-board computer. There are currently more than 5,500 repeaters and 16,000 "hotspots" linked to the BrandMeister system worldwide. The low-cost and increasing availability of internet-linked systems has led to a rise in DMR use on the amateur radio bands. Some Raspberry Pi-based DMR hotspots, often those running the Pi-Star software, allow users to connect to multiple internet-linked DMR networks at the same time. DMR hotspots are often based on the open source Multimode Digital Voice Modem, or MMDVM, hardware with firmware developed by Jonathan Naylor.
The most common Talkgroup for Southern California is 31066
Live TG31066 Dashboard
Listen live the the Brandmeister Network
https://hose.brandmeister.network/
