DMR stands for Digital Mobile Radio and uses the Motorola TRBO protocol for communications. Like other digital modes such as D-Star, C4FM and APCO P25, the TRBO protocol converts your voice into a digital form and sends it out via RF (with other bits of information included) and allows you to communicate to other DMR radios and also DMR repeaters, which are networked together around the world via the internet.
What makes DMR stand out from some of the other digital modes is that it utilizes TDMA (Time-Division Multiple Access) to divide a single frequency into 2 distinct “channels” or time slots. By doing this, you can have two conversations going on at the SAME TIME, using one frequency.
I finally decided to give DMR a try after serval weeks of researching and reading but I was still confused on how it works.
SD card that is a 16GB minimum is for putting the image (software) on to the raspberry p i. The SD card stays in the Pi-3b to run the system.
First things first.
DMR Repeater or DMR hotspot?
DMR Radio: I went with the TYT 390G. I wanted a dual band radio for 2M and 440 that could operate in both Digital & Analogue modes. It complies with Mototrbo Tier I & II and has an advanced GPS function for emergency communication.
I orderred it from Radioddity. https://www.radioddity.com/digital/tyt-14/md-390.html
DMR-ID Number: A Radio ID is a unique number assigned to you (and your callsign) by the European DMR-ID Team. Like a telephone number or IP address, your Radio ID identifies you as a unique radio user on the various DMR networks and repeaters around the world.
The Updated site to register for a DMR ID was changed from the MARC DMR-ID Registration system to the European DMR-ID registration system.
To get a DMR-ID Number for your radio you need to register. it is free and I got my number within 24 hours. https://register.ham-digital.org
The mini DMR repeater board connects to the Raspberry Pi 3 in a straightforward way. Just put the pins into the mini DMR and push down until it is in place. The board plugs into the pi on the gipo pins, the sd card goes into the pi as it’s hard drive, the image for it can be downloaded from http://www.pistar.uk
This board acts like a mini repeater with both time slot’s 1 and 2 on it, it’s short range good for around the house or block and fits in the palm of your hand giving you access to the full brandmeister DMR experience. You can also connect it to a hotspot and travel with it as well.
Software: You need to install the image on the PI card. Go to http://www.pistar.uk/downloads/ and select the one that says “RPI”. Those work on the Raspberry pie.
Then you will need two programs to burn that image to the SD card for the pi. https://www.sdcard.org/downloads/formatter_4/
Choose the windows version you have i.e. 10/8/7 download and install
SD card goes into your computer, unzip the image, run sdformatter on the sd card drive and then use a program to burn the image to SD Drive. I used a program called Etcher, it was free and easy to use.
Then once done burn the image to the sd card from your computer. Place the SD card in the PI, Plug in a ethernet cable to our router and the other end into the Pi-3b and then provid power to your pi with the mini DMR board connected to it. The system should light up. I used a USB cable and powered it off of the laptop and it seems to work fine.
You can listen to live DMR Radio on different talk groups around the world at; http://www.pistar.uk/dmr_bm_talkgroups.php
Register at Brandmeister network and you will be able to change some options on your system. https://brandmeister.network/
N0GSG DMR Contact Manager
To program your system type in your browser bar; http://pi-star.local/.
There are several videos on how to set up your repeater, lucky I had an experience person to share screenshots and walk me through it. It is pretty easy, the only problem I had was I had the frequencies on the radio and PI-3b set as the same. The RX and the TX should be reversed.
I can tell it is working by looking at the dashboard.