A while ago I overheard a conversation between two radio amateurs discussing DMR and that DMR Repeaters will not function once the Internet goes down. They were of the opinion that these new digital repeaters are useless if the Internet is down during a disaster or emergency. This discussion set me thinking - always dangerous but I decided there must be a way/ways to run a DMR Repeater without the Internet. Before I explain one of the methods I found to work flawlessly when there is no Internet, lets first look into the reasons why one would run a DMR Repeater without the Internet.
The question was how to run a standalone MMDVM DMR Repeater with no access to the Internet. The first question is why?
DMR systems must be connected to the Internet, otherwise it just does not work correctly and does not make any sense. Well, it is not entirely true and I will prove the point that DMR Repeaters can still operate locally when there is no Internet.
There are two reasons for running a standalone DMR repeater in a very remote locations with no chance of having Internet access. You can use Talk Group 9 to communicate within direct range of the repeater. More on how to setup your DMR Radio in this regard can be found further on in this article.
The second reason of running a standalone DMR repeater is for use during natural disasters and any other random legitimate reasons. Make sense in this day and age to be able to use a digital repeater for emergency communications.
The first thing I found is if the repeater is connected to the Internet (through a router) using an Ethernet cable and if the cable gets unplugged, the repeater is still working locally (TG9) without any problem.
However – once the repeater restarts, and there is no access to the Internet network (even local RF transmissions) the repeater does not work anymore.
I hear you say but I told you so and that the two radio amateurs having the discussion were not wrong.
Your DMR Repeater is useless without the Internet!!
Well there are several ways to solve this issue of no Internet to a standalone MMDVM DMR Repeater. In part 1 we will be looking at setting up a DMR repeater on a AREDN Mesh Network without the Internet. Let's get cracking!
Image: AREDN ZS1I Main Node
Setting up a DMR repeater on a AREDN mesh network enables off-grid digital voice communications by replacing Internet backhaul with RF links. Use AREDN firmware on compatible nodes to establish a "tunnel" or direct RF link, mapping your node to the network. An MMDVM-based repeater connects directly via Ethernet to the AREDN node.
Key Components & Setup Steps
- AREDN Node: Ubiquiti or Mikrotik radio flashed with AREDN firmware.
- DMR Repeater: An MMDVM-compatible repeater (e.g., using a Raspberry Pi and MMDVM modem).
- Networking: The MMDVM node connects to the LAN port of the AREDN node.
- DHCP/Routing: The AREDN node acts as the network gateway, providing an IP address to the MMDVM Repeater.
Integration Process
- Mesh Link Establishment: Ensure your AREDN node has a strong, reliable link to the mesh network using directional antennas.
- DMR Setup: Configure the MMDVM host (Pi-Star or WPSD) to use a static IP within the AREDN network range or DHCP.
- Bridge Connection: Use a DMR bridge (like cBridge) to connect to a Master Server over the mesh instead of the public internet.
- Network Testing: Check for 100% connectivity. AREDN nodes should show the MMDVM IP in their DHCP table.
I will not be going into great detail here as AREDN Main Mesh Nodes differ from one to the other depending on which equipment you are using. My equipment is fairly old as I started playing around with mesh networking in early 2002 when it was called HSMM (High Speed Multi Media) which used Linksys WRT54GL routers. In 2015 I moved to AREDN which at the time was mainly using Ubiquity equipment. In November 2016, I started a community organization called Mossel Bay Initiative (MBI) a pilot program for the AREDN Mossel Bay Mesh Network. More on this in a future posting. Through the years several other products were added to use with AREDN. Comprehensive list of equipment available HERE.
View the video below for my setup and an overview of how I used AREDN with my DMR Repeater while there is no Internet connection.
In short crypto I setup the equipment as follows:1. I use a Netgear GS105E Switch that connect all the equipment together. The switch has 5 Ethernet ports and I allocated them as below:
Port 1 = ZS1I Mesh Server (Web Pages) running on a Raspberry Pi.
Port 2 = ZS1I-2 AREDN Node running a Ubiquity Nano Beam M5 16
Port 3 = Windows 7 Desktop PC to view dashboards etc.
Port 4 = ZS1I DMR Repeater using a Raspberry Pi
Port 5 = Internet connection when available from a Router. This port stayed open as we do not want any Internet connection.
2. Startup AREDN Main Node, Computer, DMR Repeater if not already running. IP addresses will be allocated by the ZS1I-2 AREDN Node. In my case 5 IP addresses were allocated. I use Advanced Port Scanner to obtain the IP addresses. For now 3 IP's are important to gain access and to view dashboards. This would be the ZS1I-2 AREDN Main Server Node; the DMR Repeater WSPD Dashboard and the Window 7 Desktop PC Browser to access the ZS1I-2 Node and the WPSD Dashboard for ZS1I (the latter not connected to the Internet but to AREDN).
3. Lets look at how to open and view AREDN node information and the WPSD dashboard.
Access the AREDN node via the Window 7 Internet Browser. Enter the allocated IP address for the node and click enter. The ZS1I-2 Mesh Node status page will open. Login under Setup and once logged in you can go through all the different screens and pages.
(Click on image for larger view.)
As far as the WPSD Dashboard, open the dashboard via the Window 7 Intenet Browser. Enter the allocated IP address for WPSD and click enter. The WPSD Dashboard for ZS1I will open. The dashboard will reflect that DMR and DMR Net are active (Green) while APRS Net and DMR Master BM 6551 South Africa is not active (Red). In other words off-line. So there is no Internet connection but the DMR Repeater is still working locally in the Mossel Bay area.
I programmed all my DMR radios to use TG65522 (World Wide Repeater Talk Group with Internet) and TG9 (Southern Cape Local Talk Group without Internet).
(Click on images for larger view.)
Setting up Talk Group 9 (TG9) on a TYT MD380 for repeater use requires
creating a digital contact for TG9, establishing a new channel with
specific repeater parameters, and adding that channel to a zone. TG9
is frequently used as the "Local" talk group on DMR
repeaters for local traffic or to link to other talk groups.
1. Create
a Digital Contact for TG9
2. Create a Channel for the Repeater
3. Add Channel to a Zone
Go to Zone Information
and select the desired zone (e.g., Zone 1).
Move the newly created channel from the "Available
Channels" list to the "Members" list.
4. Finalize Programming
Important Notes for TG9 Usage:
Local Communication:
TG9 is designed for local QSOs and is not typically transmitted over
the internet to other repeaters.
Linking: In some
systems, such as FreeDMR, you can link to other talk groups by using
TG9 and the "Dial-a-TG" function (using manual dial).
Timeslot: Always confirm with the local
repeater manager whether they use TS1 or TS2 for local traffic.
Parrot Channel: It is recommended to create a
“Parrot” (Echo) channel to test that your radio’s settings
work correctly.
Repeater Access: Ensure you have the correct
frequencies (Offset) for the repeater and that your colour code is
correct.
Promiscuous Mode: If using custom firmware you can turn on
Promiscuous Mode to hear all talk groups regardless of the RX Group
List.
Above: Video of the equipment setup and demonstrating the use of the DMR Repeater without the Internet.
The information provided in this article resolved the problem of no Internet for my DMR Repeater while it usually work with Internet access. As already stated this is one solution. In future topics I will be looking at other methods on how to run a DMR Repeater with no access to the Internet. Some of these solutions are quite simple but seeing that I have an AREDN Mesh Network running, I wanted to use the method described in this article.
