IRLP in plain terms
IRLP stands for Internet Radio Linking Project. It is a system that connects amateur repeaters, and sometimes simplex stations, to each other over the internet using voice-over-IP technology. A person with a handheld in one city can, through a linked repeater, talk to a repeater user in another city or another country. The project was started by David Cameron, VE7LTD, in Canada in the late 1990s and was one of the early systems that tied repeaters together over the internet.
How it works
At its core, IRLP turns the audio from a repeater into data, sends it across the internet to another node, and converts it back to audio for that repeater to transmit. The radio side stays analog FM, so ordinary radios can be used. Only the link between the nodes uses the internet.
What is an IRLP node?
A node is the station that does the linking. It typically includes:
- A computer running Linux with IRLP software.
- An interface board that connects the computer to a radio or repeater controller. It carries audio and push-to-talk signals and decodes DTMF tones.
- A radio or repeater that the node controls.
- An internet connection.
Each node is assigned a node number, which is how other users call it. The node owner is the station licensee and is responsible for what is transmitted through it.
How to connect using DTMF
Users control the link using the DTMF (touch-tone) keypad on their radio. In general, you dial the number of the node you want to reach, and the local node attempts to connect. When the remote node answers, the two repeaters carry the conversation, and a disconnect code ends the link. The exact codes, whether you need to listen first, and whether the repeater allows connections, vary from node to node. Ask the local repeater owner or club for the rules and codes.
Before pressing keys, listen, as good repeater etiquette requires. A node that is already connected may be in use, and some repeater groups restrict who may start a link.
Reflectors
IRLP also supports reflectors, which are shared hubs connecting many nodes at once. They resemble a group conference call or net, and are used for regional and special-interest groups. Each reflector has its own etiquette and often a regular schedule of nets.
IRLP vs other linking systems
| System | Radio side | Link side |
|---|---|---|
| IRLP | Analog FM | Voice over IP between nodes |
| EchoLink | Analog FM nodes, also computer and phone clients | Voice over IP |
| AllStar | Analog FM | Voice over IP with a Linux-based controller |
| DMR | Digital voice radios | Digital networks, see DMR explained |
Each system has its own community and tools. Some repeaters support more than one.
Can a ham radio be traced?
Radio signals can be located with direction-finding equipment (see can ham radio be traced), and amateur stations identify with their call sign, which is public in license databases in many countries. IRLP nodes are tied to a node number and a licensed operator. Nothing in this article should be treated as guidance on avoiding identification, which is required by the rules.
Current status
IRLP has been in use for many years, but newer systems have since become popular and activity differs between regions. Some nodes remain active, while some have gone offline. Before building a node, check the project’s current documentation and see what linking systems your local clubs actually use.
Related guides
If you are interested in linking over the internet with data modes rather than voice, read about mesh network ham radio. For other signals you might hear on a repeater or band, see digital mode identification.