IRLP
| IRLP | |
|---|---|
| Full name | Internet Radio Linking Project |
| Founded | 1997, in British Columbia, Canada |
| Founder | David Cameron, VE7LTD |
| Operating system | Linux |
| Network | |
| Node numbers | Four digits, 1000–8999 |
| Reflectors | 9000-series numbers, the last digit choosing a channel |
| Access | By radio only, using DTMF tones |
| Hardware | PC or small computer, IRLP interface board, radio |
The Internet Radio Linking Project, or IRLP, is a network that connects amateur repeaters and simplex stations over the internet. It was started in 1997 by David Cameron, VE7LTD, in British Columbia, Canada, making it one of the oldest internet linking systems in amateur radio. An IRLP node is a computer running Linux, attached to a radio through a dedicated interface board. Unlike EchoLink, IRLP can be used only from a radio, a design choice summed up in the project's motto, "Keeping the Radio in Amateur Radio."
History
The first IRLP nodes went on the air in late 1997 using commercial internet telephone software on Windows, which proved unreliable. The system was rebuilt on Linux, and the first Linux node went live in 1998 at the University of British Columbia in Vancouver. From there the network spread across Canada, into the United States and then worldwide. IRLP's long-standing nets and its reflectors made it, for many years, the standard way to hear distant repeaters on a local handheld.
How it works
Each IRLP station is a node with a four-digit number. The node computer is connected to the radio through an interface board supplied by the project. The board decodes DTMF tones, the touch-tone digits sent from a radio keypad, senses when the radio is receiving a signal, and keys the transmitter. Because every node must use the official board and is registered with the project, IRLP is a more closed system than EchoLink or AllStarLink, and that control helps ensure that only licensed operators using radios reach the network.
To make a call, a user transmits the number of a distant node as DTMF tones. The local node connects to the distant one, and from then on whatever is said into either repeater is heard on both. Many nodes require an access prefix before the number, and the usual command to disconnect is 73, though owners can change their codes. The link radio is normally set up with CTCSS so that only intended signals, and not courtesy tones or IDs, travel across the internet.
Reflectors
A reflector is a server that lets many nodes join one conversation, much like a conference bridge on a telephone. IRLP reflectors use numbers in the 9000 range. The first three digits identify the reflector and the last digit chooses one of its channels, so a reflector may host several separate conversations at once. Reflectors carry regular nets, special-interest groups and emergency-preparedness exercises, and some are linked to other networks. Because a reflector feeds every transmission to dozens of repeaters, operators should leave generous pauses so stations on other nodes can be heard.
IRLP today
IRLP is still active, though newer systems such as AllStarLink and the digital voice networks of DMR, D-STAR and System Fusion now draw many of the hams who once used it. Current software runs on Debian Linux, and some node owners run IRLP and EchoLink on the same computer so that a single repeater can reach both networks. The project's website publishes a live list of nodes and reflectors, which is the best place to check what is currently on the air.
Every IRLP connection ends at a radio, so Part 97 rules apply as they do on any repeater: users identify with their call signs, and the repeater's own rules and time limits still apply. Many repeater owners ask that users announce their intention before connecting to a distant node, to avoid interrupting local conversations.