Santa Barbara Amateur Radio Club
Internet Repeaters

IRLP (Internet Radio Linking Project)

The IRLP system links over 1000 repeaters around the world together using the Internet. In essence a computer connected to a repeater controller acts as an additional radio and allows voice coming in over RF to be sent out the Internet and vice-versa. In order for this to be useful, the local IRLP computer must be connected to a remote IRLP node. At that point it is as if the local repeater users and the remote ones were on one and the same repeater system, just as if the repeaters had been linked using conventional technology.

The IRLP system numbers all the nodes and our La Vigia UHF/IRLP repeater is node number 3672. Normally only two nodes can be linked together, so for example we could link with node 3217 in Honolulu. However, nodes in the 9000's are so-called reflectors which allow many nodes to be linked together and these reflectors actually do not have any attached radios: they only serve to link any node that connects to them together with all other nodes. For example the "western reflector" is node 9250 and often has plenty of activity.

On order to use IRLP you should consult the status of nodes and choose one to connect to. Click on a country to see a list of available nodes there. Or scroll down to the list of reflectors and pick one with some activity.

To connect to a node, simply key-up the La Vigia UHF repeater (446.4Mhz) and dial the 4 digit node number on your radio's keypad. You should hear a welcome message from the remote node shortly, something on the order of "Welcome to <callsign> in <location>. Node <number> now connected."

To disconnect dial 73 on your keypad. You should then hear a good-bye message. Links are disconnected automatically after 10 minutes of inactivity.

Note that the courtesy tone is different when a link is in effect: instead of a single tone you will hear high-high-low after each transmission coming in over the internet.

Our IRLP node runs on an old Linux computer shared with the APRS I-Gate. The computer connects to the repeater controller using its sound card and a special interface board which generates PTT, signals COR, and detects DTMF tones.

General information about IRLP can be found at http://www.irlp.net/.

APRS I-Gate

We now have an APRS I-Gate running at La Vigia on the standard 144.390Mhz APRS frequency. This APRS I-Gate has three functions: it digipeats APRS packets as any regular digipeater would, it forwards APRS packets received over RF to the global APRS database at http://www.find-u.com/, and it forwards global APRS traffic of interest to local nodes onto RF.

The first benefit of the I-Gate is that if you have a local APRS station you can see its position reports on the Internet. For example, check out the location of our I-Gate (it's not moving...) at http://www.findu.com/cgi-bin/find.cgi?k6tz-10 or get the current weather at Diablo Peak from http://www.findu.com/cgi-bin/wxpage.cgi?call=k6tz&last=24. What the I-Gate does is to forward all packets it receives on RF to a small set of central APRS-IS servers that keep track of all APRS nodes world wide!

The second benefit of the I-Gate is that it can forward global APRS information onto the local radio. For this purpose it keep track of all "local" nodes that it hears on RF over a small number of digipeater hops (currently 2 max). If any message targeted to one of these local nodes is sent to the central APRS-IS servers, it will find its way to our I-Gate which will broadcast it on the radio. This allows messages to be sent to local APRS nodes from anywhere in the world!

The I-Gate also acts as a normal digipeater such that APRS data can be forwarded on RF and "find its way" in case the local internet connection is dead.

The I-Gate software we use is called javAPRSSrvr and runs on the same Linux computer that is also used for IRLP.

WinLink 2000

A WinLink 2000 email system is currently being installed for ARES purposes. The first step will be to install a TelPac node at La Vigia and to revive the 9600 baud packet backbone in the tri-county area. More information forthcoming...