What In The World Is This IRLP Thing?

 

What in the world is this IRLP thing? In short IRLP is the world on VHF via the Internet. Formally it is a way of linking together various repeaters throughout the world using the Internet as it's backbone. IRLP has it's roots in Voice-over-IP technology. Voice-over-IP is just a fancy way of sending audio frequency signals over the Internet using Internet-Protocol or IP. The system is built by putting a computer running Linux on the net and piping audio from a radio into and out of it. There are a few control lines to hook up but for the most part it's very similar to other "sound card digital modes" you may have heard about. Thankfully you don't have to know a whole lot about the underlying technology to use IRLP.

Here in Fairbanks we have a "node" or IRLP repeater setup at KL7JM's house. Using Jim's 2-meter antenna atop his tower and a bit of his Internet access we have IRLP coverage over most of the Tanana Valley. The node listens on 147.55mhz simplex with a 123Hz PL tone. Access is open all the time and you'll often hear stations calling from the UK and all over the United States. To talk on the node just setup your radio appropriately and send out your call sign. Operating etiquette is to key down for 2 to 3 seconds before speaking to give all the connected radio's time to key up and retransmit your messages. Typically you will hear a station send their call sign followed by the city they are currently in. I like to mash the PTT while raising the mic to my face while thinking about the money I've spent on my radio gear before I send a "This is KL1RL in Fairbanks". Often you'll get a response from someone listening in the United States or elsewhere. That's all there is to it! Of course you'll want to follow all those good operating procedures your Elmer taught you including occasional breaks between transmissions to allow others to jump in. I've found that longer breaks are helpful to allow for the extended key down time necessary for the Internet's tubes to warm up.

There are a few terms you may run into while operating the IRLP node. Often you will hear someone refer to a reflector. A reflector does just what it says, it reflects your audio to a group of nodes. Reflectors are a great way to speak to a certain region of the network. Here in Alaska most of the nodes on IRLP will be connected to the Alaska reflector enabling the state to be linked together over VHF quite easily. A reflector can also be linked to another reflector to group together even more nodes. Typically the Alaskan reflector is linked to the Western reflector in this way.

Each node has a specific ID associated with it. The node here in Fairbanks is node ID 3459. You can connect to and from other nodes or reflectors by sending "73" via DTMF to the node radio to tell it to disconnect from the current node. You should hear a voice announcement from the node indicating it has disconnected. To connect to your chosen node simply send the four numbers corresponding to the target node/reflector. For example, if I wanted to connect to the UK reflector I would send "73" and wait for the disconnect notice. Once I heard the notice I would follow up and send "9750" and wait for the connect notice to come back. If you want to move the node make sure you let those around Fairbanks know beforehand. A simple "This is KL1RL. I'm going to move the node to the UK reflector unless anyone object" will be enough. Dave likes to have all the Alaskan nodes connected to the Alaskan reflector most of the time so he has a program running on the node computer to move it back to Alaskan reflector after 15 minutes of inactivity.

IRLP is very low impact and quite a lot of fun to chat while driving to and from work. You'll find most of the operators are very polite and quite willing to chat about anything you could think of. The exchanges are often casual rag chews and you won't find people calling DX or running contests. Stray CW ID's and courtesy beeps are bared but you'll often hear fun trivia nets and other net traffic. When the shuttle is launching you'll also hear a copy of the shuttle radio traffic. Have fun and I hope to hear Fairbanks on IRLP.

Quickie Reference Chart
Frequency	147.55mhz
Split:	None, simplex only
PL Tone:	123hz
Control via DTMF: 73 to disconnect. Send the 4 number node/reflector after the disconnect notice to reconnect elsewhere
Operating Etiquette: Don't call DX or send CW. Please remember to give plenty of key down time to allow the other radios time to key up.

 

Justin KL1RL

The comments above are my personal opinion and in no manner reflect upon KL7KC or the AARC membership. AD4BL