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What is IRLP?

IRLP – The Internet Radio Linking Project

By Bill Sloan, NZ9S

Many of you have asked about the mysterious "IRLP" net hosted by The American Legion Amateur Radio Club the second Saturday each month at 1800 UTC (or 2:00 pm EDT).  IRLP was initiated by Dave Cameron, VE7LTD, back in the late 1990s as a way of using the Internet to link one or more amateur radio stations together.  Using VoIP, or Voice over Internet Protocol, IRLP allows even a handheld station, if within range of an amateur radio station connected to the Internet, to communicate worldwide.

Each station connected to the Internet is called a node, and can be a simplex station or a repeater.  Each node has a computer that links the station's UHF/VHF radio to the Internet through the computer's sound card.  Each node also has a unique four-digit identifier.  For instance, a local repeater here in Indianapolis is node 9200.  If you are within range of a node in your area, you have the capability of worldwide communication simply by using the DTMF keys on your radio to connect to your desired destination with a simple four-digit code.

One of the requirements of IRLP is that the node must be connected to a radio on the ham bands - either a repeater or a radio on a simplex channel.  Both amateur radio and the IRLP are international in scope, and subject to international agreements which require that regulations in other countries be followed when the IRLP system is used there. By keeping to the rule that all IRLP traffic must originate from a locally received RF signal it prevents non-amateur operators from transmitting over amateur frequencies. It also promotes the use of radios in Amateur Radio, hence the IRLP motto "Keeping the Radio in Amateur Radio".

Where can I find a node?

You can look up more than 3,000 nodes listed at http://status.irlp.net.  Once you have identified the node you will find a link that makes it easy for you to contact the station owner to ask permission to use the node.  For a more complete picture about how IRLP works, visit www.irlp.net

How does it work?

In the real world, computers connected to the Internet are identified by "IP Addresses" that look similar to this: 233.000.33.33.  In IRLP, the four-digit node identifier corresponds to the particular address of the computer you seek—the one connected to a radio.  IRLP also confirms that the computers now connected to each other are actually authentic amateur radio stations by performing a series of checks, called "handshaking."  Now communications by voice can begin.

You might call and connect to a nearby node using a handheld radio, and key in a four-digit identifier for a node in a city on the other side of the country.  The node's radio picks up the RF signal and converts the analog signal through the computer's sound card into the same digital packets as used by VoIP or Skype.  The packets travel over the internet to the destination node's computer, where they are converted back into analog voice signal and passed to the microphone input of the node's radio station.  You may be using a handheld in central Indiana, but your "CQ" is now heard in Brisbane, London, Tokyo, or any number of destinations you might select.  Any amateur answering your call through the now-open connection is heard on your handheld.

Reflectors

Reflectors are a special kind of node, really a computer server that takes in digital packets and shares them with all other nodes that are connected to the reflector.  In this way multiple users can all talk to each other in the same way local hams might rag-chew together on HF.  There are some 300 reflectors around the world, and today each of these reflectors has 10 available "channels" with a unique four-digit identifier.  Reflector nodes have identifiers that begin with the number nine, so a reflector indentified by "9200" is actually channel 0 of the 920X reflector.  9205 is channel five of the same reflector (and is our IRLP net channel for The American Legion Amateur Radio Club Net, courtesy of the reflector's owner, Dave Gingrich, K9DC here in Indianapolis.)  There are many reflector channels unused today, although nets are springing up all over for a variety of clubs and even for specific topics, like antenna construction, QRP operation, and yes, IRLP.  For a list of such topics, visit www.irlptopics.net.

Connecting to the TALARC Net

Let's say you're interested in giving IRLP a try—what better way than to call in during our regular 2nd Saturday of the month net for TALARC?  Briefly, here's how. (For a more detailed explanation, visit www.irlp.net).

  •  You've gotten permission from the repeater owner to use the local node through your club or through http://status.irlp.net...
  • After you have programmed the proper offset, tone, and frequency to access your local node, take a deep breath, key your mike, wait a moment, say your call sign, and while still holding the transmit button press in the four-digit node identifier for the Crossroads Reflector channel 9205.  "THIS IS KC9ANG [immediately press 9, 2, 0, 5]" and release the transmit button.  After a moment, if you have connected properly, you will get a recorded announcement saying you have reached the correct reflector and channel.
  • At this point listen for 30 seconds or so for operators that may already be using the reflector.  If you connect during the net, we won't hear you unless you key your microphone and speak as directed by net control.  Just like a local UHF or VHF net!
  • While communicating using IRLP, remember to pause for a breath after keying your mike before speaking.  It takes a second or two for the handshaking to occur and for the various nodes to make the connections.
  • It is helpful to net control, as it is in all nets operating over a wide area with a variety of strange call sign prefixes, to give your call sign phonetically and slowly so that a good ID can be made.  For local nets, we all can usually recognize the call from the voice…for IRLP, not so much.
  • After your call-in, your local node owner may prefer that you not "stick around" for the rest of the net to finish since some nodes may be pulling double duty as local UHF/VHF repeaters when not connected to the internet.  Most owners are happy to have folks using the service, but common courtesy dictates that you ask.  To disconnect, transmit "99" or "73" as seen below.

DTMF Control Codes that may be useful

You may also, while connected, use some of the following DTMF codes during your session.  You might, for example, transmit DTMF 73 after you have finished your call, or if after several minutes you become aware that no one is currently using the link and you wish to call up a new node:

  • 00 - Returns the current node connection status.
  • 73, or 99 - Disconnects an IRLP connection in progress.
  • *411 - Speaks the last node connection information.

Remember

  • First, Transmit your ID. Wait and listen for a moment to see if the node repeater is in use. Verify that the node is not already connected by sending 00.
  • ID and announce your intent to connect to a node and then...
  • To Connect, send the 4 digit number of the IRLP node you wish to connect to. (For example 9250 connects to the Western Reflector channel 0.  9205 connects to the Crossroads Repeater channel 5, and our TALARC net when in progress.)
  • To disconnect from the currently connected IRLP node send 73.  This does not interrupt our net—it only disconnects your local repeater for normal use again.
  • ID after disconnect to clear your repeater.

Reflector use

With reflector use, the first thing we must all remember is to leave a gap between transmissions and wait before you speak for a second after you key up. Having said that, this is a good time to list the three main rules when connected to a reflector:

  • Pause
  • Pause
  • Pause
  • Due to the slight increase in delays created by multiple Tone Squelch radios in the links between the repeater and IRLP link radio, a slight change in our normal operating procedures is required with IRLP.
  • By leaving a pause between transmissions it.....
  • allows users on other nodes a chance to check in.
  • allows other nodes time to send touch-tone commands to drop their node.
  • The most important guideline to remember is leaving a pause after pressing the PTT button as well as between transmissions

A fun way to operate—give it a try.

There you have it.  If you haven't tried worldwide communication over the Internet Radio Linking Project, give it a try.   IRLP gives an interesting new twist to our hobby, and allows amateurs of every license class access to worldwide voice communication.  You might also explore the many reflector channels with interesting content and gatherings of like-minded hams.  Best of all, band conditions and propagation is never a problem…

Our thanks to www.irlp.net and to the Crossroads Repeater (Dave, K9DC, who in fact also has a very good primer on the use of IRLP at http://www.irlp.net/ref9200-policy.html).  You may also wish to review general IRLP guidelines at http://www.irlp.net/guidelines.html.  There is a wealth of information out there about IRLP. Grab it and get on the air.

Bill Sloan, NZ9S, is the IRLP Net Manager for The American Legion Amateur Radio Club