VE3RBM Now Linked to the World via IRLP by Paul Cassel VE3SY

After reading about this new robust repeater linking method at www.irlp.net, I ordered the hardware and software from the project engineer Dave Cameron VE7LTD. It arrived at the post office as promised within about 10 days.

Before proceeding to far my first task was to get the blessing of our Tech Committee and our Board of Directors.  Luckily, an Executive meeting was the following day and my proposal of a club experiment with no-cost to the club was accepted.

This method of repeater linking requires a full time high speed internet connection. Since a local wireless ISP is using my tower as a relay point, I am lucky enough to have a full Ethernet connection direct to the wireless backbone which is 11mb and only 2 hops away from an OC3 fibre connection. You can see the three microwave dishes in the adjacent picture pointing to Kitchener, New Hamburg and New Dundee. My feed comes from Kitchener while the other dishes relay to the other towns.

What Is IRLP
IRLP stands for Internet Radio Linking Project the brainchild of Dave Cameron VE7LTD of Vancouver BC. Dave was frustrated with the unreliable operation of the Windows based IPHONE and decided to build a better mouse trap on a LINUX platform. Iphone and other systems use VOX where the IRLP digital concept reduces delays to almost nil thus many less missed first words of a transmission.

Eight months later in 1998 the IRLP network was born and is now on Version 2.0 of hardware/software and serving well over 65 nodes and growing in leaps and bounds. When we ordered our interface hardware 3 weeks ago (mid Feb) there were 26 new node orders shipped with ours.

IRLP allows the linking of two or more repeaters together using Voice over IP technology (VoIP) where the analogue radio audio is converted to digital Internet Protocol packets and sent over the net.

Our IRLP Node
With some hesitation I sacrificed my Windoze 98 based P133 machine in favour of the more robust Linux operating system (O/S) for which I had no previous experience. Following the detailed instructions posted on the web, the installation went very smooth and I had the PC talking to the net within a few hours thanks to some assistance from our resident Linux guru, Dave VA3DGS. Dave helped out with a weird problem where inbound telnet sessions were not possible.

Our IRLP Node equipment Paul VE3SY is kneeling beside the LINUX computer on which is sitting the GE Phoenix Link Radio. The PC speakers allows Paul to monitor the network traffic. The audio levels were set using the Cushman CE50 service monitor.

Now that I had the Linux box talking both ways to the internet I had to install the IRLP hardware and a Windows based Plug-n-Play SoundBlaster card. Since many hardware manufacturers do not "support" the most powerful operating system in the world, this is where the fun began. My sound card wanted to use the same machine resources being used by the Ethernet card causing interesting issues such as trashing my BIOS settings leaving the machine almost brain dead. After a day I was able to locate a DOS utility to talk to the sound card which I put on a DOS boot disk and booted the now Linux box in DOS and changed the conflicts. After this the machine booted flawlessly and recognized the sound card. This was Friday March 9th and I was ready to go on the air however Dave, the IRLP project leader was sick and unable to send me access codes.

On Saturday morning "AJ", VE3ABZ checked in and indicated he had codes from the London club and keyed in the four digit code to bring up VE3SUE in London. Typical of many repeaters, no one was on the air so AJ then brought up the reflector in Oklahoma City (now in Denver). A reflector has a number of repeaters connected to it allowing multiple links and we were able to talk with stations in California, Pennsylvania and Yellowknife in the NWT.

How Does It Work
IRLP requires a full time high speed Internet connection, a dedicated Linux computer, some custom hardware and a link radio. Each Linux box on the IRLP network is assigned a code and a central server keeps track of the IP addresses (IP= the routing code used by all packet of internet data flowing on the internet) in use by all nodes.

The IRLP uses a Voice-Over-IP (VoIP) streaming software called Speak Freely. Speak Freely is very similar to other VoIP software packages (such as Microsoft NetMeeting and VocalTec Iphone) with one difference... It runs under Linux.
Linux is the operating system of choice for the IRLP system as it allows the best in reliability, programability, efficiency, and functionality. Most IRLP nodes use RedHat Linux 6.2 as it is a very stable release and runs very smooth on any 486 Dx100 class or better computer.

Dave's custom software takes the audio from the receiver which is fed into the sound card where it is converted into digital data. The Linux PC then converts this digital information into digital packets each assigned with addresses for the destination node. These packets now flow through the internet to the destination Linux PC where the packets are decoded then sent to the sound card and out to the transmitter. The transmitter is keyed as soon as these TCP/IP (Internet Protocol) packets start to arrive. As soon as the data stops the link radio automatically un-keys and process reverses.

The logic control of the radio is performed using a small custom board build by Dave VE7LTD which is connected to the parallel port of the computer. This board samples the received audio for Touch Tone audio - detects when the link receiver is active - and feeds the TX PTT line to the radio.
The whole system is DTMF (touch-tone) controllable. The control codes lie imbedded in a separate program that reads the DTMF tones from the decoder located on the interface controller board and activates various parts of the software. DTMF codes are used to enable/disable linking, open/close links and set identifiers. Every site has the ability to connect direct to any other site(s), either using direct connections or reflector sites.

Using the IRLP Repeater Linking
Since the VE3RBM repeater is not a heavily used machine, users usually monitor the Oklahoma City Reflector during times of light use.  

Making a Link Request
Consult the node list that has been already distributed to you and note the 3 digit Node ID number of your destination repeater or reflector.  Always identify yourself before dialing giving your call and the destination you are calling. To connect to this node simply dial on your TT pad the node access info previously distributed.  If successful that node will ID in plain voice. If the node is busy you will get a busy signal. Once connected always wait for 5 - 10 seconds to make sure the other node is not active with traffic. If you hear activity just wait for a break and announce yourself and the node you have connected from. For example… "This is VE3XYZ connecting from VE3RBM Kitchener"

Before placing a call you can always check the status of any node by going to http://status.irlp.net  and look at the node you wish to connect to. This page updates every minute so it is always current.

Just as with any linking system, the IRLP is subject to some audio delays. These delays are caused by the amount of time digital information can take to be compressed and travel across the internet between the nodes. So the first thing to remember is to slow down and be patient. When in a conversation, remember to press your PTT and then leave a brief pause before speaking. 

During your QSO you should remember to hold the PTT before talking for a just a bit longer than usual for local calls.  It is also important to leave a space between transmission to allow other stations to break in.   This takes a bit getting used to but is necessary on VE3RBM due to the Tone Squelch and to allow time for the internet link to open.

Ending A Link Connection
When completed with your QSO announce your call and that you are going disconnect from VE7RVN then dial the OFF code.

Using the Reflectors
A reflector is a server that allows multiple nodes (repeaters) to be linked together at the same time. When VE3RBM is not being used locally, you can connect to the Oklahoma City reflector (Reflector 2). This reflector usually has a number of US and Ontario repeaters connected so any conversation that occurs on one is heard on all connected stations.

If you just wish to see who is out there listening on a reflector, consult the reflector codes and turn one of them ON. The reflectors are all listed on the node list with the Oklahoma reflector being the most popular. As usual announce your call and intent and dial the ON code. When the greeting plays announce your call and location and indicate you are QRZ looking for any other IRLP connected stations listening on the reflector. Should a reflector or another node connection already be in progress, a recording will tell you what connection is already in place.

Always be sure to disconnect from the reflector when you leave the air or if you start a local QSO.

Enjoy this new service brought to you by your KWARC Executive and pass the word encouraging non members to join or rejoin KWARC. Please direct any questions or suggestions on improving these directions to the author by phone at 519 634-5139 or by e-mail ve3sy@kwarc.org

de Paul Cassel VE3SY
your IRLP node host

Click for IRLP Operating Guidelines

Tnx to Ben VA3BNY for the photos