The Internet Radio Linking
Another Canadian Invention is Sweeping the
|Thanks to an innovative Canadian, we now
have a new and powerful recruitment tool for the younger generation
interested in technologies like the Internet, Linux and Ham Radio.
By enabling our standard FM repeaters and simplex channels with this
new IRLP technology, we can provide instant on-demand linking with
one or more repeaters world-wide. And if you're concerned about
cost, this entire project is definitely within a "Ham
Approved" -cheap- budget of under US$125 including hardware and
IRLP is the brainchild of Dave Cameron, VE7LTD of Vancouver BC.
IRLP is the abbreviation used for the Internet Radio Linking Project which
Dave developed over the past several years. Back in 1998 Dave became
frustrated with the unreliable operation of the Windows based Voice over
IP software. All Windows based amateur linking software used VOX and were
not secure from non-amateur access. The IRLP network uses a digital
switching concept and produces an instant and secure link between licensed
repeaters around the world.
Eight months after Dave started his design work in 1998, the IRLP
network was born and is now on Version 2 of his hardware and software. As
of this posting, IRLP is serving over 1,000 repeaters (nodes) and
growing in leaps and bounds. When I ordered our interface hardware here in
Kitchener, Ontario, CANADA last February (2001) there were only 63 active
How It Works
Dave's custom IRLP software - takes the audio from the receiver which
is then fed into the sound card - where it is converted into ADPCM digital
data. The Linux PC then converts this digital information into digital
packets each assigned with IP 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 microphone of the link radio which then transmits the audio
out over the local repeater. 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.
To assure security of the system, PGP keys are assigned to each node.
When a connect request is made the connecting node exchange key challenges
which must be correct or the connection is refused.
Click to view full image
Security From Hackers and Non-Amateur PC access
Unlike some systems that allow users access from a PC with minimal if
any security, IRLP uses a 100% authentication system to assure the
connecting nodes are authenticated and authorized to transmit on the
Here are some points on the IRLP connect request authentication
- IRLP uses public/private key authentication (512 bit PGP keys)
- The calling node has to authenticate against the node called
- Once this is done, the called node has to prove to the calling node
that he is who he claims to be.. So the authentication is
bi-directional.. Ensures machines can't masquerade as another
- The PGP key is created ONLY by the IRLP Installer and uploaded to
the master IRLP server.
This method of authentications assures licensing agencies that all
audio being repeated on a node in another country has originated from a
radio and not a PC.
Even though the IRLP uses the internet it does MAXIMIZE the RF content
. The philosophy behind IRLP is to have a radio as an entry and exit point
in the system.
Under the Hood
The underlying audio processing technology in IRLP is a modified
version of the UNIX freeware application called "Speak Freely".
Speak Freely produces Voice-Over-IP (VoIP) audio streaming and is very
similar to other VoIP software packages such as Microsoft NetMeeting and
the VocalTec iPhone with one major difference - It runs under Linux not
Windows. Linux was Dave's operating system of choice for the IRLP system
as it allows the best in reliability, programmability, efficiency, and
functionality. Since our repeaters don't need anything even close to MP3
audio quality, IRLP is using a low-bitrate VoIP to communicate. Most nodes
use an encoding system that requires only 32KB/s of bandwidth, however
some nodes with extremely limited bandwidth, use a GSM encoding method
which only requires 17KB/s albeit at the cost of some audio quality. A
full time internet connection with DSL, Cable modem or ISDN is required.
The control of the radio is performed using a small custom logic board
which is connected to the computers parallel port. This board samples the
received audio for DTMF audio, detects the link receiver COS for positive
and instant remote keying, and generates the TX PTT line for the link
radio. All of the command I/O between the PC and the IRLP board is handled
by a connection to the PC's parallel port.
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
Hosting an IRLP Node
To host an IRLP node you require:
- a full time DSL, Cable modem or ISDN connection
- a dedicated Linux computer - a 486 DX100 or better is
- the IRLP custom software/hardware and
- a link radio or direct connection to the repeater controller.
Each node on the IRLP network is assigned a four digit ID code and
multiple redundant servers spread around the world manage the BIND process
(DNS) IP address routing required to complete connections.
IRLP Reflectors and Super Reflectors
A reflector is a Linux server that allows unlimited multiple node
(repeaters) to be linked together at the same time. As of posting time
there were 11 reflectors located in Toronto , Saskatoon , Yellowknife
(Canadian Arctic), Sydney Australia, Lancaster UK, Las Vegas NV, Raleigh
NC, Fredericton, Pennsylvania, New Brunswick and Vancouver Canada. The
most commonly used world-wide reflector is 9200 in Indianapolis Indiana.
Most reflectors are hosted by public service minded companies who offer
lots of bandwidth to support the requirements of a reflector.
The new super reflectors, launched in October of 2002 provide 10
channels each boosting the number of reflectors to 65. The super
reflectors are 9200, 9100, 9210, 9500 and 9250.
The bandwidth requirement for a reflector is directly related to the
number of simultaneously connected nodes. During one Sunday evening net
with 33 nodes connected, the bandwidth being used on the Denver reflector
was just over 1mb. This reflector usually has a number of US, Canadian,
Australian and Caribbean repeaters connected so any conversation that
occurs on one is heard on all connected stations.
The super reflectors now each support two channels of GSM to allow
dial-up nodes the ability to use multiple reflectors.
For those outside of IRLP coverage repeaters, a streaming audio feed of
the main reflector 9200 is available on the internet. Click
here or paste http://live.irlp.net:8000
into your favourite MP3 player
CANWARN net controllers in Southern Ontario are linking themselves via
IRLP using the new Ontario 10 channel Super Reflector hosted by Group
Telecom in their Toronto Central Office. This allows the CANWARN
controllers to rapidly exchange severe weather information between
themselves and the Environment Canada Toronto Severe Weather Desk without
interfering with the local CANWARN nets.
The Kitchener Ontario IRLP Node
I had read about Dave’s work on his web site and based on
the low cost of entry US$120 I ordered the IRLP package which
arrived within 10 days.
The first thing I had to do was sacrifice one of my retired Windows 98
based P133 machine in favour of Linux.
As I had no previous experience with Linux I was a bit hesitant
of getting into the Linux operating system, however as you will see this
fear was unfounded.
Following the very detailed installation instructions posted on the
IRLP web site , the installation went very smooth however I did encounter
a weird inbound Telnet problem that was quickly resolved thanks to the
prompt assistance from Dave VE7LTD.
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 yet "support"
this most powerful operating system, this is where my fun began. The sound
card wanted the same machine resources used by the Ethernet NIC card
causing interesting issues such as trashing my BIOS settings and leaving
the machine almost brain dead. After a day I was able to locate a DOS
utility which I put on a DOS boot disk and booted the now Linux box in DOS
and changed the conflicts. The machine then booted flawlessly under Linux
and recognized the sound card immediately.
"AJ", VE3ABZ checked in and keyed in the code to bring up
VE3SUE in London. Typical of many repeaters these days, no one was on the
air so "AJ" then brought up the Denver reflector - Now connected
to the reflector we were able to talk with amazing clarity to stations in
California, Pennsylvania and Yellowknife in the Canadian Arctic. The audio
was awesome and anyone listening would swear the Yellowknife station was
in Kitchener not the North West Territories in minus 35F degree weather.
Using the IRLP Network
To connect to another repeater you simply dial a 4 digit on-code. (some
node operators require a pre-access code much like an autopatch code)
Within a few seconds that node will ID in plain voice with it's callsign
and location. If the node is currently connected to another or to a
reflector, you will receive a recording telling you which connection the
other repeater is currently engaged with.
Before placing a call you can always check the status of any node in
real time by going to http://status.irlp.net
and look at the node you wish to connect with. This page updates in
real-time and refreshes every minute so it is always current.
Just as with any linking system, IRLP is subject to some minor audio
delays which are mostly radio related. These delays are caused by the
amount of time it takes for numerous radios to decode the Tone Squelch
information so the first thing to remember is to slow down and be patient.
(to dispel internet delay myths, the audio delay over the internet is
the same as you experience when using a digital cell phone)
When completed with a QSO, announce your call and dial the OFF code at
which time a voice ID indicating the link is dropping will play. Since
many repeaters are not heavily used, there are always a number of nodes
left connected to the Denver CO Reflector allowing you to place a CQ, or
ORZ type call with an excellent chance of speaking with someone somewhere
in the world.
Refer to the following list of nodes (repeaters) and find one close to
your QTH. If one of the members brings up one of the reflectors you will
be able to simply key your microphone and talk but we do advise to contact
the node operator and determine if local membership is required.
Active nodes around the World
New repeaters and new countries continue to join the IRLP family.
Current countries that are active around the world include Canada, USA,
United Kingdom, Dominica, Trinidad, Australia, Tasmania, New Zealand,
South Africa, Sweden, India, Sweden, Belgium, Ecuador, Scotland, Japan and
the Netherlands plus the node on Scott Island in Antarctica. Nodes are
also under construction in other countries around the world.
Click Here for
complete node list and current status
As for DX stations you can look for McMurdo Station on Ross Island in
Antarctica, SK6RAB in Sweden, Johannesburg South Africa, two nodes in The
Commonwealth of Dominica (not the Dominican republic) where it's not
unusual to hear Bernadine, the Mayor of the capital city Roseau on the air
promoting the Island. As well you may hear J79 stations from neighbouring
St. Lucia accessing the Roseau repeater across the Caribbean. As well,
Trinidad have 2 nodes on the air. There is lots of activity from the half
dozen or so UK nodes and the 30 + active nodes in the "land down
under" which reminds you of the movie "Back To The Future"
as most QSOs with VK land are taking place tomorrow.
This exciting new technology will be a tremendous catalyst to bring new
young blood into our hobby. Where else can you witness an open world-wide
VoIP wireless network using a free and open protocol like IRLP? As we all
know there has been a real challenge for us to draw kids into our hobby as
they could previously talk on their poor quality iPhone connections over
the Internet. Now with a basic HT they can enjoy far superior audio and be
talking with their friends across town and around the world.
Since we brought our node on here in Kitchener, Ontario our membership
has taken a real boost and we have subsequently added two additional
nodes. Many former members see the excitement back in the hobby and many
new members are joining to be part of the IRLP system. The VE3RBM repeater
has gone from possibly 2 QSOs per week to our busiest repeater and is now
dedicated to IRLP use. It is highly recommended that an IRLP node not be
added to a high traffic repeater unless the reflector feature is locked
out which is easily done.
I would like to personally thank the IRLP designer Dave Cameron
VE7LTD for his assistance in preparing this article and for his dedication
to this wonderful project.
Are You Interested?
If this article has piqued your interest and you seek additional
information please browse the official IRLP web site at www.irlp.net
and feel free to contact the IRLP designer Dave, VE7LTD at firstname.lastname@example.org
or the author at email@example.com.
The IRLP Designer and Project Leader
Dave Cameron VE7LTD
4708 Caufield Drive
West VANCOUVER, BC
Paul Cassel VE3SY
Box 29 RR2
Phone: (519) 634-5139
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