IRLP is the brain child of David Cameron,
VE7LTD. David was looking for an inexpensive, reliable method of linking
repeaters throughout Canada. After trying other methods, he developed the
IRLP which not only serves as a linking system for ham radio repeaters, but
is also being used to link other types of radio communications systems.
The aim of the Internet Radio Linking Project
(IRLP) is to provide a simple and easy system to link radio systems
together using the Internet as the communications backbone.
Similar linking options exist, but they use
expensive leased telephone lines or satellite equipment. It is not the goal
of this project to compete, but to work along with other networks to
improvethe technology and improve
radio linking for all involved parties. The people who benefit most from
the IRLP are its users.
The software and hardware requirements are
minimal and the cost to set up a node are low. This brings the opportunity
for smaller more remote locations or small clubs to experience
international linking without large capital cost of a satellite or leased
The December 1996 issue of QST Amateur Radio
magazine had the words “Link your repeater to the Internet” on the cover.
Inside was a well written article by James Millner, WB2REM, entitled ‘A New
“Band” for Your Radio’.
The original article by WB2REM used Iphone to
send voice over the Internet. However, Iphone was not very stable nor was
it controllable via the radio link. After running Iphone for 6 months on
active links between Vernon,BC and St. John, NB, it was decided that
stability and control were key. Thus enter LINUX as an OS and Speak Freely
as the client/server software.
Speak Freely is a Voice over IP (VoIP)
client/server package that transmits live audio over the Internet with good
clarity and quality. This program allows any two parties anywhere on the
Internet to have a voice conversation in real time. The objective was to
use this program to link radio equipment so that voice connections could be
made without the operator being tied to a computer. This would allow hams
from all over the world to talk to one another without relying on radio
Many amateurs have raised a very important
question; “What if non-hams start connecting to ham repeaters?” There are
safeguards built into IRLP to reject calls from “non-hams”.
The main hurdle to overcome was the interface
between the computer an the radio. There had to be a better way than using
VOX circuits to control the flow of audio. Since the source code for Iphone
was not available, Speak Freely was chosen because of it’s being
Speak Freely was modified so that the software
keys the link radio transmitter when packets are being received over the
Internet and unkeys when they stop. The software starts sending audio when
the link radio receives a signal and continues to send until the input
signal is removed. A small circuit board was design to handle the interface
between the computer and link radio. This interface handles the PTT and COS
signals and provides a DTMF decoder so that the system could be remotely
controlled via the radio.
Thewhole system is DTMF controllable. The control codes lie embedded in
a separate program that reads the DTMF tones from the decoder chip on the
IRLP interface 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 directly to any other
site, either using direct connections or reflector nodes.
So in a period of 8 months, new software and
hardware was built which solved all the problems experienced with the
Since it’s release, IRLP has been experiencing
explosive growth and over the past year has grown from about 40 systems to
just about 300! There are nodes in Canada, UK, United States, Australia,
Trinidad, Dominica and Antarctica. More nodes are coming online daily.
IRLP is like having a worldwide linked repeater
system. The only difference is that the link is done over the Internet
instead of a wire-line or RF.
What this means is that when you push your PTT,
you are keying ALL of the repeaters in the current connection.
- This could be two repeaters in a Point-to-Point connection or many, many
repeaters all over the world in Reflector Mode.
Through IRLP, you have access to nodes worldwide
that can be linked to via DTMF commands.
Contact your local Node Op for the “Rules” on
use of the repeater, link system and the IRLP interconnect.
In general, some node ops leave their nodes
connected to a Reflector. The most active and common reflector is Reflector
#2 in Denver, CO. Other node ops leave their nodes disconnected but
available to be connected by DTMF commands.
Once the local repeater is connected to the IRLP
network, you can commence with a normal QSO as you would with a local.
There are some courtesy’s and protocols that you
As mentioned on previous slides, you are keying
up two to many transmitters around the world. This takes TIME!! Before you
speak, press your PTT and pause 2-3 seconds to allow all the systems to
When a person comes back to you, WAIT for 3-4
seconds before responding… this allows others to join in the QSO and more
importantly, allows time for node control ops to disconnect from the IRLP
Network. Only one node can “talk” at a time and that includes controlling!!
When you “sign on” the custom is to ID and give
your geographic location or node you are coming in on.
***REMEMBER*** Like other Amateur Radio modes,
IRLP is a GLOBAL medium and your actions are a reflection of you, the node
owner, hams in your area and the citizens of the country you are from!!!