IRLP
LINKING
Peter Barry,
VA6PJB / KE5HQC
4/13/2015
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Topics of Discussion
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What is IRLP?
Basic Node Set up
Direct Connect to Repeater
Connecting With a Link Radio
How IRLP works
Local IRLP Nodes
Reflectors
Raspberry Pi
PiRLP
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Invented and Programmed by Dave
Cameron, VE7LTD in 1997
First nodes Vancouver and Saint
John, NB… now more than 1700
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How IRLP WORKS
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Voice-over IP (VoIP) streaming
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“Speak Freely” software for voice
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Runs under Linux….more stable
than Windows, open source
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IRLP VoIP
1. Sample analog voice
with PC sound card to
get a continuous
mono 16-bit digital
stream of raw audio at
8000Hz (120000 bps).
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2. Compress the audio
to reduce the size of the
stream by a factor of
four (32000 bps)
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the sample into small
IRLP VoIP 3. Split
chucks (or packets)and
transmit the packets to the
remote host using a User
Datagram Protocol (UDP)
stream. UDP does NOT
confirm the reception of
packets, so it uses a "fire
and forget" method.
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4. Receive the packets on the remote host
and join them back into a 4-bit stream.
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IRLP VoIP
5. Uncompress the ADPCM stream
back into an 16-bit raw stream of
audio and play the raw audio stream
through a digital to analog (D/A)
converter (the output device of the
PC sound card)
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IRLP VoIP
The control software controls the
stream using carrier operated
squelch (COS) or continuous tone
coded subaudible squelch signals
(CTCSS) to start and stop the
stream. When COS is present, the
computer detects it through the IRLP
interface board.
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IRLP VoIP
The PTT is controlled by the
buffer which joins the split
packets back into the audio
stream. The IRLP interface
board receives a "transmit"
signal from the computer
while there are packets in
the buffer, and a "unkey"
command when the buffer
is empty.
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IRLP VoIP DTMF
The user interfaces to the IRLP computer using
DTMF signals sent over the radio.
DTMF sequences are owner programmable,
and can accomplish almost any function
imaginable.
The DTMF signals are detected on the IRLP
interface board and sent directly to the
computer in binary, where they are
converted into numbers. A DTMF software
program then runs commands on the
computer depending on the code entered.
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IRLP CALGARY AREA
CALGARY:
1230 VE6ZV 444.275
1810 VE6PWT 147.550 simplex
1537 VE6SQU146.895 simplex
1260 VE6OIL 146.610
(connect to SARA backbone 660*
/ 661*)
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IRLP CALGARY AREA
AIRDRIE
1860 VE6JBJ 147.5400 simplex
OKOTOKS
1483 VE6LK 147.51
(FARS simplex, not connected to
network)
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IRLP Direct Connect
Direct connect - repeater (node) "A"
connects direct with node "B".
With this type of link the two nodes
are interconnected and no other
IRLP connections are possible.
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While repeaters "A" and "B" are
connected, all local traffic on each
repeater will be heard on the other
repeater as well.
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IRLP Direct Connect
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Node Status www.irlp.net
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IRLP Reflectors
“Reflector” is a Linux computer
with a high bandwidth
connection capable of allowing
many repeaters to be interconnected together by
streaming the received audio
back to all other connected
stations. It does not have its
own radio connection..
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IRLP Reflectors
Each reflector has 9 sub
channels allowing up to 10
separate virtual reflectors to
operate.
These are identified by the last
digit. For example - 9250 is
the main channel with 9251,
9252 9253 etc being virtual
reflectors with identical
capability as the main channel.
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IRLP Reflectors
Check on reflector status at:
http://status.irlp.net
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IRLP Reflectors
Check on reflector status at:
http://status.irlp.net
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IRLP Discovery
Reflector
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IRLP REFLECTOR
NETS
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Raspberry Pi
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Raspberry Pi board
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PiRLP
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