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Learn about IRLP, its basic node setup, connecting to repeaters and link radios, how it works, local IRLP nodes, reflectors, and Raspberry Pi. Discover the history of PiRLP and its programming by Dave Cameron. Explore the process of IRLP VoIP streaming, sample analog voice, compression, packet transmission, D/A conversion, and control software. Understand the usage of COS, CTCSS, and DTMF signals. Explore IRLP nodes in the Calgary area and the concept of direct connect and reflectors.
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Topics of Discussion • 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
Invented and Programmed by Dave Cameron, VE7LTD in 1997 • First nodes Vancouver and Saint John, NB… now more than 1700
How IRLP WORKS • Voice-over IP (VoIP) streaming • “Speak Freely” software for voice • Runs under Linux….more stable than Windows, open source
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). • 2. Compress the audio to reduce the size of the stream by a factor of four (32000 bps)
IRLP VoIP 3. Split the sample into small 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. • . 4. Receive the packets on the remote host and join them back into a 4-bit stream.
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)
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.
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.
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.
IRLP CALGARY AREA CALGARY: 1230 VE6ZV 444.275 1810 VE6PWT 147.550 simplex 1537 VE6SQU 146.895 simplex 1260 VE6OIL 146.610 (connect to SARA backbone 660* / 661*)
IRLP CALGARY AREA AIRDRIE 1860 VE6JBJ 147.5400 simplex OKOTOKS 1483 VE6LK 147.51 (FARS simplex, not connected to network)
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. While repeaters "A" and "B" are connected, all local traffic on each repeater will be heard on the other repeater as well. .
IRLP Direct Connect • Node Status www.irlp.net
IRLP Reflectors “Reflector” is a Linux computer with a high bandwidth connection capable of allowing many repeaters to be inter-connected together by streaming the received audio back to all other connected stations. It does not have its own radio connection..
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.
IRLP Reflectors Check on reflector status at: http://status.irlp.net
IRLP Reflectors Check on reflector status at: http://status.irlp.net
