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(Pdf) Download 1 2 • Winlink programs group: “Official Group to support Winlink Team developed Products, both user and gateway software” • Winlink_for_EmComm: “Supports the discussion and use of the Winlink network and Winlink products for emergency or event support communications. ” 3 4 5 6 7 8 1. Digital voice radio works in exactly the same fashion, except that it deals with audio input, not text. 2. PACKET-1200 uses frequency shift keying (FSK) modulation with a 1000Hz shift and 1200 Bd symbol rate. There are a number of variations for PACKET-1200, including a PSK-based satellite version. PACKET-1200 can be seen in the VHF and UHF bands with indirect FM Modulation. FM bandwidth is 12 kHz. 3. See https://www.sigidwiki.com/wiki/PACKET#PACKET-1200 9 10 11 12 • That’s the packet sound • Each individual packet! • Carrier detect • ”NAK” = “NO ACKNOWLEDGEMENT” – resend • ”ACK” – “ACKNOWLEDGEMENT” – send the next packet • Too many retries, and the sending station stops sending (connection is dropped) • Breaking the message into small packets makes it easier to send a large message. But ALL packets MUST be received in order for the message to be read, 13 • One bye = 8 bits = 1 alphanumeric character • See https://tapr.org/pub_ax25.html • FLAG: start and end of each packet • Address: sender, receiver, and the path in between • Control (CTRL): The control field is responsible for identifying the type of “frame” being sent, and is also used to convey commands and responses from one end of the link to the other in order to maintain proper link control • The length of DATA is ≤ 255, and is set by the use. Recommended length is 128 characters • Frame Check Structure (FCS): Contains the CHECKSUM for the error correction process 14 Automatic Packet Relay System (APRS) uses packet, but WITHOUT the error correction. It is either received, or it is not. 15 16 17 18 • Networking Schemes: see https://www.tapr.org/pr_intro.html • During the early days of amateur packet radio, it became apparent that a packet network was needed. To this end, the following packet network schemes were created. • Digipeaters. Digipeaters would simply look at a packet, and if its call was in the digipeater field, would resend the packet. Digipeaters allow the extension of range of a transmitter by retransmitting any packets addressed to the digipeater. This scheme worked well when only a few people were on the radio channel. However, as packet became more popular, digipeaters soon were clogging up the airwaves with traffic being repeated over long distances. • KA-Nodes. Kantronics improved on the digipeater slightly and created KA-Nodes. As with digipeaters, KA-Nodes simply repeat AX.25 frames. • NET/ROM. NET/ROM was one of the first networking schemes to try to address the problems with digipeaters. A user connects to a NET/ROM station as if connecting to any other packet station. From there, he can issue commands to instruct the station to connect to another user locally or connect to another NET/ROM station. This connect, then connect again, means that to a user's TNC, you are connected to a local station only and its transmissions do not have to be 19 digipeated over the entire network and risk losing packets. This local connection proved to be more reliable. • G8BPQ. In the early 1980s John Wiseman, G8BPQ, wrote a Personal Computer (PC) to NET/ROM multi-TNC gateway to support W0RLI, F6FBB, PRMPS and other BBS. The self-named G8BPQ code could interact with a network of TNCs and act as a driver for the BBS application program. As of 2015 John still adds to and supports that program and it is now available for most MSWindows, MacOSX, and LinuX (including one for the Raspberry Pi) distributions in pre-compiled and source file downloads. • ROSE. ROSE is another networking protocol derived from X.25. Each ROSE node has a static list of the nodes it can reach. For a user to use a ROSE switch, he issues a connect with the destination station and in the digipeater field places the call of the local ROSE switch and the distant ROSE switch the destination station can hear. • TCP/IP. TCP/IP stands for Transmission Control Protocol/Internet Protocol. TCP/IP is commonly used over the Internet wired computer network. The TCP/IP suite contains different transmission facilities such as FTP (File Transfer Protocol), SMTP (Simple Mail Transport Protocol), Telnet (Remote terminal protocol), and NNTP (Net News Transfer Protocol) The KA9Q NOS program (also called NET) is the most commonly used version of TCP/IP in packet radio. • TexNet. TeXNet is a 3-port switch designed to create a 9600 baud backbone with 2 local access channels. The TeXNet network provides transparent network access to the user. The user simply accesses his/her local TeXNet node and then either connects to a user at another node or accesses various system services. TeXNet provides the stability of fiXed routing, while allowing new nodes to be automatically brought into the network. 19 1. Network diagram and other information available at http://www.felge.us/digitalmessaging.html 20 21 22 • A distributed system is a network that consists of autonomous computers that are connected using a distribution middleware. They help in sharing different resources and capabilities to provide users with a single and integrated coherent network. • Interoperability: The ability of emergency responders to communicate among jurisdictions, disciplines, frequency bands, and levels of government as needed and as authorized. System operability is required for system interoperability. 23 1. Go to https://www.winlink.org/RMSChannels 24 1. Network diagram and other information available at http://www.felge.us/digitalmessaging.html 2. Note that gateways on WL2K map do NOT reflect available nodes or digipeaters. There is no overall “organization” that coordinates this. It’s what individuals decide to do. 25 • Interoperability: The ability of emergency responders to communicate among jurisdictions, disciplines, frequency bands, and levels of government as needed and as authorized. System operability is required for system interoperability. • Redundancy: The provision of additional or duplicate systems, equipment, etc., that function in c ase an operating part or system fails. • Peer-to-peer (P2P): A computer network designed so that computers can send information directly to one another without passing through a centralized server • With the advent of the INTERNET, the expectations for “business as usual” now includes e-mail and other digital communications. Without the INTERNET, those expectations are still there. Most EM agencies realize that such capabilities have lower bandwidth, and hence slower traffic. But they still want their e-mail. 26 • Winlink front end designed to look like typical e-mail application, but it does include NON-STANDARD features • Automatic message compression reduces transmission time, but a size limit is imposed given limited bandwidth on RF. • SPAM control – an advanced topic • Can operate 24/7 with suitable power supply • Does NOT need to be attended, but must be monitored • “station-to-station propagation” means that messages can be relayed without error • Built in forms and reports • Commonly used 27 • This a RADIO based system. The laws of physics still apply, and propagation must always be considered. • Bandwidth limits size and transmission times. • Message is plain text; attachments may be binary. • The security issue is always there for amateur radio, but especially so for packet, as it APPEARS to be secure, and more so for Winlink which compresses the file to speed up transmission using the B2F protocol. That’s an open source algorithm, and is LEGALLY not an encryption protocol. • Updates and issues do NOT have 24/7 helpdesk. You have to learn how to troubleshoot. And throw them a few dollars now ands then. • Updates are key for mutual compatibility. Keep your computer connected to the INTERNET, with Winlink turned on, for updates. Or manually install latest version. Beta testing is voluntary. 28 29 • Telnet: requires INTERNET connection • VHF/UHF: line of sight OR through nodes • “Poor man’s PACTOR” – still reliable. • PACTOR – protocol is copyrighted for commercial use, but is available to amateur radio operators. 30 31 • Linux installation possible, but is unstable • Just about any radio can be used, but may require tinkering to make work. • TNC – to be discussed 32 The basics of packet radio has not changed since it was originally developed. As such, packet radio is a “legacy” technology, a step back to pre-INTERNET data communications. This does not make it obsolete, but it does mean that you, as the operator, have more responsibilities in overseeing the operation. 33 1. Some 2 meter radios can handle 9600 baud, but this is not a common feature, so 1200 baud is the most common protocol in the region. 2. 70CM packet can’t be feed through the microphone or speaker because the signal processing schema doesn’t provide the full bandwidth for 9600 baud. Either the radio has to be built for the purpose, or the amateur has to modify the rig to bypass that component. 34 • TNC types: • Kantronics KPC3+: Stand alone TNC, 2 meters only. Reliable design, but has issues in KISS mode. Also available as 9612 (runs 9600 baud packet) • Byonics TinyTrak 4: Very small, KISS only. The firmware is flashable, so this is used as a KISS TNC or an APRS controller. • Coastal Chipworks TNC-X. Inexpensive and reliable, KISS only. Optional APRS board is available. • Timewave PK-96: Stand alone TNC, either 2 meters or 70 CM. Reliable design. • Definitions: • KISS (keep it simple, stupid) is a protocol for communicating with a serial terminal node controller (TNC) device used for amateur radio. This allows the TNC to combine more features into a single device and standardizes communications.
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