Packet Radio Murray Amateur Radio Club (MARC) Jan L. Peterson (KD7ZWV) What is it? u Packet Radio is a digital communications mode where data is sent in ”packets.” u So what are packets? u Packets are discrete collections of data, typically called “datagrams”, that have assorted headers and trailers added to handle things like addressing, routing, and data integrity. u I’ve never heard of such a thing? u Sure you have... you’re using it right now. The Internet uses packet technology, and if you are using Wi-Fi, you are already using a form of packet radio! History u Radio is essentially a broadcast medium... many or all nodes are connected to the same network. u In the early 1970s, Norman Abramson of the University of Hawaii developed the ALOHAnet protocol to enable sharing of this medium. u Work done on ALOHAnet was instrumental in the development of Ethernet in the mid-to-late 1970s, including the choice of the CSMA mechanism for sharing the channel. u In the mid-1970s, DARPA created a system called PRNET in the bay area to experiment with ARPANET protocols over packet radio. History u In 1978, amateurs in Canada started experimenting with transmitting ASCII data over VHF using home-built hardware. u In 1980, the Vancouver Area Digital Communications Group started producing commercial hardware to facilitate this... these were the first Terminal Node Controllers (TNCs). u The FCC then authorized US amateurs to send digital ASCII data over VHF, also in 1980, including the facility for “digipeaters” or digital repeaters. u This started rolling out in San Francisco in late 1980 with a system called AMPRNet. At this time the IP address range of 44.0.0.0/8, a class A network with 16 million host addresses was assigned to AMPRNet. How does it work? u Three pieces come together to make a packet radio station: u A data terminal device (terminal or PC). u A terminal node controller (TNC)... essentially a modem. u A radio! How does it work? u Physically, your components may differ... u You might have a radio with a TNC built in (Kenwood TH-D7, TH-D72, TH-D74, TM- D700, TM-D710, TS-2000) u You might connect your radio directly to the sound card on your computer and use a software TNC (Direwolf, Soundmodem) u Essentially, though, any packet station will have three logical components, terminal/PC, TNC, and radio. NOTE: APRS is not the same as Packet Radio! APRS uses the packet radio protocols but does not work in the same way. How does it work? u You type commands in your terminal/PC. u Your TNC interprets those commands and turns what you type into packets. u Your TNC converts those packets into an audio stream and sends it to your radio. u Your radio transmits the data. u Someone else’s radio receives the data. u Their TNC decodes the audio stream back into digital data. u Their TNC interprets the data and presents it to them via their computer/terminal. How does it work? u Communications Modes: u command mode u connected mode u “unproto” (unconnected) mode u KISS mode How does it work? u Command Mode u used to issue commands to the TNC itself. u things like changing modes, setting up the TNC, accessing information from the TNC. u Connected Mode u things you type are put into packets and sent out. u they are tagged with the intended recipient. u responses from the other station you are talking to are displayed. u Unproto Mode u lets you construct raw packets with anything you want in them! How does it work? u KISS mode u developed to simplify the hardware in the TNC u essentially passes raw data back and forth over the serial connection u very low-level u lots of software that you would use (e.g. Winlink) already supports KISS mode What can I do with it? u Bulletin Board System (BBS) u Mail u File upload/download u Callsign lookup u Bulletins/info (like what we use the web site for) u Propagation info/DX Cluster/Satellite Data (“keps”) u Winlink u One-to-one chat u Group chat u Satellite communications (BBS on a satellite) What do I need to play? u A radio (duh) u VHF is king for packet, so you want something with 2m support. u there is some UHF usage, so if you want to play with that, get a dual bander. u make sure it either has a speaker and microphone jack, or even better, a data port (typically a DIN connector that provides access to the pre-squelch audio, an input audio pin, and a PTT). u A TNC u Something like a Kantronics KPC-3. You can buy them already built or buy them as a kit and assemble them yourself. Alternately, your radio might have a TNC built in (see the earlier slide) or you might choose to use a software TNC on your computer. What do I need to play? u A computer (or a dumb terminal) u If you are using a Windows PC, you will want to get a terminal program called PuTTY (a free download) u If you are on a Mac, you can use screen or cu (included with the OS) or get and install a terminal program like Minicom (these programs run inside the Mac Termi nal or iTerm applications) u If you are on Linux, screen, tip, cu, and minicom are available there, too, although you might have to install them using whatever package management system your system supports (yum, apt, etc.) WARNING: if you get a TNC that only operates in KISS mode, you will need more than just a simple terminal program... you will need some software that actually understands the KISS protocol. Something like AGWPE or Linux with AX.25 built in will do the job. I have not been able to track down suitable software on the Mac, but I’m still looking. Demo u Insert Live Demo Here Q & A and References u https://en.wikipedia.org/wiki/Packet_radio u https://www.vhfclub.org/packet_radio_primer.html u https://tapr.org/ u https://www.soundcardpacket.org/ u https://www.youtube.com/channel/UCSQhXfGo_68Ta8-2wStAWkw u http://utahvhfs.org/simpfreq1.html (search for Packet Frequencies) u http://www.wvcarc.com/p/resources-packet.html.