K4HM PACKET PRIMER
Warning
This is a heavy construction area. These pages are undergoing
a major renovation.
Broken links, rough reading, missing images, and unexpected
spelling errors could be encountered at any time.
Continue at your own risk.
This primer was written while I was living in Shelby County Alabama and the examples used are based on station activity there at the time.
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What is this stuff called pack it? How much hardware is required to operate packet? Getting the TNC and terminal to TALK to each other The repeaters of the digital world Bigger and smarter digital repeaters Packet operators had Email before the World Wide Web Bulletins, personal mail, NTS traffic, files, and more 1 node + 1 node = 1 network Wormholes and Frequency Warp for Packet radio Nodes in North Central Alabama |
Packet is part of the evolution of digital radio communications. First there was spark gap, then CW came along and allowed hams to tune in a narrower portion of the rf spectrum which allowed many users to share the band at the same time, then came RTTY which allowed hams to use machines to send BAUDOT characters at speeds faster than most hams could operate cw. Then in 1980 the FCC authorized US amateurs to use ASCII for data communications which opened the door for new modes of digital communications including something called Packet Switched Network communications. (Canadian hams started expiramenting with packet switched communications in 1978.) Hams started using their computers to send text over radio frequencies using this new method called "Packet" which not only had higher speed, but even more important, it offered 100% accuracy.
A communications dictionary will explain that a Packet is a group of binary digits containing both data and control information. Packet Switched communication is based on transmission of packets of information between stations. Each packet contains some data, and some control information that describes how to handle the data - sort of like sending a package in the mail.
There is information on the outside of the package in a standard format that tells the post office how to handle the package (name, address, and return address) and the post office adds information about how they handled the package (post mark). The content of the package is independent of the information on the outside and is usually of no interest to the post office. Although the information on the outside may interesting to the recipient to show how the package was routed, it generally has nothing to do with the contents of the package.
A PACKET is a digital package delivered by a TNC and it can include
- text (or other data) to be delivered to the receiving station
- an indication of the size of the packet is i.e. how much data you are sending
- the name of the station the data is headed for (name)
- how to get there (address)
- the name of the station that originated the packet (return address)
- some information used to check the accuracy of reception (postmark)
Did you notice and wonder why some of the information sent was "how to get there"? Packets of information can be automaitically relayed from one station to another like a bucket brigade so that you can talk to stations you can't even hear - with 100% accuracy! This ability to relay messages is provided by stations serving as Nodes and Digi-peaters.
SCARC operates a packet node on a frequency of 145.030 MHz. The node is managed by Gary Lucas - KJ4GH. The node operates as KJ4GH-1 and answers to the alias SHL1.
| SHL1 can be used to: |
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access a packet BBS talk to other hams send NTS traffic send mail to packet mailboxes participate in group discussions using TALK mode |
This guide is an attempt to explain all of this in simple terms so that the first time packeteer can get started quickly in this facet of amateur radio.
Although 145.030 MHz is the most popular VHF packet frequency in the area, you will also find activity on 145.010 MHz, 145.630 MHz, 145.670 MHz and a DX cluster on 144.950 MHz. You will also find packet on the HF bands but it is best to stick with VHF until you are familiar with operating packet. These instructions will not detail HF operation.
Many SCARC members are active on packet and would be happy to find a message from you in their packet mailbox. Simply connect to their mailbox and leave a message. Don't forget to leave instructions on how they can contact you. The most common method is to leave your radio and TNC "ON THE AIR" so they can leave a message for you there. Any of them would be glad to answer questions and give sage advice. See the SCARC web site for a list of mailboxes you might try in the area.
The minimum equipment configuration required to operate packet consists of a Radio, a TNC (Terminal Node Controller) and a terminal with a keyboard and either a printer or a diaplay. Most hams replace the terminal with a PC and program that works like a terminal.
ANTENNA
---+--- RADIO TNC TERMINAL
\ | / +-----------+ +-----------+ +--------------+
\ | / | mike|--< <--|AUDIO OUT | | DISPLAY |
\|/ | | | |--[ ]--|rs232 |
+-------+ speaker|--> >--|AUDIO IN | | AND KEYBOARD |
+-----------+ +--+--------+ +--------------+
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When a signal is received at the radio it is passed as audio tones to the TNC over the radios audio output or speaker connection to the audio in at the TNC. The TNC converts the tones to ASCII text and passes it over the RS232 connectin to the terminal or PC where it is displayed for you to read.
When you respond at the keyboard the PC or terminal sends ASCII characters to the TNC over the RS232 port. The TNC converts the ASCII characters to audio tones, keys the transmitter, and passes the tones from the TNC AUDIO OUT to the transmitters mic input. The transmitter sends your reply to the other station.
Many newer radios have a DIN or similar connector provided for packet operations. If your radio has such a connection you will need to check your owners manual to determine what type of cable is needed to connect to your TNC. Also check the TNC instruction manual for instructions on how to connect to your radio. The TNC manual will probably include a section on testing your setup.
Now your equipment is all hooked up and you're ready to get started.
First of all lets make sure the TNC is talking to your terminal or PC. Hold the <Ctrl> key while you press the C key (this is called control-c and is usually written as <Ctrl>-C or simply CTRL-C). The CTRL-C tells the TNC you want it to go into command mode (it should have been there already). Now press the Enter key. The TNC should respond with "cmd:".
- If you get a response but the characters are not readable it indicates you are
connected to the hardware but your terminal and TNC do not have the same settings.
Some TNCs will try to find the settings when they are first started. Reset your TNC and watch the terminal screen. It should show some information when the TNC software loads.
Now try the CTRL-C and ENTER keys again. If you still don't get a good response you will have to look in the TNC and Terminal manuals to find how to control the com port settings for the serial port. The settings for BAUD (or speed), Parity, Start bits, and Stop bits must be the same for both the TNC's RS232 port and the terminal or computer.
If your typing does not show up on the screen but the TNC responses do show up, the TNC is not "echo"ing back your input to the screen. You should be able to resolve this by typing the command "echo on".
If your typing shows up on the screen twice (LLIIKKE TTHHIISS) then your terminal and the TNC are both set to echo your typing. It is best to let the TNC provide the echo. Check your terminal or terminal software to see if you can turn ECHO off.
You must get the TNC and terminal to talk to each other before going any further.
It's also a good idea to make sure that FLOW CONTROL is set to software control instead of hardware control.
- Once your terminal and TNC are on speaking terms you need to tell the
TNC to remember a few things. The TNC will remember your settings even if
powered off, so you should not have to do this often. You can check the
individual settings by just entering the name of the setting without a
value -- the TNC will display the name and current value of the setting.
- Enter "mycall your-call-sign". For example "mycall K9DOG".
This tells the TNC what callsign to use when it transmitts. Now
enter "mycall" (without your callsign) to see if you were successfull.
The TNC should respond with your callsign. When operating packet
you don't have to remember to send your callsign every 10 minutes.
The TNC will send your callsign with each packet transmission.
- Enter "beacon 0". This tells the TNC not to transmit a beacon.
A beacon is an automatic message that is sent at regular intervals.
It is intended to be a general interest announcement - like the name
and location of your station. This tells others that your station
is available - usually for mailbox or digipeater functions. Most
operators today frown on the use of beacons because it can cause
congestion on the frequency. "0" should be the default value but
it's best to verify. So to check the value
for beacon you could just enter "beacon". The TNC should respond "0". If the TNC
has beacon set to something other than 0 it means to transmit the "beacon text" each
beacon*10 seconds - so if beacon is set to 60 it will cause the beacon text
to be transmitted each 600 seconds (5 minutes). If you absolutely must play with
the beacon, use the "btext" command to change the text that will be transmitted.
- Check the documentation for your TNC to see how to set the speed of the text to and from the radio. For now use 1200 baud on VHF. HF is limited to 300 baud.
- Enter "mycall your-call-sign". For example "mycall K9DOG".
This tells the TNC what callsign to use when it transmitts. Now
enter "mycall" (without your callsign) to see if you were successfull.
The TNC should respond with your callsign. When operating packet
you don't have to remember to send your callsign every 10 minutes.
The TNC will send your callsign with each packet transmission.
Packet frequencies get fairly busy at times so try to pick a BBS you can hear well, then listen to the activity on the frequency. If it seems busy you will probably get slow performance. If there is not much activity on the frequency you can get a lot of information in a short time.
Downloading files is not quite the same as on a wire line BBS. On a packet BBS the files are usually in plain text and down loading them just scrolls them over your screen. If you are using a computer your software probably has the ability to capture to a file. This will allow you to save the information and study it in detail later.
Packet BBS systems around Birmingham:
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W4CUE - Birmingham AL
You can also find the W4CUE BBS on 145.030 MHz and 145.670 MHz. - QJGBBS:WB7QJG - Clay AL
- BLTBBS:WD4PPF - Blountsville, AL
- N4WOM - Piedmont AL
- WARBBS:KD4CIF - Warior,AL - access via COR1 on 145.030 MHz.
Any TNC and radio can be used as a digipeater if the station operator has not restricted this function. Many hams leave their radio and TNC on all the time making it available for use as a "DIGI". You can digipeat through them using the Via command.
For example, to connect to my TNC for a live QSO (on the keyboard) using Ron Arant's TNC as a digipeater you would key:
If I don't respond you can disconnect, and leave a message on my mailbox by keying:
A node is usually a dedicated TNC at a high location, with special programming that allows it to become an intelligent member of a packet network. All nodes support a help function. Use it to learn about the node and what it can do for you.
The software keeps track of ROUTES to other nodes heard on the frequency. Nodes support a "Connect" (C) command instead of the Via command used by digipeaters.
To connect to another station by using a node you would first connect to the node. After getting a "connected" message back from the node you would send a connect for the target station (or bbs, or node) as if you were trying to connect directly to it.
For example, if you wanted to connect to my mailbox through the SHL1 node you would first key
After connecting to SHL1 you will get a message similar to:
At this point you would enter
"c k4hm-1"
and be greeted by my mailbox message.
A useful command when connected to a node is the ROUTES command. This will list the adjacent nodes (routes) this node is aware of. You can use these nodes to hop to other nodes, stations, mailboxes, BBS, etc. For example, if you are connected to node SHL1 and want to see what other nodes are accessible from SHL1 you would enter the command Routes (just the letter R will suffice). You should get a response that looks something like: SHL1:KJ4GH-1} Routes: 0 BHMW:KB4UPI-1 192 25 > 0 CLAY03:WB7QJG-3 192 22 0 COR1:KD4CIF-1 192 26 0 BHM1:WB4FAY-1 192 4 0 WIN1:N4EB-3 192 2 Each line tells you information about a "Route" or direct connection to another node. Direct means without relays. There are many other places the "Node" knows how to reach, but they involve relaying transmissions through other nodes. The First column is always 1 or 0. 1 indicates a physical link (wire or cable) connection and 0 indicates a radio link. The next column gives the alias and call sign of the node. You use the alias to connect to the node. The last two columns indicate the "health" of the connection to the node. In general - the higher the numbers, the more dependable the link. Physical connections of course will be more reliable than RF. The NODES command displays a list of other nodes that are known to this node. Remember that a node is "intelligent" and remembers information about other nodes it hears on the same frequency. You can have the node display that information with the NODES command (or just "n"). Sending this command to SHL1 will produce a report similar to this: SHL1:KJ4GH-1} Nodes: ALA:N4KMJ-2 BHM1:WB4FAY-1 BHM3:WB4FAY-3 BHM7:WB4FAY-7 BHMW:KB4UPI-1 BLT4:WD4PPF-4 BLTBBS:WD4PPF CLAY03:WB7QJG-3 COR1:KD4CIF-1 COR2:KD4CIF-2 COR4:KD4CIF-4 COR6:KD4CIF-6 EBHMSW:N4KNB-5 HSV10:WD4CPF-10 HSVS:WB4UFQ-1 IP8018:AD4DB-2 QJGBBS:WB7QJG SAWNEE:WB4OSD-1 VFFIP:N4VFF-5 WAR1:KD4CIF-10 WARBBS:KD4CIF WIN1:N4EB-3 WIN6:KC4RNF-7 Notice that there are a lot more entries in the NODES list than there are in the list of ROUTES. You should recognize some of them as the Routes you displayed before. This is because routes are nodes that can be contacted directly by this node - the definition of a route. Some of the entries in the node list may be several "hops" away from this node. You can often get an idea of where or what the node is by its alias. BHMW for example is Birmingham West, BLT4 is in Blountsville, and IP8O18 will be an IP node providing specialized IP connections. Notice that several contain BBS in the alias. You can safely bet these will provide packet BBS connections. The NODES command can also show you what ROUTES it intends to use to access a node. For example look at the command below. nodes blt4 SHL1:KJ4GH-1} Routes to: BLT4:WD4PPF-4 143 7 0 CLAY03:WB7QJG-3 143 7 0 COR1:KD4CIF-1 107 7 0 BHMW:KB4UPI-1 Blountsville is to the north, but to far for a direct connection. SHL1 knows however that there have been messages sent to BLT4 through the nodes listed above. It may have even sent messages over that route itself. If you send a connect command for blt4 it will try to connect through these nodes. Note that these nodes may not be able to directly connect to BLT4 either. They also may send through another node. There could be several hops through other nodes to get to the destination but SHL1 remembers the path and you only need to ask it to connect for you. The numbers to the left of the route are another "health" indicator. They are lower numbers because of the additional nodes you must traverse to send messages there. In general the more nodes you go through the lower the health rating. With a little detective work you may be able to find the route. Try connecting to what looks like the best route, then issue a ROUTES command. If the node you are seeking is not shown try the NODES commands as discussed above. If the NODE can find it you should be able to find it also, it just takes us longer. One note of caution - these commands can cause a lot of information to be sent across nodes you can't even hear. If those nodes are busy with local users, they may not appreciate your long displays. It's best to do this kind of exploring at times when the nodes are not likely to be busy.
Some packet nodes in the Birmingham area: 145.03 MHz: BHM1:WB4FAY-1 BHM7:WB4FAY-7 BHMW:KB4UPI-1 SHL1:KJ4GH-1 South bham? East B'ham ? West B'ham ? Shelby Co. Routes: Routes: Routes: Routes: 1 BHM3:WB4FAY-3 1 BHM1:WB4FAY-1 0 BHM1:WB4FAY-1 0 BHMW:KB4UPI-1 1 BHM7:WB4FAY-7 1 BHM3:WB4FAY-3 0 COR1:KD4CIF-1 0 COR1:KD4CIF-1 0 BHMW:KB4UPI-1 0 SHL1:KJ4GH-1 0 CLAY03:WB7QJG-3 0 COR1:KD4CIF-1 0 CLAY03:WB7QJG-3 0 BHM1:WB4FAY-1 0 SHL1:KJ4GH-1 0 WIN1:N4EB-3 0 CLAY03:WB7QJG-3 COR1:KD4CIF-1 WIN1:N4EB-3 CLAY03:WB7QJG-3 Warrior AL Bluff, AL Pinson, AL Routes: Routes: Routes: 1 COR4:KD4CIF-4 COR1:KD4CIF KB4UPI-1 1 COR6:KD4CIF-6 BHM1:WB4FAY-1 KD4CIF-2 0 BHM1:WB4FAY-1 BHMW:KB4UPI-1 KD4CIF-1 0 WIN1:N4EB-3 WB4FAY-1 0 SHL1:KJ4GH-1 KJ4GH-1 0 BHMW:KB4UPI-1 AD4DB-2 WB4UFQ-1
145.67 MHz BHM3:WB4FAY-3 EBHMSW:N4KNB-5 Homewood, AL. Birmingham Routes: Routes: 1 BHM1:WB4FAY-1 0 BHM3:wb4fay-3 1 BHM7:WB4FAY-7 0 EBHMSW:
145.63 mHZ JVL:N4QLB-5 HSR1:N4DKE-10 Jacksonville AL Mtn Brook, AL Routes: Routes: 1 JVL01:N4QLB-1 0 JVL 0 CCEOC:N4QLB-3 0 CCEOC 0 HSR1:N4DKE-10 0 N4WOM-BBS
145.010 MHz JVL01:N4QLB-1 WGA1:W4FWD-2 Jacksonville AL Carrolton GA Routes: Routes: 0 WGA1:W4FWD-2 1 FWD1:W4FWD-1 1 JVL:N4QLB-5 1 WGA70:W4FWD-4 0 DLTN01:KD4NDV-2 0 JVL01:N4QLB-1 0 IP8017:N4WOM-2 0 PHX1:N4TKT-1 0 BDG1:W4NHU-3 0 SAWNEE:WB4OSD-1 0 DHN1:KA4WVO-1 0 TLHFL:WR4Z-1 0 DLTN01:KD4NDV-2
51.780 MHz COR6:KD4CIF-6 Warior AL Routes: 1 COR1:KD4CIF-1 1 COR4:KD4CIF-4 0 WAR1:KD4CIF-10 0 WIN6:KC4RNF-7