Commands for the TNC2 Back to Menu page

8BITCONV
This command enables the transmission of 8-bit data in converse mode. Used with AWLEN - see below. For normal packet operation, such as keyboard to keyboard transmissions, use of bulletin board systems, and the transmission of ASCII files, 8BITCONV should be OFF. If you need to transmit 8-bit data, set 8BITCONV ON and set AWLEN to 8. Make sure that the TNC at the receiving end is also set up this way. This procedure is normally used for transmission of executable files or a special non-ASCII data set.

AWLEN
This parameter defines the word length used by the serial input/output port of your TNC. For normal packet operation, as described above, AWLEN should be set to 7. Set to 8 only if you're going to send 8-bit data.

AX25L2V2
This command determines which level of AX.25 protocol you're going to use. If OFF, the TNC will use AX.25 Level 2, Version 1.0. If ON, the TNC will use AX.25 Level 2, Version 2.0. Note: Some early TNCs will not digipeat Version 2.0 packets. With AX25L2V2 OFF, if your TNC sends a packet and the packet doesn't get acknowledged the first time it was sent, it will send it again and again, until an "ack" is received or the TNC retries out. With AX25L2V2 ON, if your TNC sends a packet and doesn't receive an "ack" the first time, it will send a poll frame to see if the other TNC received the packet. If yes, then it would continue, if not then it would send the last packet again. The advantage here is that short poll frames are sent, rather than long packets containing data. This can greatly reduce channel congestion. For VHF/UHF operation, it is almost essential that every TNC have AX25L2V2 ON. Many operators have suggested that Version 2.0 NOT be used on the HF bands as it tends to clutter the frequency with poll frames. See the CHECK command below for related information.

BEACON
Used with EVERY or AFTER to enable beacon transmissions.

n = 0 to 250 - specifies beacon timing in ten second intervals: 1 = 10 seconds, 2 = 20 seconds, 30 = 300 seconds or 5 minutes, 180 = 1800 seconds or 30 minutes, etc.
Examples:

The text of the beacon is specified by BTEXT and can contain up to 120 characters. The path used for the beacon transmission is specified by the UNPROTO command. YOU SHOULD USE BEACONS INTELLIGENTLY! Beacons are often a point of controversy in the packet community because they tend to clutter the frequency if used too frequently. You should keep your beacons short and infrequent, and they should only be used for meaningful data. Bulletin boards use the beacon for advising the community of who has mail waiting for them, clubs use beacons for meeting announcements, and beacons are used for severe weather warnings. In areas with heavy packet activity, beacons should not be used just to let everyone know that you're monitoring the frequency, that your mailbox is ready, or that you'd like someone to connect to you. You should monitor the frequency for activity and make some connections yourself.

BTEXT
Can contain up to 120 characters.

CHECK n
Sets a timeout value for a packet connection. When a connection between your station and another seems to "disappear" due to changing propagation, channel congestion or loss of the path, your TNC could remain in the connected state indefinitely. If the CHECK command is set to a value other than 0, the TNC will attempt to recover the connection or disconnect. The action taken depends on the setting of AX25L2V2. The value of CHECK (n) may be set from 0 to 250 and the timing is based on the formula of n * 10 seconds. (n = 1 is 10 seconds, n = 5 is 50 seconds, n = 30 is 300 seconds or 5 minutes, etc. A value of 30 is a recommended value to use.) If CHECK is set to 0, it disables the command. If AX25L2V2 is ON, the TNC will send a "check packet" to verify the presence of the other station if no packets have been heard after (n * 10) seconds. If a response to the "check packet" is received, the connection will remain. If no response is received, the TNC will begin the disconnect sequence, just as if the DISCONNECT command had been sent. If AX25L2V2 is OFF, after no packets are heard for n * 10 seconds, the TNC will not send a check packet, but will begin the disconnect sequence.

CMSG
Enables the automatic sending of a connect message whenever a station connects to your TNC. If CMSG is ON, the TNC will send the message contained in CTEXT as the first packet of the connection. CTEXT can contain up to 120 characters. Of course, you must have a message in CTEXT for CMSG to function. This feature is often used when the station is on but the operator is not present. The connect message is used to advise the other station of that fact, and often says to leave a message in the TNC buffer or mailbox. If CMSG is OFF, the CTEXT message is not transmitted.

CONV (converse mode)
Your TNC will automatically switch to this mode when you connect with someone, but you can also switch to this mode by entering CONV <CR> at the Cmd: prompt. When you're in converse mode and are NOT connected to another station, anything you type will be transmitted via the path you set with the UNPROTO command.

CTEXT
Can contain up to 120 characters.

DAYTIME
Command has been used to set the date and time.

DISCONNECT
Command had been sent to disconnect the whole packet.

DWAIT
Used to avoid collisions, DWAIT is the number of time units the TNC will wait after last hearing data on the channel before it transmits. I have DWAIT set to 16, and have found that to work well.

ECHO
If you do not see anything on the screen when you type, blindly enter the following: ECHO ON <CR>
If you see two of everything that you type, such as MMYYCCAALLLL, enter: ECHO OFF <CR>

FRACK
Determines how long your TNC will wait for an acknowledgement before resending a packet. It shouldn't be set too low, or you'll simply clutter up the frequency, yet it shouldn't be too high, or you'll spend too much time waiting. I use FRACK set to 7, and have found that to be a good overall value.

HEADERLN
If you have this turned ON, the header of each packet is printed on a separate line from the text. If OFF, both the header and packet text are printed on the same line.

KISS
Enables the TNC to act as a modem for a host computer, allowing programs such as TCP/IP, the G8BPQ Packet Switch, various BBS programs, and other programs using the Serial Link Interface Protocol (SLIP) to be run. Before turning KISS on, set the radio baud rate and terminal baud rate to the desired values. Set KISS to ON and then issue a RESTART command.

MALL
If MALL is ON, you receive packets from stations that are connected to other stations, as well as packets sent in unproto (unconnected) mode. This should be ON for "reading the mail". If MALL is OFF, you receive only packets sent in unproto mode by other stations.

MAXFRAME
Sets the upper limit on the number of unacknowledged packets the TNC can have outstanding at any time. (The outstanding packets are those that have been sent but have not been acknowledged.) MAXFRAME also determines the maximum number of contiguous packets that can be sent during one transmission. The value can be set from 1 to 7. The best value to use depends on the frequency conditions. The better the conditions are, the higher the value you can use. If conditions are poor due to frequency congestion, noise, or other variables, (shown by lots of retries) MAXFRAME should be reduced to improve throughput. The best value of MAXFRAME is determined through experimentation. MAXFRAME of 1 should be used for best results on HF packet.

MCOM
If ON, you see connect <C or SABM>, disconnect <D>, acknowledge <UA> and busy <DM> frames in addition to information packets. If OFF, only information packets are seen.

MCON
If ON, you see packets from other stations while you're connected to someone else. This can get very confusing, but is useful when your path is bad and you want to see if your packets are being digipeated okay. If OFF, the monitoring of other stations is stopped when you're connected to another station.

MFILTER
This command allows you to enter up to four ASCII character codes, 0 - $7F, for the control characters that you want eliminated from your monitored packets. Codes may be entered in either Hex or Decimal. Here are the ASCII codes for some of the more troublesome control characters found in monitored packets:

   HEX   DEC   FUNCTION   POSSIBLE RESULT
   $07    07   Control G  Rings your bell or "beeps" your speaker
   $0C    12   Control L  Form feed - could clear your screen
   $13    19   Control S  Can cause your screen to stop scrolling
   $1A    26   Control Z  Can clear your screen
   $1B    27   Escape     Can cause your cursor to move to a random         
                          point on your screen and can raise havoc          
                          with printer control.

AEA has added a new code, $80, that will not allow ANY control characters to be displayed on the user's screen from monitored packets.

MHEARD
An immediate command that causes the TNC to display a list of stations that have been heard since the command.

MHCLEAR
was given or the TNC was powered on. This command is useful for determining what stations can be worked from your QTH. Stations that are heard through digipeaters are marked with an * on most TNCs. On the AEA PK-232, the stations heard direct are marked with the *. (Check your TNC manual.) The maximum number of stations in the list is 18. If more stations are heard, earlier entries are discarded. Logging of stations heard is disabled when the PASSALL command is ON. (See below.) If the DAYTIME command has been used to set the date and time, entries in the MHEARD list will show the date and time the stations were heard.

MONITOR
This must be ON for you to monitor anything. When ON, you see packets from other stations on the frequency you're tuned to. What packets you see is determined by other commands from the list below. If MONITOR is OFF, you only see the packets that are sent to you while you're connected to another station.
Note: On some TNCs, such as the AEA PK-232, monitoring functions are selected by a number after the MONITOR command, such as:
MONITOR 3 or
M 3
Refer to your TNC operating manual for details.
The following commands affect "monitoring", which is what you see on your screen from stations you're NOT connected to.

MRPT
If ON, you see a display of all the stations used as digipeaters along with the station originating the packet and the destination station. If OFF, you see only the originating and destination stations. For example, if you have MRPT ON, you might see a transmission such as this:
K9AT>WB6QVU,W6PW-5*: I'll be leaving for the meeting at about 7:30.
If MRPT was OFF, the same transmission would look like this:
K9AT>WB6QVU: I'll be leaving for the meeting at about 7:30.
In the first case, you can see that the W6PW-5 digipeater was being used. The asterisk indicates which station you were hearing the packet from. In the second case you have no idea if digipeaters are being used or what station you were receiving.

MSTAMP
The date and the time the monitored packets are received is indicated if the MSTAMP command is ON. If it's OFF, the date/time stamp is not shown. NOTE: The date and time must be entered into your TNC memory using the DAYTIME command before the MSTAMP command will function.

I run my station with all of these commands, except MCON, turned ON so that I can really see what's happening on the frequency I'm monitoring. Try various combinations of these commands and then decide on the combination you like best for your station.

MYCALL
MYCALL ---- with your callsign in place of the dashed lines, such as: MYCALL WB9LOZ followed by a carriage return <CR>. (The carriage return key is labeled "Enter" or "Return" on most keyboards.) All commands must be followed by a <CR>. This sets into the TNC memory the call that you're going to use on the air. Now if you type: MYCALL <CR> it should respond with your callsign. If it does, you've proven that the computer to TNC link is working fine.

PACLEN
Indicates the number of characters in the packets you transmit, ranging from 0 to 255. (A value of 0 equals 256.) The more characters you send per packet, the longer it takes to transmit the information and the greater your chances are of noise, interference or another station wiping it out. I've found a PACLEN of 80, which is the length of one line, to be a good value. When working a station nearby, PACLEN can be increased. When working a distant station, it should be decreased.

PASSALL
Causes the TNC to display packets that have invalid checksums. The error-checking is disabled. If PASSALL is ON, packets are accepted for display, despite checksum errors, if they consist of an even multiple of eight bits and are up to 330 bytes. The TNC attempts to decode the address field and display the callsigns in standard format, followed by the text of the packet. PASSALL can be useful for testing marginal paths or for operation under unusual conditions. PASSALL is normally turned OFF.

PERSIST
Used in conjunction with the SLOTTIME command to provide less clutter on a busy packet frequency. As more and more TNCs are upgraded to include the PERSIST and SLOTTIME commands, fewer and fewer packet collisions will occur. If you have these commands available in your TNC, you should set DWAIT to 0 and set these commands for use. Note: On some TNCs, such as the PK-232, you have another command that determines whether you use DWAIT or PERSIST/SLOTTIME. PERSIST specifies a threshold value for a random-number attempt to transmit. The value ranges from 0 to 255. 0 signifies a 1/256th chance of transmitting every SLOTTIME; 255 allows the TNC to key the transmitter every SLOTTIME. Through experimentation, it has been determined that the best value for PERSIST is in the 60 to 70 range.

PPERSIST
command (with 2 P's). Set it ON to use PERSIST/SLOTTIME; set it OFF to use DWAIT. I strongly recommend that you set PPERSIST to ON.

RESTART

RETRY
Your TNC will retransmit a packet if it doesn't receive an acknowledgement from the station you're working. RETRY indicates the number of times the TNC will try to get the packet through before giving up and disconnecting. This can be set from 0 to 15, but I've found 8 to 10 to work well. Less than that causes an unnecessary disconnect if the channel happens to be busy, but more than that clutters up the channel. Do NOT set RETRY to 0. That means infinite retries, and serves no useful purpose. It simply clutters up the frequency needlessly.

SCREENLN n
This parameter determines the length of a line of text on your computer screen. The value may be 0 to 255, and is usually set to 40 or 80 depending on the screen display you have. A carriage return and line feed <CR/LF> are sent to the terminal in Command and Converse modes when n characters have been displayed. A value of zero inhibits this action. If your computer automatically formats output lines, this feature should be disabled.

SLOTTIME
This command determines the time interval the TNC waits between generating random numbers to see if it can transmit. This random number generation and the value of PERSIST work together to provide smoother operation on a busy packet frequency. The SLOTTIME value may be set from 0 to 250. Through experimentation it has been determined that the best value for SLOTTIME is in the range of 10 to 20.

TRANS
This is an immediate command causing the TNC to change from Command mode to Transparent Mode. Transparent mode is used when you want to send data such as executable programs where characters in the data would conflict with the operation of the TNC. Characters such as "Control C", "Control R", "Control S", "carriage return", "linefeed", etc. all effect the operation of the TNC when in Converse Mode. In Transparent Mode none of the data characters affect the operation. All eight bits of each character are sent to the radio exactly as they are received by the TNC from the computer or keyboard. Packets are transmitted at regular intervals set by the PACTIME command or whenever a full packet of information is ready. The receiving TNC must also be in Transparent mode and nodes and digipeaters cannot be used in the transmit path. Since the characters normally used for TNC operation have no affect in this mode, a special procedure is required to exit Transparent Mode and return to Command Mode. Refer to your TNC operating manual for details on how this procedure is performed on your particular TNC.

TXDELAY n
This parameter tells the TNC how long to wait before sending data after it has keyed the transmitter. All transmitters need some start up time to put a signal on the air. Some need more, some need less. Synthesized radios and radios with mechanical relays need more time, while crystal controlled radios and radios with diode switching require less time. External amplifiers usually require additional delay. Experiment to determine the best value for your particular radio. TXDELAY can also be useful to compensate for slow AGC recovery or squelch release times at the distant station.

UNPROTO
Designates the path used when you send BEACONS or when you're in converse mode and NOT connected to another station. The default is CQ, but you can enter a series of digipeaters if you wish, or a specific group or club name. Some examples:

If you include digipeaters in your UNPROTO path, you will have to change the information for each frequency you use. (BEACONS will be discussed in a later part of this series.)
Packets sent via UNPROTO are sent only once and are not acknowledged, so there is no guarantee that they'll get through. This mode is used frequently for sending CQ's.

There are many additional commands available to you. You should also check your manual for information on the CMDTIME, PACTIME, START, STOP, TRFLOW, TXFLOW, XFLOW, XOFF and XON commands before using Transparent Mode.


Back to Menu page