Mfj1270 MFJ 1270c 1274c Packet Radio Controller Manual

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o 15.838 Class B computing device: information to user.
This equipment generates and uses radio frequency energy and if not installed
and used properly, that is, in strict accordance with the manufacturer's
instructions, may cause interference to radio and television reception. It has
been type tested and found to comply with the limits for a Class B computing
device in accordance with the specifications in subpart J of Part 15 of FCC
Rules, which are designed to provide reasonable protection against such
interference in a residential installation. However, there is no guarantee that
interference will not occur in a particular installation. If this equipment does
cause interference to radio or television reception, which can be determined by
turning the equipment off and on, the user is encouraged to try to correct the
interference by one or more of the following measure:
Reorient the receiving antenna
Relocate the computer with respect to the receiver
Move the computer away from the receiver
Plug the computer into a different outlet so that computer and receiver are
on different branch circuits.
If necessary, the user should consult the dealer or an experienced
radio/television technician for additional suggestions. The user may find the
following booklet prepared by the Federal Communications Commission
helpful:
"How to Identify and Resolve Radio-TV Interference Problems".
This booklet is available from the U.S. Government Printing Office,
Washington, DC 20402, Stock No. 004-000-00345-4.
Warning-When connecting this device to your computer,
shielded interface cables must be used.

MFJ ENTERPRISES, INC.

Model MFJ-1270C/1274C
Packet Radio Controller
Revision 10
SYSTEM MANUAL

Fourth Edition
(c) Copyright 1993, MFJ Enterprises, Inc.

i

TNC 2 SOFTWARE SOURCE CODE and TNC FIRMWARE
Copyright (c) 1985 - 1993
Systek
MFJ-1270C/1274C SOFTWARE SOURCE CODE and FIRMWARE
Copyright (c) 1993
MFJ Enterprises, Inc.
All rights reserved.

Reproduction or translation of any part of this work beyond that permitted by
Sections 107 or 108 of the 1976 United States Copyright Act (or its legal
successor) without the express permission of the copyright owner is unlawful
except as noted below. Requests for permission to copy or for further
information should be addressed to MFJ Enterprises, Inc. P. O. Box 494,
Mississippi State, MS 39762, USA.
The information contained in this document has been carefully checked and is
believed to be entirely reliable. However, no responsibility is assumed for
inaccuracies. MFJ Enterprises, Inc. reserves the right to make changes to any
product to improve reliability, function or design without obligation to
purchasers of previous equipment. MFJ Enterprises, Inc. does not assume
any liability arising out of the application or use of any product or circuit
described herein; neither does it convey any license under its patent rights to
others.

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MFJ-1270C/1274C MANUAL

TABLE OF CONTENTS

TABLE OF CONTENTS
TABLE OF CONTENTS .........................................................................iii
INTRODUCTION....................................................................................1
Items supplied with MFJ TNC package ......................................2
Optional items available for the MFJ TNC .................................3
COMPUTER INTERFACING .................................................................4
MFJ Terminal Software Starter Packs.........................................4
Computer Interfacing with MFJ Starter Packs...............5
Computer Interface without MFJ Starter Pack...............5
Serial Port Signals......................................................................5
Computers with Specific Serial Interfaces .....................7
Apple Macintosh.............................................7
Commodore C64, C128 and VIC-20 ...............8
IBM PCjr ........................................................9
Radio Shack Color Computer..........................9
Radio Shack Model 100/102 and NEC 8201....9
IBM PC/XT/AT/386/486 and compatibles
Computer........................................................10
Other Computers with Non-standard Serial Ports..........12
Terminal Software Requirements ...............................................12
Apple Macintosh ..........................................................13
Apple II, II+, IIe, IIc.....................................................13
Commodore C64, C128 and VIC-20 .............................13
IBM PCjr......................................................................14
IBM PC and Compatible Computers .............................14
Radio Shack Color Computer........................................15
Radio Shack Model 100/102 and NEC 8201 .................15
MFJ TNC Serial Port Pin Functions ..........................................15
Computer Baud Rate ..................................................................16
Verifying Serial Port Operation ..................................................17
RADIO INTERFACING..........................................................................20
MFJ TNC Radio Port.................................................................20
Radio Port Connection..................................................21
Handheld Radio Connection .........................................21
RADIO INTERFACING METHODS .........................................23
Method 1: Direct Connection to Microphone and
Speaker.........................................................................23
Transmit Audio Level Adjustment for
Method I Interface...........................................24
Setting the Receiver Audio Input Level.........................25
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Method 2:
Accessory Jack or Interface Box
Connection ...................................................................25
Transmit Audio Level Adjustment for
Interface Method II .........................................27
Receiver Audio Setting....................................28
Monitor Speaker Connection ........................................29
GETTING STARTED .............................................................................30
First Steps ..................................................................................30
Basic Parameters Setup.................................................31
Serial Port Configuration............................................................31
Parity and Word Length................................................32
Echos............................................................................33
New Lines and Line Wrapping .....................................33
Tuning Indicator (MFJ-1274C) ..................................................34
PACKET OPERATION ............................................................34
VHF Packet ..................................................................34
A Connecting and Disconnecting Exercise......35
Digipeating .....................................................37
Unsuccessful Connections ...............................38
Monitoring Channel Activity ..........................39
Your First Packet QSO....................................40
Starting the QSO.............................................41
Digipeating .....................................................42
Monitoring on the Air.....................................43
Special Input Characters...............................................43
HF Packet Basic Operation ...........................................46
HF Packet Operation Hints:.............................47
FAX OPERATION ....................................................................47
FAX FREQUENCY......................................................48
FAX STATION FREQUENCIES....................49
Other FAX Frequencies ..................................49
ADVANCED PACKET OPERATION.....................................................50
Special Characters......................................................................50
Packet Operating Modes ..........................................................................52
Command Mode.........................................................................52
Entering Data-Transfer Modes......................................53
Converse Mode.............................................................54
Transparent Mode ........................................................56
Flow Control ..............................................................................57
XON/XOFF Flow Control.............................................58
Hardware Flow Control ................................................59
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Type-in Flow Control ...................................................59
Detail VHF Packet Operation .....................................................60
Station Identification ....................................................60
Automatic Operations...................................................61
Unattended Operations .................................................62
Packet Formatting.........................................................62
Packet Timing Functions ..............................................64
Transmit Timing.............................................64
Packet Timing.................................................65
Radio Baud Rate .............................................66
Special Protocol Times....................................67
Monitor Functions......................................................................68
Real-Time Clock and Time Stamping.........................................70
Multi-Connect Guide..................................................................70
Setting the MFJ TNC to Normal Operation...................70
How to Invoke Multi-Connect? .....................................71
Easy-Mail Mailbox.....................................................................72
Set Up your Easy-Mail Mailbox ....................................72
Mailbox Operation........................................................78
Additional Mailbox Features ...........................83
Forwarding........................................83
Eliciting Reverse Forwards................84
Remote Heard Log.............................84
Chat Mode: .......................................85
Page SYSOP .....................................85
Remote SYSOP .................................85
Mailbox CText ..................................85
Idle Timeout......................................85
Abort:................................................86
Mailbox Messages ......................................................................86
Slotting and Acknowledgment Priority.....................................................88
Description.................................................................................89
New Parameters............................................................90
Other Related Parameters .............................................93
Initial Parameter Settings Summary..............................94
What to Expect .............................................................95
Packet Picture Transfer ..............................................................96
Receiving Packet Pictures on Printer.............................97
Packet Picture transfer to the computer screen ..............97
Detail HF Packet Operation........................................................98
Radio Setup for HF Packet Operation............................98
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HF Packet Operation ..................................................................102
MFJ TNC KISS MODE AND HOST MODE .............................109
KISS Interface for TCP/IP ............................................109
OPERATION COMMANDS ...................................................................111
Entering Commands...................................................................111
COMMAND NAME ....................................................112
Default............................................................113
Parameters ......................................................113
Remarks..........................................................114
TNC MESSAGES....................................................................................196
Packet Messages.........................................................................196
Mailbox Messages ......................................................................197
Command Mode Error Messages .............................................................199
Link Status Messages .................................................................201
HARDWARE ..........................................................................................204
MFJ-TNC Specifications.............................................204
General Description ...................................................................206
Detailed Circuit Description .......................................................206
Oscillator......................................................................206
Dividers and Baud-rate Generator.................................207
CPU Complex...............................................................207
Serial Interface .............................................................208
Watch-dog Timer .........................................................208
Modem .........................................................................209
Power Supply................................................................209
RS-232C Handshaking Protocol .................................................210
Jumper Functions .......................................................................211
HF Tuning Indicator...................................................................217
TROUBLESHOOTING............................................................................218
General Tests .............................................................................218
Step 1: Power Supply...................................................218
Step 2: Obvious Problems ............................................219
Step 3: Assembly Problems..........................................219
Step 4: Cabling Problems.............................................219
Specific Symptoms .....................................................................220
Symptom: TNC appears dead .....................................................220
Oscillator and Reset Circuits ......................................................220
Digital Logic Lines.....................................................................220
Symptom: Modem won't calibrate or key transmitter. .................221
Symptom: Uncopyable transmitted or received packets ...............222
Terminal Interface Troubleshooting .........................................................222
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Symptom: MFJ-TNC won't sign on to the terminal.....................222
Symptom: The MFJ-TNC appears to be signing on but only
gibberish is printed on the terminal. ...........................................223
Symptom: The MFJ-TNC signs on OK but won't accept
commands..................................................................................223
Symptom: The MFJ-TNC appears to have "locked-up" i.e. not
responding to any commands. ....................................................224
PACKET RADIO PROTOCOL ...............................................................225
Explanation of Protocol ..............................................................225
Physical Layer ..............................................................225
Data Link Layer............................................................226
HDLC Frames ..............................................................226
AX.25 Level Two.......................................................................227
Channel Use and Timing Functions .........................................................230
Channel Flow Control..............................................................................232
RADIO HOOKUP....................................................................................233
MODEM CALIBRATION .......................................................................234
Modulator and Demodulator Frequency Calibration ...................234
Method I.......................................................................234
HF Modem......................................................234
VHF Modem ...................................................235
METHOD II .................................................................235
Set Modulator Tones Using Built-in Calibration
Software .......................................................................236
Demodulator Center Frequency Alignment ...................237
Tuning Indicator Alignment .........................................238
MFJ-TNC Adjustment Location Map .......................................239
AUDIO OUTPUT CALIBRATION ............................................241
Audio Output Level Adjustment Procedure.................................241
HF RADIO ALIGNMENT.......................................................................243
First method: NOISE AVERAGE FREQUENCY.......................243
Second method: FILTER SKIRT AVERAGE FREQUENCY .....243
MFJ-TNC 2400 PACKET OPERATION ...............................................245
2400 Packet Operation Setup......................................................245
B. Receive Audio Setting .............................................245
C. Transmit Audio Setting...........................................246
JUMPER FUNCTIONS AND LOCATIONS............................................247
COMMAND SUMMARY........................................................................250

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MFJ-1270C/1274C MANUAL

INTRODUCTION

INTRODUCTION
Thank you for purchasing the MFJ TNC Packet Data controller.
The MFJ TNC interfaces your radio with any personal computer that has an
RS-232 or TTL level Serial Port and a terminal program. While most
communications programs will work, MFJ recommends the use of MFJ Starter
Pack for those who have IBM or compatible, Macintosh, Amiga or Commodore
C64/128 computers. With an IBM or compatible computer, the MFJ Multicom
terminal program gives you added feature like VGA packet picture transfer
(IBM & compatible version) that a standard terminal program just can not
offer.
This compact versatile controller employs the genuine TAPR TNC 2 AX.25
protocol packet firmware. Special firmware like ROSE, NETROM, TheNet are
compatible with the MFJ TNC.
In addition, the advanced new DCD circuit in the MFJ TNC has been
optimized for HF packet. It can be adjusted to ignore background noise while
still being able to respond to a valid data carrier. The new "packet collision
prevention" features -- Prioritized Acknowledgments and Slottime are installed.
This new technology helps prevent many packet collisions inherent in the
current packet protocol.
The MFJ TNC offers the most versatile mailbox available when compared to
the mailbox in other controllers. This mailbox allows dedicated mailbox
callsign so that the mailbox stays on while you operate packet. Other features
like auto forward or reverse forward mail to and from other BBS, remote sysop
access, sysop paging, mailbox ctext, chat mode and a "has mail" LED indicator.
The MFJ TNC has an 8K bytes memory mailbox. Mailbox memory is user
expandable to 32K, 128K or 512K by simply replacing the mailbox memory IC.
If you purchased the MFJ-1274C, you also get MFJ's 20- segment, 10 Hz
Precision Tuning Indicator that makes tuning simple for HF Packet.
The EPROM containing the MFJ TNC firmware is 256K bits. It is expandable
to 512K bit or 1 Megabits giving the MFJ TNC a lot of room to grow in.
A speaker jack lets you plug in a speaker and monitor both transmit and receive
audio. Speaker output also provides packet connect signal alarm.
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MFJ-1270C/1274C MANUAL

INTRODUCTION

A 20-pin header provided for the MFJ TNC to operate packet at 2400 or 9600
baud packet by simply pluging in an optional modem board. The MFJ-1270CT
and the MFJ-1274CT already has a 2400 modem installed. If your MFJ TNC
does not have the 2400 modem installed, it can be purchased separately (MFJ2400) and installed by you. With the 2400 modem installed, your MFJ TNC
can operate 300, 1200 and 2400 packet. You may also purchased the MFJ9600 modem board that allows the MFJ TNC to operate at 9600 baud packet.

Items supplied with MFJ TNC package
1. One MFJ TNC Packet controller.
2. One AC adapter power supply for 110V AC. 240V AC adapter supplied
for MFJ-1270CX or MFJ-1274CX (export model for country which operate on
220-240V AC).
3. One open end radio port cable with 5-pin DIN male connectors.
4. One 8-pin connector for the TTL port.
5. One TNC system Instruction Manual.
6. One TNC Fast-Start Manual.

MFJ also has accessory items available for the MFJ TNC. A list of these items
follows on the next page.

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MFJ-1270C/1274C MANUAL

INTRODUCTION

Optional items available for the MFJ TNC
Model No
MFJ-1289
MFJ-1282
MFJ-1287
MFJ-1290
MFJ-1272B
MFJ-5024
MFJ-5026
MFJ-5080
MFJ-5084
MFJ-5086
MFJ-280
MFJ-40E
MFJ-43
MFJ-45A
MFJ-45B
MFJ-45C
MFJ-2400
MFJ-9600

Description
Advanced Starter pack for IBM & compatibles
Starter pack for Commodore C64/128
Starter pack for Macintosh
Starter pack for Amiga
MFJ TNC to Microphone switch box
Radio connecting cable for Icom/Yaesu/RS HTs
Radio connecting cable for Kenwood HTs
Radio connecting cable for Yaesu 8-pin radio
Radio connecting cable for ICOM 8-pin radio
Radio connecting cable for Kenwood 8-pin radio
Monitor speaker for transmit/receiver audio
Packet encryption EPROM
TNC Real time clock, keeps your TNC on-time
32K RAM IC for additional mailbox memory
128K RAM IC for additional mailbox memory
512K RAM IC for additonal mailbox memory
2400 bps internal modem for packet
9600 baud internal modem for packet

The above items are available from MFJ dealers or directly from MFJ
Enterprises, Inc.

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MFJ-1270C/1274C

COMPUTER INTERFACING

COMPUTER INTERFACING
You are now ready to attach your MFJ TNC to your station computer or
terminal. Throughout this manual we will use the term "computer" to refer to
the computer or terminal you use to communicate with your MFJ TNC .

The MFJ TNC communicates with your computer through a serial port using
signals corresponding to a standard called RS-232C. Why an RS-232C
interface? Nearly every computer in production today either incorporates an
RS-232C style serial port as a standard feature, or has one available as an
optional accessory, either from the computer manufacturer or from a
manufacturer of computer accessories. In addition to the RS-232C port, the
MFJ TNC has a built- in TTL port to allow interfacing with computers which
need TTL signals such as the Commodore C-64, C-128 or the VIC-20.
Computer program\, see Terminal program
In order to use the MFJ TNC with your computer, the computer must have an
RS-232C serial port, or a TTL serial port and a program to support the serial
or TTL port. The program will typically be called a modem, terminal emulator,
or communications program.
Since there are so many computers on the market today, it is impractical for
this chapter to provide detailed instructions for each computer. Detailed
information is given for some of the popular models available in the United
States. Also provided is general computer interfacing information.

MFJ Terminal Software Starter Packs
MFJ Enterprises, Inc. offers a Starter Pack for some of the most popular
computers. These Starter Packs contain a terminal program and a cable for
connecting the MFJ TNC to your computer. The Starter Packs available are
listed below and also on the following page:
MFJ-1282:Commodore VIC-20, C64, C128 on 5-1/4" diskette.
MFJ-1283: Commodore VIC-20, C64 on tape.

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MFJ-1270C/1274C

COMPUTER INTERFACING

MFJ-1284: IBM PC & compatibles on 5-1/4" diskette.
(Supports 2-level FAX)
MFJ-1284M: IBM PC & compatibles on 3-1/2" diskette.
(Supports 2-level FAX)
MFJ-1287B: Macintosh, on 3-1/2" diskette.
(Supports 2-level FAX)
MFJ-1290: Amiga on 3-1/2" diskette.
(Supports 2-level FAX)

Computer Interfacing with MFJ Starter Packs
If you are using one of the MFJ Starter Packs, you should use the cable
provided to connect the MFJ TNC and your computer. Follow the instruction
manual provided with the Starter Pack to operate the terminal program and to
connect the MFJ TNC to your computer. After connecting the MFJ TNC to
your computer you can then proceed to the "Computer Baud Rate" section in
this chapter to continue installing the MFJ TNC .

Computer Interface without MFJ Starter Pack
If you are not using a MFJ Starter Packs you should follow the instruction in
this chapter for computer interfacing.

Serial Port Signals
The serial port connector on your MFJ TNC is on the rear panel and is marked
"SERIAL." There are several signals available at this connector. You won't
need all of them for standard normal operation. For some special applications,
such as binary file transfers or some Bulletin Board operations, you may want
to use more of them. In that case, see MFJ TNC Serial Port Pin Functions
in this chapter.
The pins on the serial port connector of the MFJ TNC that must be connected
are shown in Table 2-1. Note that the MFJ TNC connects to a computer
exactly as if the MFJ TNC were a standard RS-232C modem. If you have
successfully used your computer with a telephone modem, hook it up to the

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MFJ TNC in the same way. Use whatever program you ordinarily use to
communicate with the modem.
The basic serial port signals reauired by the TNC for normal operation are
listed below in Table 2-1.

Pin
2
3
7

Signal Name
Transmit Data
Receive Data
Signal Ground

Description
Serial data from your computer to the MFJ TNC
Serial data from the MFJ TNC to your computer
The common ground for both data lines.

Table 2-1. Serial port signals required by MFJ TNC .

If your computer is listed below in Table 2-2, refer to the specific information
in the following sections to connect your MFJ TNC to your computer.

Manufacturer
Apple
Commodore

IBM
Radio Shack
Amiga
NEC

Model
Macintosh (tm)
Apple II,II+,IIe,II-gs(tm)
VIC-20 (tm)
C-64 (tm)
C-128 (tm)
PCjr, PC-XT, PC-AT, 386/486
most PC compatibles
Color Computer (tm)
PC Compatiables
500, 3000
8201

Table 2-2. Computers with specific serial interfacing instructions.

Many computers require a serial port adapter card. These cards incorporate the
circuitry necessary to add an RS-232C port to the computer. Some popular
models in this category are the Apple II series, the IBM Personal Computer,
many Radio Shack computers, and the Sanyo MBC-55X series. If you have one

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MFJ-1270C/1274C

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of these computers with an "add-in" serial port, or if you have another
computer we haven't mentioned, you should skip to one of the sections on
"other computers." If your computer has a 25-pin RS-232C serial port, refer to
the section on Other Computers with 25-pin RS-232C Ports. Otherwise refer to
the section Other Computers with Nonstandard Serial Ports.
Some computers have no serial port and no adapter is commercially available.
Such computers are not suitable for use with the MFJ TNC.

Computers with Specific Serial Interfaces
Apple Macintosh

The Macintosh serial port is an RS-422 compatible port, but it will work fine
with the RS-232C serial port on your MFJ TNC .
MFJ Enterprises, Inc. offers an optional Starter Pack for the Macintosh. It can
be purchased from MFJ Enterprises, Inc. or any MFJ dealer. The Starter Pack
includes an interface cable for connecting the MFJ TNC to the Macintosh and
a terminal program. The Starter Pack for Macintosh is MFJ-1287. If you wish
to use your own cable, you will need a cable wired as shown in Fig. 2-1.
Macintosh
8 pin
1 (HSKO)
2 (HSKI)
3 (TXD-)
4 (GND)
5 (RXD-)
6 (TXD+)
7 (GPi)
8 (RXD+)
Shield

MFJ TNC
DB-25P
4
5
2
7
3
N/C
8
7
1

Macintosh
DB-9P
1
5
9
3
7
6

MFJ TNC
DB-25P
1
2
3
7
8
4

Macintosh To MFJ TNC Cable Wiring
Fig. 2-1. Serial port wiring for Apple Macintosh.

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Note that pin 1 of the DP-9P connector is not connected inside the Macintosh
or the MFJ TNC . If you use a shielded serial cable, which we recommend,
connect both pin 1s to the shield and connect pin 1 of the MFJ TNC serial
connector to digital ground on the MFJ TNC circuit board. A printed circuit
board pad is provided for this purpose near pin 1 of the serial connector.

Commodore C64, C128 and VIC-20
The MFJ TNC has a built-in TTL-level port for interfacing with the
Commodore C64, C128 or the VIC-20 computers. You do not need a RS-232C
converter to interface with the MFJ TNC.
An optional Starter Pack for the C-64, C-128 or the VIC-20 can be purchased
from MFJ Enterprises, Inc. or from any MFJ dealer. The Starter Pack includes
an interface cable from the MFJ TNC TTL port to the user I/O port on the
Commodore computer. A terminal program is also included. To order, specify
MFJ-1282 for software on disk or MFJ-1283 for software on tape.
If you wish to construct your own cable, the information is as follows:
MFJ TNC
J-5 Pin#
1
2
3
4
5
6
7

Mnemonic

Name

RXD
DCD
GND
RTS
TXD
DSR
CTS

Receive Data
Data Carrier Detected
Ground(Frame & Signal)
Ready To Send
Transmit Data
Data Set Ready
Clear To Send

C-64/128*,
VIC-20 Pin#
B,C
H
N
E
M
L
K

Fig. 2-2A TTL port wiring for VIC-20, C64 and C128

*C-128 is used in the C-64 mode for these connections.
**Pin E is not needed when using terminal program
chapter for the Commodore computers.

referred

to in this

The pin connections for the TTL port (J-5) are numbered from left to right as
you look at the back of the MFJ TNC . All of these connections are not
necessarily used by your terminal program. The MFJ TNC needs RXD, TXD

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MFJ-1270C/1274C

COMPUTER INTERFACING

and GND connected. Programs which utilize file transfer and printer routines
will probably use RTS and CTS as well. Consult your software documentation.

IBM PCjr
The PCjr uses standard RS-232C voltage levels for its serial interface; however,
the connector used is non-standard and not readily available from electronic
supply dealers. Pinout information for this connector is given in the IBM PCjr
Technical Reference Manual.
IBM dealers sell the "IBM PCjr Adapter Cable for Serial Devices" for
converting the connector on PCjr to a standard RS-232C terminal connector.
This cable attaches directly between the MFJ TNC and the PCjr. It is only
about 3 inches long, however, so you may want to obtain a male-to- female RS232C extension cable, which should be readily available.

Radio Shack Color Computer
The Color Computer series (except for the Micro Color Computer) uses a 4-pin
DIN-style connector for its serial interface. Wire a cable as shown in Fig. 2-2
to interface your MFJ TNC to a Color Computer. All necessary parts should be
available from Radio Shack dealers.
Color Computer
4
2
3

DB-25P
2
3
7

Fig. 2-2
Serial port wiring for Radio Shack

Radio Shack Model 100/102 and NEC 8201
These computers have built-in standard RS-232C serial ports that are
compatible with the MFJ TNC . You will need a standard male-to-male RS232C extension cable to connect the computer to the MFJ TNC .

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IBM PC/XT/AT/386/486 and compatibles Computer
If your computer is a IBM or compatible, you should have a serial port with
standard DB-25 or DB-9 pin connector. You may used a standard IBM serial
modem cable with the correct gender on each end of the cable.

MFJ Enterprises, Inc. offers optional Starter Pack (MFJ- 1284) for the IBM or
compatible computers. The Starter Pack is supplied with the computer
connecting cable (DB-25 male to DB-25 female) for connecting your MFJ TNC
For other computers with a 25-pin RS-232C port, you should consult your
computer manual or accessory manual to see which pins it uses to send and
receive data on, as well as which pin is used for signal common. Follow the
computer manufacturer's recommendations for connecting the serial port to a
modem. You may also find the technical information in this section useful.
Your MFJ TNC is configured as Data Communications Equipment (DCE), the
technical term for an RS-232C modem. Most computers are configured as Data
Terminal Equipment (DTE). If this is the case for your computer, you will
probably be able to simply wire pin 2 of the MFJ TNC connector to pin 2 of
your computer's RS-232C port, pin 3 to pin 3 and pin 7 to pin 7. You can
provide these connections with a standard 3- wire male-to-female or male-tomale RS-232C extension cable, depending on whether your computer has a
DB25S or DB25P connector.
If your computer is configured as DCE, you will have to wire pin 2 of your MFJ
TNC to pin 3 of the computer connector, and pin 2 of the computer connector
to pin 3 of your MFJ TNC . Pin 7 of the computer connector will still connect
to pin 7 of your MFJ TNC serial port. Some computers may require that pin 5
of the computer serial port connector be connected to an appropriate signal.
Others may require connections for pin 8 and pin 20. You can use the
computer's output signals on pins 4 and 6 as shown in Fig. 2-3.

MFJ TNC
RS-232c
2
3
7

Computer
2
3
7

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4
5
6
8
20
Fig. 2-3. Serial port wiring with jumpers for auxiliary signals.

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Other Computers with Non-standard Serial Ports
Computers with non-standard serial ports must meet the following conditions.
First, the signal levels should be RS-232C compatible. The MFJ TNC requires
that the voltage levels sent from the computer be greater than about +3 volts in
one state and less than about +1 volt in the other state.
Second, the polarity of the signals must conform to the RS-232C standard.
This means that the low voltage state must correspond to a logical "1" and the
high voltage state to a logical "0".
Third, the computer must be able to correctly receive a signal which meets the
RS-232C specification. The MFJ TNC supplies signals that meet this
specification.
Make or buy a cable that provides the following connections. The computer
serial port common pin must be tied to the MFJ TNC serial port connector pin
7. The data line that sends data from the computer must be tied to the MFJ
TNC connector pin 2. The pin on which your computer receives data on must
be tied to the MFJ TNC connector pin 3.
If your computer requires any other signals, you must arrange to provide them.
The documentation provided with your computer or its accessory serial port
should clarify any special requirements of your port.

Terminal Software Requirements
Any software package that enables your computer to act as an ASCII terminal
with an ordinary telephone modem should work with your MFJ TNC. If you
have a program that you have used successfully with a telephone modem and
that you are familiar with, use that program to communicate with your MFJ
TNC.
If you are using a terminal program provided by the MFJ Starter Pack, proceed
to the "Computer Baud Rate" section in this chapter. Follow the instruction
provided by the program.
If you are not using a MFJ terminal program, then proceed with the instruction
for your type of computer.

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Note: Some terminal programs (such as the Apple II+ Super Serial Card)
requires DCD to be asserted before they receive any characters. If this is the
case, place a jumper across pin 1 and 2 of JMP 1. The DCD LED on the front
panel will function normally indicating received packets.

Apple Macintosh
The MFJ Starter Pack for the Macintosh (MFJ-1287) includes a terminal
program and a cable to connect the MFJ TNC to the Macintosh. If you should
want to use a terminal program such as MacTerm set the options according to
Table 2-3.

Compatibility
1200 baud
7 bits/character
even parity
Handshake Xon/Xoff
modem connection
"telephone" port

Terminal
VT100
ANSI
UNDERLINE
US
80 Columns
ON LINE AUTOREPEAT

Table 2-3. MacTerm option settings for operation with MFJ TNC

Apple II, II+, IIe, IIc
For the Apple II family of computers with Apple or third- party serial interface
cards, you may use ASCII Express Pro, Hayes Smartcom IIe and DataCapture
4.0 for the MFJ TNC . There are others which may be compatible with the
MFJ TNC , but have not been tested.

Commodore C64, C128 and VIC-20
The optional Starter Pack for the C-64, C-128 and VIC-20 can be purchased
from MFJ Enterprises, Inc. or from any MFJ dealer. Starter Pack includes an
interface cable from the MFJ TNC TTL port to the user I/O port on the
commodore computer. A terminal program is also included. To order, specify
MFJ-1282 for software on disk or MFJ-1283 for software on tape.

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If you do not have the MFJ Starter Pack then you may use the BASIC
communications program is given in the Programmer's Reference Guide
published by Commodore. Use the program listing for "true ASCII," as these
computers use a modified ASCII format internally. You will probably want to
run your MFJ TNC at 300 baud on the serial port with these computers.
NOTE:
When using the above program, you must first use the
"COMMODORE" key to shift to lower case before using this program. Also
line 200 should read For J=0 to 64:T%(J)=J:NEXT.
When making the connecting cable from TTL port of the MFJ TNC to the I/O
port of the Commodore computer you may use the wiring information given on
page 2-3 in this chapter. However, do not use pin E connection for this
program.

IBM PCjr
The IBM PCjr has a built-in terminal program in the BASIC cartridge. Start
this program by typing TERM. Refer to your PCjr BASIC manual for details
on this program. For best results with PCjr, do not run the MFJ TNC serial
port faster than 1200 baud.

IBM PC and Compatible Computers
The optional Starter Pack, MFJ-1284) for the IBM PC and compatibles
computers can be purchased from MFJ Enterprises, Inc. or from any MFJ
dealer. These Starter Packs include a graphics terminal program, and a
connecting cable for connecting the MFJ TNC to your computer. MFJ-1284
program allows you to receive 2-level FAX display on the screen. It will also
store the pictures on disk for later viewing.
You may also use many commercial, "shareware" and public- domain terminal
programs for the IBM PC and compatibles computers. Special program written
for packet radio and packet bulletin board service can also be used with the
MFJ TNC . Note that these type of programs will not support printing of
graphics to the computer screen.

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Radio Shack Color Computer
There are several terminal programs available for the Color Computer. You
will probably want to use a commercial program (rather than writing your own)
since the Color Computer has a "software UART" that is difficult to program in
BASIC.
Some of the terminal programs available are COLORCOM 64, AUTOTERM
and RICKEYTERM (for Coco III). Others are WIZ and XTERM for OS-9.

Radio Shack Model 100/102 and NEC 8201
These computers have built-in terminal programs in ROM.
computer's documentation for instructions in their use.

Consult your

MFJ TNC Serial Port Pin Functions
This section describes the pins used on the MFJ TNC RS-232C serial port
connector. It is intended for users with special applications requiring hardware
handshaking. This information should not be needed by most users.

Pin #
1
2
3
4
5
6
7
8
9
10

Mnemonic
FG
TXD
RXD
RTS
CTS
DSR
SG
DCD

Name
Frame Ground
Transmit Data
Receive Data
Request To Send
Clear To Send
Data Set Ready
Signal Ground
Data Carrier Detect
+ 12V unregulated reference
- 12V unregulated reference

Table 2-4. RS-232C Pin Designations

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Frame Ground is provided for attachment to the chassis of the MFJ TNC and
the chassis of the attached device (computer or terminal). This pin is brought
out to a feedthrough on the MFJ TNC PC board near pin 1 of the serial
connector. It is not electrically connected anywhere else on the MFJ TNC
circuit board.
Transmit Data is an input line to the MFJ TNC on which the attached device
sends data.
Receive Data is an output line from the MFJ TNC on which the attached
device receives data.
Request To Send is an input line to the MFJ TNC which the attached device
requesting clearance to transmit.
Clear To Send is an output from the MFJ TNC signaling the attached device
to send or refrain from sending data to the MFJ TNC . This line is used for
hardware flow control.
Data Set Ready is an output from the MFJ TNC telling the attached device
that the MFJ TNC is operational.
Signal Ground is the common, or return, path for all signals between the MFJ
TNC and the attached device.
Data Carrier Detect is an output from the MFJ TNC . As normally
configured, DCD reflects the status of the CON LED: It is true when an AX.25
connection exists between your MFJ TNC and another station; it is false when
no connection exists. This configuration is useful when the MFJ TNC is used
with a telephone style Bulletin Board system, since the AX.25 connection,
analogous to a modem signal on the telephone, indicates the presence of a user.
Shorting pin 1 and 2 of JMP1 on the MFJ TNC board will cause this output to
always be true.

Computer Baud Rate
Turn off the power to your computer and to your TNC. Connect the computer
and TNC with a properly configured serial cable. Set the DIP switch on the
rear panel of the TNC to the desired baud rate as shown in Table 2-4. The
power must be OFF when these switches are set.
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NOTE: The serial port baud rate used between the TNC and the computer has
no relationship to the baud rate used over the radio. The serial port baud rate
you set on your TNC must match the baud rate used by your computer serial
port.
Turn on your computer and start the terminal program. Follow the directions
for the program you are using to match the computer's baud rate with that
selected on the TNC, and to set other options. Set your computer's port options
to 7 bits even parity and select either 1 or 2 stop bits.
Turn on your TNC. You should see a sign-on message, which should be a
readable text message, printed on your computer screen. This demonstrates the
ability of your computer to accept data from your TNC. If you see nothing,
switch off your TNC for a few seconds, then on again. If you still see nothing,
verify your wiring and restart your terminal program. If you see gibberish on
your screen you should verify that you have set the same baud rate for the TNC
and the computer.

Verifying Serial Port Operation
Now that you have a terminal program and the hook-up cable for connecting
the MFJ TNC to your computer, you are ready to verify that MFJ TNC will
communicate with your computer.
1.

Turn on your computer. Load and run the terminal program.

2.

Set the parameter of the terminal program as follow:
word length: 8 bits
duplex: full
parity: none
stop bit: 1
baud rate: select on of the following:
300, 1200, 2400, 4800, 9600, 19,200

3. Locate the DIP switch in the back panel of the TNC. Set the Dip switch as
according to Table 2-4 follows:

Table 2-4. DIP switch settings for computer serial port baud rates.

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MFJ-1270C/1274C

Baud Rate
300*
1200
2400
4800
9600
19200*

COMPUTER INTERFACING

Dip Switch
1
ON
OFF
OFF
OFF
OFF
ON

2
OFF
ON
OFF
OFF
OFF
OFF

3
OFF
OFF
ON
OFF
OFF
OFF

4
OFF
OFF
OFF
ON
OFF
OFF

5
OFF
OFF
OFF
OFF
ON
OFF

CAUTION: Only one of these switches may be ON at any time.
*The MFJ TNC terminal baud rates of 300 and 19,200 is selected by a jumper
on JMP 18 on the mother board. For 300 baud set the shorting jumper to
position 2-3 and for 19,200 baud set the shorting jumper to position 1-2
(factory default).
4. After properly set the DIP switch on the back of the TNC, turn on your
MFJ TNC . Note that PWR, STA and CON LEDs will be lit.
5. If the MFJ TNC terminal parameters match your terminal program
parameter, the MFJ TNC will sign on and the STA and CON LEDs will
extinguish. If TNC failed to sign-on, verify that the terminal parameters and
the TNC computer baud rate is set correctly.
6. Upon signing on, the MFJ TNC will display the following sign-on
message on the computer screen:
*:J
bbRAM:LOAD WITH DEFAULTS
|A
MFJ ENTERPRISES, INC.
MODEL MFJ TNC
AX.25 LEVEL 2 VERSION 2.0
RELEASE XXXXX (date) - 32K RAM
CHECKSUM XXX
cmd:
After sign-on the STA and CON on the MFJ TNC will extinguish.

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If the sign-on message fails to appear, you should check the connecting cable
between and the computer and the MFJ TNC .
When you have successfully read the sign-on message from the MFJ TNC ,
type:
DISPLAY
followed by a carriage return. You should see a lengthy list of items on your
screen. This verifies the ability of the MFJ TNC to accept and respond to input
from your computer. Your serial interface is now working.

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RADIO INTERFACING

RADIO INTERFACING

Computer interfacing, covered in the previous chapter, is only half the
interfacing task. The other half is connecting your MFJ TNC to your radio.

MFJ TNC Radio Port
Interfacing the MFJ TNC to your radio involves connecting the following
signals at the TNC Radio Port as shown in Fig. 3-1.

Pin 1 Microphone audio, from the MFJ TNC to your transmitter.
Pin 2 Ground, audio and PTT common.
Pin 3 Push-to-talk, to allow the MFJ TNC to key your transmitter.
Pin 4 Receive audio, from your receiver to the MFJ TNC .
Pin 5 Squelch input (optional) to allow the MFJ TNC to detect activity on a
shared-mode channel.

Fig.3-1 TNC Radio Port Connector

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This chapter describes how to connect these signals between your MFJ TNC
and your radio and how to adjust the receive and transmit audio levels
appropriately. The interconnection should be planned so as to minimize pickup
of stray audio and RF noise by the lines. If possible, you should set up your
station with a monitor speaker and be able to operate on voice without
disconnecting the MFJ TNC .

Radio Port Connection
Use Fig. 3-2 to wire a microphone connector (not provided) to the 5 pin DIN
cable provided.
You may obtain the specific microphone connector pin designation for your
radio from the your radio's manual. Appendix A at the end of this Instruction
Manual lists pin assignments for some of the most popular radios. The
accuracy of this information is not guaranteed. You should verify this
information with your radio manual.

Fig. 3-2 Radio Port Cable with Connector
A 5-pin male DIN connector cable are provided with the MFJ TNC for wiring
to the microphone connector for your radio.
CHECK THIS CABLE WITH AN OHM METER TO IDENTIFY EACH
WIRE BEFORE WIRING IT TO THE MIC CONNECTOR THAT FITS
YOUR RADIO.

Handheld Radio Connection
Some HTs key the transmitter by drawing a small amount of current from the
microphone input pin (see Fig. 3-3 below). Radios with this type of special
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RADIO INTERFACING

keying circuit are ICOM-2AT (tm) and Yaesu FT-x09, FT-x3, FT-727 (tm) and
others.
Appendix A at the end of this instruction manual provided pin designation for
some of the radios. Also consult the instruction manual of your radio.
If your HT has this type of microphone input, you can wire the microphone like
the one shown in Fig. 3-3 or you can remove the cover of the MFJ TNC and
install a shorting jumper at JMP L. Installing JMP L will eliminating the need
of soldering "Cx" and "Rx" to the microphone cable. "Cx" and Rx" are
installed on the MFJ TNC mother board. Fig. 3-4 shows the location of JMP L
header. On the MFJ TNC mother board, the "Rx" resistor for radio port is
R140. If you find the your radio still would not key properly after installing
JMP L, it may be necessary for you to change the value of R140 to a smaller
value.
Be sure to remove JMP L when connecting the MFJ TNC to another type of
radio.

FIG. 3-3 HT Special Keying Circuit

FIG. 3-4 MFJ TNC JMP L Header Location

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RADIO INTERFACING

RADIO INTERFACING METHODS
The MFJ TNC was designed to allow hook-up without any modifications to the
radio or any signal level balancing devices in the cables. Two interfacing
methods are presented.

Method 1: Direct Connection to Microphone and Speaker
For Method 1, shown in Fig. 3-5, the MFJ TNC 's audio will be fed directly into
the microphone connector or similarly connected auxiliary jack, and the output
of the MFJ TNC will be adjusted to give a proper modulation level. The
receiver audio will be taken from an earphone plug or speaker jack and fed
directly to the MFJ TNC . A monitor speaker can be connected to the
SPEAKER jack of the MFJ TNC . This allows you to monitor the channel.

Fig. 3-5 Method One Interconnect.
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The transmit audio level for the radio port is factory preset at 250 mV p-p to be
compatible with the mic input of most radios. However, if the transmit audio
is too low or distorted, adjustment may be needed. Use the following procedure
to calibrate:
Transmit Audio Level Adjustment for Method I Interface
1. Connect your MFJ TNC and radio as shown in Fig. 3-5. Turn on the
MFJ TNC and computer and start your terminal program. Connect the radio
to a dummy load and listen to the transmission with another nearby radio.
2.

Enter the modem calibration procedure by typing
CALIBRA

and a carriage return. Press the K key on your keyboard to key the transmitter,
then tap the space bar until the higher of the two tones is heard. Pressing the K
key again will unkey the transmitter. After the transmitter has been keyed for a
few seconds, it will be shut off automatically by the transmit watch-dog circuit.
As you perform the adjustments below, you will have to periodically unkey then
re-key the transmitter by typing the K key. If you wish to defeat the watch-dog
timer, install a shorting jumper at JMP4.

3. With the MFJ TNC keying the transmitter and transmitting the higher
of the two tones, adjust the transmit audio level as follows. With a small
screwdriver, adjust trimpot located on the left side of them MFJ TNC while you
listen to the monitoring receiver. Turn the adjustment on the trimpot clockwise
(CW) until no increase in output level is heard at the monitoring receiver.
4. Rotate the adjustment on the trimpot counter-clockwise until the audio
signal on the monitoring receiver is reduced by half of the maximum level.
This can be estimated by ear or accurately by measuring the output voltage at
the transmitting audio pin of the radio port with an oscilloscope or A.C.
voltmeter.
5. Press the K key to return to receive mode and type Q to exit the
calibration routine. Be sure to remove JMP4 if you placed it to defeat the
watch-dog timer.
You have now set your transmitter deviation to
approximately the correct level.

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RADIO INTERFACING

If you notice a significant hum level in the monitored audio in Step 3, take
measures to remove it. This may require shielded wire (recommended in any
event) in your microphone audio circuit. If your transmitter has an adjustable
microphone gain control, try reducing the sensitivity of the transmitter
microphone circuit and increasing the signal level from the MFJ TNC to
minimize hum or other noise problems.

Setting the Receiver Audio Input Level
The modem in your MFJ TNC is equipped with an advanced phase coherence
type data carrier detector (DCD) with a sensitive tuning indicator. These can
be used in combination to set the correct receive audio level for the modem and
to optimize the DCD characteristics for the HF operation.

Method 2: Accessory Jack or Interface Box Connection
If your radio has an accessory jack with PTT, transmit audio, and receive audio
signals, the interface can be done through this jack (shown in Fig. 3-6).

Fig. 3-6 Accessory Jack Interface.

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RADIO INTERFACING

If your radio does not have an accessory jack and you don't wish to add a
connector to your radio, you may construct a separate external interface box.
This box will permit simultaneous connection of your MFJ TNC and a
microphone. A schematic of an external interface box is shown in Fig. 3-7.
An interface box similar to the one shown in Fig. 3-7 is available from MFJ
Enterprises, Inc. or from any MFJ dealers. Model No. is MFJ-1272B.
Regardless of whether you use an accessory jack or an external interface box,
you should use shielded wire for all signal carrying leads. The connector
types and pinouts will be determined by the connector jacks on your radio.

Fig. 3-7 External Interface Box
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MFJ-1270C/1274C MANUAL

RADIO INTERFACING

If you built the external interface box as in Fig.3-7, then follow this procedure
to adjust R(s).
1.

Install JMP J on the MFJ TNC PC board.

2. Temporarily solder a variable resistor in place of R(s) Fig. 3-7. The
maximum value of this resistor must be determined by experiment, but 500K
should handle most cases. Connect your MFJ TNC to the radio. Connect the
microphone to the radio, or to the interface box if one is being used. Connect
the radio to a dummy load and listen to the transmission with another nearby
radio. Adjust R(s) for proper modulation as follow:
Transmit Audio Level Adjustment for Interface Method II
1. Turn on the MFJ TNC and computer and start your terminal program.
Enter the modem calibration procedure by typing
CALIBRA
Press the K key to key the transmitter, then tap the space bar until the higher of
the two tones is heard. Pressing the K key again will unkey the transmitter.
After the transmitter has been keyed for a few seconds, it will be shut off
automatically by the transmit watch- dog circuit. As you perform the
adjustments below, you will have to periodically unkey then re-key the
transmitter by typing the K key. If you wish to defeat the watch-dog timer,
place a shorting jumper at JMP4.
2. With the MFJ TNC keying the transmitter and transmitting the higher of
the two tones, adjust the transmit audio level as follows.
3. Adjust R(s) the variable resistor installed for proper modulation level
(typically between 3.0 and 4.5 kHz deviation. for Amateur FM). If FM test
equipment is not available, adjust R(S) until the audio signal on the monitoring
receiver is reduced by half of the maximum level. This can be estimated by ear
or accurately determined by measuring the output voltage across the speaker
with an oscilloscope or A.C. voltmeter. If there is not adequate audio level
from the MFJ TNC to make adjustment of R(s), then you can increase the
output level of the MFJ TNC by the transmit audio control on the left side of
the TNC. The transmitting audio output of the radio port is factory set at 250
mV p-p.

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4. Press the K key to return to receive mode and type Q to exit the
calibration routine.
You have now set your transmitter deviation to
approximately the correct level. Remove JMP4 if you placed it in Step 4.
5. Carefully remove the variable resistor and measure its value. This is the
proper value of R(S) for your particular radio.
6. Select the nearest standard value fixed resistor (1/4 watt is fine) and
permanently install this resistor as R(S) in the interface circuit.
7. If you have access to FM test equipment, check to see that the modulation
level is still within the limits of 3 to 4.5 kHz deviation. If it is not, make a final
adjustment with the MFJ TNC transmit audio level control.
Receiver Audio Setting
The modem in your MFJ TNC is equipped with an advanced phase coherence
type data carrier detector (DCD) with a sensitive tuning indicator. These can
be used in combination to set the correct receive audio level for the modem and
to optimize the DCD characteristics for HF operation.
With your radio in the receive mode, open the squelch control so that a steady
hiss is heard on a speaker. Set the volume control to the minimum volume
position. The tuning indicator on the MFJ TNC should drift off to one side of
the display and become stationary. It may drift enough to disappear off the end
of the display. Slowly advance the audio output level with the volume control
until the tuning indicator "springs to life" and dances around a point near the
middle of the display. This is the absolute minimum audio level for marginal
copy. Continue to advance the volume control until there is approximately
twice as much audio present at the receiver output. This can be estimated by
ear or measured with an oscilloscope or A.C. voltmeter. This will be near the
correct amount of audio for NBFM operation. Levels higher than this will not
degrade the modem performance solong as the receiver audio amplifier is
capable of producing the chosen output level without distortion (clipping).
IMPORTANT NOTE: Harmonics Interference
If you experience interference from one of the harmonics of the crystal
oscillator in the MFJ TNC , trimmer capacitor, C47 (near the crystal) can be
adjusted to move the frequency of the harmonic.

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Monitor Speaker Connection
MFJ TNC has a built audio amplifier to provide audio for an external monitor
speaker. Monitor speaker such as the MFJ- 280 can be can be connected to the
SPEAKER jack on the MFJ TNC.
If wiring of a speaker plug is necessary, use a 3.5 mm (1/8") mono or stereo
plug for this connection. Wire the plug so that the tip of the plug is connected
to the speaker and the sleeve is connected to ground. The ring (if a stereo plug
is used) is not used.
The speaker jack on the MFJ TNC is for monitoring of received and
transmitted audio. It is also used to provide a signal to the operator when a
packet connection is made. A small audio amplifier is built in the MFJ TNC to
drive the external speaker. Volume of the monitor speaker can be adjusted by
using the "Monitor" control on the left side of the MFJ TNC . If the internal
amplifier of the MFJ TNC does not provide adequate volume you may use an
external audio amplifier.
You can disable received audio, transmitted audio or the packet connect tone
from the speaker monitor jack by cutting a trace between the pins of the
following jumpers. See Appendix G for the locations and functions of JMP
jumpers.
JMP X : Transmitting Audio
JMP Y : Receiving Audio
JMP Z : Packet Connect Tone.
For example, if you like to have the packet connect tone but do not wish to hear
the racket of packet, then you should disconnect JMP X to disable the
transmitted audio and disconnect JMP Y for received audio.

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BASIC OPERATION

GETTING STARTED
This chapter will guide you through the basic packet operation on your MFJ
TNC.

First Steps
1. Make sure that your computer is connected to the RS-232C port or the
TTL port on the MFJ TNC according of Chapter 2.
2. Make sure that your radios are connected to the MFJ TNC according to
Chapter 3.
3.

Turn on your computer. Load and run the terminal program.

4. Turn on the MFJ TNC. The MFJ TNC will sign on with "cmd:" prompt
sign.
*:J
bbRAM:LOADED WITH DEFAULTS
|A
MFJ ENTERPRISES, INC.
MODEL MFJ TNC
AX.25 Level 2 Version 2.0
Release XXXXX (date) - XX K RAM
Checksum XXX
cmd:

Note: The "|A" may display as a vertical-bar and any capital letter from "A"
through "J".
The first five lines are the sign-on message, which you will normally see only
when you power up the MFJ TNC . The Command Mode prompt cmd: will
appear when the MFJ TNC is in Command Mode and is ready to accept your
instructions. Before the MFJ TNC can be fully operational, some of the basic
parameters must be set.

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Basic Parameters Setup
With the MFJ TNC sign-on, you are now ready to start setting up the
parameters you will use. You may be satisfied with most of the defaults for
now, but a few parameters will have to be changed! Let's try entering your call
sign. Type:
cmd:MYCALL K5FLU
MYCALL was NOCALL
cmd:
Type the text, MYCALL K5FLU, following the command mode prompt. Of
course, you should substitute your own call sign for K5FLU. Don't forget the
 at the end of the line. Your call sign will be used by the MFJ TNC as its
"address." The MFJ TNC responds by telling you the previous value of the
MYCALL parameter, and gives you a new Command Mode prompt.
Note that commands are entered by inserted a carriage return  after each
command is typed. Note also that carriage return may also be marked as
 on some computer keyboards.
Now try typing just the command by itself:
cmd:MYCALL
MFJ TNC will respond with:
MYCALL

K5FLU

You can see the current value of most parameters by typing the command that
sets the parameter followed by just a . This verifies that the MFJ TNC
accepted your call sign.
The next section describes the commands you will use to configure the MFJ
TNC for proper text display for your particular computer. You may not use
these commands again unless you change computers or terminal programs.

Serial Port Configuration

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MFJ-1270C/1274C MANUAL

BASIC OPERATION

This section describes the commands you will use to set up the MFJ TNC to
work best with your computer.

Parity and Word Length
If you are using one of the optional starter packs by MFJ Enterprises, Inc. then
you should follow the instructions given by the terminal program
documentation with the starter pack. If you are not using the MFJ starter pack
then you should use the following instructions to set the parity and word length
for the MFJ TNC.
If messages from the MFJ TNC appear garbled, with incorrectly displayed
characters, you may need to change the MFJ TNC 's serial port parity and word
length. (We assume that you have set the baud rate correctly. See Chapter 2 if
the baud rate needs to be changed.) The MFJ TNC 's default value is 8 bits and
no parity. If your computer receives 8 bits as data, you may have to set space
parity, since text may otherwise be interpreted as graphics or other special
characters. To set 8 bits, no parity, use the following combination:
AWLEN 8
PARITY 0

(8-bit words)
(no parity bit)

For wordlength of 7 bits, even parity, set
AWLEN 7
PARITY 3

(7-bit words)
(even parity)

One of these combinations will satisfy most computers. You are more likely to
require a different setting if you have a terminal rather than a computer, or if
you have configured your terminal port for some special application.
If your computer requires odd parity, set PARITY 1. If your computer detects
framing errors, try setting
AWLEN 7
PARITY 0

(7-bit words)
(no parity bit)

for shorter characters. For longer characters, set:
AWLEN 8
(8-bit words)
PARITY 1 or PARITY 3

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Echos
You may see two characters on your screen for every character you type, for
example:
cmd:RREESSEETT
Your computer is echoing the characters you type, and the MFJ TNC is also
echoing them. In this case, set duplex to FULL on your terminal to stop the
terminal from echoing characters to your screen.

New Lines and Line Wrapping
If everything displayed appears to be double-spaced, your computer is adding
an extra linefeed () whenever it displays a carriage return (). Set
AUTOLF OFF to keep the MFJ TNC from also adding an . If you
change equipment you may have to set AUTOLF ON to restore the MFJ TNC
's automatic linefeeds.
The screen-width parameter is set by default to 80, the width of many CRT
displays. The MFJ TNC will send an extra  (or   if
AUTOLF is ON) when 80 characters have been displayed on a line. If your
computer does not automatically break long lines, you will need to set the
screen width to the width of your display. For example, for a computer using a
TV set for a display, you would set SCREENLN 40. If your computer does
automatically break long lines, you should set SCREENLN 0 to disable this
feature on the MFJ TNC. Otherwise, you will get two s when the line
wraps around.
A few computers will frequently lose the first characters of a line when several
lines are typed in rapid succession, for example, in the sign-on message. You
can give the computer more time between lines by setting NUCR ON (delay
after ), or NULF ON (delay after ). The delay is adjusted by
NULLS, which sets a number of character-times for the delay.
With the basic parameters set up which enable the MFJ TNC to be able to
communicate with your computer, we can now discuss some basic functions
and features of the MFJ TNC .

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Tuning Indicator (MFJ-1274C)
Your MFJ TNC is equipped with a tuning indicator which is sensitive,
very accurate and extremely useful not only for tuning to signals for optimum
reception but also for filter alignment and audio level indication.
The position of the tuning indicator LED is only meaningful for tuning a
signal under the following conditions:
1.

The station is transmitting data (both tones NOT just a single carrier).

2. The DCD LED is lit indicating that the signal is within the capture range
of the PLL demodulator.
3. There is sufficient audio output from the receiver for proper operation of
the demodulator.
Assuming that
tuning indicator
tuning indicator
which represent

the conditions above are met, tuning in a station with the
is quite simple. Just set the receiver frequency so that the
LED is centered in the display. Actually there are 2 LEDs
the center of the display. Either or both may be used.

PACKET OPERATION
VHF Packet
If you are not familiar with packet operation, then you can learn quite a bit
about it with the MFJ TNC without actually transmitting anything. For your
first experiments, the MFJ TNC will be "talking to itself," allowing you to
become familiar with it before you go on the air.
If you are already familiar with the packet operation, then you may not want to
perform this exercise. In this case go the other modes of operation in this
chapter.
Disconnect your radio from the MFJ TNC and turn off the MFJ TNC. Install
the digital loopback jumper, JMP10. The analog loopback jumper, JMP7,
should not be installed at the same time. Connect your computer to the MFJ

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TNC with your serial cable. Turn on the computer and start your terminal
program.
A Connecting and Disconnecting Exercise
Packet radio QSOs are started by a connect process, which sets up the
"handshaking" between the two stations that insures error-free
communications. QSOs are terminated by a disconnect process, which leaves
both stations free to start new QSOs. Packet QSOs can also make use of
digipeaters, other packet stations which can automatically relay packets from
one station to the other over a specified route.
To see how this works, you can have the MFJ TNC connect to itself. Since you
have set the MFJ TNC up for digital loop-back, it will receive all packets that
it sends. Try the following:
cmd:FULLDUP ON
cmd:CONNECT K5FLU
*** CONNECTED to K5FLU
replacing K5FLU with your own call sign. The MFJ TNC generates packets
initiating and confirming the connection. The packets aren't actually converted
to audio signals and transmitted over the radio, but they are otherwise just like
packets you will be transmitting later on.
The *** CONNECTED to message tells you that the connection was
successful. You should also notice that the CON LED has lit up and that you
do not see a new cmd: prompt on the next line. You are now in Converse
Mode, ready to start talking. Try it. Type your message, ending the line with a
.
Hello, there.
Hello, there.
The  causes your message to be put into a packet, or "packetized," and
transmitted. (We explain in the next chapter how you can use a different
character to send packets.) The underlined text is a message that the MFJ TNC
received in a packet and displayed. Whenever you are in Converse Mode anything you type will be assembled into a packet addressed to the station you are
talking to and transmitted. If there isn't a QSO (connection) in progress, the
packet will be sent to the address CQ.
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In the example above, the MFJ TNC entered Converse Mode automatically
after the connect took place. You can also command the MFJ TNC to move
back and forth between Command Mode and Converse Mode.
To return to Command Mode, you must enter a special character, Control-C
(abbreviated ), or else send a BREAK signal. "Control" characters
are usually entered by holding down a special control key and then typing
another key without releasing the control key. If your keyboard doesn't have a
key marked CTRL or something similar, consult the documentation for your
computer or terminal program to see how to enter control characters. A
BREAK signal is a special transmission (not an ASCII character) which your
computer may be able to produce.
NOTE: If  will cause your computer to do something to interfere
with packet operations, such as halting the terminal program, and you can't
send BREAK signals, you will have to change the character that returns you to
Command Mode. See the section on "Special Input Characters," below.
Now type a . The MFJ TNC doesn't echo the , but you
should immediately see a Command Mode prompt. To return to Converse
Mode, enter the command CONVERS:

cmd:CONVERS
Whatever I type in Converse Mode is transmitted.
Whatever I type in Converse Mode is transmitted.

cmd:
To terminate the QSO, you must end the connect by giving the DISCONNE
command. The MFJ TNC will transmit packets terminating the conversation
and notify you when the disconnect is complete:
cmd:DISCONNE
*** DISCONNECTED
An actual QSO might be terminated by the other station, of course. In that
case, you would see the *** DISCONNECTED message without having issued
the command.

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You have just performed the basic operations of any packet QSO. You
established a connection with the desired station to begin the QSO, sent and
received some messages, and disconnected from the station at the end of the
QSO.
Be sure to remove JMP10 after you complete this "Connecting and
Disconnecting Exercise".
Digipeating
You may wish to have a QSO with another packet station that is beyond your
direct radio range. If a third packet station is on the air and both you and the
station you want to talk to are in range of this third station, that station can
relay your packets. You set up the packet routing when you initiate the
connection. The MFJ TNC will then automatically include the routing
information in the packets it sends.
The diagram below shows an example situation in which digipeating is useful.
AD7I
/ \
N2WX _________/
\_________ K5FLU
You are station K5FLU, and you want to have a packet QSO with N2WX.
There is a mountain in the way and you are not in simplex range of each other.
However there is a station located on the ridge, AD7I, which is in range of both
you and N2WX.
You direct the MFJ TNC to set up a connection to N2WX using AD7I as an
intermediate digipeater as follows:
cmd:CONNECT N2WX VIA AD7I
You can specify a routing list of up to eight intermediate stations. For example,
consider a modification of the example above:
____
N2WX _________/
\_________ K5FLU
.
.
.
.

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KV7D . . . NK6K
AD7I has turned off his station, but you can contact N2WX by going around
the mountain through NK6K and KV7D. This time you issue the connect
command like this:
cmd: CONNECT N2WX VIA NK6K, KV7D
You specify the digipeaters in the order you would encounter them going from
your station to the station to which you wish to connect.
Your station can also act as a digipeater for other stations. This doesn't require
any special actions on your part -- the MFJ TNC will do everything
automatically. If your station is digipeating, you may occasionally notice your
transmitter keying during lulls in your own conversations.
Unsuccessful Connections
Sometimes you will initiate a connect sequence that can't be completed. The
station may not be on the air, or it may not be within range of your station.
You may have even mis- typed the other call sign. If the MFJ TNC does not
get a response to its first connect packet, it will try again. You can control the
number of attempts the MFJ TNC will make with the command RETRY. The
default number of retry attempts is 10. If the MFJ TNC doesn't get an answer
after this number of transmissions, it will give up and display the message
*** retry count exceeded
*** DISCONNECTED
The retry count is also used once the QSO has started. Each transmission sent
to the other station is "acknowledged," or ACKed by the other station, and vice
versa. The ACK means that the packet was received and that the CRC
checksum indicated that it was received without errors. This is the means by
which packet radio can ensure error-free communications. Sometimes a packet
won't be received correctly by the other station, either because of accidental
interference from another packet station (a collision), or because of other
channel noise. If the MFJ TNC doesn't get an ACK soon enough, it
retransmits the packet and increments the retry count. If the count set by
RETRY is exceeded, the MFJ TNC will automatically disconnect and display
the same message:

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*** retry count exceeded
*** DISCONNECTED
The automatic disconnect feature keeps a MFJ TNC from indefinitely
retransmitting a packet and tying up the channel under hopeless conditions.
For example, an intermediate digipeater might have been shut down, or the RF
channel might have deteriorated to the point of being unusable. The other
operator might have even turned off his station without disconnecting. If you
are operating under special conditions, such as a marginal HF channel, you can
set RETRY 0 to disable all automatic disconnects (the retry limit is never
reached).
Monitoring Channel Activity
In addition to displaying messages from the station you are connected to, the
MFJ TNC can allow you to monitor other packet activity on the channel. You
can "read the mail," displaying packets between other stations. The MFJ TNC
will also keep track of stations heard during a session. This section will
describe some of the monitor functions.

Monitoring is enabled or disabled by the MONITOR command. You can try
this out in digital loop-back mode while disconnected. Type:
cmd:MONITOR ON
cmd:CONVERS
This is a test packet.
K5FLU>CQ:This is a test packet.
Since you aren't connected to another station your packets are sent to the
address "CQ," i.e., anyone. The packet you sent was "heard" by the MFJ TNC
and displayed, along with the sending station and the destination.
If you also want to see any intermediate digipeater stations being used, you can
set MRPT ON. This feature would be useful if you later want to connect to one
of the stations you are monitoring and will need a digipeater route in order to
reach it. For example, you might see the following display:
WB6YMH>WD0ETZ,KV7B:Hello, Bill!

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This packet was sent from WB6YMH via KV7B to WD0ETZ.
If there are several digipeaters, or if the message lines are long, the display may
be difficult to read. You can put the address header on a separate line from the
text by setting HEADERLN ON:
WB6YMH>WD0ETZ,KV7B:
Hello, Bill!

Ordinarily, the MFJ TNC will stop displaying monitored packets if you
connect to another station, permitting you to converse without interruption. If
you want to monitor activity while connected to a packet station, set MCON
ON.
To display a list of stations heard since the last time your MFJ TNC was
powered up, type
cmd:MHEARD
AD7I
WA7GXD
N2WX
NK6K
KV7B*

The last several stations whose packets were heard by your MFJ TNC are
displayed. The entry "KV7B*" means that KV7B was heard digipeating a
packet rather than sending one of his own. You can clear the "heard log" with
the command MHCLEAR.
You can see the settings of the monitor parameters described above, as well as
several others, by typing DISPLAY MONITOR.

Your First Packet QSO
Although there are still a number of features you should be familiar with for
comfortable packet operation, you are probably eager to get on the air and try
out the MFJ TNC . Arrange to have another packet operator get on the air to
help you get started. Make sure that your friend will be close enough to ensure

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solid copy, with no FM "popcorn" noise. It's best if you can get an experienced
packet operator to help you get started. If you are both beginners, try to have
both stations in the same room and operate on low power or into dummy loads.
Remove the digital loopback jumper, JMP10. Connect your radio to the MFJ
TNC. Turn on your computer, the MFJ TNC, and your radio. Be sure you
have adjusted the MFJ TNC and radio according to one of the methods
described in Chapter 3. When the other station transmits, the DCD LED on
the MFJ TNC should glow steadily for the duration of the transmission. You
can work through the remainder of the examples in this chapter while you try
out the MFJ TNC on the air.

Starting the QSO
You are ready to initiate a connect. For the sake of example, we will continue
to use K5FLU in place of your call sign, and we will use WB0QRP for your
friend's call. Make sure you are in Command Mode, and type
cmd:CONNECT WB0QRP
After a moment you should see the message
*** CONNECTED to WB0QRP
and you will be in Converse Mode. Your friend will see the message
*** CONNECTED to K5FLU

and he will also be in Converse Mode. You have begun your first QSO.
If you have trouble connecting, make sure your microphone drive level is set
properly, as described in Chapter 3. It may be helpful to have an experienced
packet operator listen to your transmissions and monitor with his TNC. You
can also try the following procedure. Both you and your friend should set
MONITOR ON, enter Converse Mode and send some packets. Each station
should display packets sent by the other. If only one station is "hearing"
properly, you can concentrate on the modulator and transmitter of that station

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and the demodulator and receiver of the other station. You can try
experimenting with the TXDELAY timing parameter for the sending TNC.
Set TXDELAY 64 for a long delay. If this solves the problem, you can back
off to the smallest value that works consistently.
Exchange several messages to get a feel for this new mode. If you monitor the
radio transmit indicators and listen to the speaker audio from the two rigs, you
will have a better idea of what is happening. You radio will be inactive most of
the time, even while you are actually typing. When you get to the end of a line
and type a , your radio will be keyed briefly and your friend will hear a
"brrrraaaap" on his speaker. As your message is displayed on his computer, his
radio will be keyed for an even shorter time and you will hear a "brraap" on
your speaker. This is the ACK, or packet acknowledgment coming back. The
MFJ TNC takes note that the packet was received correctly, but nothing is
displayed on your screen.
Digipeating
Now that you are on the air, you and your friend can try out the MFJ TNC 's
digipeating capabilities. This is actually more interesting if you have at least
three stations participating, but you can get the feel for it with two stations.
Return to Command Mode and disconnect from the other station:

cmd:DISCONNE
*** DISCONNECTED
Now issue the following command.
cmd:CONNECT K5FLU VIA WB0QRP
As before, substitute your call for K5FLU and your friend's call for WB0QRP.
You are requesting a connect to yourself, as you did before in digital loop-back
mode, but this time you are using a sort of RF loop-back. You transmit packets
to your friend's TNC, which relays them back to you. When the connection is
established you will see
*** CONNECTED to K5FLU VIA WB0QRP

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and you will be in Converse Mode. Your friend won't see anything displayed
on his computer and his TNC's state won't be affected at all by your QSO. In
fact, your friend could issue this connect request,
cmd:CONNECT WB0QRP VIA K5FLU
and you can carry on two separate conversations completely independently.
Monitor the radio transmit indicators and listen to the speaker audio. See if
you can follow the packets and the acknowledgments back and forth.
Monitoring on the Air
This is a good time to try out the MFJ TNC 's monitor functions. While you
and your friend are separately connected, type

cmd:MONITOR ON
cmd:MCON ON
cmd:CONVERS
You will be able to see both your "conversation" and your friend's conversation.
Also try HEADERLN ON and MHEARD.

Special Input Characters
The MFJ TNC has a number of special characters that can be used to control
its actions. Many of these special characters can be used to "edit" commands
and packet text as they are entered. These features can all be customized to suit
you and your computer. Most of the special input characters we will describe
are active in both Command Mode and Converse Mode; the exceptions will be
noted.
The character used to return to Command Mode from Converse Mode is by
default a . (Sending a BREAK signal also works.) This character
does nothing in Command Mode, so if you accidentally enter it twice you won't
mess up the next command line. You can change the Command Mode entry
character with the command COMMAND. This is one of several commands
that set special character functions. You can choose any character for this

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function, by entering the ASCII character code for the key. For example, you
can use a  to enter Command Mode by setting
cmd:COMMAND 5
was
$03
The MFJ TNC displays the previous value in hex, and you can also enter
character codes in hex if you prefer. All of the special characters described
below can be changed in the same way as COMMAND.
We have already mentioned that you can erase mis-typed characters by typing
the  character. You can change this character with the
command DELETE. If you set DELETE ON, you can erase characters by
typing the  character; setting DELETE OFF returns to using
. You will probably want to use the same key that your
computer normally uses to rub out characters.  is more
commonly used than  by personal computers. If you aren't sure
whether your rubout key produces  or  characters,
you can try both settings of the DELETE command and see which works.
When you rub out a mis-typed character, the MFJ TNC will attempt to correct
the screen display. This will work for most computers as well as display-type
terminals. It won't work for hardcopy-type terminals or possibly with a few
computers. If your display doesn't look right after you rub out a character, try
setting BKONDEL OFF. The MFJ TNC will not try to correct the display but
will indicate the rubout with a "\" character (). You can
restore display correction by setting BKONDEL ON.
If you make several mistakes in a line, or if you change your mind, you may
want to cancel the whole line rather than rubbing out the characters one at a
time. You can cancel the line by typing . The MFJ TNC will
display a  followed by . If you are in Command Mode,
you will see a new prompt:

cmd:Hi, John, how are you?\
[You started typing text while in Command Mode.]
cmd:CONVERSE
Hi, John, how are you?
The cancel-line character can be changed to any ASCII character by the
command CANLINE.

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If you have changed your input by rubbing out and retyping characters, you
may want to see a "fresh" copy of your input, especially if you have set
BKONDEL OFF. The MFJ TNC will retype the line you are entering when
you type :

cmd:CONNECT KB7\\\WA7\

[You mis-typed the call sign.]
cmd:CONNECT WA7GXD
Here the user mis-typed the first three characters of the call sign and rubbed
them out. The MFJ TNC displayed "\" for each character rubbed out. The
user then retyped the characters correctly and redisplayed the line. He finished
typing the call sign on the new line. The redisplay-line character can be
changed to any ASCII character by the command REDISPLA.
If the MFJ TNC displays information faster than you can read it before it
scrolls off the screen, you can halt the display by typing . To resume
output from the MFJ TNC to your computer, enter . These
characters can be changed to any ASCII character by the commands STOP and
START, respectively.
You may occasionally want to include one of the special input characters in a
packet. For example, to send several lines at once in the same packet, you
would have to include  in the packet at the end of each line, bypassing its
"send-packet" function except at the actual end of the packet. You can include
any character in a packet including all special characters by prefixing it with
the pass character, . For example,
I wasn't at the meeting.
What happened?
Ordinarily, this message would be sent as two packets. By prefixing the first
 with , the operator sends it all at once, but maintains the
 in the text. The pass character can be changed to any ASCII character
by the command PASS.
We will discuss operation of packet in more detail in the next chapter. For now
let us discuss the operation of HF packet with the MFJ TNC.
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HF Packet Basic Operation
The requirements for optimum performance with a typical HF or OSCAR 10
path are very different compared to local VHF FM environment. Lower signal
to noise ratios require lower baud rates, noise spikes and fades require shorter
packet lengths, and a higher rate of false carrier detects lowers the total usable
dynamic range in the audio input. The MFJ TNC hardware and software are
configured to improve throughput in these environments. The MFJ TNC s
settings of MAXFRAME and PACLEN provide the possibility of several
continuous frames of long data length. For HF operation at 300 baud, we
recommend setting MAXFRAME to 1.
The MFJ TNC detects a busy channel by monitoring the lock- detect signal
from the demodulator. The presence of a lock- detect signal is indicated by the
Data Carrier Detect (DCD) LED. Each time DCD goes off the MFJ TNC will
start a DWAIT interval which must elapse before the channel is considered to
be available. On a noisy channel spurious lock-detect signals may be
generated. For HF and OSCAR operation you should set DWAIT to 0. The
random wait before retry transmissions can be disabled by setting TXDELAY
0 and using AXDELAY to set the required keyup delay. Of course, AXHANG
should be 0 for this application.
If you are operating a full-duplex radio station (simultaneous transmit and
receive) such as an OSCAR 10 station, you should set FULLDUP ON. The
MFJ TNC is always electrically capable of full duplex operation, but this
parameter causes the protocol to behave differently in acknowledging packets.
In addition, the MFJ TNC will ignore the state of the DCD line.
Although intuition tells you that lower baud rates will reduce the number of
packet retries, there is usually a small range between "too fast" and "too slow."
A slower packet takes longer to transmit and is therefore a larger target for
fades and static crashes. The entire packet must be received correctly in order
to be accepted. Data rates of 1200 baud have been used on both HF and
through OSCAR 10.
HF activity may generally be found on 7.093 or 14.107 MHz. Use LSB or USB
- it really doesn't matter (although most stations use LSB when referring to the
suppressed carrier frequency).

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Tune through a few packet signals. Tune slowly! You will find a point at
which the display becomes bright. As you continue tuning, you will see the
moving bar display slide across your tuning indicator. When one of the center
LEDs is illuminated, you are tuned in and you should be able to copy the
packets.
Each bar on the tuning indicator represents about 10 Hz. Thus, if a packet
comes through and you are 4 bars off, re- tune your transceiver 40 Hz in the
indicated direction. The direction depends on the sideband you selected and the
manner in which you have the tuning indicator oriented. One or two tries will
quickly tell you which way to go! Bars to the left of center indicate you should
tune higher, while the other side of center means to tune lower.
Many BBS station forward traffic on HF at the above frequencies. Call CQ a
couple KHz away from such channels. If you can't raise anyone, call CQ on
one of the above frequencies, but QSY immediately after establishing
contact! Be careful on 20 meters especially that you don't operate +/- 2KHz
around 14.100 MHz (you will cause interference to propagation beacons and
give packet a bad name...)

HF Packet Operation Hints:
1.
2.
3.
4.
5.

Try to keep all packets below 80 characters in length.
Set MAXFRAME to 1. This will minimize transmission time.
Avoid multiple connections and digipeated packet operation.
Qsy away from the standard calling frequencies as soon as possible.
Set FRACK to a sensible long value.

More detail on HF packet operation is discussed in the next chapter in this
instruction manual.

FAX OPERATION
The MFJ TNC is capable of receiving 2-level FAX. FAX receiving is possible
only if you are using an optional terminal progrom provided by the MFJ Starter

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Pack. The MFJ TNC supports only the Weather FAX mode (120 line per
minute) format.
If you are interested in FAX receiving and transmiting, we suggested that
contact MFJ Enterprises, Inc. to inquire about about the MFJ TNC muiltmode
data controller which is capable of receiving and transmitting up to 16 graylevel. MFJ also offers model MFJ-1214 for IBM and compatible PCs. It is
capable of transmit and receive 16-levels FAX and color FAX. It also supports
RTTY and CW modes.
MFJ Enterprises, Inc. offers terminal software for some computers to support
this operation. This software allows you to print FAX pictures to screen in near
real time and to save FAX pictures to disk. FAX pictures saved on disk can
be recalled for viewing on the screen at any time.
MFJ terminal programs which support 2-level FAX receiving operation are as
follows:
1.
2.
3.
4.

MFJ-1284 for IBM PC and compatibles in 5-1/4" disk.
MFJ-1284M same as above but in 3-1/2" disk.
MFJ-1287 for Apple Macintosh computer.
MFJ-1282 for Commodore C-64 and C-128 in 5-1/4"disk.

If you are using one of the above terminal programs which supports 2-level
FAX operation you should follow the instruction given by the terminal program
to receive FAX.

FAX FREQUENCY
FAX transmitting stations are usually found on the HF bands.Weather FAX
stations are generally upper sideband. Some of these stations maintain a
regular schedule. The following table lists the frequencies of some FAX
stations.

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FAX STATION FREQUENCIES

Service
Weather

Band
USB

Photographs

LSB

Frequency (KHz)
3,357.00 4,268.00 4,975.00 6,946.00
10,865.00 12,125.00 20,015
10,680.70 17,673.90 18,434.90,
20,738.00

Other FAX Frequencies
The following frequencies
Magazine:

were

obtained

from Popular Communication

FREQUENCIES(KHz, USB)

LOCATIONS

4,271.00
8,502.00
9,389.50
4,793.50
9,157.50
8,080.00
4,802.50
7,770.00
8,459.00
4,346.00
8,646.00

Halifax, Canada
Boston, MA
Brentwood, NY
Washington, DC
Mobile, AL
Norfolk, VA
Hawaii
Hawaii
Alaska
San Francisco, CA
San Diego, CA

9,890.00 13,510.00
12,750.00
11,035.00
10,185.00 12,201.00 14,671.50
17,447.50
10854.00 15,957.1 16,410.00
9,440.00 13,862.50
11,090.00 13,627.50
8,682.00 12,730.00 17,151.20
17,410.50

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ADVANCED PACKET OPERATION
This chapter describes some aspects of packet operation that you don't need to
be concerned with for everyday conversational operation. You will want to
consult this chapter if you are using your station for special applications such as
a Packet Personal Mailbox, Bulletin Board, binary file transfers, Packet picture
transfers or running a "host" program. This chapter also discuss use of the
newly developed packet anti-collision feature. HF and OSCAR packet
operation is also discuss in detail in this chapter.
We will use the term "computer" to refer to computers or terminals. In the
command examples, the MFJ TNC's prompts and other messages are shown in
ordinary type, your responses are shown in bold face, and received packets are
shown underlined. Commands and other special keywords are shown in upper
case; other text entered to the MFJ TNC is shown in upper and lower case.

Special Characters
The MFJ TNC recognizes a number of special characters for input editing,
flow control, and other control functions. You can change any of these special
characters to customize the MFJ TNC to suit your applications, your computer,
or your whim. Most of the characters are set by commands which specify the
ASCII character code for the desired character. You can disable any special
character feature by setting the character value to 0. Input editing characters
may be disabled with no serious effects. You should use caution in disabling
the flow-control or Command Mode entry characters. Also be careful not to set
two special characters to the same value.
Special characters are normally set to various control characters. Control
characters are entered by holding down a special control key while typing
another key. For example, control-C, or  is entered by holding
down the control key while typing C. If your computer doesn't have a special
control key, you will have to consult your computer's documentation to see how
to enter these characters. If you will have difficulty entering control characters,
you can change the special characters to, for example, seldom- used
punctuation.

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The action of each special character is described in detail under the entry in
Chapter 6 for the command that sets that character.
You can enter the code for a character in either hex (base 16) or decimal
notation. The MFJ TNC displays character codes in hex. A number in hex
notation is indicated by beginning the number with a $. The "digits" of a hex
number represent multiples of powers of 16. The values 10 through 15 are
represented by the letters A through F, which may be upper or lower case. For
example,
$1B = 1 x 16 + 11 = 27.
Tables of ASCII character codes are available in most computer manuals. A
table of ASCII codes for control characters follows.
Dec
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

Hex
$00
$01
$02
$03
$04
$05
$06
$07
$08
$09
$0A
$0B
$0C
$0D
$0E
$0F

Control

















Mnemonic
NUL
SOH
STX
ETX
EOT
ENQ
ACK
BEL
BS
HT
LF
VT
FF
CR
SO
SI

Dec
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
127

Hex
$10
$11
$12
$13
$14
$15
$16
$17
$18
$19
$1A
$1B
$1C
$1D
$1E
$1F
$7F

Control


















Mnemonic
DLE
DC1
DC2
DC3
DC4
NAK
SYN
ETB
CAN
EM
SUB
ESC
FS
GS
RS
US

Table 5-1. ASCII Codes for Control Characters.

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Packet Operating Modes
In Chapter 4 we discussed two of the packet operation modes, Command Mode
and Converse Mode. Packet also can operate in the third mode, Transparent
Mode which is a data-transfer mode like Converse Mode but is intended
primarily for computer data interchange rather than human conversation. We
describe all three of these modes below.

Command Mode
Command Mode is used to enter commands which alter the MFJ TNC's
operating parameters. The other modes are entered from Command Mode.
When the MFJ TNC is in Command Mode, the Command Mode prompt,
cmd:
is printed at the beginning of each input line. Note, however, that if the MFJ
TNC has received and displayed packets, the prompt may have scrolled off the
screen.
The MFJ TNC will be in Command Mode after a reset or power-up. After a
power-off, power-on sequence, all operating parameters of the MFJ TNC are
re-initialized to the parameter stored in battery backed-up RAM (bbRAM) by
the resident software. After the RESET command is issued all operating
parameters are reset to the default values stored in EPROM. The values of
most parameters are stored in a permanent but easily changed form in the
bbRAM memory.
The following commands set special characters which are active in Command
Mode. Refer to the discussions of these commands in Chapter 6 for details on
the operation of the characters in Command Mode. Also see the section on
special input characters in Chapter 4.
CANLINE
Cancel current line
CANPAC Cancel output (Command Mode function only)
DELETE Character deletion
PASS
Insert following special character
REDISPLA Re-display current line
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START, STOP
User's flow control characters (sent to MFJ TNC)
XOFF, XON MFJ TNC flow control characters (sent to terminal)
The following commands enable display features which are active in Command
Mode. Refer to the discussions of these commands in Chapter 6 for details on
the operation of these characters in Command Mode. Also see the section on
terminal configuration in Chapter 4.

AUTOLF
BKONDEL
ECHO
FLOW
LCOK
NUCR
NULF
NULLS
SCREENLN

Add  after  in data sent to terminal
Echo after character deletion
Automatic echo of serial port input
Type-in flow control
Lower case translation
Nulls after 
Nulls after 
Null count
Automatic  insertion

Entering Data-Transfer Modes
There are several ways to enter a data-transfer mode from Command Mode.
You can type the command CONVERS or K to enter Converse Mode or the
command TRANS or T to enter Transparent Mode, and the MFJ TNC will
immediately enter the specified mode. The MFJ TNC will automatically enter
a data-transfer mode if you are in Command Mode when a connection is
completed. You can specify the data-transfer mode for automatic entry with the
command CONMODE:
cmd:CONMODE TRANS
will specify Transparent Mode, and
cmd:CONMODE CONVERS
will return to the default choice of Converse Mode.
The timing of the automatic entry into data-transfer mode depends on whether
you or the other station initiated the connection. If you receive a connect
request which your MFJ TNC accepts, you will enter data-transfer mode when
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the MFJ TNC sends the connect acknowledgment (ACK) and types the
message *** CONNECTED TO .
If you initiate the connection with the CONNECT command, you can control
the timing of the mode change with the command NEWMODE. If
NEWMODE is OFF, the mode will change when the connect ACK is received
and the *** CONNECTED TO:  message is typed.
If
NEWMODE is ON, you will enter data- transfer mode immediately, without
waiting for a successful connection. Any text sent to the MFJ TNC at this
point will be queued up in packets which will wait for a successful connection
before being sent. If the connect attempt fails, you will be returned to
Command Mode. You will also be returned automatically to Command Mode
when either station disconnects and ends the QSO.

Converse Mode
The data mode used most often for ordinary QSOs is Converse Mode. In
Converse Mode, the information you type is assembled by the MFJ TNC into
packets and transmitted over the radio. The send-packet character causes the
input to be packetized for transmission. If you type a full packet- length of
characters without typing the send-packet character, your input will be
packetized and transmitted anyway.
The default send-packet character is , but you can specify any character
with the command SENDPAC. You may also choose to have the send-packet
character transmitted in the packet or not. If the send-packet character is
 it is natural to include it in the packet as part of the text as well as
interpreting it as a command. This is accomplished by setting CR ON. If you
use some other character to force packet transmission, you may want to set CR
OFF and inhibit transmission of the send-packet character. If you set the sendpacket character to something other than , you can cancel packets of
more than one line with the cancel-packet character, which is set with the
command CANPAC. Single-line packets can be canceled with either the
cancel-line character or the cancel-packet character.
To return to Command Mode from Converse Mode you must type the
Command Mode entry character, or send a BREAK signal over the serial port.
A BREAK is not a regular ASCII character, but it can frequently be transmitted
by typing a special key on the keyboard.

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A BREAK signal is a continuous space (or 0) signal on the serial port Transmit
Data line lasting approximately 0.2 second. In fact, the timing of the signal is
not very important, and most serial ports will recognize a BREAK if the space
signal lasts significantly longer than the time required for a character
transmission. Because of the simple nature of this signal, it is easily possible to
generate a BREAK with circuitry external to the computer, thus guaranteeing
entry to Command Mode in automatic station operation.
The following commands set special characters which are active in Converse
Mode. Refer to the discussions of these commands for details on the operation
of the characters in Converse Mode.
CANLINE
CANPAC
COMMAND
DELETE
MFILTER
PASS
REDISPLA
SENDPAC
START, STOP
XOFF, XON
terminal)

cancel current line
cancel current packet
Command Mode entry
character deletion
characters to be filtered in monitored packets
insert following special character
re-display current line
send current packet
user's flow control characters (sent to MFJ TNC)
MFJ TNC flow control characters (sent to to

The following commands enable display features which are active in Converse
Mode. Refer to the discussions of these commands for details on the operation
of these characters in Converse Mode.
8BITCONV
Retain high-order bit from serial port in converse
mode
AUTOLF
Add  after 
BKONDEL
Echo after character deletion
ECHO
Automatic echo of serial input
ESCAPE
 translation
FLOW
Type-in flow control
LCOK
Lower case translation
NUCR
Null characters after 
NULF
Null characters after 
NULLS Null count
SCREENLN
Automatic  insertion

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Transparent Mode
Packet radio is very well suited to the transfer of data between computers. In
some cases Converse Mode will work well for computer data transfer.
However, files such as a .CMD file on a CP/M system, a BASIC program, or
even a word-processor text file, may contain characters which conflict with special characters in Converse Mode. Some of these files may utilize all eight bits
of each byte rather than the seven bits required by ASCII codes. If you transfer
such files you will have to use Transparent Mode.
Transparent Mode is a data-transfer mode like Converse Mode. In this mode
there are no special characters, everything you type (or everything your computer sends to the MFJ TNC) is sent over the radio exactly as it was received by
the MFJ TNC. There are no input editing features and there is no send-packet
character. Packets are sent at regular time intervals or when a full packet of
information is ready. The time interval at which data is packetized is set by the
PACTIME command.
The display characteristics of the MFJ TNC are also modified in Transparent
Mode. Data is sent to the computer exactly as it is received over the radio,
including all 8 bits of each byte received. Features such as auto-linefeed
insertion and screen wrap are disabled, and echoing of input characters is
disabled. The parameters that control these features in Command Mode and
Converse Mode are not changed by entering Transparent Mode, and all display
features are re-enabled when the MFJ TNC is returned to Command Mode.
Most of the link status messages that appear as the MFJ TNC moves between
disconnected and connected states are also disabled in Transparent Mode.
In order to permit the Command Mode entry character to be transmitted freely
in Transparent Mode, the escape to Command Mode from Transparent Mode
has been made a little more complicated. You can still return to Command
mode by transmitting a BREAK signal, just as in Converse Mode. You can
also utilize the Command Mode entry character in the following way.
You must wait for a time period after typing the last character to be sent. This
time is set by the command CMDTIME. Following this wait, you must type
three Command Mode entry characters (default ) within an interval
CMDTIME of each other. After a final CMDTIME interval in which no
characters are typed, you will see the

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cmd:
prompt. If any characters are typed during this interval (even Command Mode
entry characters) the escape will be aborted and all the Command Mode entry
characters that have been typed will be sent as packet data. If you set
CMDTIME to zero you will not be able to escape from Transparent Mode
using this second procedure.

Flow Control
Whenever data is transferred to computers (home computers or TNCs), there is
a chance that the data will be received faster than the computer can handle it.
Some programs try to deal with this by providing data buffers for storing
incoming data until the program is ready for it. However, this merely
postpones the problem, since there is a limited amount of room in any buffer.
In order to prevent loss of data the computer must be able to make whatever is
sending data stop sending, and later tell it to resume sending. If you are a home
computer user, you are probably already familiar with one type of flow control,
which allows you to stop the output from the computer while you read it and
restart it when you are ready for more.
The MFJ TNC's input buffer may fill up in Command Mode if you try to type
too long a command. In Converse Mode the buffer may fill up for any of
several reasons: you may be using a faster serial port baud rate than the radio
data rate; radio data transmission may have slowed down because of noise or
other users on the channel; the person or computer at the other end may have
stopped output from that TNC. The MFJ TNC will signal the computer to stop
sending data when there is room remaining for about 80 characters in the
buffer. When the buffer fills up entirely, data will be lost. When the buffer
empties so that there is room for at least 270 characters, the MFJ TNC will
signal the computer to start sending data again.
A computer file transfer program may be unable to process data fast enough to
keep up with output from the MFJ TNC. In order to be sure of reading every
character, a computer must respond to interrupts from its I/O devices. Some
simple programs may poll the input register for new data. If the polling is not
done often enough, data may be lost. Some computers disable interrupts during
disk accesses. If the program enters a routine which will not allow it to check
for data or respond to it, it should signal the MFJ TNC to stop sending data.

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There are two methods of providing flow control which are supported by the
MFJ TNC. XON/XOFF flow control, sometimes called "software flow
control," is accomplished by sending a special character (usually ) to
request that the output stop and another special character (usually )
to restart output. Hardware flow control may be used if both computers use the
C,ear To Send (CTS) and Data Terminal Ready (DTR) lines of the RS-232C
standard. Data is also halted if you press the space bar while in command
mode. Press  to resume.
Some commonly used terminal programs and file transfer programs for home
computers do not implement flow control in software, and many serial ports do
not support hardware flow control. Although the DTR and CTS lines appear at
the connector, they may not be used on some computers unless the software
reads the state of the CTS line. If you find that the MFJ TNC seems to lose
data during file transfers, you should immediately suspect a flow control
problem.

XON/XOFF Flow Control
If you are using a terminal (rather than a computer) or if your computer does
not support DTR/CTS flow control, you should use XON/XOFF flow control,
which is enabled by setting XFLOW ON. The special flow control characters
are set to  and  by default, but they may be changed.
The commands XON and XOFF set the characters which will be sent to the
terminal by the MFJ TNC, and the commands START and STOP set the
characters to be sent to the MFJ TNC by the terminal. Your computer may
receive as many as 4 characters from the MFJ TNC after sending a STOP
character, since some characters may already be "in route" through serial I/O
chips.
If you send a STOP (START) character to the MFJ TNC when it is already
stopped (started), the character will be ignored. If the STOP and START
character are the same character, this character will "toggle" the output, turning
it off if it is on, and on if it is off.
You can disable XON/XOFF flow control in one direction only by setting the
appropriate flow control characters to 0. If you do this, the MFJ TNC will
automatically use CTS flow control to stop input from the terminal.
XON/XOFF flow control is normally disabled in Transparent Mode, since all

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characters are treated as data. If you cannot use DTR/CTS flow control, you
may enable the XON and XOFF characters (the commands from the MFJ TNC
to the terminal) by setting TXFLOW ON and XFLOW ON. The START and
STOP characters (the commands to the MFJ TNC from the terminal) can be
enabled in Transparent Mode by setting TRFLOW ON. Note that the mode is
no longer truly transparent when these features are enabled.

Hardware Flow Control
Hardware flow control is less likely to depend on the programming of a particular communications program. DTR and CTS are normally used for flow
control signals in Transparent Mode. The command XFLOW OFF enables
hardware flow control in Converse Mode and Command Mode. Your computer
may receive as many as 2 characters after it signals the MFJ TNC to stop
sending, since some characters may already be "in route" through serial I/O
chips. Refer to Chapter 7, Hardware for details on the interface required for
hardware flow control.

Type-in Flow Control
Type-in flow control, enabled with the command FLOW, is really a display
feature. It can keep the MFJ TNC from interrupting you with incoming
packets when you are in the middle of typing a command line or an outgoing
packet. As soon as you type the first character of a line, the MFJ TNC will put
a "hold" on all output (except for echoing your input). The "hold" remains
ineffect until you type a  to end the command line, or a send-packet
character to mark the end of a packet, or until you erase or re-display the line
you have started.
Some computers have difficulty simultaneously sending and receiving
characters over the serial port. This is most commonly the case for computers
with "software UARTs." Type-in flow control will improve the operation of
such computers with the MFJ TNC.

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Detail VHF Packet Operation
The previous chapter's discussion of "Basic Operation" contains enough
information for most packet operation. This section describes a few other
aspects of packet operation.

Station Identification
Your station identification (call sign) is set with the command MYCALL, as
described in the previous chapter. If you will have more than one station on the
air operating with the same call sign, they must be distinguished -- no two
stations can have identical station identifications, or the packet protocol will
fail. You can distinguish additional stations by setting the "secondary station
ID", or SSID. This is a number from 0 to 15, appended to the call sign with a
dash:
cmd:MYCALL W3IWI-3
If you don't specify the SSID extension, it will be 0, and the MFJ TNC won't
explicitly show SSIDs that are 0. If you want to connect to a station with a
SSID other than 0, or use such a station as a digipeater, you must specify the
SSID:

cmd:CONNECT AD7I-2
or
cmd:CONNECT WA7GXD VIA N7CL-5
The MFJ TNC can send an automatic identification packet every 9-1/2 minutes
when your station is operating as a digipeater. You can enable this feature with
the command HID ON. An ID packet is displayed as follows by a monitoring
station:
W3IWI-3>ID:W3IWI/R
You can request a final identification as you take your station off the air with
the command ID. The MFJ TNC will only send identification packets if it has
been digipeating.

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Automatic Operations
Normally, any packet station can be used by other stations for relaying, or
digipeating, packets to a more remote destination. If you don't want your
station digipeating packets, you can give the command DIGIPEAT OFF.
Unless there are special circumstances, such as a station operating on
emergency power, most packet operators set DIGIPEAT ON in the spirit of
Amateur cooperation.
Your station will normally accept a connect request from another station if it
isn't already connected. You can disable this capability by setting CONOK
OFF. If you receive a connect request when CONOK is OFF, the MFJ TNC
will display the message
*** connect request: 
and send a "busy signal" rejection packet to the other station. If you receive a
rejection packet from a station you try to connect to, your MFJ TNC will
display
***  busy
*** DISCONNECTED
If you want to have a special message sent automatically to stations connecting
to you, you can specify the message with the command CTEXT. This message
can consist of any text string up to 120 characters, and you may include s
by prefixing them with the pass character:
cmd:CTEXT Sorry, I can't talk right now.
I'll be on the air again after 8 PM.
Joe
In order for this message to be sent to stations connecting to you, you must set
CONOK ON so that the connection takes place (default), and enables the
automatic message with CMSG ON.
If you want to leave your station on but inhibit transmitting, you can set
XMITOK OFF. If you do this, you would normally set CONOK OFF as well.
You can have your station periodically send an automatic message by enabling
"beacons." A beacon can be used to make general-interest announcements,

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provide packets for other stations to use to test their ability to receive, or
announce the presence of a bulletin-board operation. The beacon message is set
with the command BTEXT, which works the same way as the CTEXT
command. You enable beacon transmission and set the frequency at which
beacons are sent with the command BEACON. To transmit the beacon at 10second intervals, for example, give the command
cmd:BEACON EVERY 1
The beacon function also has a transmit-after mode, enabled by using the
keyword AFTER in place of EVERY, in which a beacon packet is only
transmitted after activity is heard on the channel. This feature might be used to
leave an announcement for other packet users. If someone transmits on an
otherwise idle channel, a beacon can be sent a short time later. No beacons are
sent in this mode if there is a lot of packet activity on the channel, since the
required period of quiet will not occur.

Unattended Operations
Individuals who want to leave their MFJ TNC on overnight can monitor
packets even with the terminal or computer off. Just type CTRL-S then turn
the terminal or computer off. The next morning turn the computer on, then
type CTRL-Q. The MFJ TNC will dump everything monitored during the
night limited only by the amount of available RAM.
The MFJ TNC can operate unattended for extended periods of time. If you
would like to have the MFJ TNC operate as a digipeater but not connect with a
station, be sure to set DIGIPEAT ON and CONOK OFF. This is probably
most useful when setting up a dedicated digipeater in a remote location.

Packet Formatting
The maximum length of a packet is determined by the command PACLEN. If
you type more than the maximum number of characters without entering a
send-packet character, the MFJ TNC will transmit a maximum-length packet.
In Transparent Mode, a packet will be sent if the maximum number of
characters is entered before the delay conditions set by PACTIME force a
packet to be sent. Some MFJ TNCs may not be able to accept packets longer
than 128 characters.

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If you have set the send-packet character to , you probably want the
 to be included in the packet for display at the other end. If you set the
send-packet character to a special non-printing character, you probably want
the character to be treated as a command only. The command CR controls
whether the send-packet character is to be echoed and included in the packet.
You can add a  after each  included in your packets by setting
LFADD ON. If the other station reports that lines are overprinted on his
display, and he can't remedy the situation at his end, you can enable this
function.

Commands Affecting Protocol This section describes some of the commands
that affect the operation of the packet protocol. Details of the protocol are
given in Chapter 9.
The MFJ TNC implements AX.25 Level 2 protocol, a set of rules for
formatting messages to other TNCs. The version of AX.25 Level 2 protocol
used by the MFJ TNC can be set to Version 2.0 with the command AX25L2V2
ON, or to Version 1.0 with the command AX25L2V2 OFF. Digipeating may
not be successful if some MFJ TNCs are running Version 1.0 and some are
running Version 2.0. In addition, the command CHECK controls a timing
function that depends on the protocol version selected.
You can specify the "address" to be used for unconnected packets, as well as
intermediate digipeaters with the UNPROTO command. The format is similar
to that of the CONNECT command:
cmd:UNPROTO QST VIA NK6K
The default address for unconnected packets is CQ.
The following functions may be useful for tracking down protocol problems.
They are seldom useful for ordinary packet operations. The error-checking
function of the protocol is disabled for monitored packets with the command
PASSALL. If you set PASSALL ON, any "packet" will be displayed if it
meets the following conditions: It must start with a flag sequence; and it must
contain an integral number of 8-bit bytes. The TRACE command enables the
display of the address and control fields of packets, as well as the text. The
trace function displays all bytes in hex as well as ASCII equivalents.

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Packet Timing Functions
Transmit Timing
Amateur radio equipment varies greatly in the time delays required in
switching from receive to transmit and from transmit to receive. If the MFJ
TNC starts sending data before the transmitter is operating or before the
receiver has had time to switch from transmitting and lock up on the incoming
signal, the packet will not be received properly. The delay between transmitter
keyup and the beginning of data transmission is controlled by the command
TXDELAY. During the time the MFJ TNC is keying the transmitter but not
sending data, it will transmit a synchronizing signal (flags).
If you are transmitting packets through an audio repeater, you may require a
considerably greater keyup delay than is required for direct communications.
Furthermore, the extra keyup delay is not required if the repeater has not had
time to "drop" since the last transmission. The command AXDELAY allows
you to specify an additional keyup delay to allow the repeater receiver and
transmitter to lock up. The command AXHANG sets the time the MFJ TNC
will assume is required for the repeater to drop. If the MFJ TNC has detected
channel activity recently enough that the repeater transmitter should still be on,
it will wait only the TXDELAY time before sending data, rather than adding
an AXDELAY time as well.
The commands TXDELAY, AXDELAY, and AXHANG all set times in units
of 10 ms. If AXDELAY is in effect the total keyup delay will be
Keyup delay = (TXDELAY + AXDELAY) * 10
in milliseconds. If channel activity has been heard more recently than
AXHANG*10 ms ago, the keyup delay will only be
Keyup delay = TXDELAY*10
in milliseconds.

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Packet Timing
The AX.25 protocol provides for re-transmitting packets if no acknowledgment
is heard from the intended destination station within a certain period of time.
A packet might not be acknowledged due to channel noise or "collision" with
another packet transmission, and since there may be other stations on the
channel, the receiving station may not be able to acknowledge the received
packet immediately. The time lapse before the originating station re-transmits
the packet is set by the command FRACK (frame acknowledge time). The
maximum number of re-transmissions before the originating station terminates
the connection is set by the command RETRY. The maximum number of
transmissions of a packet is RETRY+1, since the initial transmission does not
count as a re-transmission. Setting RETRY to 0 specifies an infinite number
of retries.
The frame-acknowledge time is automatically corrected for the additional time
required for digipeating. The time interval before MFJ TNC re-transmits an
unacknowledged packet is
Retry interval = FRACK * (2*n + 1)
in seconds, where n is the number of digipeaters in use for this connection.
Acknowledgments of digipeated packets are made from end to end, and
digipeaters do not acknowledge the packets they relay. If there are several
intermediate relays, the chance of either the original packet or the
acknowledgment to be lost increases drastically. To reduce this problem, an
automatic wait time can be imposed on any station not transmitting a
digipeated packet. Stations waiting for a clear channel to transmit packets wait
for this time interval after the channel clears before transmitting. This wait
does not apply if the station will be transmitting one or more digipeated packets. This usually gives the digipeater a clear chance at the channel.
The wait time is set by the command DWAIT, which specifies 40 ms intervals.
If no digipeating is being done by anyone in the local area, this parameter can
be set to 0, but in any event it should be set to the same value by all members of
a local packet group.
In order to avoid unnecessary packet retries, the MFJ TNC implements a
collision-avoidance strategy which applies to all packets except those being
digipeated. On the second and subsequent transmissions of a particular packet,

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the MFJ TNC waits an additional random time after detecting a clear channel
before beginning transmission.
This prevents repeated collisions of
transmissions by the same two stations. The random time is a multiple (0-15)
of the TXDELAY time.
The interval, in milliseconds, between the MFJ TNC detecting carrier-drop
and beginning to transmit is
Wait time = DWAIT * 10
for the first transmission of a packet. For subsequent transmissions of the same
packet the interval is
Wait time = DWAIT * 10 + ( r * TXDELAY ) * 10
where r is a random number from 0 to 15. Thus, if your MFJ TNC is forced to
re-transmit packets, you will occasionally hear a fairly long delay before
transmission begins.
Multiple packets may be transmitted before waiting for an acknowledgment.
This permits more efficient channel use when large amounts of data are being
transferred. The maximum number of packets which the MFJ TNC will send
before waiting for acknowledgment is specified by the command MAXFRAME. This does not mean that t(e MFJ TNC will wait until several
packets have been entered before transmitting. MAXFRAME in combination
with the command PACLEN, which sets the maximum number of characters
in a packet, determines how much information can be sent in a single
transmission. The best combination for efficient data transfer is determined
partly by the channel quality and partly by the rate at which the terminal can
process data. For a 1200 baud terminal data rate, you should start with a
combination that produces about 300 characters outstanding at one time.

Radio Baud Rate
The radio data transmission rate is selectable for 300 baud and 1200 baud.
High speed modem such as the MFJ-2400 and MFJ-9600 modem, if installed,
can also be selected with the dip switch on the back of the TNC.
Note that there is no relationship between terminal baud rate and radio baud
rate. In order to communicate with another packet station you must use the

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same radio baud rates. The length of time required to send a given amount of
information increases as the baud rate decreases. For example, it takes four
times as long to send data at 300 baud as at 1200 baud. If you use slow radio
baud rates, you should limit the length of transmissions by setting
MAXFRAME to 1 and choosing PACLEN so that the hardware watchdog
timer does not disrupt your transmissions and channel traffic is broken up
frequently.
The Bell-202 compatible modem is optimized for a 1200 baud radio data rate.
The on-board modem is not useful at rates higher than 1200 baud. The MFJ
TNC can provide data signals up to 9600 baud, but an external modem is
required for operation above 1200 baud. Optional 2400 bps PSK and 9600 baud
modem boards are available from MFJ Enterprises, Inc. These high speed
modem boards can be installed inside the MFJ TNC. When an optional modem
board is installed and when it is in selected to operate the TURBO LED on the
front panel of the MFJ TNC will light. Contact MFJ Enterprises, Inc. for more
detail. For installation of an external modem, see APPENDIX F in this
manual for more details.
Special Protocol Times
You can set up a connection time-out with the command CHECK, which
specifies a time in multiples of 10-second intervals. This function prevents the
MFJ TNC from getting stuck in a connection when the other station disappears
for longer than the specified time. The MFJ TNC uses this time somewhat differently depending on the setting of AX25L2V2.
The command RESPTIME sets a delay between the receipt of a packet and the
transmission of the acknowledgment packet. This delay is used to prevent
collisions between an acknowledgment and another packet from the sending
station. This is primarily necessary during file transfers; otherwise the delay is
best set to 0. During file transfers the stations receiving the file should set
RESPTIME to 10 or 12 (default).
The timing of packet transmission in Transparent Mode is determined by the
command PACTIME. You can choose the way packet transmission is timed.
If you are typing input to a remote computer it is usually best to have packets
transmitted at regular intervals. If your computer is operating a remote-host or
bulletin board program you should send packets after an interval with no
further input from the computer. You can enable the use of PACTIME in
Converse Mode with the command CPACTIME.

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Monitor Functions
The MFJ TNC's protocol is designed for setting up "circuits" between two
stations. However it can also operate in a mode more suitable for a "net" or
"round-table" discussion with several participants, although reliable reception
of all transmissions by every station cannot be guaranteed. This is done by
enabling the monitor functions. Most of the monitor functions are described in
Chapter 4.
Monitoring is enabled by the command MONITOR ON, and separate monitor
functions are individually enabled.
If connected packet QSOs are taking place on the frequency of your group
conversation, you may wish to ignore all connected packets while your group
operates in unconnected mode. The command MALL OFF causes the MFJ
TNC to ignore connected packets.
If you want to be able to monitor packet activity when your station is not
connected, but have all monitoring automatically cease when you connect to
someone, set MCON OFF.
If you want to monitor stations selectively, you can set up a list of up to eight
callsigns with the command LCALLS. The callsigns in this list are regarded
as "buddies," i.e., the only stations you want to listen to if BUDLIST is ON.
Otherwise, the stations in the list will be ignored, and all other stations will be
monitored.
You can operate a group conversation with some data integrity by having the
stations connect in pairs and setting MALL ON and MCON ON. This does
not insure that every packet is received at every station, but it does insure that a
packet involved in a collision will be retried. If you have an odd number of
stations participating in this sort of conversation, one station can connect to
himself via another station as digipeater.
or example, WB6YMH, WD0ETZ, WA0TTW, W1BEL, and K9NG wish to
carry on a group conversation. In order to make all the transmissions as
reliable as possible, the following connections are made.
WB6YMH connects to W1BEL
WA0TTW connects to K9NG
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WD0ETZ connects to WD0ETZ via W1BEL
If each station specifies MCON ON and MALL ON, each station will see the
packets sent by all the others.
Ordinarily, only text packets are displayed. If you want to see some of the
protocol packets, you can set MCOM ON and connect, disconnect, disconnect
acknowledgments, and DM (connect-request rejection) packets will be
displayed. For example,
WB9FLW>N7CL 
KV7B>N2WX 
indicate connect and disconnect packets. Disconnect acknowledgments are
designated , and DM packets are .
You can cause the MFJ TNC to "filter" certain characters from monitored
packets with the command MFILTER. This allows you to remove, for
example, form-feeds, bell characters, or extra s that may be necessary to
the stations involved in a connection, but which may interfere with your
display. You can specify up to four characters by giving the ASCII character
codes in hex or decimal.

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Real-Time Clock and Time Stamping
You can enable the MFJ TNC's real-time clock by setting the date and time
with the command DAYTIME. Once you have set the clock, you can request
the time by entering DAYTIME with no parameters. The format of date and
time display is controlled by the command DAYUSA. If the MFJ TNC is
powered off, DAYTIME will have to be reset.
An optional Real-time clock module (MFJ-43) may be installed inside your
MFJ TNC to keep the TNC clock running when the TNC is powered off. With
this clock module installed you will no longer need to reset the TNC clock.
Contact MFJ or MFJ dealer for information on the MFJ-43 TNC real-time
clock.
Monitored packets can be time-stamped if DAYTIME has been set. To enable
this function, set MSTAMP ON. You can also time-stamp connect and
disconnect messages with the command CONSTAMP ON.

Multi-Connect Guide
Multiple connection capability is a very powerful addition to the MFJ TNC It
is very useful for traffic net operation, multi-user bulletin boards, path checking
and so forth.
Multiple connection operation is not the same as multi-way operation. With
multiple connect, you may establish several point-to-point "links" with various
stations. Multi-way, which is not available, would enable multiple stations to
be simultaneously interconnected to each other, with each station seeing all
data passed from any station in the group, error free.
Multiple connection operation is another step on the road to proper networking,
and networking should eventually allow multi-way operation.

Setting the MFJ TNC to Normal Operation
The MFJ TNC defaults the multi-connection-related commands to the
following parameters:

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CONPERM
STREAMCALL
STREAMDouBLe
STREAMSWitch
USERS

ADVANCED OPERATION

OFF
OFF
OFF
|
1

This sets up the MFJ TNC to act just like a "normal" TNC does, that doesn't
support multiple connections. The key to obtaining this traditional operation is
to set USERS 1.

How to Invoke Multi-Connect?
If USERS is not 1, you are telling the MFJ TNC to allow multiple connections
to your stations from other stations. In addition, TRANSPARENT mode will
operate differently, in that incoming data will be prefixed with the current
STREAMSWitch character and identifier (such as "|A"). Thus, truly transparent operation is not possible with this software release supporting multipleconnections.
The STREAMSWitch character, defaulted to "|", should be set to a character
you won't normally use. Note that this character may be set to a hex value
between $0 and $FF. This may allow you to use 8-bit characters (AWLEN 8)
if your terminal or computer is capable of generating such "characters." This
could help prevent confusion in interpreting incoming data from other stations
if they happen to send data that includes your selected STREAMSWitch
character.
Although not fool proof, enabling STREAMDBL may also help in sorting out
STREAMSWitch characters included in the received data from a valid stream
switch generated by the MFJ TNC.
STREAMCAll should be especially helpful when manually operating a station
in which you allow multiple connections.
When in CONVERSE mode, you may switch streams by entering the
STREAMSWitch character (default "|"), followed by a stream identifier ("A"
through "J"), followed by the data you wish to send to the station on that
stream. See the example in the description of STREAMCAll for an
illustration of this.

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If all this seems a bit confusing, don't worry, it is! The only way to really
understand multiple connect operation is to try it! Tested and on-the-air, Once
you have gained confidence in "normal" packet operation, try setting USERS 2
and get a couple of friends to connect to you. Play with the commands (you
can't hurt the MFJ TNC by issuing commands to it!) and see their effects.

Easy-Mail Mailbox
The Easy-Mail mailbox feature is only valid for the HF and VHF packet mode.
The operation of the Easy-Mail mailbox is quite simple. There is a command in
the MFJ TNC called MAILBOX. Being as the MAILBOX command in your
MFJ TNC is already turned on, makes your Mailbox ready for use, as soon as
your MFJ TNC is powered on. Anyone who operates AX.25 packet can access
your mailbox by establishing a connection to your station by using the standard
packet CONNECT command. Once the connection is made, he can send a
message, obtain a list of the messages in your mailbox, read the messages or
kill any messages addressed to him.
The Easy-Mail mailbox in the MFJ TNC provides approximately 8K bytes of
memory for message storage. However, you can increase the mailbox memory
on your MFJ TNC to 32K, 128K or even an enormous 512K by simply replace
the mailbox RAM chip on the MFJ TNC motherboard. This additional
memory is also battery back-up by the lithium battery on the MFJ TNC mother
board. Addition memory chip can be purchased separately from MFJ
Enterprises, Inc. and it can be easily installed by the user inside the MFJ TNC.
Order MFJ-45A for 32K, MFJ-45B for 128K RAM IC or MFJ-45C for 512K
RAM IC. The number of slots and space available for each memory size are as
follows:
Memory Size
32K
128K
512K

# of Slots
99
99 per Bank
99 per Bank

Bytes Avail.
32,000
128,000
512,000

Set Up your Easy-Mail Mailbox
The MFJ Easy-Mail Mailbox can now be operated independently from the
standard packet operation. There are certain commands which need to be set.
These will be explained later in this instruction.

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NOTE: Whenever  is found in this instruction this means to press the
RETURN key, not to type .
1.

Under the cmd: prompt, type:

MYMCALL n
mailbox.
2.

; where n is the callsign you wish to for your

Type:
USERS 1 

3. If you want your messages time and date stamped, then set DAYTIME
with the current information.
Note: An optional TNC real-time clock (MFJ-43) for the MFJ TNC is
available from MFJ Enterprises. With this real-time clock module installed in
your MFJ TNC, the clock will continues to keep time even with the MFJ TNC
turned off. You will not have to set your MFJ TNC's "DAYTIME" every time
your MFJ TNC is powered up.

4.

Type:
MAILBOX ON



Now your MFJ TNC is ready for simultaneous Mailbox/Packet operations. You
as the SYSOP can access your Mailbox by typing:
SYSOP



Your MFJ TNC will respond with:
|K[MFJ-2.0-M$]
Mailbox ready
n free Mailbox (B,E,H(elp),J,K,L,M,R,S,T) >
First of all lets find out what the n free is for. The n free is a "Bytes Free"
indicator. This applies only to the Mailbox. This is a great feature, because all
users will always know how much space is left in your Mailbox. The Mailbox

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will update the "Bytes Free" whenever messages are forwarded, added or
deleted.
Now you are ready to operate your mailbox. However, lets take first things first.
You very well cannot operate the Mailbox without knowing the functions of the
commands. So, lets take a look at the functions of the Mailbox commands. The
functions are as follows:

B

Logout: This initiates a disconnect sequence from the Mailbox.

E Edit Message Header: This allows editing of the message header. This is
necessary for the Forward and Reverse Forward functions of the Mailbox. The
current is first displayed, then the Mailbox gets the new values, according to
what is entered at the prompts it gives the user. The local and remote SYSOPs
may edit any messages in the Mailbox. Remote users may only messages TO
and FROM himself, and any message of 'T'raffic. Below are the edit prompts
and an explanation as to what their functions are:
To: The callsign of the person the message is going to goes here. It must
be different than MYcall or MYMcall.
@: The callsign of the BBS you wish to Forward the message to
is placed here. This BBS should be the one where the person whom you are
sending the message to gets his mail.
From:

The callsign of the person who originated the message is placed

here.
Type: The Type of message you are sending is placed here. This will turn
on a flag in the first flag box. There are a few message types, and here are a
couple listed below:
1. "T" messages -- These are NTS (National Traffic System) type
messages. This message system was developed by the ARRL. These messages
must be formatted in a certain way. Please refer to the ARRL Net Directory
for more detailed view and information on this message system.
2. "P" messages-- These types of messages are still private to the
sender, recipient, and the SYSOP.

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There are other types of messages supported by the Mailbox but without special
features.
Flag:
The message Flag is now very important. All of flags can be set
via the S (send) or E (edit) commands. This flag will either be an N or a Y.
This will appear in the flag block closest to To: block in the message header.
There are different types of flags are as follows:
N Messages with this flag set are all able to forwarded, providing all
other criteria is met for a message to be forwardable). Only messages with the
N flag set, trigger the "You have new mail!" message.
T

The T flag indicates that the message is an NTS message.

Y Messages with the Y flag set are eligible to be killed by the "K"
global kill command.
F
This flag is set when a message is forwarded. Messages which are
eligible to forwarded are:

1.
2.

Messages where the N flag is set.
Messages that have no @ addresses that are
different from MYMcall.

P
Messages with this flag set are private to the sender, recipient, and
the SYSOP. Only the person to which the message is addressed to can read or
kill it. The local or remote SYSOP can read or kill any message in the system.
Here is an example of a Mailbox message with a Type flag and a message flag
inserted:
Slot:1 PN To:KB5JNZ

From:KF5C

BBS Bulletin

The P is in the Type flag block, which indicates that the message is a Private
message. The N is in the Message flag block, which tells you that the message
has not been read by the callsign KB5JNZ. When KB5JNZ reads the message
the N flag will become a Y flag.
H(elp)
This command displays the Mailbox command list. A brief
description of the commands available to user is given.
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J
This command replies with the TNC's MHeard list. The eleven most
recently heard callsigns will be displayed. The "J" command only applies to
remote users.
K Allows you to kill messages which are addressed to you. This works in
conjunction with the Y flag. In order to perform a Global Kill, first of all of the
messages to be killed during this must have the Y flag set in the header.
Secondly, all messages to be killed must have the same callsign as MYMcall.
K## Allows you kill the message in slot nn, where nn is a particular slot
number. Remote users may only kill messages which are addressed only to
them or originated by them. The local and remote SYSOP can kill any
messages, depending on the setting of the new command REMsysop. Please
refer to the REMsysop for more detailed information.
L This command allows the remote user, local or remote SYSOP to list all
messages in the mailbox. All of slots which are currently in use will be listed.
They all will have the slot number, flag field, the destination callsign,
originator callsign, subject field. Also the Mailbox command line will be on the
next line.
M This allows the remote user, local or remote SYSOP to change memory
banks in the mailbox ram. The current memory bank is indicated on the
mailbox command line. The bank will be inside a pair of{}, which will be after
the "bytes free" indicator. Below is an example of a typical command line from
the mailbox:

nn free {n} Mailbox (B,E,H(elp),J,K,L,M,R,S,T) >
Where {n} is the bank number. The bank number will vary from 0 to 7
depending on the size of the expanded memory ram. The bank numbers in
relation to the RAM size are as follows:
MEMORY SIZE
32K
128K
512K

BANK NUMBER
0
0 or 1
0 thru 7

NOTE: There will be only one (1) number in the { } at anytime.

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For example let's say that you are running a 128K mailbox, and a remote user
wants to access memory bank #1. First a connection to your mailbox must be
made. Once the Mailbox command line is obtained the user will type:
M 0 
This will be received by your Mailbox and then your Mailbox will send back a
new Mailbox command line:

nn free {0} Mailbox (B,E,H(elp),J,K,L,M,R,S,T) >
Thus the {0} indicates the memory bank has been switched to bank #1.
NOTE: The "M" function applies only to an MFJ TNC which have expanded
mailbox memory.
R This command lets you read messages addressed to you. When you list
the messages in the mailbox you notice an N flag next to the messages which
you have not read. Once you read those messages the N flag will change to a Y
flag. This is an indicator to both you and the SYSOP that the messages have
been read. From there you can perform a global kill on all of your messages or
the SYSOP can kill them individually.
NOTE: The only way an N flag can get changed to Y flag during a read is that
the person who the message is addressed to needs to read it. The flag will not
change for any other person who reads the message.
R## Allows you to read the message in slot nn. Where nn is a particular slot
number. This command works the same as the R command, except its for
reading the individual slots.
S call
This allows the remote user, local or remote SYSOP to send a
message to the designated callsign. "CALL" must be a callsign valid under the
same format as the MYCALL, CONNECT or other callsign commands. You
can also send messages in NTS (National Traffic System) format. You will
need to refer to the ARRL NET DIRECTORY for more detailed information on
the NTS system.
SP call This allows the remote user, local or remote SYSOP to send a
personal message to the designated callsign. This is a private message and only
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the person to whom the message is addressed can read or kill it. The SYSOP
can also read the private messages. When a private message is listed a P flag is
shown in the "Message Type" flag block. The P flag can also be inserted by the
originator or the SYSOP through the Edit command.
T This command allows the remote user to page the SYSOP. When the T
command is invoked from the remote user the following message appears on
the SYSOP's computer screen and it also is sent back to the remote user's
screen:
Paging SYSOP; any key aborts
The Mailbox will page the SYSOP by ringing the SYSOP's terminal bell 30
times. If the SYSOP is at his or her terminal, the asterisk character will appear
on the screen every time the terminal bell (CTRL-G) rings. If the SYSOP does
not answer the Mailbox will send the message back to the user saying no
answer. Below is an example of a typical screen:
Paging SYSOP; any key aborts...
******************************No answer
The remote user may abort the SYSOP page by sending packet to the Mailbox.
If the SYSOP does answer the page then the SYSOP can enter CHAT
command, then converse one-on-one with the remote user.
This concludes the explanation of the commands which are on the Mailbox
command line. Now lets get into a little of the Mailbox operation. If you have
any questions about the Mailbox commands, we believe they will be answered
in this section.

Mailbox Operation
1.

First establish a connection to the Mailbox station.

2. If the Mailbox of the station to which you are trying to connect with is
ON, then it will answer back with the Mailbox prompt:

Mailbox Ready
nn free {n} Mailbox (B,E,H(elp),J,K,L,M,R,S,T) >

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Note: The nn free indicates the amount of RAM space available for messages in
the Mailbox to which you are connected to. The nn will be no higher than 65K,
if a 512K or a 128K Mailbox is in operation. If the Mailbox is 32K then nn will
be 32K.
Note: The{n} indicates the memory bank being used for the Mailbox. Please
refer to the explanation of the M command for the Mailbox, in this section.
Now at this point all of the Mailbox are available to you. You may then type M
to switch the memory bank of the Mailbox, K to kill a message, L to list all
messages, R to read the messages, S to send a message, B to logout and
disconnect from the Mailbox or H for the HELP menu.
3. To send a message the S or the SP commands must be used. It must be
used in conjunction with a callsign as in the examples below:
S KB5JNZ
KB5JNZ.

, this will send an ordinary message to the callsign

or
SP KB5JNZ , this will send a private message to the callsign
KB5JNZ.
The Mailbox will respond with:
Title:
_
The user will enter the message subject (title) at cursor prompt, then press the
"RETURN" key.
The Mailbox will respond with:
Send msg; Control-Z or /EX to end:
_
The user will then enter the message at the cursor prompt. If you are using a
512K or 128K Mailbox then you can actually upload disk files into the
Mailbox. The 32K version has the same capability but with 32K RAM capacity.
At the end of the message press a Control-Z and the RETURN key. The
message will be sent.

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Your message will be seen on the mailbox station's screen, then the mailbox
will respond with the mailbox command prompt:
nn free {n} Mailbox (B,E,H(elp),J,K,L,M,R,S,T) >
Where nn is the "bytes free" indicator. This tells the user how much ram space
is available in your Mailbox. Also {n} is the indicator of the current memory
bank in use by the Mailbox.
4. There are two (2) different ways to kill messages. The first is give in the
example below:
I.

To kill a message in a particular slot type:

K## 
Where the ## is the message number you want to kill.
The Mailbox will respond with:
Message ## deleted;
nn free {n} Mailbox (B,E,H(elp),J,K,L,M,R,S,T) >

This is whether or not the message flag is set to an N or a Y. Note that the
remote users may only kill messages which are addressed them. The originator
can also kill the message. The local SYSOP can kill any or all messages in the
Mailbox.
II. You can perform a Global Kill on a group of messages which are under
the same callsign. To perform this two (2) conditions must be met:
a. All messages must have been read and the message flag must be a Y.
b. The callsign contained in the MYMcall must be the same as the
callsign in the MYcall command.
If the above conditions are met then all the user must type:
K



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This will go out to Mailbox, then the messages with the message flags set to Y
and all of the proper callsigns will be killed. The Mailbox will respond back to
the remote user with all message numbers killed during the Global Kill process.
Also the Mailbox prompt will be given again. The "bytes free" indicator will be
updated also. The SYSOP either remote or local can do a Global Kill. The
SYSOP must individually kill any messages.
5. The remote user or local SYSOP can List messages from the Mailbox. In
order to do this first the Mailbox prompt must be obtained by either a
connection to the Mailbox or through the local SYSOP command. Then to List
messages from the Mailbox:
A. Type:
L 
B. The Mailbox will respond with a list of currently used slots in the
following format:

Slot:## To:

From:

Subject:

Where Slot## column is the number of the slot which the messages are in. The
lower case t is the Type Flag block. The lower case m is the Message Flag
block. The To: column will contain the callsign of the person who the message
is addressed to. The From: column will contain the callsign of the person who
left the message. The Subject: column will contain a brief message title.
Note that the number of slots for an MFJ TNC without expanded memory is
30. For an MFJ TNC with the expanded mailbox memory installed the
maximum slots per memory bank is 99.
After the Mailbox lists all messages it will issue the Mailbox prompt:
nn free {n} Mailbox (B,E,H(elp),J,K,L,M,R,S,T) >
6. Anyone who accesses the Mailbox can read messages or which are
addressed to him/her. Also a message which is a addressed to ALL, such as
bulletins can be read by anyone. Messages can be read by two (2) different
methods. Below are the two methods:

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A. This method will allow the remote user, local or remote SYSOP to read a
group of messages. This is only good for a group of messages with the same
callsign as MYcall. The set conditions of the Type or message flags have an
effect on a read process. They can be set to an N, Y or an F. To perform this
type:
R



B. Messages can also be read individually by the slot number. This is good for
reading other messages like bulletins or messages addressed to ALL. In order
do an individual read type:

R## 
Where ## is the slot number of the message that you wish to read.
C. The Mailbox will respond with the message from the slot specified.
All messages read will be in the following format.
Slot## To: From: Subject:
This is an example of a message from the Mailbox
Where Slot## column is the number of the slot which the messages are in. The
lower case t is the Type Flag block. The lower case m is the Message Flag
block. The To: column will contain the callsign of the person who the message
is addressed to. The From: column will contain the callsign of the person who
left the message. The Subject: column will contain a brief message title.
Then at the end of the message the Mailbox prompt will be issued.
7. The remote user can also disconnect from the Mailbox without having to
issue a CTRL-C, D and a RETURN. All that needs to be done is to type: B to
logout of the Mailbox and disconnect from the it. If you access your Mailbox
via the SYsop command, then you must issue a CTRL-C to exit the Mailbox
and return to command mode. The command prompt will indicate the stream
you are on. The command prompt may look like this:
|Acmd:

where |A indicates that you are on packet stream A.

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This is the only way the remote users can access your Mailbox. If you stay in
the SYSop mode then when a user tries to connect to your Mailbox he will a
message like this:
***CALLSIGN Busy
Disconnected
The SYSOP will receive a message like the example below when he is in the
SYSOP mode and someone tries a connect:
***connect request:CALLSIGN

Additional Mailbox Features
Other MFJ TNC mailbox features are as follows:
Forwarding
The MFJ TNC Mailbox now has the ability to Forward mail to most full
service and personal mailboxes. This feature allows you to compose your mail
on your TNC, at your leisure, and then Forward the resulting messages for
eventual delivery.
Messages may be forwarded any one of three ways either manually, by
command, or by automatic forward. You can either forward messages hourly,
or by your local full-service mailbox's reverse forward request.
Manual and hourly forwards may proceed through up to eight (8) digipeaters,
allowing the messages to be forwarded through ROSE switches. Also NODE
forwarding is can be done too, thus allowing you to forward mail through
NETROM, THENET, and KA- NODE switches. Please refer to the NODeforw
command in this manual.
In order to conserve RAM, space the SYSOP may specify that forwarded
messages be killed upon successful forwarding. However, if conserving RAM is
not a concern, then forwarded messages will be flagged "F". This flag will
appear in the message flag block. Messages with F flags will be saved in the
mailbox for the SYSOP's disposition.
All forwarding events are monitored on the screen, in order to inform the
SYSOP of the forwarding progress.

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In order for a message to be eligible for the forwarding process two (2)
conditions must be met:
1.

Messages must have N flags in the message flag block.

2.

All messages must have an @ callsign in the message header.

The command used to forward a message is FO. All forwards must be done in
the stream cmd:mode. This command is by pressing a CTRL-C while in the
SYSOP mode. Below is a typical example as to how to use the FO command:
FO CALLSIGN



Where CALLSIGN is the callsign of the destination mailbox. This callsign
must also reside in header of the message to be forwarded. The message header
can be altered through the Mailbox Edit command. Please refer to the EDIT
command in this manual. When the FO CALLSIGN is issued the MFJ TNC
will initiate a connect request to the destination BBS. If the connection is
successful the your mailbox will proceed to send the message to the destination
BBS.
Eliciting Reverse Forwards
This very unique feature, when combined with the hourly automatic forward,
enables the MFJ mailbox to query another BBS, regularly and automatically,
for the purpose of polling the other BBS for the TNC user's mail. Thus, even if
your local full-service BBS operator is unwilling to forward to you, you can still
have most of the benefits of auto-forwarding because your own TNC will elicit
your mail for you on an hourly basis.
Reverse forwards may be restricted to a particular callsign. This prevents others
users from "stripping" messages off of the mailbox prior to their being
forwarded to the legitimate destination.
When all messages are forwarded, if the destination mailbox supports reverse
forwarding (as determined by $ in it's SID) then the MFJ TNC will attempt to
elicit a reverse forward.
Remote Heard Log

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This handy feature allows the remote user to query the TNC heard log at any
time. From this log the remote can determine band conditions, or just see who
has been around. The log holds eleven (11) of the most recently stations.
Chat Mode:
The Chat mode feature in the MFJ TNC Mailbox is similar to the standard
TNC "converse mode". It enables the SYSOP to break onto a mailbox link, and
get one-on-one with mailbox user. This is just like a regular "Packet QSO".
This is good for discussing problems maybe with the link or with the mailbox
in general. Chat mode terminates any user or forwarding operation in progress.
The mailbox will stay in Chat mode until the SYSOP returns to command
mode.
Page SYSOP
This allows the remote user to "Page" the SYSOP by ringing the SYSOP's
terminal bell. This is done by the SYSOP's mailbox sending a CTRL-G to the
SYSOP's terminal. The SYSOP's mailbox will poll the terminal's bell 30 times.
If the SYSOP does not answer the remote user will receive a message back
saying No Answer. If the SYSOP does answer then he can go into the Chat
mode, and converse with the remote user. For more detailed information on this
feature please refer to the section on Mailbox Set Up in this manual.
Remote SYSOP
The Mailbox has the capability to be remotely controlled. A callsign can be
specified by the SYSOP for this purpose. This would be useful in the case
where the SYSOP is out in the field. It would allow him to control the mailbox,
and do most of the local SYSOP's duties, such as killing messages, reading,
editing message headers for forwarding purposes.
Mailbox CText
This is a message dedicated to the Mailbox, but is used when a connect is made
to the MYMcall callsign. It is limited to 120 characters in length. If MCText is
empty, then no message will be sent.
Idle Timeout

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The Mailbox incorporates an idle timeout function. This is to ensure that the
mailbox is still accessible in the event of a remote user drop out during a
connection or walks away from the TNC for too long. The Mailbox will
automatically do a disconnect from the link after the time which the SYSOP
specifies.
Abort:
This command gives the SYSOP control over the mailbox by allowing him to
force a disconnect on the mailbox link. It may also be used to avoid any QRM,
to abort a forward-in-progress. You can also use it to terminate mailbox usage
by an unwelcome user.
The new Mailbox system is fully compatible with NTS packet messages also. It
allows you to format NTS type messages, and send them to another destination.
The MFJ TNC also incorporates a new "bytes free" counter. It is updated as the
mailbox fills or empties. It keeps up with the available RAM in multiple
memory banks.
The Mail waiting is indicated by the flashing of the STA/MAIL LED on the
front of the MFJ TNC.
The STA/MAIL LED of the MFJ TNC serves two functions. It lights when
unacknowledged packets are pending during a packet connection. If you have
mail waiting, the STA/MAIL LED will flash on and off if the MFJ TNC is not
connected to another packet station.
The "mail-waiting" LED function can be disabled by using the MAILLED
command. MAILLED is defaulted to ON. When MAILLED is OFF or when
MFJ TNC is in a connected state, STA/MAIL LED will not flash.

Mailbox Messages

You have mail!
Upon access to a mailbox, this message will appear if there are messages
addressed to you.
?EH

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This message occurs when a command issued is not understood by the mailbox.
This could be out of range slot number, missing slot number where one is
required, or bad command.

Cannot, not yours
This message occurs when a remote user attempts to kill a message which is
not his, or he tries to read personal message by or for someone else.

?Mailbox full
This message occurs when either all of the available slots are full, or the actual
message space is full. Messages must be killed to recover from this error.

Not found
This message occurs when one attempts to read or kill a non- existent message
from an empty slot.

None found
A parameterless Kill or Read command did not find any messages addressed to
the user.

No mail
A parameterless read command did not find any mail addressed to user or due
to mailbox being empty.

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Slotting and Acknowledgment Priority
The SLOTTING AND ACKNOWLEDGMENT PRIORITY feature is
installed in the MFJ TNC in an attempt to prevent or minimize packet
collisions in a busy channel.
Use of the optional SLOTTING and ACKNOWLEDGMENT PRIORITY
procedures now in the MFJ TNC firmware significantly improve the reliability
of packet radio connections on shared channels. The greatest improvement is
yielded when all stations in a network are so equipped and configured with the
appropriate, matching parameters.
SLOTTING improves channel efficiency by requiring each TNC to "flip" a
many sided die whenever the channel goes from busy to not-busy. The result of
the "flip" is the number of 10ms DEADTIME intervals the TNC waits before
transmitting.
SLOTTING solves most of the problems that occur when there are two or more
stations waiting to transmit when a third is already transmitting. Before
slotting, the first two stations are definitely going to transmit at the same time,
guaranteeing a collision. With slotting, the first station will probably choose a
"slot" different from the second. If everyone is hearing everyone else, collisions
are very unlikely.
In conjunction with slotting, the ACKNOWLEDGMENT PRIORITY feature
helps improve channel utilization by assigning priority to acknowledgments
(AX.25 frame types "S"), i.e. acknowledgments are never delayed by slotting.
The reason this works is because each TNC recognizes when another is
transmitting. It also recognizes the destination of each packet it hears. If a
TNC hears a packet not addressed to it, it can assume that somewhere another
TNC will send an acknowledgment. Therefore, on hearing packets for others, a
TNC will always wait at least one slot time in case the addressed TNC
acknowledges. And it will never delay it's own acknowledgments.

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Description
The idea behind the prioritized acknowledgment (ACK) protocol is quite
simple. The idea is to give ACKs priority access to the channel so that time is
not wasted retrying packets that have already been correctly copied but for
whatever reason, the ACK is not received within the time limit defined by the
FRACK timer.
The present protocol does not handle a simplex LAN with hidden terminals as
well as it possibly could. This is primarily because, the present protocol is
more likely to synchronize collisions with acknowledgment packets than with
any other type of packet.
To this collision synchronization mechanism the current version of AX.25 adds
a propensity to cause even ACKs which are not from hidden terminals (&
therefore less susceptible to collision) to be delayed beyond even generous
FRACK timer settings when the channel gets busy.
Once the FRACK timer times out, even if the ACK finally makes it through
before the retry is sent, the original packet is retried anyway. This obviously
wastes a lot of time which could be better used clearing the channel of some of
the legitimate offered load.
It is this feature of the current AX.25 protocol that accounts for most of the
abysmally poor performance of the currently popular NETROM and THENET
nodes when they are used as omnidirectional single channel (or even
multichannel if there is more than a single other node on each channel)
systems. It should be noted that these node chips CAN handle point to point
links to a single other node perfectly adequately.
The prioritized ACK protocol avoids the above problems by giving ACKs
priority access to the channel. It does this in such a way that even ACKs
coming from hidden terminals are protected from collision.
The current protocol gives a limited version of this priority access only to
digipeated frames. Although it will be possible to support digipeating in a
compatible (with the new protocol) fashion, compatible digipeating support was
not an objective that was addressed in this release.
Ack prioritization works with slotted channel access in the following way:

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1
Response frames (ACKs) are always sent immediately with no time delays
unrelated to hardware limitations applied. Ultimately, not even DCD will be
checked for sending an ACK. However, in this release DCD will still hold an
ACK off the channel.
2
Stations queued up to access the channel but waiting for a channel busy
condition (DCD true) to clear, will start a slotted access procedure only AFTER
enough time for a response frame to clear the channel has transpired (weather
or not the response frame is detectable by the queued up station).
3. Slot time windows are selected to be large enough that the local TNC will
be able to unambiguously determine whether any other detectable station has
selected any slot, preceding the slot selected by the local TNC.
This is to prevent two TNCs which have selected adjacent slots from colliding.
As you can see, under this protocol there will never be a condition where an
ACK is delayed from being sent beyond the FRACK timer limitation. In fact,
the FRACK timer becomes relatively meaningless in this context. However, in
the current firmware release, The FRACK timer is still active and must be set
to a value that is long enough to allow time for PACLEN + ACKWAIT to
expire before FRACK does. This time will depend on the radio baud rate in
use. The TNC knows that if it doesn't see the ACK immediately when expected,
it is never going to see it. See discussion of new parameters below for
definition of ACKWAIT.
Enforcing a channel access delay for all stations on the channel for whom the
packet that caused the queue was not intended (& who therefore aren't going to
ACK it) allows even ACKs from hidden terminals to get back to the expecting
station. This clears that traffic from the offered load list. If the packet was
indeed copied and ACKed, further retrys of the same information will not be
necessary.

New Parameters
There are several new parameters that relate to this modification of the
protocol. They are as follows:

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ACKPRIOR

ADVANCED OPERATION

ON|OFF

This enables prioritized acknowledgments if turned on.
If ACKprior is turned off and SLots (see below) is set to 0, this modification of
the AX.25 protocol is effectively disabled. The MFJ TNC will behave like
normal AX.25 protocol.
Prioritized acknowledgments and slotted channel access can be enabled or
disabled independently of one another. So you could if you wished run normal
AX.25 with slotted channel access or the new protocol without slotted channel
access.

DEADTIME 0 - 250 (each increment represents 10 milliseconds)
This is the time between when a remote TNC has pressed PTT and when the
local TNC can reasonably be expected to detect this fact.
This must be set to a value that accounts for the slowest acceptable station on
the channel. It includes the time required for the remote station's radio to come
on the air properly after assertion of PTT (TXDelay) and the time required for
the local station's squelch (if used) and TNC DCD circuits to allow generation
of a "DCD true" signal in the local TNC. Ideally, once the proper value for this
timer is ascertained, all stations on the channel will use the same value.
Very preliminary testing done here on VHF indicates that measurements of the
above delay times should be multiplied by 1.5 for use as the DEAdtime
parameter. We had carefully measured the times for all stations participating
in our tests. This gave us a worst case delay total of 210 milliseconds. When
we ran the test, we were still getting about a 5 percent collision rate on the
acknowledgments. We were required to increase the DEAdtime parameter to
30 (300 milliseconds) to completely eliminate collisions with ACKs.
The current default for this parameter is a ridiculously short 30 milliseconds.
This represents only the worst case delay for the TNC's DCD circuit and
completely ignores the radio delays.
A much more reasonable value for this timer on VHF NBFM 1200 baud AFSK
is 300 milliseconds (DEAdtime 3et to 30). This represents a relatively safe
time for a radio that is usable for serious packet work.

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Most HF linear mode radios are MUCH faster than VHF FM radio. A
reasonable setting for HF work is 120 milliseconds (DEAdtime set to 12). This
should work fine with virtually any HF radio stable enough to consider using on
HF packet.
ACKTIME

0 - 250 (also 10 millisecond increments)

This represents the time required to send a response frame (with no I field
appended) at the baud rate being used on the radio port.
The current 100 millisecond default is close but should be adjusted for 1200
baud work to 130 milliseconds (ACKTime set to 13).
For 300 baud HF work this parameter should be set to 520 milliseconds
(ACKTime set to 52).
SLOTS n 0<=n<=127
This parameter determines how many sides are on the slot time dice. SLOTS
represents an n+1 sided dice the MFJ TNC "throws" before transmitting. The
SLOTS command allows any number of slots from 1 thru 127 to be defined.
SLOTS (n)
1
2
4
8
16
32
64
128

REMARKS
Disables Slotting
This should be the default setting
Use only if the channel is VERY busy.
VERY VERY VERY busy !
You get the idea.
Might as well print it out & send it in the mail.

The value used on a particular channel should be agreed on by the channel
users. Access to the channel will be equitably distributed among all users if
everybody is using the same value for the SLotmask and DEAdtime parameters.
The idea is to pick a value large enough that the probability of two queued up
stations picking the same value is relatively small. On the other hand, the

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value chosen should be small enough that most of the time, ONE of the queued
up stations will have a significant probability of picking the first available slot.
In this way, the channel is reliably arbitrated and at the same time the overhead
required for the arbitration is minimized so that overall throughput on the
channel is maintained.
The actual value used will depend on the average number of queued up stations
there are on the channel during busy periods.

ACKWAIT

(not directly user settable)

This timer actually consists of the sum of the 2 user settable parameters
ACKTime and DEAdtime. It represents the time the queued up TNC will wait
before transmitting if it has selected slot 0. This allows time for a completely
inaudible (to this TNC) ACK to have been sent on the channel without
molestation. It was split into two timers because it has two unrelated
components. One is related only to the baud rate being used on the channel.
The other is related only to the absolute times the hardware requires to
transport carrier information from one station to another on the channel.

Other Related Parameters
Several of the existing TNC parameters will affect the operation of the modified
protocol. Most of these are parameters in TNCs on the channel which AREN'T
using the new channel access procedure. One, FRACK, must be set correctly in
any TNC which IS using prioritized ACK protocol.
FRACK should be set to a value which allows time for the TNC to send its
packet AND receive the ACK. This value will depend on the settings being
used for PAClen and the radio port baud rate. This is because, for some reason
which I can't even begin to understand, the FRACK timer starts at the
BEGINNING of the packet rather than at the end. For this reason, it is
probably best to set FRACK to its worst case value for whatever baud rate you
are using on the radio port. This way you can make adjustments to PAClen
without having to worry about interaction with the setting of FRACK.
The FRACK settings that should be used (at least initially for BETA testing)
are as follows:

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BAUD RATE
1200
300

ADVANCED OPERATION

FRACK (SECONDS
3
8

Note that these settings apply when everyone on the channel is running the new
protocol. This assumes that all stations on the channel have both DWait and
RESPtime set to 0.
If you are running the new protocol on a channel where some of the stations
have long RESPtime delays, those stations will not be able to successfully
communicate with you after connecting. If you wish to communicate with
these stations you will have to set your FRACK timer to a number which is
longer than the other stations RESPtime delay.
Both DWait and RESPtime are meaningless in the context of the new protocol.
However, in this release both timers are still active and should be set to 0 when
using the new protocol.

Initial Parameter Settings Summary
The settings for use at 1200 baud on a VHF FM channel are:
ACKprior
ON
SLots
3
DEAdtime
33
ACKTime
13
RESPtime
0
(If you require a nonzero value for this
parameter in order to prevent ACKing individual packets in a
MAXframe greater than 1 blast, your DCD circuit is not working.
Please get it fixed.)
DWait
0
(DWait should be set to 0 even if there are
digipeaters on the channel. The new system will not degrade the
performance of digipeaters on the channel because the ACKWAIT can
be used by the DIGI.)
MAXframe
1 - 7 depending on channel quality
FRACK
3
The settings to use for 300 baud work on a linear mode HF channel are:

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ACKprior
SLots
DEAdtime
ACKTime
DWait
RESPtime
MAXframe
FRACK

ADVANCED OPERATION

ON
3
12
52
0
0
1
8

What to Expect
This modification to the protocol is compatible with stations using the current
protocol in the following respect. A station using the new protocol will not
degrade the channel for users of the current protocol. So there is nothing
wrong with firing up the new stuff on a channel where the majority of the users
aren't yet using it. You will be able to communicate with users of the other
system without difficulties.
However, if the users of the old channel access procedures have DWait and
RESPtime set to 0, they will tend to hog the channel from users of the newer,
more polite access system.
Therefore, for purposes of testing the effect of the new system on channel
throughput, if there are stations on channel which are NOT using the new
system, they should set their DWait value to one that is compatible with the
new system users. A reasonable DWait setting for 1200 baud use would be 73.
For 300 baud work, it would be 76.
While these settings seem extremely long, they will assure that the stations
NOT using the new protocol always get a shot at slot #1. With these settings,
the users of the NEW protocol will occasionally capture the channel.
Settings of 43 for 1200 baud and 64 for 300 baud could be used to assure that
stations NOT using the new protocol always have a shot at slot #0. This will
result in users of the new protocol almost never being able to capture the
channel unless all traffic from users of the old protocol has been cleared. This
should NOT be done unless ALL stations are using some type of slotted

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channel access procedure with compatible numbers of slots and compatible slot
times.
Remember that the objective of the new channel access procedures is to
increase aggregate throughput for the CHANNEL, not necessarily for an
individual user (not even you!). It may seem to you at first when you get on a
very busy channel where you are the only station that is using the new system,
that you aren't getting to transmit very frequently. This is because you aren't
getting to transmit very frequently. However, the OTHER users on the channel
will see an incremental increase in the overall amount of data that the channel
can pass per unit time because you are being such a nice guy. Remember that
transmitting isn't necessarily communicating.
There is ONE benefit that you should be able to see even under the above
circumstances. If you are communicating with another station who is also
running the new system, the channel should appear more reliable to you even if
quite slow. You should not be getting retried out waiting for his ACK to come
back & have to keep reconnecting.
As a higher and higher percentage of the users on the channel begin using the
new system, the performance of the channel should increase quite a bit.
However, we all must remember that if a channel is mathematically capable of
transferring (for example) 1000 characters per unit time, the very best it can
possibly do (if CSMA is working right) is reliably pass about 620 characters per
unit time. If it is offered more than this to handle, performance falls off sharply
with increased offered load. Currently the typical AX.25 simplex channels
observed on the HAM bands tend to hover around 10 to as high as 18 percent
throughput. This is far below the 62 percent that is possible when the protocol
is working right.

Packet Picture Transfer
The MFJ TNC gives you the unique ability to transmit and receive Packet
Pictures. Unlike the binary file transfer ability common to all packet
controllers that lets you transmit and receive picture files, MFJ TNC lets you
transmit and receive actual packet pictures directly. You can also transmit and
receive FAX, SSTV and other graphics formats pictures with the MFJ TNC in
the VHF packet mode. Packet pictures received are directed to and printed on
the built-in printer port on the MFJ TNC. Any EPSON (tm) or IBM (tm)

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graphics compatible printer may be used. Packet pictures can also be sent to
the computer screen if special software, such as the MFJ-1284, is used.

Receiving Packet Pictures on Printer
Packet pictures data transmitted from the connecting packet station are received
and data is sent directly to the printer attached to the MFJ TNC, without any
intervening modification. Therefore, all data MUST use the same printer
control codes that your printer uses. Typically EPSON format codes will be
used.
The PKTPIX command provides a method for the MFJ TNC to print packet
pictures other graphics-format data transmitted by another station in the VHF
packet mode. When you set PKTPIX, your MFJ TNC becomes ready to print
graphics data.

Using PKTPIX
Packet picture printing to the MFJ TNC printer port requires you to first
establish a packet connection with the station who is going to send the picture.
Note that you won't be able to call up PKTPIX until the connection is made.
You must have the printer powered and selected before MFJ TNC will let you
use the PKTPIX command.
Once these conditions are met, all data received over the packet link are sent
directly to the printer. You can exit PKTPIX by using the escape-to-cmd: mode
sequence for TRANSPARENT connections. Use CTRL-C three times (default),
or asynchronous BREAK.

Packet Picture transfer to the computer screen
Packet pictures can also be received and displayed on the computer screen in
real time. To achieve this a special terminal program must be used. The MFJ
Starter Pack for IBM and compatible computer includes terminal program,
Multicom that allows you to transmit and receive SVGA, VGA, EGA or CGA
pictures in real time and display them on the screen. Multicom can transfer
binary files in additional to picture files. It also allow you to set up your
personal packet pictures bulletin board. Graphics that you create with certain
"paint" software, such as QSL cards, drawings and pictures can be saved and
transmitted to the connecting packet station with Multicom. Also, pictures
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created with digitizers, such as the MFJ-1292 "Picture Perfect" video digitizer,
can be transmitted and received using Multicom. Digitized pictures may also
be "enhanced" with drawing or "paint" software.

Detail HF Packet Operation
Radio Setup for HF Packet Operation
Setting up your Radio interface will follow exactly the same procedure as for
VHF NBFM operation with the exception that you will probably not need to set
the modem output level. This is because linear mode radios typically have a
transmit audio level control on the front panel and an indicator which tells you
when you have set the level correctly. You will adjust the audio level just as
you would for SSB operation.
If you are using the auxiliary audio input connector (other than microphone
input), you MAY need to adjust the transmit audio level from the MFJ TNC
modulator. This is because many auxiliary audio inputs are intended for phone
patch audio. These levels are typically much higher than microphone levels.
If you do adjust the output level of the MFJ TNC to a relatively high value for
this type of application, do not operate the MFJ TNC with a VHF NBFM radio
unless you take steps to assure that the audio level for the FM radio will not
produce excessive deviation. If both radios are to remain connected to the
MFJ-1270C, you can set the audio level for each radio independently by using
the audio output level adjustments, R157, on the left side of the MFJ TNC with
a small screw driver.
The modem center frequency used by the MFJ TNC for all of the narrow
shift AFSK modes including HF packet operation is 2200 Hz (2125 and 2295
Hz tones). Most frequencies listed for packet operations in the HF bands were
established using a modem center frequency of 1700 Hz (1600 and 1800 Hz
tones) in lower sideband mode. This is a 520 Hz offset (2220-1700) between
the two modem standards. So a listed frequency of 7093, for example, will
cause you to have a frequency display on your radio of 520 Hz PLUS the listed
frequency (IF you are also using lower sideband mode). Thus you should find
the 7093 KHz packet activity centered around 7093.52 KHz.
Your tuning indicator (MFJ-1274C only), when properly centered, is easily
capable of 10 Hz alignment accuracy.
It should be used as the tuning

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reference on any individual signal regardless of the frequency indicated on the
radio dial.
NOTE: The signal actually transmitted by your SSB transceiver ( F(emission) )
when using the MFJ TNC for AFSK HF packet operation using lower
sideband will cover a band of frequencies approximately 400 Hz wide and
centered at the transmitter indicated carrier frequency (F(ind)) minus the
modem center frequency (Fc).
So you would use:

F(emission) = [ F(ind) - Fc ]
to determine the actual operating frequency for band edge or netting purposes.
Remember to consider that you will be occupying a few hundred Hz on either
side of F(emission).
NOTE: Regardless of the type of modem, whether or not the modem has
audio filtering built in, 300 baud AFSK modem performance on a High
frequency linear mode (SSB as opposed to NBFM) radio channel will NOT
be optimum UNLESS a filter of approximately 500 Hz bandwidth is used in the
radio IF strip.
There are two reasons why this is the case. First, for the filtering to be fully
effective, it has to precede the first hard limiter in the system. This limiter
is typically located in the first stage of the demodulator. Second, no filter at
n prevent an off channel interfering signal from capturing the receiver AGC
system and causing wide variation in the level of the audio presented to the
demodulator. All demodulators are affected by audio level variations.
If a narrow (approximately 500 Hz) filter is to be used in the radio for HF
packet and RTTY operation (and this is STRONGLY recommended), it
may be necessary to use a tone pair centered on the radio's filter rather
than the "standard" 2125/2295 or 1600/1800 Hz pair. If the radio lacks IF
shift capability, this will almost certainly be necessary. If this is the case, it
will be necessary to determine the center frequency of the audio spectrum
output from the receiver when the narrow filter is selected and the radio is in
the LSB mode.
Most radios which provide for direct FSK RTTY operation use the radio's
narrow CW filter if one is installed. Packet operation using direct FSK is a

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viable mode but extreme caution should be exercised to make sure TX and
RX frequencies are identical and that the transmitted frequency pair is
centered in the radio's 500 Hz filter passband. Once the required modem
center frequency for the particular radio's FSK mode has been determined,
the modem alignment procedure presented in the trouble shooting / calibration
section of the owners manual may (should) be used to align the modem for
this mode.
Since there is no standardization among the various radio
manufacturers in this regard, a method for making the determination of
transmitter FSK output frequencies and their relation to the LSB carrier
oscillator and center of the 500 Hz filter is NOT presented here. Contact
the manufacturer of the radio to obtain this information.
Radios which have provision for an auxiliary "narrow SSB" filter can have the
500 Hz bandwidth filter installed instead of the approximately 1.8 KHz
wide "narrow" SSB filter. This will allow direct selection of the narrow
filter for AFSK work when in SSB mode. If the filter is also desired for CW
operation and you don't want to invest in 2 identical filters, it is usually a
relatively simple modification to cause the radio to also select this filter when
in CW mode.
Some of the newer HF radios (and many older ones) allow selection of
filter independent of mode. For these radios it is a simple matter to select
the required mode and the optimum filter independently of one another.

If the HF radio is to be dedicated to packet use, the 500 Hz filter can be
installed in place of the SSB filter. This is possible on ANY radio designed for
SSB and CW use.
It is important to use lower sideband rather than upper sideband if you are
going to use a CW filter in the radio for packet operations. The reason for
this is simple. The filter designed for CW operation is usually centered
approximately 800 Hz away from the upper sideband suppressed carrier.
This is the carrier oscillator which is normally used as the BFO on CW. This
means that if the two carrier oscillators are 3 KHz apart, the CW filter center
will be near 2200 Hz below the lower sideband carrier. This is the reason 2220
Hz was selected for the center frequency of the modem.
If you are going to use a narrow filter, and serious HF operation is NOT
recommended without one, it will be necessary to take steps to be certain

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that the filter passband is centered over the modem center frequency. If
your radio has IF shift, this is a simple matter. The tuning indicator and
DCD LED are used to give you an indication of filter centering. The
following discussion assumes that your radio has provision for IF shift.

To center your radio passband over the modem, use the following procedure:
1.

Set your radio for maximum RF gain.

2.

Set the radio for lower sideband operation.

3. Make sure the MFJ TNC is in HF Packet mode and that the HF Packet
modem has been selected.
4. Set the audio output level so that the tuning indicator is responding to the
background noise coming through the filter. This can be verified by observing
whether or not the tuning indicator "follows" the noise as the IF shift control is
rotated.
5. Tune to a frequency which has ABSOLUTELY NO signals in the
passband. It is very important that only noise is coming through the filter. If
you have access to a RX noise bridge, an alternative is to use the bridge as a
noise source for the receiver. No antenna is required in this case.
6. Adjust the IF shift control on the radio so that the tuning indicator on the
MFJ TNC is centered in its display area.
7. Adjust the audio output of your radio to TNC so that the DCD LED is
flickering with false DCD indications. Make the adjustment so that the DCD
duty cycle is more than 10 but less than 50 percent.
8. Carefully adjust the IF shift control on the radio to produce maximum
DCD activity. This is the optimum point for the filter center frequency. Note
the position of the IF shift control for future reference. This is the position
you will want to use for all of the narrowband FSK modes.
If your radio has no provision for IF shift, you will have to determine the
center frequency of the audio which is passed through the filter and realign
the modem to the center frequency of the filtered audio. If you are lucky,
this may turn out not to be necessary. The tuning indicator and DCD LED can

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be used to give you an indication when the modem is aligned with the filter
similar to the indications described above. If the tuning indicator hovers
around the center of the display when the modem is listening to noise being
passed through the narrow filter as described above, realignment of the modem
is unnecessary.
If you have determined that it is necessary to realign the modem center
frequency to the radio filter center frequency, You should refer to Appendix D
at the end of this instruction manual for the alignment procedure.

HF Packet Operation
Much has been said and written about the relative merits of HF versus VHF
packet operation. HF packet operation is made to appear more difficult than
VHF NBFM packet operation by several factors. Some of these are:
1. HF propagation is much more time variable and is more prone to produce
intersymbol errors than is VHF propagation.
2. On the "published HF packet frequencies" many more stations are trying
to use a single channel simultaneously than is the usual case on VHF.
3. Due to the wide area propagation characteristic of HF radio waves
(sometimes nonreciprocal) with relatively dead "skipped" zones , the carrier
sense multiple access (CSMA) feature of packet radio is a less than perfect
arbitrator for time sharing the channel between users.

4. Many of the commercially available Terminal Node Controllers (TNC) for
use on HF packet have data carrier detect (DCD) circuits which are of limited
use or no use at all on a HF packet channel. This further degrades the
effectiveness of CSMA.
The DCD circuit in the MFJ TNC has been optimized for the HF packet mode.
It can be adjusted to ignore background noise while still being able to promptly
respond to a valid data carrier. It has a "hang time" feature that prevents DCD
dropouts when short multipath hits occur or collisions put phase discontinuities
in the received data carrier. Thus, most multipath conditions will not cause
the MFJ TNC to begin transmitting before the other station is in a listening
mode. The DCD hang time also prevents the MFJ TNC from "piling on" a

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collision between 2 other stations on the channel. The DCD circuit in the MFJ
TNC is NOT affected by the fact that there is a large amplitude difference
between different signals on the same channel. So it will not allow you to
collide with a relatively weak station which is transmitting immediately after a
relatively strong station has finished.
5. Many of the stations on HF packet have no tuning indicator at all and
many others have an indicator that is only marginally useful. Unlike VHF FM
operation, frequency error between transmitter and receiver cause frequency
errors in the modem tones. This is the reason that a good tuning indicator is
absolutely essential for HF packet operation. The tuning indicator makes it
possible for the operator to reduce the modem to modem frequency error to near
zero. Reliable HF packet operation requires tuning errors of +\- 30 Hz or less.
6. Many of the stations currently operating HF packet do not have their radio
bandwidth matched to the characteristics of a 300 baud 200 Hz shift FSK
signal. This causes a severe degradation in modem performance resulting in
unnecessarily increased numbers of retries and drastic reduction in data
throughput for the SHARED channel.
Serious HF packet operation should not be considered without a 500 Hz filter in
the receiver IF. An audio filter is NOT an acceptable substitute.
"Squeezing" the edges of SSB filters together with so called variable bandwidth
tuning (VBT or PBT) to produce a 500 Hz bandpass is difficult to properly
align and results in operation near the edges of the filters where the phase
response and group delay characteristics are particularly poor. So while this
offers some marginal improvement over wide filters, it is not a good substitute
for a real 500 Hz filter.

In spite of the above factors, HF packet communications can be a reliable and
enjoyable mode. The trick is to operate in a manner that allows you to avoid
the problems mentioned above. Your purchase of an MFJ TNC has already
helped you avoid the DCD and tuning indicator difficulties. Configuring your
radio bandwidth to match the spectral characteristics of the HF packet FSK
signal will allow you to avoid the modem performance degradation that results
from excessive radio bandwidth. However, you will still be affected by other
station's problems in these areas when operating on a crowded packet channel.

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If you do have your radio configured for the proper bandwidth, you will notice
that many stations you connect to will seem to not be able to copy you as well as
you copy them. Don't worry, your transmitter output isn't low, you are just
observing the difference between a good demodulator behind the correct radio
bandwidth and any kind of demodulator behind a radio which has far too much
bandwidth for the mode.
The actual mechanics of operating the MFJ TNC in the HF packet mode are
the same as for the VHF packet mode. The main differences that will be
apparent to you will be the slower baud rates, the higher incidence of
propagation related effects and QRM, and the requirement for accurate tuning.
It will take some practice before you can rapidly acquire another station's signal
and initiate a contact.
Set the audio input to the TNC so that the DCD LED on the TNC just flickers
occasionally. Set it so that the DCD duty cycle is between 10 and 20 percent.
DO NOT set the audio level so that the DCD LED never comes on even when
receiving a signal!
Tuning in a signal is relatively easy to do once you get the hang of it. You
must wait until the other station is sending a packet, and then tune the
transceiver so that the tuning indicator LED is centered. If the DCD LED is
not lit, the tuning indicator information is NOT valid.
Each bar on the tuning indicator represents about 10 Hz. Thus, if a packet
comes through and you are 4 bars off, re- tune your transceiver 40 Hz in the
indicated direction. The direction depends on the sideband you selected and
the manner in which you have the tuning indicator oriented. One or two tries
will quickly tell you which way to go! Bars to the left of center indicate you
should tune higher, while the other side of center means to tune lower.
Once you have the other station tuned in, you may initiate a connect request
just as you would on VHF.
Many BBS stations forward traffic on HF at the above frequencies. Call CQ a
couple KHz away from such channels. If you can't raise anyone, call CQ on
one of the above frequencies, but QSY immediately after establishing
contact! Be careful on 20 meters especially that you don't operate +/- 2KHz
around 14.100 MHz (you will cause interference to propagation beacons and
give packet a bad name...)

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Calling CQ on HF is a bit different than on VHF. One technique which has
proven effective when NOT operating on one of the congested calling
frequencies is to do the following:
1. Find a clear frequency and monitor it for long enough to make sure it
really is clear.
2. Set "UNProto" to CQ if it isn't already. This is the default field for this
parameter.
3.

Command the MFJ TNC into converse mode by typing either:
K

or
CONV 
4. Rapidly type a string of 15 to 20 carriage returns . This will cause
the MFJ TNC to send a continuous string of unconnected information (UI)
frames. Since this will be a relatively long burst of packet transmission, the
potential receiving station will have plenty of time to tune your signal in. To a
receiving station this will appear on his screen as:

YOURCALL > CQ:
YOURCALL > CQ:
YOURCALL > CQ:
YOURCALL > CQ:
YOURCALL > CQ:

One for each carriage return you typed.
Even a station which has no tuning indicator can eventually get you tuned in
using this type of signal as he can tune around and watch his screen to see
where printing is effective.

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If you are meeting a friend on a schedule, you just set the "UNProto" field to
"HISCALL" and do the same thing. When your friend finds you, this will
appear on his screen as:
YOURCALL > HISCALL:
YOURCALL > HISCALL:
YOURCALL > HISCALL:

For as many s as you typed. Your friend will have little trouble finding
you and tuning you in for the QSO.
5. After the MFJ TNC finishes sending the string of CQ packets, listen for
5 to 10 seconds to allow a station to attempt to connect with you. If you don't
get any nibbles, send another string of CQ packets.
The above method of calling CQ is NOT appropriate for use on one of the
crowded calling frequencies. There, everyone is already tuned more or less to
the same frequency. To call CQ on one of the calling frequencies do the
following:
1. Find the "center" of the channel by tuning the radio so that the tuning
indicator is centered on most of the signals.
2.

Make sure your "UNProto" field is set to CQ.

3.

Enter converse mode.

4. Occasionally strike a  (2 a minute or so if DCD lets your packets
clear the channel that fast) and wait for the MFJ TNC to get an opportunity to
squeeze the packet into the activity on the channel. Allow some time after your
packet has been sent for someone to attempt a connect with you and then send
another CQ packet by typing a .

5. If (when) someone connects, immediately negotiate a QSY to a clear
channel. Then call him on the new frequency as outlined above (in the clear
channel CQ procedure) for a scheduled contact.

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Please use care in selecting the QSO frequency so as to avoid unnecessary
interference to other amateur services. As in all amateur communication
modes, it is polite to listen before you transmit!
Monitoring a propagation beacon frequency will not necessarily be sufficient to
reveal this activity to you. It is best to make a note of which INDICATED
frequencies you should avoid so that your radiated packet spectrum (from
F(emission) above) will not get within several hundred Hz of a propagation
beacon.
HF packet operation is fundamentally different than other modes of operation
in 1 major respect. If you are on a clear channel, talking to only 1 other
station, there will be long periods of silence. People using other modes and
tuning around looking for a clear frequency to use may be fooled by the silence.
Don't assume that an interfering station who shows up considerably after you
have begun using the frequency is interfering on purpose, he may honestly not
have been aware of your QSO in progress. For this reason, it is a good idea to
keep the flow of the conversation going so that the lapses aren't too long. It can
also be advantageous to have more than one packet QSO on the channel but if
more than a very few get on the same channel, the throughput falls off very fast
as the likelihood that all stations are properly configured and have working
DCD circuits is small.
Here are a few simple suggestions for operating HF packet which should help to
get you started.
1. Do NOT try to hold a QSO on one of the calling frequencies. Use the
calling frequency only to establish contact and then MOVE OFF TO A CLEAR
FREQUENCY to carry on the QSO. Remember to be aware of the frequencies
your station is actually transmitting so you can avoid interference to other
services such as propagation beacons etc.
2. Configure your station so that you can hear the activity on the channel.
This will allow you to easily avoid interfering with other stations and also to
quickly diagnose the problem when throughput suddenly falls off for some
reason (usually propagation or interference).
3. If possible, use the highest frequency band possible to communicate with
any specific station. The closer you are to the maximum usable frequency
(MUF) the less intersymbol interference you will have from multipath effects.

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If you have a schedule with another station, arrange your times and frequencies
accordingly.

4. Set the following parameters off unless you have some specific reason for
doing otherwise:
DIGIPEAT
HF mode)

OFF (there is NO logical reason to enable this function in the

DWAIT

0 (off)

AX25V2 (off)
CHECK

0 (off)

CMSG

(off)

RETRY
0 (try forever , but NOT if unattended operation. This allows
YOU to be the one to decide when or whether to give up rather than the MFJ
TNC. Typically you know more than the MFJ TNC does about whether the
other station is still trying or is likely to recover from the latest fade.)
MAXFRAME 1 (multiple frames off) RESPTIME 0(some stations may have
trouble copying your ACKnowledgments (ACKs) when you respond this fast.
This is due to the fact that some radios pump up the AGC voltage during
transmit and if the AGC time constant is long, they are essentially deaf for a
while after transmitting. You will want to experiment with this value. In
general, you will want to use the minimum usable amount.)
5. Set FRACK to at least 8. A value of 10 or 12 may be better on a very
busy channel.
6. Restrict your use of beacon transmissions as much as possible. If you
MUST use a beacon, keep it short and keep the repetition rate as low as
possible. More than once a minute is definitely too frequent. once or twice in
10 minutes is more polite. Do not allow your beacons to continue if you are not
in attendance. Nobody wants to connect to you just to be ignored.
7. If your radio allows you to select the AGC time constant (fast or slow
AGC), set it to the fastest setting available to you.

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If you cannot select fast AGC, it may be advantageous under some
circumstances to partially defeat the AGC function by reducing RF gain and
increasing AF gain. The demodulator in the MFJ TNC is extremely
insensitive to absolute audio level. It will function properly with input levels
from the low hundreds of millivolts up to many tens of volts. Thus, the
variation in audio level produced by partially defeating the AGC system will
not degrade the modem's ability to copy. The limiting factor on the high end is
usually the ability of the receiver output stage to produce the voltage without
clipping. The limiting factor on the low end is the hundred millivolts or so
required to exceed the MFJ TNC's digital system noise seen at the demodulator
input.

MFJ TNC KISS MODE AND HOST MODE
One unique feature offered by the MFJ TNC is that it can be switched into
KISS mode to run programs such as TCP/IP.
Host Mode installed in the MFJ TNC requires a special terminal program to
operate. Documentation for Host Mode is available on disk from MFJ upon
request.

KISS Interface for TCP/IP
The KISS interface is installed in firmware of the MFJ TNC.
modification or replacement of firmware is not necessary.

Additional

KISS enables the MFJ TNC to act as a modem for a host computer. Turning
KISS on allows the MFJ TNC to run programs such as TCP/IP, MSYS and
other programs which use the Serial Link Interface Protocal (SLIP).
Before enabling KISS, make sure radio baud rate and terminal baud rate are
set to the desired values. The terminal baud rate that's determined at sign on
is the same that will be used for KISS.
Once the operating parameters have been selected, set KISS ON and then
issue a RESTART command. The CON and STA LEDs will blink on and off
three times to indicate that the MFJ TNC has entered the KISS mode. Now
you may call up a TCP/IP, or another host program that can use KISS or
"SLIP".

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If you are using the TCP/IP program and wish to switch to the AX.25 mode of
operation, you can issue the command: param ax0 255, then press
"RETURN". This command must be issued under TCP/IP "net>" prompt and
in lower case letters.
Once the MFJ TNC receives the "param ax0 255" command, it turns KISS off
and will revert back to ordinary AX.25 mode of operation. When the MFJ
TNC is powered on again, it will sign on to the AX.25 operation mode.
For details of operation the TCP/IP user should consult documentation provided
with the TCP/IP program.

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OPERATION COMMANDS
This chapter serves as a complete reference to all MFJ TNC commands.
Commands are used to control the many variable values,which affect the MFJ
TNC's operation, as well as causing it to perform specific functions, such as
connecting to another station to start a QSO. You can enter a command to the
MFJ TNC whenever you see the command-mode prompt:
cmd:
You will change parameters and issue instructions to the MFJ TNC by typing
commands composed of English-like words or word abbreviations, which are
called keywords, and variables which are numbers or strings of characters
chosen by the user. You will probably never change some of these parameters;
however, one of MFJ's goals is to allow each user maximum flexibility to adapt
the MFJ TNC to his environment.

Entering Commands
You may use either upper case (capital letters) or lower case (small letters)
when you enter commands. In order to have the MFJ TNC accept a command,
you must finish command entry with a , or carriage return character.
This won't be mentioned explicitly in the examples below. Before you type the
final  of your command, you can correct typing mistakes or cancel the
line completely. If any command is misspelled to the point where the MFJ TNC
does not understand it, then an error message will occur. See Chapter 4 for a
discussion of input line editing.
This chapter will use UPPER CASE for commands and lower case for explanatory text. In examples showing input typed by the user together with the
responses of the MFJ TNC, the user's input will be shown in bold face.
Whenever the MFJ TNC accepts a command which changes a value, it will
display the previous value. For example, if you type
XFLOW OFF
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you might see the display
XFLOW was ON
This reminds you of what you have done, and indicates that the value has been
successfully changed.
If you type something the MFJ TNC can't understand you will get an error
message. If you type an unrecognized command, you will see the message
?EH. If you get a command name correct, but the arguments are wrong, you
will see the message ?BAD. A complete list of error messages appears at the
end of this chapter. For example,
cmd:ASDFASDF
?EH
cmd:BEACON E
?BAD

This isn't a command.
A parameter was left out.

Command List
The commands are listed alphabetically, and each command entry contains
several sections, as follows.

COMMAND NAME
The boldface command name at the top of the entry is the word you will type in
order to have the MFJ TNC execute this command. The command name is
printed with some letters underlined. These letters form the minimum abbreviation that you may use and still have the MFJ TNC understand your
command. Of course, you may type out the entire command word, or any
abbreviation longer than the minimum abbreviation, if you like. The command
will still be accepted.
For example, the command MYCALL may be specified by simply typing MY.
The abbreviation M is not sufficient (and will be interpreted as a different
command), but MY, MYC, MYCA, MYCAL or MYCALL are all acceptable.
If the command requires parameters, they will be indicated after the command
name.

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Default
For commands that set values, the MFJ TNC assumes a "most often used" or
default condition. The defaults are the values stored in EPROM which are
loaded into RAM when the system is first powered up, or when you give the
RESET command. Immediate commands perform particular functions rather
than setting values, and don't have defaults.
Parameters
There are several types of parameters. Some parameters can have one of only
two values, such as ON and OFF or EVERY and AFTER. If a parameter must
be one of two values, the choices are shown separated by a vertical bar. You
may use YES instead of ON and NO instead of OFF.
A parameter designated as n is a numeric value. These values may be entered
as ordinary decimal numbers, or as hexadecimal, or "hex", numbers by
preceding the number with the $ symbol. When the MFJ TNC shows some of
these numeric parameters (those which set special characters), they will be
given in hex. The "digits" of a hex number represent powers of 16, analogous
to the powers of 10 represented by a decimal number. The numbers 10 through
15 are denoted by the hex digits A through F. For example,
$1B = 1*16 + 11 = 27
$120 = 1*16*16 + 2*16 + 0 = 288
A parameter designated as text, such as the argument to CTEXT, may be
entered in upper or lower case, and may include numbers, spaces, and
punctuation. The text is accepted exactly as typed by the user.
Several commands require callsigns as parameters. While these parameters are
normally Amateur call signs, they may actually be any collection of numbers
and at least one letter,up to six characters; they are used to identify stations
sending and receiving packets. A callsign may additionally include sub-station
ID (SSID), which is a decimal number from 0 to 15 used to distinguish two or
more stations on the air with the same Amateur call (such as a base station and
a repeater). The call sign and SSID are entered and displayed as call-n, e.g.,
K0PFX-3. If the SSID is not entered, it is set to 0, and SSIDs of 0 are not
displayed by the MFJ TNC.

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Some commands have parameters which are actually lists of items. For
example, you may specify as many as eight callsigns to be selectively monitored
with the command LCALLS. The second and later items in the list are
optional, and you may separate the list items with blank spaces or with commas.
These examples may help you to understand the explanations
above.
BEACON EVERY|AFTER n
means that the command BEACON requires an argument which must be either
EVERY or AFTER (abbreviated to E or A), and an argument n which the user
may choose from a range of values. An acceptable command might be
BEACON E 2.
CONNECT call1 [VIA call2[,call3...,call9]]
means that the command CONNECT requires a callsign argument call1. You
may optionally include the keyword VIA, followed by a list of one to eight
callsigns, call2 through call9. The callsigns in the list, if included, must be
separated by commas (as shown), or by blank spaces. An acceptable command
might be C N2WX V AD7I WB9FLW.
You can see the current value of the command's arguments by typing the
command name by itself, without any arguments. For example,
cmd:CONOK Y
CONOK was OFF
cmd:CONOK
CONOK ON

Sets the value to YES (ON).
Displays previous value.
Command with no arguments
displays present value.

A special command, DISPLAY, allows you to see the values of all parameters
or groups of related parameters.
Remarks
This section describes the command's action and the meaning of each
argument. Examples may be included of situations in which the command
might be used.

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8BITCONV ON|OFF

COMMANDS

Mode: Packet

Default: ON

Parameters:
ON

The high-order bit is not stripped in Converse Mode.

OFF

The high-order bit is stripped in Converse Mode.

This command enables transmission of 8-bit data in Converse Mode. If
8BITCONV is OFF, the high-order bit (bit 7) of characters received from the
terminal is removed before the characters are transmitted in a packet. The
standard ASCII character set requires only 7 bits, and the final bit is used as a
parity bit or ignored. Setting bit 7 in text characters transmitted over the air
may cause confusion at the other end.
If you need to transmit 8-bit data, but don't want all the features of Transparent
Mode, you should set 8BITCONV ON and AWLEN 8. This may be desirable,
for example, if you are using a special non-ASCII character set.
Bit 7 is always removed in Command Mode, since commands require only the
standard 7-bit ASCII character set.

ABOrt

Mode: Mailbox

Immediate Command

This command gives the SYSOP total control over the Mailbox by allowing
him to force a disconnect on the Mailbox link. It immediately terminates any
mailbox activity currently in progress. You may use it to avoid any QRM, to
cancel a FORWARD or NODEFORW in progress. You can also use it to
terminate mailbox usage by an unwelcome mailbox users.
ACKPRIOR ON|OFF

Mode: Packet

Default: ON

ACKPRIORITY permits an acknowledging TNC to transmit without regard
to the slotting delay. Turning ACKPRIORiyty ON to enable prioritized
acknowledgement.

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If ACKprior is turned off and SLots (see SLots) is set to 0, the modified AX.25
protocol is effectively disabled. The MFJ TNC will behave like normal AX.25
protocol.
Prioritized acknowledgments and slotted channel access can be enabled or
disabled independently of one another. So you could if you wished run normal
AX.25 with slotted channel access or the new protocol without slotted channel
access.

ACKTIME nnnn

Mode: Packet

Default: 14 (140 ms)

Parameters:
nnnn

0 - 250, in 10 ms intervals.

The ACKTIME parameter controls a delay that occurs whenever any packets
have been received by the MFJ TNC that are not addressed to the MFJ TNC.
ACKTIME should be calculated by the radio channel baud rate, and by the
keyup and keydown (TXDELAY and fixed timer, in TNC) delays. It should
reflect the time it takes for an acknowledging TNC on the channel to keyup,
send it's acknowledgement, and release the PTT. This represents the time
required to send a response frame (with no I field appended) at the baud rate
being used on the radio port.
The current 100 millisecond default is close but should be adjusted for 1200
baud work to 130 milliseconds (ACKTime set to 13).
For 300 baud HF work this parameter should be set to 520 milliseconds
(ACKTime set to 52).

ANSWRQRA ON|OFF

Mode: Packet

Default: ON

Parameter:
ON MFJ TNC responds to non-digipeated UI frames
addressed to QRA, within 1 to 16 seconds, with an
empty ID packet.

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OFF Disables MFJ TNC 's ping-response function.
QRA ("Who are you") pinging is supported by the MFJ TNC. A QRA ping polls
all of the TNCs within range. A random number of seconds later, each TNC that
heard the QRA ping will transmit its identification packet. The purpose of this
feature is to reveal to the packeteer, particularly the transient one, the names of
all reachable TNCs and digipeaters.
Sending a QRA ping:
1)

Set the unprotocol callsign to QRA
cmd: UNPROTO QRA

2)

Manually send an unconnected packet
cmd: CONVERSE

^C
cmd:

This sequence will send an unconnected packet. Once the local TNCs have
responded with ID packets, then the user can press a "CRTL-C". The MFJ TNC
will respond with the cmd: prompt.

AUTOLF ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

A linefeed character () is sent to the terminal
after each carriage return character ().

OFF

A  is not sent to the terminal after each .

AUTOLF controls the display of carriage return characters received in packets
as well as echoing those that are typed in.
If the MFJ TNC's sign-on message lines appear to be typed over each other, you
should set AUTOLF ON. If the MFJ TNC sign-on message appears to be

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double-spaced, you should set AUTOLF OFF. If the MFJ TNC's sign-on
message appears to be single-spaced, you have AUTOLF set correctly.
This command only affects what is displayed, not the data sent in packets. If you
want to add linefeed characters to outgoing packets, use the command LFADD.
AWLEN n
Mode: All
Default: 8
Parameters:
n

7 - 8, specifying the number of data bits per word.

This value defines the word length used by the serial IO terminal port.
For most packet operations, including conversation, bulletin board operation, and
transmission of ASCII files, you should set AWLEN 7. If 8 bit words are
transmitted to the MFJ TNC in Command Mode or Converse Mode, the eighth
bit is normally removed, leaving a standard ASCII character, regardless of the
setting of AWLEN.
To transmit and receive packets retaining all 8 data bits of each character, as you
need to do if you send executable files or other special data, you should use
Transparent Mode and set AWLEN 8. Alternatively, you can use Converse
Mode and set AWLEN 8 and 8BITCONV ON (however, the data you then send
must handle the Converse Mode special characters with the PASS prefix).
If the AWLEN command is changed, then the user must perform a RESTART on
the MFJ TNC. If not, the command will remain unchanged.

AX25L2V2 ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

The MFJ TNC will use AX.25 Level 2 Version 2.0
protocol.

OFF

The MFJ TNC will use AX.25 Level 2 Version 1.0 protocol.

Some implementations of the earlier version of AX.25 protocol (e.g., TAPR's
TNC 1) won't properly digipeat version 2.0 AX.25 packets. This command

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exists to provide compatibility with these other TNCs until their software has
been updated.
During the protocol transition period, you should set AX25L2V2 OFF.
After your local area TNCs are updated to the newer protocol version, you should
set AX25L2V2 ON.
When AX25L2V2 is ON, the MFJ TNC answers L2 UI frames with P and C set
with either: RR if connected (regardless of rcvr flow control state), or DM if not
connected.
If retry limit is exceeded, or the MFJ TNC receives a "disconnected" response to
a poll, the connection is ended.

AXDELAY n

Mode: Packet

Default: 0

Parameters:
n 0 - 180,

Specifying the voice repeater keyup delay in 10 ms
intervals.

AXDELAY specifies a period of time the MFJ TNC is to wait, in addition to the
normal delay set by TXDELAY, after keying the transmitter and before data is
sent. This feature will be used by groups using a standard "voice" repeater to
extend the range of the local area network. Repeaters with slow mechanical
relays, split sites, or other circuits which delay transmission for some time after
the RF carrier is present require some amount of time to get RF on the air.
If you are using a repeater that hasn't been used for packet operations before, you
will have to experiment to find the best value for n. If other packet stations have
been using the repeater, check with them for the proper setting. Note that this
command acts in conjunction with AXHANG.
Note that the TAPR TNC 1 and other TNCs using the same version 3.x firmware
interpret n in 120 ms intervals. The value set by AXDELAY on MFJ TNC will
thus be 12 times the value used by a TNC 1 user to give the same delay time.

AXHANG n

Mode: Packet

Parameters:

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n 0 - 20, Specifying the voice repeater hang time in 100 ms intervals.
This value can be used to increase channel efficiency when an audio repeater
with a hang time greater than 100 ms is used. For a repeater with a long hang
time, it is not necessary to wait for the repeater keyup delay after keying the
transmitter if the repeater is still transmitting. If the TNC has heard a packet
sent within the hang period, it will not add the repeater keyup delay
(AXDELAY) to the keyup time.
If you are using a repeater that hasn't been used for packet operations before, you
will have to experiment to find the best value for n. If other packet stations have
been using the repeater, check with them for the proper setting.
Note that the TAPR TNC 1 and other TNCs using the same version 3.x firmware
interpret n in 120 ms intervals. The value you set on MFJ TNC for AXHANG
will thus be 6/5 the value used by a TNC 1 user for the same hang time (when
converting, round down to the nearest integer).

BBSMSGS ON|OFF

Mode: Packet

Default: OFF

This command controls how the MFJ TNC displays certain messages in
command and CONVERSE modes. The messages affected are described below:
MESSAGE

EFFECT WHEN BBSMSGS ON

***CONNECTED to xxxx

A newline is added just before"***"

***DISCONNECTED

"

"

***retry limit exceeded

"

"

***xxxx Busy

"

"

***FRMR sent

"

"

***FRMR rcvd

"

"

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***Connect request:xxxx

This message is omitted.

The BBSMSGS command is primarily useful for host operation. Primarily with
WORLI and like bulletin board systems that require link status messages to begin
in the first output column.
The connect request message is omitted during BBSMSGS mode. This should be
most useful for preventing corruption of messages when forwarding with small
frames.

BEACON EVERY|AFTER n

Mode: Packet

Default: EVERY 0

Parameters:
EVERY

Send beacon at regular intervals.

AFTER

Send beacon once after the specified time interval with
no packet activity.

n

0 - 250, specifying beacon timing in 10 second
intervals. A value of 0 disables the beacon.

This command enables beacon sending and causes the first beacon frame to be
transmitted. A beacon frame consists of the text specified by BTEXT in a packet
addressed to "BEACON" and sent via the digipeat addresses specified by the
UNPROTO command, if any.
If the keyword EVERY is specified, a beacon packet is sent every n*10 seconds.
This mode might be used to transmit packets for testing purposes.
If AFTER is specified, a beacon is sent only after n*10 seconds have passed with
no packet activity. In this case, the beacon is sent only once until further activity
is detected. This mode can be used to send announcements or test messages only
when packet stations are on the air. If you choose n properly you can avoid
cluttering a busy channel with unnecessary transmissions.
Beacon frames from other TNCs can be monitored by setting MONITOR ON.
NOTE: BEACONS will not be sent if BTEXT is null.

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BKONDEL ON|OFF

COMMANDS

Mode: Packet

Default: ON

Parameters:
ON
OFF

The sequence    is
echoed when a character is deleted from the input line.
The  character (\) is echoed when a character
is deleted.

This command determines the way the display is updated to reflect a character
deletion in Command Mode or Converse Mode.

The    sequence will properly update
the screen of a video display. If you have a video display terminal or computer,
you should set BKONDEL ON.
The    sequence on a printing
terminal would result in overtyped text. If you have a paper-output display, or if
your terminal does not respond to the  character (),
you should set BKONDEL OFF. The MFJ TNC will type a 
for each character you delete. You can display the corrected input line by typing
the redisplay-line character, which is set by the command REDISPLA.

BLP ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Puts MFJ TNC into Host Mode

OFF

Takes MFJ TNC out of Host Mode

When the BLP command is turned ON, the MFJ TNC is put into Host Mode.
After you turn BLP ON and enter transparent mode the host code will run. Once
BLP is on, subsequent RESTARTS and power up cycles will be directly and
silently into transparent mode and it will continue to do so until you turn BLP
back OFF or the bbRAM fails.
In order to run the Host Mode code the following commands must be set up as
stated:

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CONMODE TRANS|CONV
You MUST set CONMODE to TRANS else the first time you're
connected you'll lose the DLC connection! This is actually putting the MFJ TNC
into Transparent mode.
PARITY 0
The Parity must be set to 0 for Host Mode operations.
AWLEN
Set the AWLEN command for 8 bits!
MON ON|OFF
If you have BLP ON and MON ON, >ALL< packets-data, command,
beacons, whatever - will be sent to the host on BLP channel 0x71. If you're being
inundated with countless frames when debugging you might want to turn monitor
off to avoid the mess.
MYDLCNUM
DEFLTDLC
Effective only when non-0 MYDLCNUM, this parm tells the TNC what
the DLC address is of the host (ex, MTHOST). Default is 254.

BTEXT text

Mode: Packet

Default: ""

Parameters:
text

Any combination of characters, numbersand paces, up to a
maximum length of 128 characters.

BTEXT specifies the content of the data portion of a beacon packet. The default
text is an empty string, i.e., no message. Beacon packets are discussed in more
detail under the BEACON command.
NOTE: BEACONS will not be sent if BTEXT is null.
You can send multiple-line messages in your beacon by including carriage return
() characters in the text. The  character can be included by preceding
it with the pass character. The pass character is set by the PASS command. If

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you enter a text string longer than 120 characters, an error message will appear
and the command will be ignored.
For example, a Bulletin Board program might set the beacon text to a message
like this, updating the text after each connection:
Mailbox on line. Messages for WB9FLW, AD7I, K9NG.
To clear the BTEXT text without issuing the RESET command, use a % or &
character as the first character in the text.

BUDLIST ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Ignore frames from stations which are not in the LCALLS list.

OFF

Ignore frame from stations which are in the LCALLS list.

BUDLIST works in conjunction with the command LCALLS, which sets up a
callsign list. These commands determine which packets will be displayed when
you have set MONITOR ON. BUDLIST specifies whether the callsigns in the
list are the ones you want to ignore or, alternatively, are the only ones you want
to listen to.
If you want to listen only for packets from a limited list, you should enter this list
with LCALLS and set BUDLIST ON. You can use this feature, for example, to
have your TNC "keep an ear out" for a particular station while you converse with
someone else.
If you want to ignore packets from a limited list, you should list the callsigns to
ignore in LCALLS and set BUDLIST OFF. For example, if there is a bulletin
board on frequency, you can ignore it while monitoring other conversations.

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CALIBRA

COMMANDS

Mode: All

CALIBRA is an immediate command, and is used to transfer control to the
modem calibration routine. Calibration may be performed at any time without
altering the current link state.
Briefly, the commands available in the calibration routine are:

D

K
Q

Switches between the Mark and Space transmit audio
tones.
Alternates between the two transmit tones at a rate
determined by the radio baud rate. This will help you
to calibrate the demodulator.
Activates the modulator and Toggles the PTT line
on/off.
Quits the calibration routine, and returns to command
mode.

CALSET n

Mode: All

Default: None

Parameters:
n

0 - 65535,

Specifying the count setting for use by the
calibration routine.

The number to be specified by CALSET is determined by the frequency f to be
calibrated as follows.
n = (525,000 / f) + 1
n = (262,500 / f) + 1

(modulator tones)
(demodulator tones)

In calibrating the modulator tones, the frequency f will be the actual modulator
tone desired. When calibrating the demodulators, frequency f is the average
frequency between the Mark and Space frequencies.
Round n to the nearest integer. To calibrate the modem tones, you will set n for
the desired frequency using CALSET.

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CANLINE n

Default: $18 

Mode: Packet

Parameters:
n

0 - $7F, specifying an ASCII character string code.

This command is used to change the cancel-line input editing command
character. The parameter n is the ASCII code for the character you want to type
in order to cancel an input line. You can enter the code in either hex or decimal.
For example, to change the cancel-line character to , you would set
CANLINE $15 or CANLINE 21.
If you cancel an input line in Command Mode, the line will be terminated with a
 character, and you will see a new cmd: prompt on the next
line. If you cancel a line in Converse Mode, you will see only the
 and a new line. You can cancel only the line you are currently
typing. Once a  has been entered, you can not cancel an input line using
the cancel-line character. Note that if your send-packet character is not ,
the cancel-line character will cancel only the last line of a multi-line packet. To
cancel the entire packet, use the CANPAC character.
Line cancellation, like all other input editing features, is disabled in Transparent
Mode.

CANPAC n

Mode: Packet

Default: $19 

Parameters:
n

0 - $7F, specifying an ASCII character string code.

CANPAC is used to change the cancel-packet input editing command character.
The parameter n is the ASCII code for the character you want to type in order to
cancel an input packet. You can enter the code in either hex or decimal.
If you cancel a packet in Converse Mode, the line will be terminated with a
 character and a new line. You can only cancel the packet that
is currently being entered. Once you have typed the send-packet character, or
waited PACTIME (if CPACTIME enabled), the packet can not be canceled
even if it has not been transmitted.

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Packet cancellation, like other input editing features, is disabled in Transparent
Mode.
Cancel Display Output
The cancel-packet character also functions to cancel display output in Command
Mode. If you are in Command Mode and type the cancel-packet character, any
characters that would be typed on the screen (except echoed characters) are
"thrown away" by the MFJ TNC. Typing the cancel-output character a second
time restores normal output. To see how this works, try typing DISPLAY, then
type a . The command list display will stop. You won't see any
response from the MFJ TNC to commands. Now type another , and
type DISPLAY again to see that the display is back to normal.
You can use the cancel-display feature if you inadvertently do something that
causes the MFJ TNC to generate large amounts of output to the terminal, such as
giving the DISPLAY command or setting TRACE ON. If you are in Converse
Mode or Transparent Mode and want to cancel display output, you must exit to
Command Mode and then type the cancel- packet character.

CBELL ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Connect bell enabled

OFF

Connect bell disabled

This command is used to control whether an ASCII $O7 or CTRL-G (BELL)
character is sent as part of the connected message.
When set ON, the bell character immediately preceeds the asterisk portion of the
connected message, e.g.:
*** Connected to: 
When CBELL is ON a tone will also be heard on the external speaker. A
speaker must be connected to the SPEAKER jack in the rear panel of the MFJ
TNC, in order to hear this tone.

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CHAT

COMMANDS

Mode: Mailbox

Default: command

The SYSOP may, at any time, break onto the mailbox's connected link. The
resulting mode is like the a typical CONVERS mode packet connection. CHAT
immediately terminates any user or forwarding operation in progress. At the
point when the SYSOP invokes Chat mode, the SYSOP and the connectee are in
an actual packet QSO. This is good to discuss problems with the Mailbox or
equipment failure. CHAT mode continues until the SYSOP returns to command
mode.

CHECK n

Mode: Packet

Default: 12

Parameters:
n

0 - 250, Specifying the check time in 10 second
intervals. A value of 0 disables this feature.

This command sets a connection timeout. If a link connection exists between the
MFJ TNC and another station, and the other station "disappears," your MFJ TNC
could remain in the connected state indefinitely, refusing connections from other
stations. This might happen if propagation changes unexpectedly or an
intermediate digipeater station is turned off. In order to prevent this sort of
lockup, the MFJ TNC will try to clean up the link if the specified time elapses
without any packets being heard from the other TNC. The operation of this
feature depends on the setting of AX25L2V2.
If AX25L2V2 is ON, the MFJ TNC will send a "check packet" to verify the
presence of the other station if no packets have been heard from it for n*10
seconds. This frame contains no information, but is interpreted by the receiving
station's TNC as an inquiry as to whether it is still connected. If the receiving
TNC is still connected, it sends an appropriate response packet. If the TNC
initiating the inquiry does not hear a response after RETRY+1 attempts, it
commences a disconnect sequence, as if the DISCONNE command had been
given.
If AX25L2V2 is OFF and the other station has not been heard for n*10 seconds,
the MFJ TNC will not attempt an inquiry, but will send a disconnect packet, just
as if you had typed the command DISCONNE.

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CHECKV1 ON|OFF

COMMANDS

Mode: Packet

Default: OFF

The CHECKV1 parameter enables the automatic idle-link- disconnect feature for
AX.25 Level 2 Version 1 connections. The idle time before disconnecting will be
equivalent to the AX.25 CHECK parameter (see CHECK command).

CONPERM ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

The current connection on the current stream will not be
allowed to enter the disconnected state.

OFF

The current stream may be connected to and disconnected
from other stations.

This command, when switched ON, forces the MFJ TNC to always maintain the
current connection, even when frames to the other station exceed RETRY
attempts to get an acknowledgment. RESTART and power off/on cycling will
not affect this connected state.
This command only takes effect when a connection is established. It functions on
a stream-by-stream basis when multiple connections are allowed.
It is useful for certain networking applications, meteor scatter and other noisy,
less-reliable links, while still allowing connections on other streams to operate
normally (automatic disconnect based on RETRY, etc.).
CMDTIME n

Mode: Packet

Default: 1

Parameters:
n

0 - 250, Specifying Transparent Mode timeout value in 1
second intervals. If n is zero, the only exit from
Transparent Mode is to send a BREAK signal or
interrupt power to the MFJ TNC.

This command sets the Transparent Mode timeout value. In order to allow
escape to Command Mode from Transparent Mode while permitting any
character to be sent as data, a guard time of n seconds is set up.

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The same Command Mode entry character used for exit from Converse Mode is
used to exit Transparent Mode, but the procedure is different. (The Command
Mode entry character is set by COMMAND.) Three Command Mode entry
characters must be entered less than n seconds apart, with no intervening characters, after a delay of n seconds since the last characters were typed. After a final
delay of n seconds, the MFJ TNC will exit Transparent Mode and enter
Command Mode. You should then see the prompt
cmd:
The diagram below illustrates this timing.
last
first
second
third
TNC
terminal
command
command
command
now in
input
mode
mode
mode
Command
|
entry
entry
entry
Mode
|
character
character
character
|
|
|
|
|
|
|
|
|
|
|
|<-----longer------>|----<-shorter->----|----<-shorter->----|<--------n-------->|
than n
than n
than n

CMSG ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

A text message is sent as the first packet after a connection is
established.

OFF

The text message is not sent.

CMSG enables automatic sending of the message set by CTEXT whenever your
MFJ TNC accepts a connect request from another TNC.
For example, if you have left your station running even though you don't want to
operate just now, you might want to set CMSG ON to let people know that you
can't talk when they connect to your MFJ TNC. When you are ready to operate,
you would set CMSG OFF.

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CMSGDISC ON:OFF

COMMANDS

Mode: Packet

Default: OFF

Parameters:
ON

Automatic disconnect enabled

OFF

Automatic disconnect disabled

This command controls whether the MFJ TNC will initiate a disconnect sequence
after it is connected to.
If CMSG is OFF, or CTEXT has no connected text, the MFJ TNC initiates a
disconnect immediately upon receiving information or acknowledgement frames
from the other station.
If CMSG is ON end CTEXT contains some text information, the MFJ TNC
initiates a disconnect after the packet containing connect text (CTEXT) is
acknowledged.
This command may be useful to bulletin board operators or others with a need to
send a short message, confirm its receipt, and disconnect.
NOTE:
Use this command with care. If you find you're able to receive
connects, yet never get data, it's possible CMSGDisc has been left on. It's also
possible is that RS-232 DCD is holding the terminal off -- see Chapter 5 for
details on hardware flow control.

COMMAND n

Mode: All

Default: $03 

Parameters:
n

0 - $7F, Specifying an ASCII character code.

This command is used to change the Command Mode entry character. You can
enter the code in either hex or decimal.
Command Mode is entered from Converse Mode when this character is typed. If
you type the Command Mode entry character while you are already in Command
Mode, nothing will happen. To see how this works, enter Converse Mode by
typing CONVERS. Anything you type will become packet data. Now type a

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. You will see the Command Mode prompt, indicating successful exit
from CONVERSE mode to Command Mode. The display might look like this:
cmd:CONVERS
Hello World! I'm on the air on packet radio!
[enter ]
cmd:
See the entry under CMDTIME or the discussion of Transparent Mode in
Chapter 5 for information on how the Command Mode entry character is used for
escape from Transparent Mode.
For terminals without a "control" key, you will have to reasign another key such
as a graphic symbol or punctuation mark which is normally not used in
operations.

CONMODE CONVERS TRANS Mode: Packet

Default: CONVERS

Parameters:
CONVERS

Sets automatic entry to Converse Mode when a
connection is established.

TRANS

Sets automatic entry to Transparent Mode when a
connection is established.

CONMODE controls which mode the MFJ TNC will be placed in after a
connection is established. The connection may result either from a connect
request received over the air or a connect initiated by a CONNECT command
that you issued. For most operations, you would set CONMODE to CONVERS.
However, if you are using Transparent Mode for a bulletin board program, for
example, you would set CONMODE to TRANS so that the correct mode will be
entered when your bulletin board receives a connect request.
If you initiate a connection with the CONNECT command, the control of
Converse or Transparent Mode is determined by NEWMODE.
If the MFJ TNC is already in Converse or Transparent Mode when the
connection is completed, the mode will not be changed. If you have typed part of
a command line when the connection is completed, the mode change will not

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take place until you complete the command or cancel the line. This prevents the
last part of your command from inadvertently being sent as a packet.

CONNECT call1 [VIA call2[,call3...,call9]]

Mode: Packet

Parameters:
call1

Callsign of TNC to be connected to.

call2

Optional callsign of MFJ TNC to be digipeated through. As
many as eight digipeat addresses can be specified.

The part of the command line in brackets, VIA call2[, call3...,call9] is optional.
The double-bracketed text, ,call3...,call9, is also optional, but would only be used
if VIA call2 is present. The brackets are not typed.
Each callsign may include an optional sub-station ID specified as -n immediately
following the callsign. The digipeat fields are specified in the order in which
you want them to relay the packets to the destination, call1.
CONNECT is an immediate command. It initiates a connect request to MFJ
TNC call1, optionally through digipeaters. If NEWMODE is ON, the MFJ
TNC will immediately enter Converse Mode or Transparent Mode, as specified
by the command CONMODE. If NEWMODE is OFF, the MFJ TNC will enter
Converse Mode or Transparent Mode when the connection is successfully completed.
An error message is returned if the MFJ TNC is in a connected state, or is
already attempting to connect or disconnect. If no response to the connect
request occurs after the number of attempts specified by RETRY, the command
is aborted and a message is typed. The MFJ TNC returns to Command Mode if

NEWMODE is ON. If NEWMODE is OFF, the mode does not change, i.e. the
MFJ TNC remains in Command Mode.
For example, to connect to WA7GXD using N0ADI-1 (who is near your QTH)
and WD0ETZ (who is near GXD's QTH) as digipeaters, you would type
CONNECT WA7GXD VIA N0ADI-1,WD0ETZ

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COMMANDS

Packets coming back from WA7GXD access the digipeaters in the opposite
order. Thus, packets from WA7GXD will first be repeated by WD0ETZ, then by
N0ADI-1.
CONOK ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

Connect requests from other TNCs will be accepted.

OFF

Connect requests from other TNCs will be rejected.

This command determines the action taken by the MFJ TNC when a connect
request for it is received though the radio. If CONOK is ON, the request will be
acknowledged, the standard connect message will be typed and either Converse
or Transparent Mode will be entered, depending on the setting of CONMODE.
If CONOK is OFF and the MFJ TNC is not in Transparent Mode, the TNC will
notify you of the connect attempt with the following message.
connect request: 
The callsign of the station trying to connect will replace .
All connect requests from stations with totally blank callsigns are rejected with a
busy response.
The MFJ TNC will also issue a DM packet, or "busy signal" to the requesting
station. The user may then issue his own connect command. If the MFJ TNC
receives a DM packet in response to a connect request, it will type the message
***  station busy
with the callsign of the station that sent the DM packet in place of .

For example, if you want to leave your station running as a digipeater you might
set CONOK OFF until you are ready for a conversation. If you get a connect
request in the meantime, you can change your mind. Stations attempting to

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connect to your MFJ TNC will be able to see that the station is up but not
available for connection (it might still be useful as a digipeater).

CONSTAMP ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Connect and disconnect status messages are
time stamped.

OFF

Connect status messages are not time stamped.

This command enables time stamping of *** CONNECTED status messages.
The date and time information is then available for use by Bulletin Board
programs or other computer applications. The date and time must be set initially
by the DAYTIME command before time stamping will occur. The date format
is determined by the DAYUSA command.
For example, if CONSTAMP is ON, DAYUSA is ON, and the date and time
have been set, a connect message might appear as follows.
*** CONNECTED to N2WX [05/28/85 16:28:31]

CONVERS

Mode: All

CONVERS is an immediate command, and will cause the MFJ TNC to exit from
Command Mode into Converse Mode. Any link connections are not affected.
Once in Converse Mode, everything you type is packetized and transmitted over
the radio. Typing the Command Mode entry character returns the MFJ TNC to
Command Mode. See the discussions of Converse Mode in Chapter 4 and
Chapter 5.

CPACTIME ON|OFF

Mode: Packet

Parameters:
ON

Packet timeout is used in Converse Mode.

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OFF
Packet timeout is not used in Converse Mode.
This command enables the periodic automatic sending of packets in Converse
Mode. This feature may be used for computer communications, such as Bulletin
Board operation, when the full Transparent Mode features are not desired.
If CPACTIME is ON, characters are packetized and transmitted periodically as
they are in Transparent Mode, but local editing and display features of Converse
Mode are enabled, and software flow control may be used. For a discussion of
how periodic packetizing works, see the command PACTIME, which controls the
rate and mode of packet assembly.
You should set CR OFF in this mode, since otherwise the send-packet character
will be inserted in the data being packetized even though it was not typed. In
order to include  characters in transmitted packets, set SENDPAC to a
normally unused character (e.g., ), at which point the TNC will treat
 as an ordinary character.
You can set CPACTIME ON for a mode of operation similar to full break-in
CW, in which your text is transmitted soon after you type it, but in short bursts of
a few characters, and the other station may break in at will. Some operators find
it easier to carry on a conversation in this mode, since it eliminates the delays
while long packets are being typed.

CR ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

The send-packet character, normally , is appended to all
packets sent in Converse Mode.

OFF

The send-packet character is not appended to
packets.

When CR is ON, all packets sent in Converse Mode will include, as the last
character of the packet, the send-packet character which forces the packet to be
sent. If CR is OFF, the send-packet character is interpreted solely as a command
to the MFJ TNC, not as data to be included in the packet, and furthermore, it will
not be echoed to the terminal.

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Setting CR ON and SENDPAC $0D results in a natural conversation mode.
Each line is sent when a  is entered, and arrives at its destination with a
 at the end of the line. If the station at the other end reports overprinting of
lines on his display, you can set LFADD ON, or the other station can set
AUTOLF ON.
CTEXT text

Mode: Packet

Default: ""

Parameters:
text

Any combination of characters and spaces, up to a maximum
length of 120 characters.

CTEXT specifies the text of the packet to be sent after a connection is made, if
CMSG is ON. The default text is an empty string, i.e., no message.
You can send multiple-line messages by including carriage return ()
characters in the text. The  character can be included by using the pass
character immediately preceding it (see the PASS command). If you enter a text
string longer than 120 characters, an error message will appear and the
command will be ignored.
For example, you might set your CTEXT message to
I'm not here right now, but you may leave a message.
To clear the CTEXT text without issuing a RESET command, use a % or & as
the first character in the message.
You cannot connect to yourself and see your CTEXT unless going thru a
digipeater. CMSG only takes effect if you are connected to by another TNC.
CSTATUS

Mode: Packet

CSTATUS is an immediate command which shows the stream identifier and
link state of all ten streams (links), the current input and output streams, and
whether or not each stream is "permanent" (see CONPERM).
An example of a display resulting from issuing a CSTATUS command is:
cmd:CS

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A stream
B stream
C stream
D stream

IO Link state is: CONNECTED to 305MLB
Link state is: CONNECTED to AD7I P
Link state is: DISCONNECTED
Link state is: CONNECTED to N0ADI
via K9NG-2

I stream
J stream

Link state is: CONNECT in progress
Link state is: CONNECTED to KV7B
via NK6K-1

The example above shows the A stream is assigned both the input and output
streams. The B stream is connected to AD7I "permanently." All other streams'
states are shown as they might normally appear with multiple connections.

DAYTIME date&time

Mode: Packet

No default

Parameters:
date&time

Current date and time to set.

This command allows you to set the current date and time for the MFJ TNC. The
format for entering the date&time is
yymmddhhmm
where yy is the last two digits of the year, mm is the two- digit month code (0112), dd is date (01-31), hh is the hour (00-23), and mm is the minutes after the
hour (00-59). All these codes must be exactly two digits, so that numbers from 0
to 9 must be entered with leading zeros. The MFJ TNC does not check
thoroughly for the correct number of days in a month, so you should use some
judgment when you set the date.
The date&time parameter is used by the commands CONSTAMP and
MSTAMP to "time stamp" received and monitored messages. Entries in the
"heard" (displayed by MHEARD) are also time stamped if date&time has been
set. The MFJ TNC's time is updated continuously as long as it is powered up.
You must reset the date and time each time you turn on the MFJ TNC. If you
don't do this, the commands CONSTAMP and MSTAMP will not enable time
stamping.

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If you type DAYTIME without a parameter, the MFJ TNC will display the
current date and time. The format of the display is dd-mm-yy hh:mm if
DAYUSA is OFF, and mm/dd/yy hh:mm if DAYUSA is ON. The format for
entering date&time is not affected. For example,
cmd:DAYTIME 8402291530
sets the date and time to February 29, 1984 at 3:30 PM. The display of the date
and time, with DAYUSA ON would be:
cmd:DAYTIME
02/29/84 15:30:26

DAYUSA ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

Date is displayed in the format mm/dd/yy.

OFF

Date is displayed in the format dd-mm-yy.

This command determines the format for the MFJ TNC's display of the date. If
DAYUSA is ON, the standard U.S. format is used; if DAYUSA is OFF, the
standard European format is used. This command affects the format of the date
display used in "time stamps" as well as the display when DAYTIME is entered
without parameters. The format for entering the time using DAYTIME is not
affected.
For example, if DAYUSA is ON, then July 2, 1984 at 9:28:44 AM would be
displayed as
cmd:DAYTIME
07/02/84 9:28:44
If DAYUSA is OFF the same date and time would appear as
cmd:DAYTIME
02-07-84 9:28:44

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DEADTIME nnn
Parameter:

Default: 33 (330 ms)

nnn

Mode: Packet

0 thru 250 in 10ms

The DEADTIME parameter selects the basic time interval used by the slotting
procedures. A delay of length = (random multiple of DEADTIME) will be
applied to the all outgoing packets that are not acknowledgmented.
DEADTIME must be set to a value that accounts for the slowest acceptable
station on the channel. It includes the time required for the remote station's radio
to come on the air properly after assertion of PTT (TXDelay) and the time
required for the local station's squelch (if used) and TNC DCD circuits to allow
generation of a "DCD true" signal in the local TNC. Ideally, once the proper
value for this timer is ascertained, all stations on the channel will use the same
value.
The current default for this parameter is a short 30 milliseconds. This represents
only the worst case delay for the TNC's DCD circuit and completely ignores the
radio delays.
Most HF linear mode radios are MUCH faster than VHF FM radio. A reasonable
setting for HF work is 120 milliseconds (DEAdtime set to 12). This should work
fine with virtually any HF radio stable enough to consider using on HF packet.

DELETE ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

The delete character input editing character is 
($7F).

OFF

The delete character input editing character is
 ($08).

This command is used to change the input editing command for character
deletion. When this character is typed, the last character from the input line is

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deleted. How the TNC indicates the deletion is controlled by the BKONDEL
command.
You can not use this character to delete past the beginning of a line, although you
can delete  characters that have been entered in the text with the pass
character.
To see a corrected display of the current line after you have deleted characters,
type the redisplay-line character, which is set by the REDISPLA command.

DEFLTDLC

Mode: Host

Default: 254

Parameters:
Effective only when non-0 MYDLCNUM, this parm tells the TNC what the
DLC address is of the host (ex, MTHOST). Default is 254.

DIGIPEAT ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

The MFJ TNC will digipeat packets if requested.

OFF

The MFJ TNC will not digipeat packets.

When this parameter is ON, any packet received that has your TNC's callsign
(including SSID) in the digipeat list of its address field will be retransmitted.
Each station included in the digipeat list relays the packet in its turn, marking
the packet so that it will not accidentally relay it twice (unless so requested), and
so that the stations will relay the packet in the correct order. Digipeating takes
place concurrently with other MFJ TNC operations and does not interfere with
normal operation of a packet station.
In the spirit of cooperation typical of Amateur operation, you will probably want
to set DIGIPEAT ON most of the time. However, you might want to disable
digipeating if you're not home, or if your transmit relay makes enough noise to
wake you up at night.

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The command HID enables automatic transmission of identification packets if
your station is acting as a digipeater.

DISCONNE

Mode: Packet

DISCONNE is an immediate command. It will initiate a disconnect request with
the currently connected station. A successful disconnect results in the display of:
*** DISCONNECTED
Other commands may be entered while the disconnect is taking place, although
connects are disallowed until the disconnect is completed. If the retry count is
exceeded while waiting for the other side to acknowledge, the MFJ TNC moves
to the disconnected state. If a disconnect command is entered while the MFJ
TNC is disconnecting, the retry count is immediately set to the maximum
number. In either case, the disconnect message is
*** retry count exceeded
*** DISCONNECTED
Disconnect messages are not displayed when the MFJ TNC is in Transparent
Mode.
DISPLAY [class]

Mode: All

Parameters:
class

Optional parameter-class identifier, one of the following:

ASYNC
CHARACTE
ID
LINK
MONITOR
TIMING
HEALTH

displays asynchronous port parameters
displays special characters
displays ID parameters
displays link parameters
displays monitor parameters
displays timing parameters
displays 25 counters*

*The twenty five counters in the MFJ TNC are 16 bits wide, and are ALWAYS
initialized to 0000 on power up or "RESTART".

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ASYFRERR:

This is a health counter reflecting the number of
hardware-detected asynchronous framing errors.
Framing errors are not fatal. They merely indicate
that the terminal attached to your MFJ TNC is not
configured
correctly
with
regard
to
AWLEN/PARITY.

ASYQOVER:

Records the number of times received- connected
packets have been rejected due to insufficient space
in the buffer holding the data going to the terminal.
No actual data loss occurs, provided the connection
remains intact. ASYQOVER counts can be avoided
by increasing the speed of the attached RS-232
terminal and/or printer. (SEE also SENTRNR)

ASYRXOVR:

Increases when the software does not service the
asynchronous receiver in time. Indicates data from
the user to the MFJ TNC is being dropped. This
error counter should never become non- zero under
supported data rates.

BBFAILED:

Counts number of times bbRAM checksum was in
error.

DIGISENT:

Each frame digipeated by the MFJ TNC causes the
counter to increase.

HOVRERR:

Increases when HDLC receiver is not serviced
rapidly enough and data is lost. This counter should
never increment at any supported data rate.

HUNDRERR:

Increases when the HDLC transmitter is not serviced
rapidly enough and frames are aborted. This counter
should never be non-zero at any supported data rate.

RCVDFRMR:

Increases when Frame reject frames are received
from a connected station.

RCVDIFRA:

Increases for each reception of an I frame from a
connectee.

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RCVDREJ:

Increases for each reception of an REJect frame from
a connectee.

RCVDRNR:

Counts the number of AX.25 L2 receiver- not-ready
frames received since power-up and during
connections. The count may be useful in gauging
system throughput.

RCVDSABM:

Each received SABM frame addressed to the MFJ
TNC causes this counter to be increased by one.

RXABORT:

RXABORT is a count of the number of hardwaredetected HDLC abort events. A large number of
counts is perfectly normal and should not cause
concern.

RXCOUNT:

Increases when any frame is received with good
CRC (or any CRC if HGARBAGE is turned on).

RXERRORS:

Increments each time a received frame is thrown out
due to it being too short, suffering overrun(s), or it
having a bad CRC. Latter occurs only when CRC
checking is enabled (i.e. HGARBAGE is OFF). This
counter will often increment in the presence of noise.

RXLENERR:

RXLENERR counts the number of too-short frames
received. The counts are of diagnostic use only and
here again, non- zero counts are not a matter of
concern.

RXRESYNC:

RXRESYNC is a diagnostic health counter recording
the number of receiver resynchronizations handled
internally to the MFJ TNC. Non-zero counts indicate
the attached radio may be either turned off or
squelched. Note that in almost every situation your
radio must to have its squelch fully opened!

SENTFRMR:

Increments each time a Frame reject frame is
transmitted.

SENTIFRA:

Increases by one each time an I frame is sent.

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SENTREJ:

Whenever a REJect frame is transmitted, this
counter is incremented.

SENTRNR:

This health counter tracks the number of times your
MFJ TNC has had to send Receiver-Not-Ready
(RNR) frames. Non- zero counts may be an
indication that the RS-232 terminal or baud rate is
too slow.

TXCOUNT:

Incremented
transmitted.

whenever

a

frame

is

correctly

TXQOVFLW: Counts how many times frames were disconnected
because the outgoing frame queue wastoo small.
TXTMO:

This register may accumulate counts as the MFJ
TNC successfully recovers from HDLC transmitter
timeouts. This is not a useful command for the
majority of the users. Default is 0.

The counters just described, and the setting of HEALLED are displayed in
response to the health inquiry.
DISPLAY is an immediate command, and with no class parameter will cause all
control parameters and their current values to be displayed. Sub-groups of
related parameters can be displayed by specifying the optional parameter-class.
Individual parameters can be displayed by entering the parameter name with no
options.

DWAIT n

Mode: Packet

Default: 33

Parameters:
n

0 - 250, Specifying default wait time in 10 ms intervals.

This value is used to avoid collisions with digipeated packets. The MFJ TNC
will wait the default wait time after last hearing data on the channel before it
begins its own keyup sequence, unless the MFJ TNC is waiting to transmit
digipeated packets. This value should be agreed on by all members of a local

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area when digipeaters are used in the area. The best value will be determined by
experimentation, but will be a function of the keyup time (TXDELAY) of the
digipeater stations.
This feature is intended to help alleviate the drastic reduction of throughput that
occurs on a channel when digipeated packets suffer collisions. It is necessary
because digipeated packets are not retried by the digipeater, but must be restarted
by the originating station. If all stations specify a default wait time, and the right
value of n is chosen, the digipeater will capture the frequency every time it has
data to send, since digipeated packets are sent without this delay.
The DWAIT timer is
ACKPRIORITY is ON.

defeated

(superseded)

Mode: All

ECHO ON|OFF

when

the

command

Default: ON

Parameters:
ON

Characters received from the computer or terminal are echoed
`by the MFJ TNC.

OFF

Characters are not echoed.

This command controls local echoing by the MFJ TNC when it is in Command
or Converse Mode. Local echoing is disabled in Transparent Mode.
If you don't see your input on the display, you should set ECHO ON. If you see
two copies of every character you type, you should set ECHO OFF. If you see
the characters you type displayed correctly, you have ECHO set correctly.

ESCAPE ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

The  character ($1B) is output as "$" ($24).

OFF

The  character is output as  ($1B).

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This command specifies the character which will be output when an 
character is to be sent to the terminal. The  translation is disabled in
Transparent Mode.
This command is provided because some terminals, and computer programs that
emulate such terminals, interpret the  character as a special
command pre&ix. Such terminals may alter their displays depending on the
characters following the . If you have such a terminal, you can
protect yourself from unexpected text sequences and from other packeteers by
setting ESCAPE ON.
See also the MFILTER command, which allows general character stripping
(rather than character translation) in monitored packets.

FIRMRNR

ON|OFF

Mode: Packet

Default: OFF

FIRMRNR controls the handling of busy states by the MFJ TNC. Setting
FIRMRNR ON improves channel efficiency, but is incompatible with earlier
TNC-2 releases. The incompatibility is a result of vague protocol specifications.
FIRMRNR should be always be set ON when conversing with network nodes,
for example, NET/ROM. In other cases, it is recommended that FIRMRNR be
left OFF unless you can be assured the other TNC you are connected to supports
FIRMRNR.

FLOW ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

Type-in flow control is active.

OFF

Type-in flow control is disabled.

When type-in flow control is enabled, any character entered from the terminal
will halt output to the terminal until: (1) a packet is forced (in Converse Mode);
(2) a line is completed (in Command Mode); (3) the packet length is exceeded; or
(3) the terminal output buffer fills up. Canceling the current command or packet
or typing the redisplay-line character will also cause output to resume. Type-in
flow control is not used in Transparent Mode.

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Setting FLOW ON will keep received data from interfering with data entry. If
you (and the person you are talking to) wait for a packet from the other end
before starting to respond, you can set FLOW OFF. Some Bulletin Board
programs may work best with FLOW OFF. Some computers with "software
UARTs" may be unable to send and receive data at the same time; users of such
computers should set FLOW ON.

FORWARD

(dest bbs,[optional via])

Mode: Packet

FOrward is an immediate command. Messages can be forwarded manually, by
command, or automatically. They can also be forwarded hourly or by your local
full-service mailbox reverse forward request. When invoked the mailbox initiates
a connect to the callsign of the destination BBS. When a connect is established
the mailbox will proceed to send your messages. Messages that qualify for
forwarding must meet two conditions, they are:
1. Have flags of 'N'ot read
2. Must have a callsign in the @ addresses that are different
from MYMCALL.
After forwarding, each message flag is set to 'F' to prevent further forwards.
When all messages are forwarded, if the dest bbs supports reverse forwarding (as
determined by "$" in its SID) then TNC will attempt to elicit a reverse forward.
For more information on Forwarding and Reverse Forwarding can be found in
the Mailbox Features section of this manual.

FRACK n

Mode: Packet

Default: 3

Parameters:
n

1 - 15, Specifying frame acknowledgment timeout in 1
second intervals.

After transmitting a packet requiring acknowledgment, the MFJ TNC will wait
for the specified frame acknowledgment timeout before incrementing the retry
counter and sending the frame again. If the packet address includes relay
requests, the time between retries will be adjusted to

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Retry interval = n * (2*m + 1)
where m is the number of intermediate relay stations.
When a retried packet is sent, a random wait time is added to any other wait
times in use. This is to avoid lockups in which two TNCs repeatedly send
packets which collide with each other. Frack will also reduce timeouts with
multiple digipeaters.
FULLDUP ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Full duplex mode is enabled.

OFF

Full duplex mode is disabled.

When full duplex mode is disabled, the MFJ TNC makes use of the Data Carrier
Detect signal from the modem to avoid collisions, and acknowledges multiple
packets in a single transmission with a single acknowledgment. When full
duplex mode is enabled, the MFJ TNC ignores the DCD signal and acknowledges packets individually. The latter mode is useful for full-duplex radio
operation, such as through OSCAR 10. It should not be used unless both your
station and the station you are communicating with are full-duplex stations.
You may find full-duplex mode useful for some testing operations, such as the
analog- or digital-loopback tests.
FULLDUP should be ON during digital loopback tests.

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HEADERLN ON|OFF

COMMANDS

Mode: Packet

Default: OFF

Parameters:
ON

The header for a monitored packet is printed on a separate line
from the packet text.

OFF

The header and packet text of monitored packets are printed
on the same line.

This command affects the display format for monitored packets. If HEADERLN
is OFF, the address information is displayed with the packet:
KV7D>N2WX: Go ahead and transfer the file.
If HEADERLN is ON, the address information is displayed, followed by the
packet text on a separate line:
N2WX>KV7D:
Sorry, I'm not quite ready yet.
If you have set MRPT ON or enabled MSTAMP, you may wish to set
HEADERLN ON, as the packet header quickly becomes long enough to fill a
screen when these functions are active.

HEALLED ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

The MFJ TNC will "dither" the CON and STA LEDs.

OFF

The MFJ TNC will control the CON and STA LEDs in
normally.

This command allows the user to redefine the functions of the two CPU
controllable LEDs (i.e. the STAtus and CONnect LEDs).
When HEALLED is set ON, the two LEDs flash in a seemingly random fashion.
At a glance, the user may be able to make a judgment on whether the software
has crashed, since the LEDs will probably not flash if the software fails
catastrophically.

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With HEALLED set OFF, the LEDs function normally as before.

HID ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Enables HDLC identification by a digipeater.

OFF

Disables HDLC identification.

This command is used to enable or disable the sending of identification packets
by the MFJ TNC. If HID is OFF, the MFJ TNC will never send an identification
packet. If HID is ON, the MFJ TNC will send an identification packet every 9.5
minutes if the station is digipeating packets. The ID command allows the
operator to send a final identification packet if the station is being taken off the
air.
An identification consists of an unsequenced I frame whose data field is your
station identification. The identification packet is addressed to the "CQ" address
set by the UNPROTO command. Your station identification is your callsign as
set by MYCALL, with "/R" appended.

ID

Mode: Packet

ID is an immediate command. It will send a special identification packet. ID
can be used to force a final identification packet to be sent as a digipeater station
is being taken off the air. The identification packet will be sent only if the
digipeater has transmitted since the last automatic identification.
An identification consists of an unsequenced I frame whose data field is your
station identification. The identification packet is addressed to the "CQ" address
set by the UNPROTO command. Your station identification is your callsign as
set by MYCALL, with "/R" appended.

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KILONFWD ON|OFF

COMMANDS

Mode: Mailbox

Default: OFF

Parameters:
ON Messages forwarded out of Mailbox will be killed after a
forwarding process is complete.
OFF Default; Messages forwarded out of the Mailbox are not killed after
a forwarding process is completed.
The setting of KILONFWD determines whether or not the TNC deletes a
message after it has been forwarded. If your Mailbox RAM space is critical then
you might want to set this command ON. Setting this command to ON, could
cause problems, because once a message is killed it cannot be recovered.

KISS ON|OFF

Mode: Packet

Default: OFF

The KISS interface is installed in firmware of the MFJ TNC. KISS enables the
MFJ TNC to act as a modem for a host computer. Turning KISS ON allows the
MFJ TNC to run programs such as TCP/IP and other programs which use
the Serial Link Interface Protocol (SLIP).
Before enabling KISS, make sure radio baud rate and terminal baud rate are set
to the desired values. The terminal's baud rate that's determined at sign on is
the same that will be used for KISS.
Once the operating parameters have been selected, set KISS ON and then issue
a RESTART command. The CON and STA LEDs will blink on and off three
times to indicate that the MFJ TNC has entered the KISS mode. Now you may
call up a TCP/IP, or another host program that can use KISS or "SLIP".
If you are using the KA7Q TCP/IP program and wish to switch to the AX.25
mode of operation, you can issue the command: param ax0 255, then press
"RETURN". This command must be issued under TCP/IP "net>" prompt and in
lower case letters.
Once the MFJ TNC receives the "param ax0 255" command, it turns KISS off
and will revert back to ordinary AX.25 mode of operation. When the MFJ TNC
is powered on again, it will sign on to the AX.25 operation mode.

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If KISS is turned ON and you have problem revert the MFJ TNC back to normal
AX.25 operation with the above procedure, you can also turn KISS OFF by
removing JMP5 on the mother board. Reinstall JMP5 after a few minutes.

LCALLS call1[,call2...,call8]

Mode: Packet

Default: ""

Parameters:
call

Callsign list. Up to 8 calls, separated by commas.

Each callsign may include an optional sub-station ID specified as -n immediately
following the call. This command works in conjunction with BUDLIST and
allows selective monitoring of other packet stations. These two commands determine which packets will be displayed when you have set MONITOR ON.
BUDLIST specifies whether the callsigns in the list are the ones you want to
ignore or, alternatively, are the only ones you want to listen to.
If you want to listen only for packets from a limited list, you should enter your
selected list with LCALLS and set BUDLIST ON.
If you want to ignore packets from a limited list, you should list the callsigns to
ignore in LCALLS and set BUDLIST OFF.
"%" and "&" may now be used to clear the LCALLS list.
LCSTREAM ON|OFF
Mode: Packet

Default: ON

Parameters:
ON

The MFJ TNC will translate the character immediately
following the STREAMSWITCH character to upper case before
processing it.

OFF

The MFJ TNC will process the character immediately
following the STREAMSWITCH character as it is entered.

When operating multi-connect, the user must enter a stream identifier (default A
through J) after the STREAMSWITCH character (default |) to select a new
logical stream to send data. Normally, the stream identifier must be in upper
case, or an error message will result.

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COMMANDS

When LCSTREAM is ON, the character immediately following the
streamswitch character is converted to upper case before being acted upon. Thus,
the case (upper or lower) becomes insignificant. Use of LCSTREAM is useful if
you are typing in lower case and don't want to be bothered with remembering to
switch to upper case when changing streams.

LCOK ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

The MFJ TNC will send lower case characters to the computer
or terminal.

OFF

The MFJ TNC will translate lower case characters to upper
case.

If LCOK is OFF, lower case characters will be translated to upper case before
being output to the terminal. This case translation is disabled in Transparent
Mode. Input characters and echoes are not case translated.
If your computer or terminal does not accept lower case characters it may react
badly if the MFJ TNC sends such characters to it. This command allows you to
translate all lower case characters received in packets, as well as messages from
the MFJ TNC, to upper case.
Since echoes of the characters you type are not translated to upper case, you can
use this command to make your display easier to read when you are conversing in
connected mode. If you and the other station's operator set LCOK OFF, you can
each type your own messages in lower case and see incoming packets displayed
in upper case. It will then be easy to distinguish incoming and outgoing lines.

LFADD ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

An ASCII line-feed character is appended to the transmission

OFF

An ASCII line-feed character is not appended to the
transmission

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When LFADD is ON and the ASCII or Packet mode is selected, MFJ TNC will
append an ASCII line feed character, $0A, to the transmission immediately
after a carriage return is sent.
LFADD should usually be switched OFF as the vast majority of TNCs (including
the MFJ TNC) are configured to automatically go to a new line whenever a
carriage return is printed.
Also see: AUTOLF parameter

LFIGNORE ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

All  characters are ignored.

OFF

All  characters will be used.

This command controls whether MFJ TNC responds to ASCII Lind Feed (
$OA) characters or ignores them in command and converse modes.
When turned on, line feeds are totally ignored except in transparent mode.

MAILBOX ON|OFF

Mode: Packet

Default: ON

When the MAILBOX command is set to ON, all of the mailbox functions are
active. Note that the MAILBOX is a single- user device; therefore, if you wish
to use the MAILBOX it is necessary for you to set USERS 1 and select stream
A. Note that these are the default settings and selections, respectively. However,
as we mentioned in Chapter 5, the Mailbox has been significantly improved. For
more extensive information on the new improved Mailbox, please refer to
Chapter 5.
If you wish to have your messages time and date stamped, then make sure that
DAYTIME is set with the correct time or else each message entered without
DAYTIME will not be shown.
A basic explaination of the Mailbox commands are as follows:

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K

Kills all messages addressed to you, depending on the setting of
the Y flag.

K ##

Kills the message in slot nn, depending of the setting of the Y flag.
Remote users may only kill message addressed to them or originated by
them. the local SYSOP,however, can kill all messages.

L

Lists the all messages in Mailbox. Listed messages will contain the slot
number, originator, destination, and subject field of all currently used
slots.

R

Allows you to Read only the messages which are addressed to you.

R ##

Allows Reading of a message in a particular slot number.

S call

Lets you Send a message to the specified callsign. "Call" must be a
callsign valid under the same format as the MYCALL, CONNECT and
other callsign commands.

SP call Lets you Send a personal message to the specified callsign. This is a
private message which can only be read by the originating station, the
station which it is addressed to and the mailbox SYSOP.
B

Logout: Initiates a disconnect sequence from the mailbox.

Edit

This allows you to Edit the message headers for a Forwarding or
Reverse Forwarding process.

J

This function when initiated responds with the TNC's MHeard list. This
list will contain the eleven most recently heard stations.

M

This will let a remote user switch memory banks in the Mailbox RAM.

T

When this command is initiated will allow a remote user to PAGE the
SYSOP.

H(elp) Displays the mailbox command list, with a brief description of
commands, available to the user.

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MAILLED ON|OFF

COMMANDS

Mode: Packet

Default: ON

Parameters:
ON
The STA led serves as a Mail present indicator and performs
normal functions.
OFF

The STA led only performs it's normal functions.

When MAILLED is ON, the MFJ TNC's STA LED will not flash while the
Mailbox is ON. However, the STA LED will flash if mail is present in the
Mailbox for the SYSOP. The STA LED reverts to its normal function, lit when
unacknowledged packets are pending, if the MFJ TNC is in a CONNECTED
state, or if MAILLED is OFF.

MALL ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

Monitored packets include both "connected" packets and
"unconnected" packets.

OFF

Monitored packets include only "unconnected" packets.

This command determines the class of packets which are monitored. If MALL
is OFF, only otherwise eligible packets (as determined by the BUDLIST and
LCALLS commands) sent by other TNCs in the unconnected mode are
displayed. This is the normal manner of operation when this MFJ TNC is being
used to talk to a group of TNCs all of which are unconnected.
If MALL is ON, all otherwise eligible frames are displayed, including those sent
between two other connected TNCs. This mode may be enabled for diagnostic
purposes or for "reading the mail."

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MAXFRAME n

COMMANDS

Mode: Packet

Default: 4

Parameters:
n

1 - 7,

Signifying a number of packets.

MAXFRAME sets an upper limit on the number of unacknowledged packets
which the MFJ TNC can have outstanding at any one time. This is also the
maximum number of contiguous packets which can be sent during any given
transmission. If some, but not all of the outstanding packets are acknowledged, a
smaller number may be transmitted the next time, or new frames may be
included in the retransmission, so that the total unacknowledged does not exceed
n.
If you perform file transfers, you should experiment with MAXFRAME and
PACLEN. If the link is good, there is an optimum relationship between the
parameters set by these commands so that the maximum number of characters
outstanding does not exceed the packet receive buffer space of the MFJ TNC
receiving the data.

MCOM ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Connect, disconnect, UA, and DM frames are monitored.

OFF

Only information frames are monitored.

This command enables monitoring of connect and disconnect frames when
MONITOR is ON.
When MCOM is OFF, only I frames (packets containing user information) will
be displayed. When MCOM is ON four protocol packets will also be displayed.
Connect, disconnect, UA, and DM packets that are monitored are indicated by
, , , and , respectively. As with other monitor commands,
the stations monitored are determined by BUDLIST and LCALLS.
Path for SABM received while in link-setup state is not checked.

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MCON ON|OFF

COMMANDS

Mode: Packet

Default: ON

Parameters:
ON

Monitor mode remains active when MFJ TNC is connected.

OFF

Monitor mode is off while the MFJ TNC is connected.

If MCON is ON, the MONITOR command will enable monitoring while your
MFJ TNC is connected to another TNC. If MCON is OFF, the display of
monitored packets is suspended when a connect occurs, and is resumed when the
TNC is disconnected.
If you want to see all packets displayed when you are not connected but have such
display suppressed when you connect to another station, you should set MCON
OFF.

MCTEXT
Text:

Mode: Mailbox

Default: " "

Any combination of characters and spaces, up to 120 characters
in length.

This command works like CTEXT except that MCTEXT is sent only when the
mailbox MYMcall is connected to. There is no express equivalent to the CMSG
ON/OFF command. If MCText is empty, no string is sent. If the is message
longer than 120 characters an error message will be given and the command is
ignored.
The command string can be cleared by typing the command, and then entering
the % sign where the text would normally be entered. Also the RESET command
will empty the MCText command.
For example you might want to set your MCText to:
Welcome to the Mailbox... I'm not here right, but feel free to use the
system...Enjoy!

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MFILTER n1,[n2],[n3],[n4]

COMMANDS

Mode: Packet

Default: none

Parameters:
n

0 - $7F, Specifying an ASCII character code. Up to 4
characters may be specified.

This command allows you to specify characters to be "filtered," or eliminated
from monitored packets. The parameters n1, n2, etc., are the ASCII codes for
the characters you want to filter. You can enter the code in either hex or
decimal.
For example, if a  character causes your screen to be cleared, and you
don't want this to happen, you can set MFILTER 12. If you also want to
eliminate  characters, which some computers interpret as end-of-file
markers, you can set MFILTER 12,26.

MHCLEAR

Mode: Packet

MHCLEAR is an immediate command. It causes the list of stations heard to be
cleared. You can use this command in conjunction with MHEARD to keep
track of the stations on the air over a given period of time, such as an evening or
a week. Clear the list of stations heard when you first begin to monitor the
packet activity.

MHEARD

Mode: Packet

MHEARD is an immediate command. It causes the MFJ TNC to display the list
of stations that have been heard since the last time the command MHCLEAR
was given. Stations that are heard through digipeaters are marked with a * in the
heard log. If you clear the list of stations heard at the beginning of a session, you
can use this command to easily keep track of the stations that are active during
that period. The maximum number of heard stations that can be logged is 18. If
more stations are heard, earlier entries are discarded. Logging of stations heard
is disabled when PASSALL is ON.

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If the DAYTIME command has been used to set the date and time, entries in the
heard log will be time stamped. For example,
cmd:MHEARD
K4NTA*
WA4ITD*
W1BEL-2*
K4NTA-2*
N2WX
cmd:

06/09/85
06/09/85
06/09/85
06/09/85

21:08:19
21:08:17
21:06:18
20:57:35

Note that no daytime string is displayed next to N2WX. This indicates that when
N2WX was last heard the clock had not been set.

MYDLCNUM

Mode: Host

Default: 0

Parameters:
Set to a non-0 number < 255 (TNCs should start at 1; hosts should start at 254
and go down). When set to a non-0 value, the addressing procedures for
multiplexing TNCs on the RS232 port are enabled.

MODE

Mode: All

MODE is a immediate command. The MODE command selects which mode
the MFJ TNC will be operating in. The MODE command is followed by two
characters which denote the mode selected. See Chapter 4 for a more detailed
discussion of the MODE command.

MNONAX25 ON|OFF

Mode: Packet

Default: OFF

MNonax25 is defaulted to OFF. When MNonax25 is OFF the display of nonAX.25 packets is inhibited. MFJ TNC will display only AX.25 packets. Setting
MNonax25 ON will cause MFJ TNC to also monitor non-AX.25 packets, for
example those associated with TCP/IP and NET/ROM or THENET links.
Display of non-AX.25 packets may not be understandable to the user.

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MNONPRIN ON|OFF

default: ON

Parameter:
ON Enables printing Non-Printable Characters
OFF Discards all Packets containing Non-Printable
Characters
The setting of the MNONPRINT parameter determines whether monitored
packets containing non-printable characters (i.e., characters other than ASCII
CR, LF, BEL, and not between $20 and $7e) are monitored or simply discarded.
The default setting permits monitoring all information packets (subject to
LCALLS, MONITOR, MNONAX25, etc). When MNONPRIN is OFF,
information packets containing one or more non-printable characters are
discarded. You may find this command helpful when there are binary transfers
on the channel that you'd rather not monitor. MNONPRIN has no effect on data
received during connections.

MONITOR ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

Monitoring of all packet activity is enabled.

OFF

Monitoring of all packet activity is disabled.

If MONITOR is ON and the MFJ TNC is not in Transparent Mode, packets not
addressed to your MFJ TNC may be displayed. The addresses in the packet are
displayed along with the data portion of the packet, e.g.:
N2WX>W5FD-3: I'm ready to transfer the file now.
The calls are separated by a ">" and the sub-station ID field (SSID) is displayed
if it is other than 0. The MALL, BUDLIST, and LCALLS commands
determine which packets are to be monitored. The MCON command controls
the action of monitor mode when the MFJ TNC is connected. All monitor functions are disabled in Transparent Mode. If MONITOR is OFF all packets are
still monitored, but only packets addressed to you are printed on the terminal
screen.

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The format of the monitor display is controlled by HEADERLN. If you want to
see the station addresses on a separate line from the text, you can set
HEADERLN ON. MRPT enables monitoring of the digipeater route as well as
source and destination addresses for each packet. MSTAMP includes a time
stamp with the addresses if DAYTIME has been set.

MRPT ON|OFF

Mode: Packet

Default: ON

Parameters:
ON

Display the stations in the digipeat path for monitored packets.

OFF

Display only the source and destination stations for monitored
packets.

This command affects the way monitored packets are displayed. If MRPT is
OFF, only the originating station and the destination are displayed for monitored
packets. If MRPT is ON, the entire digipeat list is displayed for monitored
packets, and stations that have already relayed the packet are indicated with an
asterisk.
For example,
WB9FLW>AD7I,K9NG*,N2WX-7:Hi Paul.
This packet, sent from WB9FLW to AD7I, has been relayed by K9NG but not by
N2WX-7. With MRPT OFF, the same packet would be displayed as
WB9FLW>AD7I:Hi Paul.
Setting MRPT ON increases the length of the address display, and you may wish
to set HEADERLN ON as well to display this information on a separate line.

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MSTAMP ON|OFF

COMMANDS

Mode: Packet

Default: OFF

Parameters:
ON

Monitored frames are time stamped.

OFF

Monitored frames are not time stamped.

This command enables time stamping of monitored packets. The date and time
information is then available for use for automatic logging of packet activity or
other computer applications. The date and time are set initially by the
DAYTIME command, and the date format is determined by the DAYUSA
command.
Setting MSTAMP ON increases the length of the address display, and you may
wish to set HEADERLN ON as well to display this information on a separate
line.

MTIMEOUT n

Mode: Packet

Default: 30

Parameters:
n

0 - 250, Specifying 10 sec. intervals

If non-zero, this is the timeout value expressed as 10s of seconds. Timeouts on
the mailbox apply only to remote users (the SYSOP can never time out). The
mailbox will timeout and discon-nect after n*10 seconds of mailbox inactivity.
Note that the synchronous 10 second clock may cause the timeout to occur as
much as 10 seconds before the calculated timeout time. So, if you want to set
your Mailbox timeout to 5 minutes then you set the MTimeout command to 30,
which would specify a time-out of 300 seconds.

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MYCALL call[-n]

Default: NOCALL-0

Mode: Packet

Parameters:
call

Callsign of your MFJ TNC.

n

0 - 15, an optionally specified sub-station ID (SSID).

This command tells the MFJ TNC what its callsign is. This callsign will be
placed in the FROM address field for all packets originated by your MFJ TNC. It
will accept frames with this callsign in the TO field and relay frames with this
callsign in the digipeat field. MYCALL will also be used for identification
packets (see HID and ID).
The default callsign must be changed for proper operation of the protocols.
There should never be more than one station with the same callsign (including
SSID) on the air at once. The SSID can be used to distinguish two stations with
the same Amateur call. The SSID will be 0 unless explicitly set to another value.

MYALIAS call[-n]

Mode: Packet

Default: 

Parameters:
call

Alternate identity of your MFJ TNC.

n

0-15, an optionally specified sub-station ID (SSID).

This command specifies an alternate callsign (in addition to the callsign
specified in MYCALL) for use as a digipeater only.
In some areas, wide coverage digipeaters operators have changed the callsign of
their machine to a shorter and (usually) easier to remember identifier.
International Civil Aviation Organization (ICAO) airport identifiers, sometimes
combined with telephone area codes, have been used.
Use of this command permits HID to identify normally with the MYCALLspecified callsign yet permit an alternate (alias) repeat-only "callsign."

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MYHIERAD
Text

COMMANDS

Mode: Mailbox

Default: " "

Any combination of characters and spaces, up to 60 characters
in length.

You may use this parameter to generate a customized "@:" portion of the tagline
your TNC will insert in forwarded messages. If MYHIERAD is blank, the
default @ portion will read "@:". It is suggested that you insert your
hierarchical address, location, and zip/postal code in this parameter. Example:
MYHIER for N2WX in Sebastian Florida in the Melbourne LAN at zipcode
32958, using N5AUV as the home bbs, would be entered like this:
cmd:MYHIERN5AUV.#MLBFL.FL.USA.NA[N2WX User/Sebastian]
Z:32958
-and the tagline would look like this
"R:920801/1200 @:N5AUV.#MLBFL.FL.USA.NA [N2WX User/Sebastian]
Z:32958 #:8"

MYMCALL [callsign]

Mode: Mailbox

Default: blank

This is the dedicated callsign for the mailbox. If MYMCALL equals MYCALL,
the TNC responds to incoming connections in mailbox mode. When there is no
callsign put in MYMcall, the mailbox is inaccessible to remote users.

NEWMODE ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON
Switching to data transfer mode occurs at the time of the
CONNECT command and return to command mode is automatic at the
time of disconnection.
OFF
Switching to data transfer mode occurs at time of connection
and no return to command mode occurs at disconnection.
The NEWMODE command may be used to select the way the MFJ TNC
behaves when connections are made and broken.

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If NEWMODE is OFF, the MFJ TNC will remain in Command Mode after you
issue a CONNECT command until a connection is actually established. When
the connection is established, the MFJ TNC will enter Converse Mode or
Transparent Mode, depending on the setting of CONMODE. When the
connection is terminated, the MFJ TNC remains in Converse or Transparent
Mode unless you have forced it to return to Command Mode. This is the same as
the behavior of TNC 1 (running version 3.x software) under these conditions.
If NEWMODE is ON, the MFJ TNC will enter Converse Mode or Transparent
Mode as soon as you issue a CONNECT command, without waiting for the
connection to be established. Anything you type will be packetized to be
transmitted once the connection is complete. When the connection is broken, or
if the connect attempt fails, the MFJ TNC will return to Command Mode.
Bulletin board systems, compatibility with TNC 1
If you have a Bulletin Board program designed to work with TNC 1 you should
set NEWMODE OFF if the program relies on the sequence of actions used by
TNC 1. Otherwise, you should choose the setting for NEWMODE that seems
most convenient to you.

NODEFORW

node

Mode: Mailbox

Default " "

[via x...], up to 8 vias.

This is an immediate command. It is similar to the FORWARD command
except that the NODEFORW parameter is the callsign+via path to your
NETROM, THENET, or KA node. When your TNC establishes the connection to
the 'node', it sends the text in NODEPATH to establish a network link to the
receiving BBS.
If all goes well, the forwardee will send its signon string, and forwarding will
commence. To detect failure, NODEFORW looks for two strings - "BUSY" and
"RETR" - as node connection failure indications. Upon finding "BUSY" or
"RETR", the forward attempt is considered failed, and the TNC disconnects from
the node. The command can contain the callsign of the "node" and up to 8
vias.

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NODEPATH

COMMANDS

Mode: Mailbox

Default:" "

Enter the command the TNC will issue to command the node connected by the
NODEFORW command to link with the receiving BBS.
Example:
cmd:NODEPATH C KB4VOL
cmd:NODEFORW PSL5
This sequence first connects to the PSL5 node. When connected, the TNC sends
the node connect command "C KB4VOL" to establish a link with the receiving
bbs, KB4VOL.

NOMODE ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

The MFJ TNC will only switch modes (command, converse or
transparent) upon explicit command.

OFF

The MFJ TNC will switch modes in accordance with the setting
of NEWMODE.

When NOMODE is ON, the MFJ TNC will never change between CONVERSE
or TRANSPARENT mode to COMMAND mode (or vice-versa) on its own.
Only user commands (CONV, TRANS, or ^C) may change the type in mode.
If NOMODE is OFF, then automatic mode switching is handled according to
the setting of the NEWMODE command.

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NUCR ON|OFF

COMMANDS

Mode: Packet

Default: OFF

Parameters:
ON

 characters are sent to the terminal following 
characters.

OFF

 characters are not sent to the terminal following
 characters.

This command causes transmission of  characters (ASCII code $00),
producing an effective delay following any  sent to the terminal. The
number of  characters is determined by the command NULLS. This
delay is required by some hardcopy terminals. You need to set NUCR ON if
your terminal misses one or more characters after responding to a . If this
is the case, you will sometimes see overtyped lines.

NULF ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

 characters are sent to the terminal following 
characters.

OFF

 characters are not sent to the terminal following
 characters.

This command causes transmission of  characters (ASCII code $00),
producing an effective delay following any  sent to the terminal. The
number of  characters is determined by the command NULLS. This
delay is required by some display terminals. You need to set NULF ON if your
terminal sometimes misses characters at the beginning of the line.

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NULLS n

COMMANDS

Mode: Packet

Default: 0

Parameters:
n

0 - 30, Specifying the number of  characters to send
after  or .

This command specifies the number of  characters (ASCII code $00) to
send to the terminal after a  or  is sent. In addition to setting this
parameter value, NUCR and/or NULF must be set to indicate whether nulls are
to be sent after , , or both. Devices requiring nulls after  are
typically hard-copy devices requiring time for carriage movement. Devices
requiring nulls after  are typically CRTs which scroll slowly. Extra null
characters are sent only in Converse and Command Modes.

PACLEN n

Mode: Packet

Default: 128

Parameters:
n

0 - 255, Specifying the maximum length of the data portion of
a packet. The value 0 is equivalent to 256.

The MFJ TNC will automatically transmit a packet when the number of input
bytes for a packet reaches n. This value is used in both Converse and
Transparent Modes.
If you perform file transfers, you should experiment with both MAXFRAME
and PACLEN. If the link is good, there is an optimum relationship between the
parameters set by these commands so that the maximum number of characters
outstanding does not exceed the packet receive buffer space of the MFJ TNC
receiving the data.
NOTE: Although there is no requirement for two TNCs exchanging
data to have the same PACLEN value, allowing more than 128
characters of data in a packet may be incompatible with some varieties
of TNCs.

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PACTIME EVERY|AFTER n

COMMANDS

Mode: Packet

Default: AFTER 10

Parameters:
n

0 - 250, Specifying 100 ms intervals.

EVERY Packet timeout occurs every n*100 milliseconds.
AFTER Packet timeout occurs when n*100 milliseconds elapse with no
input from the computer or terminal.
This parameter is always used in Transparent Mode, and will also be used in
Converse Mode if CPACTIME is ON. When EVERY is specified, input bytes
are packaged and queued for transmission every n*100 ms. When AFTER is
specified, bytes are packaged when input from the terminal stops for n*100 ms.
In no case will a zero length packet be produced, and the timer is not started until
the first byte is entered. A value of 0 for n is allowed, and causes packets to be
generated with no wait time.

PARITY n

Mode:All

Default: 0 (none)

Parameters:
n

0 - 3,

Selecting a parity option from the table below.

This command sets the parity mode for terminal or computer data transfer
according to the following table:
n
0
1
2
3

Parity
no parity
odd parity
no parity
even parity

The parity bit, if present, is automatically stripped on input and not checked in
Command Mode and Converse Mode. In Transparent Mode, all eight bits,
including parity if any, are transmitted in packets. If "no parity" is set and
AWLEN is 7, the eighth bit will be set to 0 in Transparent Mode.

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COMMANDS

PASS n

Default: $16 

Mode: Packet

Parameter:
n

0 - $7F, Specifying an ASCII character code.

This command selects the ASCII character used for the "pass" input editing
command. The parameter n is the ASCII code for the character you want to type
in order to include the following character in a packet or text string. You can
enter the code in either hex or decimal.
You can use this character to send any character in packets, even though that
character may have some special function. For example, suppose you have set
COMMAND 3, specifying that  is your Command Mode entry
character. If you use a Bulletin Board program that requires a  to
escape from some operation, you will type
 
to insert a  character in your packet. Of course, if you do this
frequently you would be better off to change your Command Mode entry
character.
A common use for the pass character is to allow  to be included in the
BTEXT and CTEXT messages. Similarly, you can include  in text when
you are in Converse Mode, to send multi-line packets. (The default send-packet
character is .)

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PASSALL ON|OFF

COMMANDS

Mode: Packet

Default: OFF

Parameters:
ON

MFJ TNC will accept packets with invalid CRCs.

OFF

MFJ TNC will only accept packets with valid CRCs.

This command causes the MFJ TNC to display packets received with invalid
CRC fields. Packets are accepted for display despite CRC errors if they consist of
an even multiple of 8 bits and up to 339 bytes. The MFJ TNC will attempt to
decode the address field and display the callsign(s) in the standard monitor
format, followed by the text of the packet.
This mode is not normally enabled, since rejection of any packet with an invalid
CRC field is what insures that received packet data is error-free. This mode
might be enabled for testing a marginal RF link or during operation under other
unusual circumstances.
If you set PASSALL ON and monitor a moderately noisy channel you will
periodically see "packets" displayed in this mode, since there is no basis for
distinguishing actual packets received with errors from random noise.
Logging of stations heard (for display by MHEARD) is disabled whenever
PASSALL is ON, since the callsigns detected may be incorrect.

RECONNECT call1 [VIA call2[,call3...,call9]]

Mode: Packet

Parameters:
call1

Callsign of TNC to be reconnected to.

call2

Optional callsign(s) of TNC(s) to be digipeated through. As
many as eight digipeat addresses can be specified.

RECONNECT is an immediate command. It may be used to change the path
through which you are currently connected to a station. It may only be used
when your MFJ TNC is connected on the current stream to the station you wish
to RECONNECT to.

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Integrity of frames in flight between your station and the RECONNECTed
station at the time of RECONNECT is not assured.

REMSYSOP call[-n]

Mode: Mailbox

Default: Blank

Parameters:
Call Callsign to be used for Remote SYSOP ops
-n 0 - 15, optionally specified sub-station ID (SSID)
Entering a callsign here permits the owner of the call to perform sysop functions
remotely. Sysop functions include editing, reading, and killing any mailbox
message. When this parameter is blank, the remote user may only read non- P
messages and messages to or from himself. Furthermore, he may only kill messages to or from himself plus any messages of type "T"(raffic).
This parameter may be reset to the blank (no remote sysop) state by entering a
"%" or "&" blanking code.

RESTART

Mode: All

RESTART is an immediate command. It re-initializes the MFJ TNC using the
commands previously set by the user, and stored in bbRAM. The effect of this
command is the same as turning the MFJ TNC OFF then ON again.
RESTART does not cause a reset of the parameters in bbRAM. See also the
RESET command.

REDISPLA n

Mode: All

Default: $12 

Parameters:
n

0 - $7F, Specifying an ASCII character code.

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This command is used to change the redisplay-line input editing character. The
parameter n is the ASCII code for the character you want to type in order to
redisplay the current input line. You can enter the code in either hex or decimal.
You can type this character to cause the MFJ TNC to retype a line you have
begun. When you type the redisplay-line character, the following things happen:
First, type-in flow control is temporarily released (if it was enabled). This
displays any incoming packets that are pending. Then a 
character is typed, and the line you have begun is retyped on the next line. If you
have deleted and retyped any characters, only the final form of the line will be
shown. You are now ready to continue typing where you left off.
You can use the redisplay-line character to see a "clean" copy of your input if you
are using a printing terminal and you have dele4ed characters. If you have set
BKONDEL OFF, deletions are designated with  characters,
rather than by trying to correct the input line display. The redisplayed line will
show the corrected text.
You can also use this character if you are typing a message in Converse Mode
and a packet comes in. You can see the incoming message before you send your
packet, without canceling your input.

RESET

Mode: All

This is an immediate command. When invoked, it resets all parameters to their
default settings and re-initializes the MFJ TNC.
WARNING: All parameter customizing and monitor lists are lost.
If you just need to re-initialize the MFJ TNC using the parameter values in
battery backed-up RAM, you can just turn the MFJ TNC OFF then ON again
rather,than using this command.

RESPTIME n

Mode: Packet

Parameters:
n

0 - 250, Specifying 100 ms intervals.

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This command sets a minimum delay that is imposed on acknowledgment
packets. This delay may run concurrently with default wait set by DWAIT and
any random wait in effect.
This delay can be used to increase throughput during operations such as file
transfer when the sending TNC usually sends the maximum number of fulllength packets. Occasionally, the sending TNC may not have a packet ready in
time to prevent transmission from being stopped temporarily, with the result that
the acknowledgment of earlier packets collides with the final packet of the series.
If the receiving TNC sets RESPTIME to 10, say, these collisions will be
avoided.

RETRY n

Mode: Packet

Default: 10

Parameter:
n

0 - 15, Specifying the maximum number of packet retries.

The protocol allows for retries, i.e., retransmission of frames that are not
acknowledged. Frames are re-transmitted n times before the operation is aborted.
The time between retries is specified by the command FRACK. A value of 0 for
n specifies an infinite number of retries. If the number of retries is exceeded, the
MFJ TNC goes to the disconnected state (with an informative message if not in
Transparent Mode). See also the FRACK command.

REVFLIM call[-n]

Mode: Mailbox

Default: " "

Parameters:
Call Callsign of BBS to enable Reverse-forwards
-n 0 - 15, an optionally specified sub-station ID (SSID).
When this parameter is empty, the mailbox reverse forwards all of its messages
eligible for forwarding to the first SID compatible BBS to elicit a reverse forward
with "F>." Since this permissive technique is vulnerable to a malevolent
operator who might attempt to connect and force your mailbox to forward to him,
the REVFLIM parameter is provided to limit your mailbox's response to other's
reverse forward requests. Simply place the callsign of the BBS you wish to enable

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reverse forwarding to in this parameter to limit remotely-initiated reverse
forwarding to
only that callsign.
Mode: Packet

RXBLOCK ON|OFF

Default: OFF

Parameters:
ON

The MFJ TNC will send data to the terminal in RXBLOCK
format.

OFF

The MFJ TNC will send data to the terminal in standard
format.

RXBLOCK is designed for automated operations, such as packet bulletin board
stations. It is intended to help such systems discriminate between data received
from the connected station and MFJ TNC-generated messages.
Correct operation of RXBLOCK is dependent on the AWLEN parameter
getting set to 8 (bits) since the character FF hex marks the beginning of a
received data unit header.

When RXBLOCK is ON, data from other stations will be sent from the MFJ
TNC in the following format:

----------------------------------------------------------------------------------------------|
$FF
L0
L1
PID
DATA
|
----------------------------------------------------------------------------------------------(prefix)

(length)

(pid)

(data)

The fields above are defined as follows:
prefix
length

$FF
L0

pid

L1
PID

= A character with all 8 bits set
= The high order length of the data, length, and pid fields
logically ORed with the value $F0
= The low order length of the data, length, and pid fields
= The Protocol IDentifier byte received for the following data
field

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COMMANDS

DATA =[Optional], variable length data

For best operation it is suggested that parameters like AUTOLF, MFILTER etc.
be set OFF in order to prevent uncertainties in the size of the data field.

RXCAL

Mode: All

IMMEDIATE

RXCAL is an immediate command. When invoked, the MFJ TNC generates
test signals (based on CALSET -- see below) that are used by the internal
tuning software to align the demodulator components.
To use the RXCAL feature,
1)

Align the modulator components as described in the owners manual.

2)

Use the MODE command to select the demodulator to be tuned.
Make sure JMP8, JMP7 and JMP4 are installed.

3)

Compute:

n=

9600/Bit Rate

Where the "bit-rate" is the same as the baud rate in packet modes and
the baud rate in all other modes. See CALSET Adjustment &
Location Map for "n" value.

4)

Type the command "CALSET n". Use the 'n' from step 3

5)

Type the RXCAL command.

6)
Tune the appropriate trimpot (R79, R113, R114, or R115) until the
DCD light is lit fully.
7)
Continue tuning this trimpot until the CON and STA
either alternately every half second, and/or both light up
8)

Return to step 2 until all the demodulators are tuned.

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CALSET Adjustment & Location Map
This is a map of the physical locations of the adjustment potentiometers on the
MFJ TNC circuit board. They are shown as they appear when looking down on
top of the board with the board oriented so that the rear panel connectors are to
the left. Information in the boxes is organized as shown below.
_________________
_________________________________
|
|
|
|
|
| PART MODE |
| PART MODE H/L | PART MODE H/L |
|
|
|
|
|
| CALSET # |
| FREQ / CALSET | FREQ / CALSET |
|
|
|
|
|
------------------------------------------------DEMODULATOR
MODULATOR
________________
______________________________
|
|
|
|
|
| R113 HP |
| R106 HP L | R77 VP H |
|
|
|
|
|
| CALSET 32 |
| 2125 247 | 2200 240 |
|
|
|
|
|
----------------------------------------------|
|
|
|
|
| R79 VP |
| R78 VP L | R119 VB H |
|
|
|
|
|
| CALSET 8 |
| 1200 438 | 2975 177 |
|
|
|
|
|
-----------------------------------------------

NOTE! Separate procedure required to do alignment of CW demodulator center
frequency.
NOTE! MCW modulator tone is also used for SSTV transmission. However,
CW receive through a narrow filter for HF CW operation will require the CW
demodulator center frequency to be selected to align with the radio's filter
passband. MCW operation on VHF FM will require that both stations have
both the modulator tone and demodulator center frequency to the same
frequency. Depending on the mode you feel is most important to you, a choice
will have to be made that can adversely affect operation on the other modes
(SSTV, MCW, or CW).

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RVfALWAY ON|OFF

COMMANDS

Mode: Mailbox

Default: ON

Parameters:
ON Initiates forwards and reverse forwards of all forwardable
messages.
OFF Mailbox ignores Forward and NODEforw commands.
The setting of RVFALWAY(s) controls whether the TNC will initiate forward
events (FORWARD, NODEFORW) in the absence of forwardable messages. If
OFF, the TNC will ignore FORWARD and NODEFORW commands entered in
the absence of forwardable messages. When ON, the TNC runs the event for the
sole purpose of eliciting reverse-forwardable messages from the remote BBS.

SCREENLN n

Mode: All

Default: 0

Parameters:
n

0 - 255, Specifying the screen or platen width, in characters, of
the terminal.

This value is used to properly format terminal output. A   sequence is
sent to the terminal at the end of a line in Command and Converse Modes when
n characters have been printed. A value of zero inhibits this action.
If your computer automatically formats output lines, you should set SCREENLN
0 to avoid a conflict between the two line formats.

SENDPAC n

Mode: Packet

Default: $0D 

Parameters:
n

0 - $7F, Specifying an ASCII character code.

This command selects the character that will force a packet to be sent in
Converse Mode. The parameter n is the ASCII code for the character you want
to type in order to force your input to be packetized and queued for transmission.
You can enter the code in either hex or decimal.

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For ordinary conversation, you will probably set SENDPAC $0D and CR ON.
This causes packets to be set at natural intervals, and causes the  to be
included in the packet.
If you have set CPACTIME ON, you will probably set SENDPAC to some value
not ordinarily used (say, ), and set CR OFF. This will allow you to
force packets to be sent, but will not result in extra  characters being
transmitted in the text.

SLOTS nnn

Mode: Packet

Default: 3

Parameter:
nnn

0 - 127, Specified the number of sides on the slot time dice.

This parameter determines how many sides are on the slot time dice. SLOTS
represents an n+1 sided dice the TNC "throws" before transmitting. The SLOTS
command allows any number of slots from 1 thru 127 to be defined.
SLOTS (n)
1
2
4
8
16
32
64
128

REMARKS
Disables Slotting
This should be the default setting
Use only if the channel is VERY busy.
VERY VERY VERY busy !
You get the idea.
Might as well print it out & send it in the mail.

The value used on a particular channel should be agreed on by the channel users.
Access to the channel will be equitably distributed among all users if everybody is
using the same value for the SLots and DEAdtime parameters.
The idea is to pick a value large enough that the probability of two queued up
stations picking the same value is relatively small. On the other hand, the value
chosen should be small enough that most of the time, ONE of the queued up
stations will have a significant probability of picking the first available slot. In

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COMMANDS

this way, the channel is reliably arbitrated and at the same time the overhead
required for the arbitration is minimized so that overall throughput on the
channel is maintained. The actual value used will depend on the average number
of queued up stations there are on the channel during busy periods.

START n

Mode: All

Default: $11 

Parameters:
n

0 - $7F, Specifying an ASCII character code.

This command selects the User Restart character, which is used to restart output
from the MFJ TNC to the terminal after it has been halted by typing the User
Stop character. You can enter the code in either hex or decimal.
The User Stop character is set by the STOP command.
If the User Restart and User Stop characters are set to $00, software flow
control to the MFJ TNC is disabled, and the MFJ TNC will only respond to
hardware flow control (CTS).
If the same character is used for both the User Restart and User Stop characters
the MFJ TNC will alternately start and stop transmission upon receipt of the
character.

STOP n

Mode: All

Default: $13 

Parameters:
n

0 - $7F, Specifying an ASCII character code.

This command selects the User Stop character, which is used to stop output from
the MFJ TNC to the terminal. You can enter the code in either hex or decimal.
This is the character you will type to halt the MFJ TNC's typing so that you can
read text before it scrolls off your display.
Output is restarted with the User Restart character, which is set by the START
command.

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If the User Restart and User Stop characters are set to $00, software flow
control to the MFJ TNC is disabled, and the MFJ TNC will only respond to
hardware flow control (CTS).
If the same character is used for both the User Restart and User Stop characters
the MFJ TNC will alternately start and stop transmission upon receipt of the
character.

STREAMCA ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Callsign of other station displayed.

OFF

Callsign of other station not displayed.

This command is used to enable the display of the connected- to station after the
stream identifier. This is particularly useful when operating with multiple
connections allowed. It is somewhat analogous to the use of MRPT to show
digipeat paths when monitoring.
In the example below, the charaters inserted by enabling STREAMCAll are
shown in bold face type.
|A:K4NTA:hi howie
hello ted how goes it?
|B:WA7GXD:*** CONNECTED to WA7GXD
|Bmust be a dx record. ge lyle
|Aunreal ted! fl-az no digis!
|B:WA7GXD:big band opening...ge
etc.
The same sequence with STREAMCAll OFF would look like the following:

|Ahi howie
hello ted how goes it?
|B*** CONNECTED to WA7GXD
|Bmust be a dx record. ge lyle

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COMMANDS

|Aunreal ted! fl-az no digis!
|Bbig band opening...ge
etc.
Thus, what would have looked like "|B" now appears as "|B::". This
option is very useful for human operators trying to operate multiple simultaneous
connections. It is probably less useful for "host" operations.

Note that, in the first example, the STREAMSWitch characters "|A" and "|B"
with no ":" after them were entered by the operator of the TNC to switch streams
for his multiple- connect QSO(s). If you intend to operate multiple connections
(as opposed to having your "host" computer operate multiple connections), use of
this option is recommended.
STREAMDB ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Double all received STREAMSWitch characters.

OFF

Do not "double" received STREAMSWitch characters.

This command is used to display received STREAMSWitch characters by
"doubling" them. The example below illustrates this action.
With STREAMDB on, and STREAMSWitch set to "|", the following might be
displayed from your MFJ TNC:
|| this is a test.
In this case the sending station actually transmitted
| this is a test.
The same frame received with STREAMDBL OFF would be displayed as:
| this is a test.

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When operating with multiple connections, this is useful for differentiating
between STREAMSWitch characters received from other stations and
STREAMSWitch characters internally generated by your MFJ TNC.
NOTE: The STREAMSWitch character must NOT be one of the stream letters
(A - J) for this command to function properly.

STREAMSW n

Mode: Packet

Default: $7C < | >

Parameters:
n

$FF, usually specifying an ASCII character code.

This command selects the character used by both the MFJ TNC and the user that
a new "stream" (connection channel) is being addressed.
The character can be PASSed in CONVERS mode. It is always ignored as a
user-initiated stream switch in TRANSPARENT mode, and flows through as
data. This means that the outgoing stream can not be changed while "on line" in
TRANSPARENT mode (you must escape to COMMAND mode to switch
streams).
For further usage of this character, see the STREAMDBL and STREAMCA
commands.

SYSOP

Mode: Packet/Mailbox

Immediate command

When the MAILBOX is ON, the System Operator can access the mailbox by
typing the immediate command, SYSOP. All commands are available to the
SYSOP. When the SYSOP has completed operating the MAILBOX, he must
return to command mode with "Control-C" (or the current COMMAND
character) to allow the remote users access to the MAILBOX.

TIMEDCMD

Mode: Mailbox

[string- max 119 chars]

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MFJ-1270C/1274C MANUAL

COMMANDS

This string in the TIMEDCMD parameter is executed as a TNC command
whenever the minutes register in the time of day clock equals the value in the
TIMEDMIN parameter. The string is executed when seconds equals one;
execution is deferred while the user is entering a command.

TIMEDMIN n

Mode: Mailbox

Default: 60

Parameters:
n

0 - 60, Specifying 1 minute intervals

The TIMEDMIN parameter is compared against the minutes register of the real
time clock to determine when the TIMEDCMD string is sent to the command
interpreter. Setting this parameter to 60 disables the feature. Combined with the
TIMEDCMD string, the user may configure his TNC to perform hourly
automatic forwards and reverse forwards.

TRACE ON|OFF

Mode: Packet

Default: OFF

Parameters:
ON

Trace mode is enabled.

OFF

Trace mode is disabled.

This command is used to enable the protocol debugging function. When
TRACE is ON, all received frames will be displayed in their entirety, including
all header information. In normal operation you will probably never need this
function; however, if you need to report an apparent software bug, we may ask
you to provide trace information if possible.
A trace display will appear in four columns on an 80-column display. Following
is an example trace display. For comparison, the frame shown in the trace
example would be monitored as follows:
KV7B>CQ,KF7B*:this is a test message

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The trace display would look like this:
byte
000:
010:
020:

-------------------hex display------------------- ---shifted ASCII--- ---------ASCII---------86A24040 40406096 AC6E8440 4060968C CQ 0KV7B 0KF ..@@@@`..n.@@`..
6E844040 E103F074 68697320 69732061 7B P.x:449.49.0 n.@@...this is a
20746573 74206D65 73736167 650D
.:29:.6299032.
test message.

The byte column shows the offset into the packet of the beginning byte of the
line. The hex display column shows the next 16 bytes of the packet, exactly as
received, in standard hex format. The shifted ASCII column attempts to decode
the high order seven bits of each byte as an ASCII character code. The ASCII

column attempts to decode the low order seven bits of each byte as an ASCII
character code. In a standard AX.25 packet, the callsign address field will be
displayed correctly in the shifted ASCII column. A text message will be
displayed correctly in the ASCII column. Non-printing characters and control
characters are displayed in both ASCII fields as ".". You can examine the hex
display field to see the contents of the sub-station ID byte and the control bytes
used by the protocol. Protocol details are discussed in Chapter 9.

TRANS

Mode: Packet

Immediate Command

This is an immediate command. It causes the MFJ TNC to exit from Command
Mode into Transparent Mode. The current link state is not affected.
Transparent Mode is primarily useful for computer communications. In this
mode, the "human interface" features such as input editing capability, echoing of
input characters, and type-in flow control are disabled. You may find
Transparent Mode useful for computer Bulletin Board operations or for
transferring non-text files. See the discussion of Transparent Mode in Chapter 5.

TRFLOW ON|OFF

Mode:Packet

Default: OFF

Parameters:
ON

Software flow control can be enabled for the computer or
terminal in Transparent Mode.

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OFF

COMMANDS

Software flow control is disabled for the computer or terminal
in Transparent Mode.

If TRFLOW is ON, the settings of START and STOP are used to determine the
type of flow control used in Transparent Mode. If TRFLOW is OFF, only
hardware flow control is available to the computer and all characters received by
the MFJ TNC are transmitted as data. If START and STOP are set to $00,
disabling the User Stop and User Restart characters, hardware flow control must
always be used by the computer.
If TRFLOW is ON, and START and STOP are non-zero, software flow control
is enabled for the user's computer or terminal. The MFJ TNC will respond to the
User's Restart and User's Stop characters (set by START and STOP) while
remaining transparent to all other characters from the terminal. Unless
TXFLOW is also ON, only hardware flow control is available to the MFJ TNC
to control output from the terminal.

TRIES n

Mode: Packet

Default: NONE

Parameters:
n

0 -15,

Specifying the current RETRY level on the currently
selected input stream.

This command is used to retrieve (or force) the count of "tries" on the currently
selected input stream.
When used with no argument: if the MFJ TNC has an outstanding unacknowledged frame, it will return the current number of tries; if the MFJ TNC has
no outstanding unacknowledged frames, it will return the number of tries
required to obtain an acknowledgment for the previous frame.
If RETRY is set to 0, the value returned by issuing a TRIES command will
always be 0.
This command is useful for obtaining statistics on the performance of a given
path or channel. It should be especially useful for automatic optimizing so such
parameters as PACLEN and MAXFRAME by computer-operated stations, such
as automatic message forwarding stations using less-than-optimum paths (noisy
HF or satellite channels, for example).

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When used with an argument, TRIES will force the "tries" counter to the entered
value. Use of this command to force a new count of tries is NOT recommended.

TXDIDDLE ON|OFF

Mode: Packet

Default: Off

TXDIDDLE determines whether or not the MFJ TNC uses a highly efficient
square wave signal in place of flags during the transmitter delay (TXDELAY)
period. When TXDIDDLE is ON, you may select even smaller TXDELAY
intervals because the square wave presents four times as many transitions as
TXDIDDLE OFF does for your connectees' receive synchronization.
TXDIDDLE is defaulted to the OFF setting to reflect that the function is
inactive. However there are a number of TNCs on the market which claim to be
AX.25 compatible, but do not recognize valid AX.25 packets preceded by the
TXDIDDLE keyup technique. You may recognize the need to set TXDIDDLE
OFF, if it appears that the station you're working is unable to successfully receive
your packets despite your adequate signal.
This failure of some TNCs to receive TXDIDDLEd packets may be a result of
some software carrier-detect schemes. All TAPR and derivative TNCs utilizing
hardware-generated carrier-detect receive both
TXDIDDLEd and nonTXDIDDLEd packets with equal efficiency.
Note that when TXDIDDLE is OFF, TXDELAYC is irrelevant! Therefore, the
actual TXDELAY yielded when TXDIDDLE is OFF is equal to
TXDELAY*100ms plus any AXDELAY time.

TXDELAY n

Mode: Packet

Default: 33

Parameters:
n

0 - 120, Specifying 10 ms intervals.

This value tells the MFJ TNC how long to wait after keying up the transmitter
before sending data. Some startup time is required by all transmitters to put a
signal on the air; some need more, some need less. In general, crystal controlled rigs with diode antenna switching don't need much time, synthesized rigs

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COMMANDS

need time for PLL lockup, and rigs with mechanical T/R relays will need time for
physical relay movement. The correct value for a particular rig should be
determined by experimentation. The proper setting of this value may also be
affected by the requirements of the station you are communicating with.
Note that the TAPR TNC 1 and other TNCs using the same firmware interpret n
in 40 ms intervals. The value of TXDELAY on MFJ TNC will thus be 4 times
the value used by a TNC 1 user to give the same delay time.

TXDELAYC nnn

Mode: Packet

Default: 2

Parameter:
nnn

0 thru 255 in 1 ms steps

The time delay between when the MFJ TNC depresses the PTT and when it starts
sending packets is specified in terms of how long it takes to send (TXDELAYC)
characters at the current radio baud rate. TXDELAYC controls a new timer that
runs after the regular TXDELAY time has expired (see TXDELAY).
High speed radio users will find this command useful because they can select
transmit delays much smaller than the 10 ms grains in TXDELAY. For high
speed use, set TXDELAY to 0 and set TXDELAYC according to the formula
below:

TXDELAYC =

Radio-PTT-delay-time
--------------------------Time-per-character

The time-per-character as related to the radio baud rate is as follows:

Baud rate
9600
2400
1200
300

Time-per-character
83 ms
3.30 ms
6.70 ms
26.00 ms

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Examples:
1.

For a 200 ms 2 meter HT at 1200 baud, TXDELAYC is:
200 ms
TXDELAYC = ---------- = 30
6.7 ms

2.

For a 400 ms HF radio at 300 baud, TXDELAYC is:

TXDELAYC =

TXFLOW ON|OFF

400 ms
----------- = 16
26 ms

Mode: All

Default: OFF

Parameters:
ON

Software flow control can be enabled for the MFJ TNC in
Transparent Mode.

OFF

Software flow control is disabled for the MFJ TNC in
Transparent Mode.

If TXFLOW is ON, the setting of XFLOW is used to determine the type of flow
control used in Transparent Mode. If TXFLOW is OFF, the MFJ TNC will use
only hardware flow control and all data sent to the terminal remains fully transparent.
If TXFLOW and XFLOW are ON, the MFJ TNC will use the MFJ TNC Restart
and MFJ TNC Stop characters (set by XON and XOFF) to control input from the
terminal. Unless TRFLOW is also ON, only hardware flow control is available
to the computer or terminal to control output from the MFJ TNC.
Note that if the MFJ TNC Restart and MFJ TNC Stop characters are set to $00,
hardware flow control will always be selected regardless of the setting of
TXFLOW.

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TXTMO n

n=0-65535

COMMANDS

Mode: Packet

Default: 0

TXTMO is a HEALTH counter that registers the number of packet
transmitter timeout/recovery events that have occurred since the MFJ TNC was
powered up.

TXUIFRAME ON|OFF

Mode: Packet

Default: ON

TXUIFRAME is used to tell the MFJ TNC what to do with unconnected
information left in its buffers. When this parameter is ON, all unconnected data
are transmitted as "UI" (unconnected) frames.
This command should be OFF for bulletin-board stations as it precludes the
unnecessary transmission of text that occurs when the BBS user disconnects and- unacknowledged packets remain.

UNPROTO call1

Mode: Packet

Default: "CQ"

[VIA call2[,call3...,call9]]
Parameters:
call1

Callsign to be placed in the TO address field.

call2

Optional digipeater call list, up to eight calls.

This command is used to set the digipeat and destination address fields of packets
sent in the unconnected (unprotocol) mode. Unconnected packets are sent as
unsequenced I frames with the destination and digipeat fields taken from call1
through call9 options. When no destination is specified, unconnected packets are
sent to CQ. Unconnected packets sent from other TNCs can be monitored by
setting MONITOR ON and setting BUDLIST and LCALLS appropriately.
The digipeater list is also used for BEACON packets (which are sent to
destination address BEACON).

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USERS n

COMMANDS

Mode: Packet

Default: 1

Parameters:
n

0 - 10, Specifying the number of active connections that
may be established to this MFJ TNC by other TNCs.

USERS affects only the manner in which incoming connect requests are handled,
and has no effect on the number or handling of connections you may initiate with
this MFJ TNC.
For example,
USERS 0
USERS 1
USERS 2
USERS 3

allows incoming connections onany free stream.
allows incoming connections on stream A only
allows incoming connections on streams A & B
allows incoming connections on streams A, B & C

and so on through USERS 10.

XFLOW ON|OFF

Mode: All

Default: ON

Parameters:
ON

XON/XOFF flow control is enabled.

OFF

XON/XOFF flow control is disabled and hardware flow
control is enabled.

If XFLOW is ON, the computer or terminal is assumed to respond to the MFJ
TNC Restart and MFJ TNC Stop characters set by XON and XOFF. If XFLOW
is OFF, the MFJ TNC will communicate flow control commands via RTS.

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XMITOK ON|OFF

COMMANDS

Mode: Packet

Default: ON

Parameters:
ON

Transmit functions are enabled.

OFF

Transmit functions are disabled.

When XMITOK is OFF, transmitting is inhibited. All other functions of the
board remain the same, in other words, the MFJ TNC generates and sends
packets as requested, but does not key the radio PTT line.
You might use this command to insure that your MFJ TNC does not transmit in
your absence if you leave it operating to monitor packet activity. This command
can also be used for testing using loopback or direct wire connections when PTT
operation is not relevant.

XOFF n

Mode: All

Default: $13 

Parameters:
n

0 to $7F,

Specifying an ASCII character code.

This command selects the MFJ TNC Stop character, which is sent by the MFJ
TNC to the computer or terminal to stop input from that device. You can enter
the code in either hex or decimal.
This character would ordinarily be set to  for computer data transfers.
If you are operating your station in a Converse Mode and there is some chance
that you might fill up the MFJ TNC's buffers, you might set this character to
 ($07), which rings a bell on many terminals.

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XON n

Default: $11 

Mode: All

Parameters:
n

0 to $7F,

Specifying an ASCII character code.

This command selects the MFJ TNC Restart character, which is sent by the MFJ
TNC to the computer or terminal to restart input from that device. You can enter
the code in either hex or decimal.
This character would ordinarily be set to  for computer data
transfers. If you are operating your station in Converse Mode, and there is some
chance that you might fill up the MFJ TNC's buffers, you might set this character
to  ($07), which rings a bell on many terminals.

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MESSAGES

TNC MESSAGES
This chapter describes the messages your MFJ TNC may produce and the
circumstances under which they may appear.

Packet Messages
*:J
bbRAM:LOAD WITH DEFAULTS
MFJ Enterprises, Inc.
Model MFJ TNC
AX.25 Level 2 Version 2.0
RELEASE X.X.X - DATE - 32K RAM
Checksum XXX
cmd:
This is the sign-on message that appears when you turn ON your MFJ TNC or
when you issue the RESET command. The release number will be updated
whenever the firmware is changed. The checksum is a hex number which you
can compare against the correct checksum given for the firmware version you
are using.

bbRAM loaded with defaults
This message appears along with the sign-on message above if the battery
backed-up RAM checksum verification fails at power-on time, causing the MFJ
TNC to load the default parameters from ROM. (This will be the case the
first time you turn on your MFJ TNC.)
This message also appears if the MFJ TNC
the RESET command.

loads the defaults in response to

cmd:
This is the Command Mode prompt. When this prompt appears, the MFJ TNC
is waiting for you to issue a command. Anything you type after this prompt
will be interpreted as a command to the MFJ TNC
If a monitored packet

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hasbeen displayed, the prompt may not be visible, even though you are in
Command Mode.
You can type the redisplay-line character (set by
REDISPLA) to retype the prompt.

was
Whenever you change the setting of one of the MFJ-TNC's parameters, the
previous value will be displayed. This confirms that the MFJ TNC properly
interpreted your command, and reminds you of what you have done.

too many packets outstanding
This message would appear in response to a CONVERS or TRANS command,
under special circumstances. If you have previously entered packet data, filling
the outgoing buffer in Converse Mode or Transparent Mode and then returned
to Command Mode. You will be allowed to enter one of these modes when
some of the packets have been successfully transmitted.

Mailbox Messages
? Expected bank n....x
This message occurs when you try to switch to an extended Mailbox memory
bank which does not exist. For example trying switch to memory bank 8, using
the 512K memory extension. Memory bank 8 does not exist, only banks 0 thru
7 are present.

You have new mail!
Upon accessing the mailbox, this message will appear if there are any new
messages addressed to you. These will be the messages with the N message flag
set. Once the message is read and the Y message is set, this message will not
occur.
Message saved
The Message Saved occurs when a Mailbox message is actually stored after
pressing the CTRL-Z and ENTER.

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Cannot, not yours
This message occurs when a remote user attempts to kill a message which isnot
his, or he tries to read personal message by or for someone else. The SYSOP
can read or KILL any message in the Mailbox system.

?Mailbox full
This message occurs when either all of the available slots are full, or the actual
message space is full. The number of slots and message space for the different
mailbox versions are as follows:
Memory size
STANDARD*
32K**
128K**
512K**
*
**

# Slots
30
99
99/Bank
99/Bank

Message Space
2,900 Bytes
32,000 Bytes
128,000 Bytes
512,000 Bytes

Denotes no memory expansion
Denotes memory expansion of the size specified by the numeric value.

Messages must be Forwarded to destinations, then killed in order to recover
Mailbox message space and to eliminate this error message.

Not found
This message occurs when one attempts to read or kill a non-existent message
from an empty slot.

None found
A parameterless Kill or Read command. The Mailbox could not find any
messages addressed to the user.

No mail
The No Mail message occurs when a Read command with no slot designator is
done, but mail does not exist for the remote user.

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Command Mode Error Messages
If you make a mistake typing a command to the MFJ-TNC, an error message
will be printed. You may see any of the fol- lowing messages depending on the
type of error you have made.

?bad
You typed a command correctly, but the remainder of the command line
couldn't be interpreted.
?call
You entered a callsign argument that does not meet the MFJ TNC 's
requirements for callsigns. A callsign may be any string of numbers and
letters, including at least one letter. Punctuation and spaces are not allowed.
The sub-station ID, if given, must be a (decimal) number from 0 to 15,
separated from the call by a hyphen.

?EH
This message occurs when a command issued is not understood by the MFJ
TNC . This will happen if you are in the mailbox or just during standard
operation.

?clock not set
This message appears if you give the command DAYTIME to display the date
and time without having previously set the clock. The DAYTIME command
sets the clock if it is given with the daytime parameters, and displays the date
and time if it is given without parameters.

?EH
The first word you typed is not a command or a command abbreviation.

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?not enough
You didn't give enough arguments for a command that expects several
parameters.

?not while connected
You attempted to change MYCALL or AX25L2V2 while in a connected or
connecting state.

?range
A numeric argument for a command was too large.

?too long
You entered too long a command line, and the line was ignored. This might
happen, for example, if you try to enter too long a message with BTEXT or
CTEXT. If you get this message, the previous text entry was not changed.

?too many
You gave too many arguments for a command that expects several parameters.
For example, MFILTER can have up to 4 arguments.
md:MFILTER $1B,$0C,$1A,$03,$07
too many

?VIA
This message appears if you attempt to enter more than one callsign for the
CONNECT or UNPROTO commands without being proceeded by the VIA
keyword.

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Link Status Messages
These messages inform you of the status of AX.25 connections your MFJ TNC
may be involved in. You can always interrogate the link status by giving the
CONNECT command without parameters. If you attempt a connection when
your MFJ TNC is not in the disconnected state, the MFJ TNC will display
the link status but will take no other action. The following messages appear in
response to the CONNECT command.

Link state is: CONNECTED to call1
IA call2[,call3...,call9]]
This display shows the station your MFJ TNC
is connected to and the
digipeater route if any. The callsign sequence is the same sequence you would
enter to initiate the connection.

Link state is: DISCONNECTED
No connection currently exists. You may issue the CONNECT command to
initiate a connection.

Link state is: CONNECT in progress
You have issued a connect request, but the acknowledgment from the other
station has not been received. If you issue a DISCONNE command, the
connect process will be aborted.
Link state is: DISCONNECT in progress
You have issued a disconnect request, but the acknowledgment from the other
station has not been received. If you issue a second DISCONNE command, the
MFJ TNC will go immediately to the disconnected state.

Link state is: FRMR in progress
The MFJ TNC is connected but a protocol error has occurred. This should
never happen when two TAPR TNCs are connected.
An

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improperimplementation of the AX.25 protocol could cause this state to be
entered. The MFJ TNC will attempt to re-synchronize frame numbers with
the TNC on the other end, although a disconnect may result. Connects are not
legal in this state, and a disconnect will start the disconnect process.
The MFJ TNC will inform you whenever the link status changes. The link
status may change in response to a command you give the MFJ TNC
(CONNECT or DISCONNE), a connect or disconnect request packet from
another station, a disconnect due to the retry count being exceeded, an
automatic time-out disconnect (CHECK), or a protocol error.

*** CONNECTED to: call1 [VIA call2[,call3...,call9]]
This message appears when the MFJ TNC goes from the "disconnected" or
"connect in progress" state to the connected state. The connection may be a
result of a CONNECT command you issued, or of a connect request packet
received from another station.

*** connect request:call1 [VIA call2[,call3...,call9]]
This message indicates that the MFJ TNC has received a connect request from
another station which it has not accepted. This can happen if you have set
CONOK OFF or if you are already connected to another station. When the
MFJ TNC types this message it also sends a DM packet (busy signal) to the
station that initiated the connect request. If the MFJ TNC rejects a connect
request because you have set CONOK OFF, you can issue your own request to
the station that called.

*** DISCONNECTED
This message is displayed whenever the MFJ TNC goes to the disconnected
state from any other link state. This message may be preceded by a message
explaining the reason for the disconnect, below.

*** retry count exceeded
*** DISCONNECTED

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This message is given if the disconnect was caused by a retry failure rather than
by a disconnect request from one of the stations.

***  busy
*** DISCONNECTED
This message indicates that your connect request was rejected by a DM packet
(busy signal) from the other station. The MFJ TNC will reject a connect
request if CONOK is OFF, or if it is already connected to another station, or
the connect request is from a station with a totally blank callsign.

frmr frame just sent:
FRMR sent: xxxxxx
The MFJ TNC is connected, and a protocol error has occurred. The MFJ
TNC has sent a special FRMR packet to attempt to re-synchronize frame
numbers with the MFJ TNC on the other end. The string xxxxxx is replaced
with the hex codes for the three bytes sent in the information part of the FRMR
frame. This message will not appear if your MFJ TNC is in Transparent
Mode.

FRMR rcvd:
This message is followed by a display of the FRMR packet received in the trace
display format. This format is explained in the TRACE command entry. This
message will not appear if your MFJ TNC is in Transparent Mode.
***LINKOUTOFORDER, possible dataloss[opt.daytime stamp]:
This message indicates failure of a CONPERMed. One or more packet nodes
in the link have failed. The time of failure may be appended to this error
message if the stamping mode is on.

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HARDWARE

HARDWARE
This chapter details the specifications and the functional description of the
MFJ-TNC hardware design.

MFJ-TNC Specifications
Processor CMOS Z-80A

Clocks
Processor master clock input frequency: 4.9152 MHz
User Port Clock: Switch selectable at 16x baud rate.

Memory All memory in industry-standard JEDEC Byte-Wide sockets.
Standard complement of ROM:
1 x 27C512

64K

Standard complement of system
AM: 32K
1x 43256C-15L
Standard complement of mailbox RAM: 0K
(expandable to 32K, 128K or 512K)

Serial
Port

Z8440 SIO/0 port B configured as UART plus low power
TTL-to-RS-232C signal level interface.
Baud rates supported: 300, 1200, 2400, 4800, 9600 and
19,200.
Standard female DB-25S (DCE) RS-232C connector 8-pin
TTL connector for TTL serial port.

Modem

Demodulator: XR2211 PLL demodulator circuit plus related
components to receive up to 1200 baud.
Modulator: XR2206 modulator circuit plus related
components to produce tones for all modes of operation.

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An external modem may be attached by a single con- nector
which completely bypasses the on-board modem.
A Tuning Indicator is built in to be used as a tuning aid for
HF (MFJ-1274C only).
bbRAM

Non-volatile storage of all important operating parameters is
accomplished by using a battery backed-up system for the
entire 32K bytes of system RAM and all mailbox RAM.

Protocol AX.25 Level 2 is supported. Pre-Version 2.0 support is
compatible with earlier TAPR TNCs running 3.x software.
Full support of Version 2.0 protocol is provided. Full duplex
radio link operation is supported.

Packet
Command Mode: accepts commands via user port.
Operating
Modes
Converse Mode: accepts digital data, transmits and receives
packets, permits terminal editing features (character delete,
line delete, input packet delete, output packet delete and
redisplay input) via special characters trapped by the MFJ
TNC. Escape to command mode via special character or
BREAK signal. Optional use of packet completion timer as
in Transparent mode.
Transparent Mode: accepts digital data, transmits packets via
packet completion timer or buffer full only, and receives
packets. No local editing features permitted. Escape to
command mode via specially timed character sequence or
BREAK signal.

Power
Required

+12 volts DC at 300 mA.

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General Description
The MFJ-TNC is based on the Zilog Z80 (tm) family of microprocessor
components.
Major electronic devices in the MFJ-TNC include a CPU (Central Processing
Unit) for controlling the MFJ-TNC and a SIO (Serial Input/Output) chip for
providing serial interface ports to the on-board modem (which connects to your
radio) and to the RS-232C or TTL serial terminal port (which connects to your
computer or terminal).
The MFJ-TNC
also includes two types of memory. ROM (Read Only
Memory) stores the program that tells the MFJ-TNC how to implement the
AX.25 protocol. Battery backed-up RAM (Random Access Memory) provides
a scratch-pad area for temporary data as well as non-volatile storage for
operating parameters such as your station call sign. The battery back-up
feature enables the MFJ-TNC to "remember" these values when power is off
so you don't have to enter them every time you want to operate.
Other integrated circuits are used for functions including clock oscillator, baudrate generator, memory-space decoder, power supply and voltage inverter, clock
recovery, transmit watch-dog timer and modem. Refer to the schematic
diagram while reading the following circuit descriptions.

Detailed Circuit Description
Oscillator
U10a, U10b, U10c, R46, R47, R48, C24, C47, C51, and Y1 provide an accurate
crystal-controlled oscillator for system timing.
R48 forces inverter U10a into its linear region and provides a load for crystal
Y1. Capacitor C47 provides an adjustable reactive element to allow the
oscillator's frequency to be precisely set (this precision is not normally
required). Inverter U10c buffers the clock for additional stability before driving
additional dividers.
Resistor R46 is used to bias "HCT" logic to the proper levels for best oscillator
operation; it is not necessary if U10 is an "HC" logic element.

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Dividers and Baud-rate Generator
U10e, U10f, U4a, U4b, U1, U30 ad U31 provide clock outputs derived from the
oscillator. Electronics switches within U30 and U31 provide all the terminal
baud rate and the RF baud rate under software command.
Inverter U10f provides buffering and isolation between the divide-by-two output
of counter U4a and the capacitive load presented by the CPU (U22) and the SIO
(U21). U10f's input may be at 2.4576 MHz or 4.9152 Mhz. MFJ-TNC
operation at the faster clock of 4.9152 MHz. Capacitors C59 and C60 are used
to slow the edges of the outputs of U4a, and capacitor C61 is used to slow the
edges from U10f, helping to reduce RFI.
Counter U1 is a multiple-stage divide-by-two circuit that divides the signal at
its input many times. This allows the switches within U30 and U31 to select
the desired signaling (baud) rate to be used for your computer or terminal as
well as the radio channel baud rate.
The output from counter U1 at pin 12 provides a real-time clock interval signal
for the SIO. During normal operation, the SIO will be programmed to
interrupt the CPU on every transition of this 600 Hz signal. This interrupt
occurs 1200 times a second, and is used for protocol and calibration timing
functions.
Inverter U10e buffers the radio port "16x" baud-rate signal in case it is routed,
via modem disconnect J4 pins 11 and 12, to an external modem. If this buffer
were not included, reflections from the distant termination might cause counter
U1 to generate count errors.
Counter U4b provides a properly scaled clock for the transmit NRZ to NRZI
encoder (see Serial Interface, below).

CPU Complex
EPROM U23 provides system ROM for program storage. Selector U12a acts as
a ROM decoder, mapping the ROM into the CPU's memory address space
beginning at address 0.

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Static RAM provides system RAM for temporary scratch-pad storage, message
buffers, etc. Also, because the RAM is backed up by a battery and will not lose
its contents when the main power is removed, it is used to provide semipermanent storage of user-supplied information (such as your callsign).
Selector U12b acts as a RAM address decoder, with RAM starting at address
8000 hex.
The sections of CMOS switch U13 are used to insure that the RAM is not
selected when main power is removed. This ensures that the contents of the
RAM are not accidentally scrambled as the CPU loses power; it also ensures
that the RAM is in the "power-down" state for minimum battery power
consumption.

Serial Interface
Serial Input/Output (SIO) device U21 provides two channels of serial I/O.
The B SIO channel is used for the computer or terminal interface. Operational
amplifier sections U3a, U3b, and U3d act as RS-232C drivers while Schmitt
trigger inverters U9a and U9b act as RS-232C receivers. These circuits consume less power than conventional RS-232C drivers and receivers.
The A SIO channel is used for the radio/modem interface and is normally
operated as a full duplex HDLC channel for compatibility with the AX.25
protocol specification. Latch U5 and ROM U6 provide a "state machine" for
recovering the clock from the received NRZI data. The state machine also
converts NRZI data to NRZ for the SIO. Inverter U9c and flip-flop U11a
provide NRZ to NRZI conversion for the transmit side of the radio channel.
This conversion between NRZ formatted data and NRZI formatted data is
necessary because the AX.25 protocol specification requires NRZI operation
while the SIO is only capable of NRZ. Jumper JMP11 may be used to bypass
the NRZ --> NRZI conversion for use with external modems, if required.

Watch-dog Timer
Inverters U7c, U7d, U7e, and Q10 and Q20 provide a "watch- dog" timer on
the transmit key line to ensure that the transmitter does not remain keyed for
more than about 30 seconds should the TNC fails. This allows you to leave a
station (such as a remote digipeater) on-the-air and unattended without much
chance of having a malfunction "lock up" the packet channel. This also helps

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ensure compliance with FCC regulations regarding unattended station
operation.
Jumper JMP4 is provided for testing purposes. When JMP4 is installed, timing
capacitor C31 is shunted, disabling the watch-dog timer.

Modem
U16, an XR2206, is a Frequency Shift Keying (FSK) modulator that generates
an audio data signal for use by the radio transmitter. Two tones are used, one
for each digital level, and these tones may be calibrated via trimpots R77/R78,
R105/R106 in conjunction with the on-board calibration support circuitry and
software. When the transmitter is not being keyed, transistor Q9 is switched
on, thus preventing U16 from producing tones. This allows you to leave a
microphone connected to your packet transmitter for voice operation.
R157 is used to set the tone output levels to the transmitter.
U20, an XR2211, provides a Phase Locked Loop (PLL) FSK demodulator. It
converts the received audio FSK signals into digital data at standard logic
levels. This data is sent to the state machine clock recovery and NRZI to NRZ
format conversion circuits. R79 and R113 are used to calibrate the PLL
demodulator's free-running frequency which is set midway between the FSK
tones being received. These tones are measured by the calibration software and
the output signal produced by U8a and U8b, which is a frequency doubling
shaping circuit.

Power Supply
Regulator Q3 and associated components provide a +5 volt regulated output for
the MFJ-TNC digital logic circuitry. In order to reduce conducted RFI from
the digital power source, series inductor L1 is provided. Transistor Q4, in conjunction with CMOS inverters in U14, provides a "power failure" circuit for the
battery-backed RAM chips to ensure that RAM is in the "power-down" state
when the main power is removed. In addition, this circuit provides the main
power- on reset signal via U7f.
Transistors Q5 and Q6 are used to isolate the battery from the +5 volt line
when main power is available. R33 protects the lithium battery from overload
conditions and provides a convenient means of monitoring battery current drain

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when the TNC is switched off. JMP5 provides a means of disconnecting the
negative side of the lithium battery for MFJ-TNC maintenance.
U2 and associated components form a charge-pump voltage inverter which
generates an unregulated negative supply for the RS-232C drivers.
U3c, Q2, CR6 and surrounding components provide a regulated source of -5
volts for the modem chips.
The modem power sources and ground are isolated from digital logic switching
noise by inductor L2.

RS-232C Handshaking Protocol
The CTS, DSR and DTR lines of the RS-232C port (J1) are used for hardware
"handshaking" protocol to control the flow of data between the terminal (DTE)
and the MFJ-TNC (DCE).

The MFJ-TNC always asserts (makes sure) Data Set Ready (DSR) on J1 pin 6
via resistor R16. Thus, whenever the MFJ- TNC is powered up, it signals to
the terminal connected to J1 that the MFJ-TNC is "on line."
The terminal indicates it is ready to receive data from the MFJ-TNC by
asserting its Data Terminal Ready (DTR) output, J1 pin 20. The MFJ-TNC
will send data when it has data to send and DTR is asserted. If the terminal is
not ready to receive data, it should negate (make false) DTR to the MFJ- TNC .
Thus, data flow from the MFJ-TNC to the terminal is controlled by the use of
the DTR line. The state of the DTR line is ignored by the software if "software
flow control" is enabled in this direction.
The MFJ-TNC asserts its Clear To Send (CTS) output, J1 pin 5, whenever it
is ready to receive data from the terminal. If the MFJ-TNC 's buffers fill, it
will negate CTS, signaling the terminal to stop sending data. The MFJ-TNC
will assert CTS when it is again ready to receive data from the terminal. Thus,
data flow from the terminal to the MFJ- TNC is controlled by the use of the
CTS line. The CTS line is always asserted if "software flow control" is enabled
in this direction.

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Some serial I/O ports do not implement CTS, DTR and DSR handshaking. If
these pins are not connected at the terminal end, they will be pulled up (and
thus asserted) by resistors at the MFJ-TNC end. However, a non-standard
serial connector may use some pins for other purposes, such as supplying power
to a peripheral device, so be sure that your system either implements the CTS,
DTR and DSR handshake or has no connections to these pins of J1 whatsoever.
Note that reference to RS-232C "compatibility" or the presence of a DB-25 type
connector does not guarantee that you have a full RS-232C serial port!
The MFJ-TNC
supports most standard baud rates from 300 through 9600.
The port supports standard parity options as well as 7- or 8-bit character
lengths. Setting these terminal parameters is discussed in Chapter 4.
If you want to interface your MFJ-TNC with a device configured as DCE, such
as a telephone modem or another TNC, a so-called "null modem" cable may be
constructed to interchange the data and handshake signals.

Jumper Functions
The following table lists the function of each jumper on the MFJ-TNC. For
normal operation a shorting jumper must be placed on the following
connectors: JMP 5; JMP 8; JMP 9 pins 2,3; JMP 13; JMP 18 pins 1,2; JMP 15
pins 2;3 JMP 26 pins 1,2;. Also on the mode disconnect header J4 the
following pins need jumpers pins 1,2 11,12 13,14 17,18.
A listing of the jumpers and their functions are listed on the following page.

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Table 8-1: Jumper Function
Jumper #

Position

Function

JMP1

Pin 1 & 2
Pin 2 & 3
OFF (default)
Pin 1&2 (default)
Pin 2 & 3
ON
OFF (default)
ON (default)
OFF
ON
OFF (default)
ON (default)
OFF
Pin 1 & 2
Pin 2 & 3 (default)
ON
OFF (default)
LEFT
RIGHT (default)
ON (default)
OFF
Pin1 & 2
Pin 2 & 3 (default)
Pin 1 & 2 (default)

!DCD (RS-232C) stays on
!DCD (RS-232C) stays off
!DCD reflects connect status
4.92 MHz CPU clock
2.46 MHz CPU clock
disable Tx watch-dog
enable Tx watch-dog
Lithium battery connected
Lithium battery disconnected
analog loopback mode
normal modem operation
demodulator enabled
demodulator calibrate
calibrate U16 tones
normal modem operation
digital loopback mode
normal modem operation
transmit data NRZ
transmit data NRZI
TTL, RTS enable
TTL, RTS disable
2400 baud ext. modem clock
9600 baud ext. modem clock
Enable 19.2K baud termial
Disable 300 baud terminal
Enable 300 baud termial
Disable 19.2K baud terminal
Enable 32K mailbox RAM
Enable 128K mailbox RAM
Enable 512K mailbox RAM
512K mailbox RAM installed
32K or 128K mailbox RAM
Enable memory RESET
Normal operation
Normal +5Vb bbRAM operation
Real-time clock installed
Baud Rate Switch SW3 Normal
Baud Rate Switch SW3 Bypass
TX audio has flat response
TX audio 6db/oct pre-emphasized
TX audio loopback to PTT

JMP2
JMP4
JMP5
JMP7
JMP8
JMP9
JMP10
JMP11
JMP13
JMP17
JMP18

Pin 2 & 3
JMP19

JMP20
JMP23
JMP26*
JMP27
JMPJ
JMPK
JMPX
JMPY
JMPZ

Bottom pair
Middle pair
Top pair
ON
OFF(default)
ON
OFF(default)
Pin 1& 2(default)
Pin 2&3
Pins 1&2 (Default)
Pins 2&3
ON
OFF(default)
ON
OFF(default)
ON(default)
OFF
ON(default)
OFF
ON(default)
OFF

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Speaker Transmit Tone Enable
SpeakerTransmit Tone Disable
Speaker Receive Tone Enable
Speaker Receive Tone Disable
Speaker Connect Tone Enable
Speaker Connect Tone Disable

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*
When JMP23 is shorted, it will RESET the MFJ-TNC. This means that
all parameters will be reset to the default values. This is the same as removing
the bbRAM battery except it is much quicker.
** MFJ offers an optional Real-time clock module (MFJ-43) that can be
installed on the MFJ-TNC mother board. This clock keep the MFJ-TNC clock
running all the time. You will not have to reset the clock everytime you turn the
MFJ-TNC on.

MFJ provides the user with a TTL Level Input/Output port. This port is usable
with computers which cannot make use of the Serial Input/Output RS-232c
port. Below is the pin out of the TTL port:
J5 Pin #
1
2
3
4
5
6
7
8

Pin Function
Receive Data
Data Carrier Detect
Ground
Request to Send
Transmit Data
Data Set Ready
Clear to Send
Audio In

J5 TTL Port Pin Out

MFJ also provides the user with an External Modem connector. This connector
can be used for adding either the MFJ-2400 or MFJ-9600 baud modems.
Below is a pin out oft the J14 External-Modem interface connector:

J14 Pin #
1
2
3
4
5

Pin Functions
-5V
+5V
Ground
Receive Audio
Transmit Audio

External Modem Interface Connector - J14
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Modem Disconnect Header- J4
The modem disconnect header, J4, on the MFJ-TNC PC board is provided for
using an external modem with the MFJ-TNC. This allows use of higher-speed
modems, such as 9600 baud, or more sophisticated, higher-performance
modems for OSCAR or other uses.
The following information is primarily for those who wish to interface external
modems to the MFJ-TNC. Familiarity with modem and serial data channel
terms is assumed.
The signals used at connector J4 are at standard TTL interface levels. A TTL
high, or 1, is greater than +2.4 volts but less than +5.25 volts. A TTL low, or
0, is less than 0.8 volts but greater than -0.4 volts. DO NOT connect an RS232C level modem directly to J4!
NOTE: The modem disconnect is similar, but not identical to that used in TNC
1. Be very careful about interfacing an external modem using the same
cabling you may have prepared for use with TNC 1!
The connector pin-outs are as follows:
Pin 1

Carrier Detect Input

This pin tells the SIO radio port that a valid data carrier has been detected. It
should be pulled high when no carrier is detected and low when a carrier is
present. This line must be implemented unless the software release notes
indicate otherwise. It is normally jumpered to pin 2 when the on-board modem
is used.
Pin 2

Carrier Detect Output

This pin is an output from the the on-board modem and satisfies the
requirements outlined for pin 1 above. It is normally jumpered to pin 1 when
the on-board modem is used.
Pin 3

SIO Special Interrupt Input

This signal is routed to the radio port DCD input pin on SIO U21. This signal
is normally used during modem calibration. It may also be used for other

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purposes; if so, these functions will be listed in the software release notes. This
pin is normally jumpered to pin 4 when the on-board modem is used.
Pin 4

SIO Special Interrupt Generator Output

This signal is an output from the on-board modem. It is normally used for
modem calibration only. If it is used for other functions, they will be stated in
the software release notes. This pin is normally jumpered to pin 3 when the onboard modem is used.
Pin 5

SIO RTS Output

This signal is used for transmitter activation. The SIO will pull this output low
when the MFJ-TNC wants to transmit; otherwise it will remain high. This
pin is normally jumpered to pin 6 when the on-board modem is used.
Pin 6 Transmitter Key Input
This signal is an input to the on-board modem. It activates the PTT pin of the
radio connector via the watch-dog timer. It should be left high and pulled low
only when transmission is desired. This pin is normally jumpered to pin 5
when the on-board modem is used.
Pin 7

CONNECT Status Output

This pin is an output from the SIO. It is normally low and goes high only when
the MFJ-TNC is in the connected (error-free) mode with another packet
station. Its status is monitored via the CON LED.
Pin 8

Unacknowledged Packets Pending Status Output

This pin is an output from the SIO. It is normally low and goes high only when
this MFJ-TNC has unacknowledged packets in its transmit buffer. Its status is
monitored via the STA LED.
Pin 9

CTS Input

This pin is an input to the SIO. It is high when the attached modem is not
ready to accept data, and low when the attached modem is ready to accept data.
The TNC will not attempt to send data when this pin is high. This pin is
normally jumpered to pin 10 when the on-board modem is used.

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Pin 10 Transmitter Key Input
This pin is physically tied to pin 6, above. It is
used in conjunction with pin
9, above to allow the MFJ-TNC to use the on-board modem whenever the
transmitter is activated.
Pin 11 Transmitter Clock (16x) Input
This pin is tied to the NRZ-to-NRZI converter, which expects a clock signal at
16 times the desired radio port data rate, e.g., 4800 Hz for 300 baud. This pin
is normally jumpered to pin 12 when the on-board modem is used.
Pin 12 Transmitter Clock (16x) Output
This pin is tied to the radio baud rate switch network. It provides a clock at 16
times the desired radio port data rate. This pin is normally jumpered to pin 11
when the on-board modem is used.
Pin 13 Receive Clock Input
This pin is tied to the SIO receive clock input pin. It expects a clock at the
desired data rate (1200 Hz for 1200 baud), of the proper phase relationship to
the received data. This pin is normally jumpered to pin 14 when the on-board
modem is used.
Pin 14 Receive Clock Output
This pin is the received data clock signal derived from the NRZI-to-NRZ state
machine. This pin is normally jumpered to pin 13 when the on-board modem
is used.
Pin 15 MFJ-TNC

Ground Reference

This pin ties to the MFJ-TNC digital ground system, at the SIO.
Pin 16 Turbo LED output
This pin is used to connect the Turbo LED on the mother board to the external
modem board. When this pin is high (+5Vdc), the Turbo LED will light.

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Pin 17 Receive Data Input
This pin is the received data input to the NRZI-to-NRZ state machine. This pin
is normally jumpered to pin 18 when the on-board modem is used.
Pin 18 Receive Data Output
This pin provides receive data from the on-board modem. This pin is normally
jumpered to pin 17 when the on- board modem is used.
Pin 19 Transmit Data Output
This line is the NRZ or NRZI (depending on the state of JMP11) data output.
This pin is normally jumpered to pin 20 when the on-board modem is used.
Pin 20 Transmit Data Input
This input line accepts data to be be transmitted by the modem. This pin is
normally jumpered to pin 19 when the on-board modem is used.
If you elect to use an off-board modem, be sure to properly shield the
interconnecting cables for RFI protection.

HF Tuning Indicator
The MFJ-TNC has a built-in tuning indicator for HF operation. It is set for a
center frequency of 2210 Hz. The incoming audio frequency is centered at
2210 Hz. This is indicated by one or two of the center most LEDs brightly lit.
When you are tuned to a lower center frequency, the LED to the left of center
lights. When you are tuned too high, the right of center LED lights. The
resolution between each bar segment is approximately 10 Hz.

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TROUBLESHOOTING
WARNING: Never remove or insert an IC with power on!
Your MFJ-TNC is a complex piece of electronic equipment. Servicing must be
approached in a logical manner. The best preparation for troubleshooting is to
study the detailed hardware description in Chapter 7. While it is not possible to
present all possible problems, symptoms and probable cures, this section of the
manual will give direction to troubleshooting based on our experience.

General Tests
In most cases we have found that careful visual inspection combined with
simple measurements generally reveals the problem. The most useful single
instrument for troubleshooting is a good DVM that can read AC and DC volts,
and can non-destructively test resistance while the ICs are still in their sockets.
While a number of checks may be made without the aid of an oscilloscope, you
will need one to check signals at various points on the board if you fail to locate
the problem by visual means or with a meter. Be very careful about shorting
pins on ICs when applying meter or scope probes to the board. It is a good idea
to attach a secure ground lead to the meter or scope, one that won't accidentally
short across components on the board. A good place to pick up this ground is
on the head of the screws which mount the printed- circuit board to the case.

Step 1: Power Supply
The first thing to check in any malfunction is the power supply. Check the
power supply levels at the outputs of the voltage regulators (Q2 and Q3) as well
as the output of the inverter (U2). Are they close to their nominal values? Do
all the ICs in the suspected area have the proper voltage on their power pins?
Is there excessive ripple in any of the DC voltage lines? If so, check the
regulator and associated components, working backwards toward the input
power switch. If the voltage is low, in conjunction with a hot regulator, suspect
a short circuit on the board.
If the problem is in the -5 volt supply, work backwards from Q2's collector
(also at U16 pin 1), which should be -5 volts regulated, to the junction of C9
and CR2 (-V unregulated). If no voltage appears at -V, then U2 or a related

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component may be at fault. Verify that U2 is oscillating by looking at the
wave form at U2 pin 5. If -V is more negative than - 7 volts (i.e., normal), but
the -5 volt regulated voltage is wrong, check the negative regulator components
U3, Q2, R5, R6, R7, R8, CR6, C10, C11 and C158. If both -V and the -5 volt
regulated voltage are wrong, look for shorts.

Step 2: Obvious Problems
CAUTION: A word of WARNING here. DO NOT touch any component
which is suspect of being HOT. This could result in BURNS from the HOT
component.
Look for any unusual physical symptoms. Are any components discolored?
Does something smell burnt? Do any of the parts seem excessively warm? If
you have never had your fingers on operating digital integrated circuits before
you may erroneously conclude they are too hot when they are actually operating
normally. Take for instance, the Z80 CPU and the Z80 SIO. They generally are
warm to the touch. In general their normal temperature will be well below the
boiling point of water, but you may not want to keep your finger on them very
long.

Step 3: Assembly Problems
Carefully inspect the PC board and component installation. Are any cold
solder joints present? Is a metal screw shorting to the board anywhere? Are all
ICs firmly seated in their sockets? Are any IC leads tucked under the chip or
otherwise bent in such a manner that they aren't making proper contact with
the IC socket?
Inspect the diodes and electrolytic capacitors for proper installation. Are the
diode cathodes pointing the correct way? Are the negative ends of the
electrolytic capacitors pointing the correct way?

Step 4: Cabling Problems
Inspect the interconnection cabling. Does it work on another TNC? Has the
radio and/or terminal been successfully used on packet with this or another
TNC? Are all the connections tight? Has the cable frayed or broken?
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Specific Symptoms
While the steps described above may seem obvious, careful inspection often will
point to the problem or give significant clues as to the probable area of the
MFJ-TNC most suspect. After the above inspection has been completed and
apparent problems are dealt with, it is time to proceed to more specific analysis.

Symptom: TNC appears dead
If the MFJ-TNC powers up with the PWR, STA, and CON LEDs lit, followed
by STA and CON extinguishing a second or so later, the processor is working
and the software is probably working correctly. You should suspect the
terminal port at this point. Check all connections and verify the logic levels
according to the terminal interface troubleshooting section in this chapter.

Oscillator and Reset Circuits
If no LEDs cycle ON then OFF during the reset cycle the problem may be more
serious. Check to see that the crystal oscillator is working and that an "M1"
signal (154 kHz square wave, 0 to +5 volts) is coming from U22 pin 27. The
crystal oscillator input to the processor (U22) is pin 6. The input clock should
be a (possibly distorted) square wave signal. Verify that the clock input at pin 6
of U22 is running at the correct frequency (near 4.9152 MHz).
Verify that the battery backed-up RAM protection circuit, composed of Q4, U14
and associated devices, is going to +5 volts at U14 pin 6 after input power is
applied. This signal enables normal operation of U24 and U25. There should
be a logical low on the output of U7 pin 12 coincident with the application of
power and lasting for a few hundred milliseconds. Without this RESET signal,
the Z80 probably won't start up properly.

Digital Logic Lines
Remember that all of the logic circuits operate at standard TTL levels (a "low"
is less than +0.8 V and a "high" is greater than +2.4 volts), and all digital
inputs and outputs switch between these two levels. Thus, if you see logic
signals switching between 0 and, say, 1 volt, you can be sure there is a problem
(usually a short). On the other hand, do not mistake switching transients on
digital logic lines for improper operation -- these show up as ringing and other
distortions.
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Verify that there is activity on the control bus READ and WRITE lines, the 3
CHIP-ENABLE lines on the memories (U23- 25, pins 20), the IOREQ line on
U21 pin 36, and the INT line on pin 16. Each of these lines should show
activity, and if any line is quiet this is a sign of trouble.
Logic lines that show no activity may often be traced to a short on the pc board,
probably due to a solder splash or bridge.
Address and data line shorts may also show up as lack of activity on the control
bus lines, especially the chip selects. Check each of the 16 address and 8 data
lines for activity. Any lines showing a lack of activity are not operating
properly.
If you suspect problems with address or data lines, try removing all the memory
chips. Each address and data line will now show a distinct pattern. The
address lines should be (possibly distorted) square waves whose periods
increase by a factor of two on successive lines as you step line by line from A0
to A15.
If you decide to use an ohmmeter to check for shorted lines, use a low
voltage/low current test instrument. (Most Modern DVMs are fine for this.) If
in doubt, remove any ICs connected to the lines you are measuring. If you
suspect a short, check the high density areas of the PC board for the problem.
In most cases the short will be found there. It is very unlikely that the PC board
itself will have a short.

Symptom: Modem won't calibrate or key transmitter.
Troubleshooting improper calibration amounts to checking for proper signals at
U21 and following up any improper signal. If the calibration signal is present,
but you cannot successfully calibrate the frequency, you may have an out-ofspec frequency determining component. Check the values of the appropriate
passive components. Also, check the placement of jumpers! As a last resort,
check the signal frequency with a frequency counter. Note that, due to frequency jitter while calibrating the demodulator, the STA and CON LEDs may blink
somewhat even when the 1700 Hz demodulator frequency is correct.
Calibration of the demodulator and the modulator tones are discuss in the
Appendix chapter.

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If the transmitter doesn't key, the problem may be in the watchdog timer, U7, or
the PTT transistors, Q10 or . Check especially for an open timing capacitor
C31 or a bad solder connection associated with R83.

Symptom: Uncopyable transmitted or received packets
If no one seems able to decode your packet transmissions, it is often the case
that your transmitter is being overdriven. The solution is to reduce the drive
level via trimpots R157 and . Note that direct connection to typical microphone
inputs requires R157 or to be turned to near the minimum signal position to
produce sufficiently low signal levels.
If you are having problems hearing other stations, the demodulator circuitry
associated with U20 may be at fault. Check the center frequency of the VCO in
U20 using the calibration procedure. Working in the direction of flow of the
input signal from the radio, verify that it is being passed through to pin 2 of
U20, the input pin. The signal there should be above 50 mV and below 3 V
peak-to-peak for proper operation of the demodulator. It should be relatively
clean, although a few tens of millivolts of noise is normal, and the signal
amplitude should not change by more than about 25% between high and low
tones.
Note:

Make sure that JMP 8 is ON.

Terminal Interface Troubleshooting
If you can't get the MFJ-TNC to sign on and accept data from your terminal or
computer, the problem may be in the RS-232C interface. The troubleshooting
guide below is provided as an aid to help in resolving problems that may be
related to the RS-232C port.

Symptom: MFJ-TNC won't sign on to the terminal.
If you find the MFJ-TNC won't send data to your terminal, one of the first
things to do is to verify that the RTS line at pin 4 of J1 is not being held low. If
the software flow control option is disabled, the MFJ-TNC will not send data
to the terminal unless its RTS is asserted. If the terminal does not implement
the RTS/CTS protocol, the RTS/CTS lines (pins 4 and 5 on J1) should remain
unconnected.

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Verify that the voltages on the MFJ-TNC are correct. If the MFJ-TNC is in
otherwise good condition, check the following pins on the SIO, U21 (Z8440).
Pin 23 should be TTL low (between 0 and +0.8 volts). If this voltage is
incorrect, check the voltage at U9 pin 3 and verify that it is greater than +3
volts. If this voltage is correct, U9 or the traces around it may be bad. If this is
not the problem, disconnect the terminal and check it again. If this doesn't
help, U9, R20 or R22 may be at fault.
If the above checks are ok, observe pin 26 of U21 with an oscilloscope and
cycle the power switch on the MFJ-TNC . Transitions on this pin shortly after
reset indicate that the MFJ-TNC is sending data. Verify that transitions are
also present on U3 pin 1. If these tests fail, the fault could be with U13, R25,
R26, U21, J1, the attached cable or faulty soldering (shorts, cold joints, etc.)

Symptom: The MFJ-TNC appears to be signing on but only gibberish
is printed on the terminal.
This indicates that some combination of the data rate (baud rate), parity option,
or number of start and stop bits are not set the same at the MFJ-TNC and at
the terminal. If possible, set your terminal to 1200 baud. Also verify that the
terminal is set for eight data bits, no parity, and 1 stop bit. These are the
default settings stored in EPROM. Perform a hard reset by the power switch
OFF then ON (out then in). The sign on message should appear.
If the MFJ-TNC still prints gibberish, verify that the terminal is set to the MFJTNC 's baud rate and do a power off then on cycle on both the MFJ-TNC and
terminal. If the message still fails to appear try troubleshooting with an
oscilloscope, looking first at the TXD pin (pin 26) of U21 (Z8440), then at the
x16 baud rate clock (19200 Hz at 1200 baud) on pin 27 of U21.

Symptom: The MFJ-TNC signs on OK but won't accept commands.
After the MFJ-TNC signs on, try giving it a command such as MYCALL or
any other command. If the default settings are in effect, it will attempt to echo
each character you type back to the screen. If it doesn't echo, be sure that U21
pin 23 has a voltage level between 0 and +0.8 volts on it. The voltage on U9
pin 3 should be greater than +3 volts. If these voltages aren't correct, the fault
could be in U9, U21, J1, R20, R22, soldering, or the interconnecting cable.

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If the above checks are OK, use an oscilloscope to verify that data is present on
U21 pin 28 and U9 pin 1 when you strike a key on your terminal. If not, the
data isn't getting from your terminal to the MFJ-TNC . Check J1, the cable
and U9 again. Finally, be sure that your terminal actually uses levels less than
-3 volts and greater than +3 volts for signal levels. 0 and +5 volts may not
work, especially if they are being used direct from a computer.

Symptom: The MFJ-TNC appears to have "lock-up" i.e. not
responding to any commands.
This may be due to some invalid parameters having been stored in the memory.
Try turning the MFJ-TNC off and disconnect JMP 5 on the MFJ-TNC board.
This will disconnect the memory back-up circuit and allow the memory to be
erased. Re-install JMP 5 after about 2 minutes and try operating again.

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PACKET RADIO PROTOCOL
Explanation of Protocol
The material in this chapter is intended to supply an overview of the packet
protocol used to transmit data by the TAPR software. The MFJ-TNC employs
the genuine TAPR TNC 2 packet software. References are given to more
detailed information required by those wishing to implement these protocols on
other hardware. The material presented below is somewhat tutorial in nature
for those who have not had previous exposure to layered network protocols, but
it presumes some knowledge of general communications hardware and
software. Persons already well versed in networking may want to skip this
chapter and refer to the primary defining document, Amateur Packet-Radio
Link-Layer Protocol, AX.25 Version 2.0, available from the ARRL, 225 Main
Street, Newington, CT 06111 ($8.00 US, postpaid in the United States as of
this writing).
The MFJ-TNC hardware and software architecture is organized in accordance
with the International Standards Organization (ISO) layered network model.
The model describes seven levels and is officially known as the ISO Reference
Model of Open Systems Interconnection, or simply the ISO Model. The model
and many other interesting topics are discussed in Computer Networks by
Andrew S. Tanenbaum.
The ISO model provides for layered processes, each supplying a set of services
to a higher level process. The MFJ-TNC currently implements the first two
layers, the Physical layer and the Data Link layer.

Physical Layer
The duty of the Physical Layer, layer one, is to provide for the transmission and
reception of data at the bit level. It is concerned only with how each bit is
physically transmitted, i.e., voltages on a hardwire line or modem tones on
phone or RF links.
The physical layer of the MFJ-TNC is described in Chapter 7, Hardware. It is
compatible with the various TNCs currently available to radio Amateurs. The
actual modem interface is compatible with the Bell 202 standard which is
similar to the CCITT V.23 standard. Any other hardware device which is

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compatible with the Bell 202 standard should be compatible with the MFJTNC, at least at level one of the ISO reference model.

Data Link Layer
The duty of the Data Link layer is to supply an error-free stream of data to
higher levels. Since level one simply passes any bits received to level two and
is unaware of the content or overlying structure of the data, transmission errors
are not detectable at level one. Level two carries the responsibility of detecting
and rejecting bad data, retransmitting rejected data, and detecting the reception
of duplicate data.
Level two accomplishes this task by partitioning data to be transferred by level
one into individual frames, each with its own error detection field and frame
identification fields. The MFJ-TNC supports two versions of a level-two
layer, AX.25 version 1.0 and AX.25 version 2.0. Each of these protocols is
based on HDLC, the High-Level Data Link Control protocol defined by the
ISO.

HDLC Frames
Exact knowledge of the format of HDLC frames has been made largely
unnecessary by the advent of LSI and VLSI communications chips which
interface directly with the level one hardware. The level two software need
only supply data to fill in various fields and the chip takes care of the rest. For
completeness however, an HDLC frame looks like this:
| FLAG | ADDRESS | CONTROL | PID & DATA | FCS | FLAG |
FLAG
A unique bit sequence (01111110) used to detect frame boundaries.
A technique called "bit stuffing" is used to keep all other parts of the frame
from looking like a flag.
ADDRESS
A field normally specifying the destination address. AX.25
uses a minimum of 14 bytes and a maximum of 70 bytes containing the actual
call signs of the source, destination, and optionally up to eight digipeaters.
CONTROL A byte which identifies the frame type. In the AX.25 protocol,
the control field may include frame numbers in one or two 3-bit fields.

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PID
A Protocol Identification byte appears as the first byte of the HDLC
DATA field in AX.25 Level Two information frames, and identifies which
Level 3 protocol is implemented, if any. In the case where no Level 3 protocol
is implemented, PID = $F0.
DATA
This field contains the actual information to be transferred.
This field need not be present. Most frames used only for link control do not
have data fields.
FCS Frame Check Sequence, a 16-bit error detection field.
The communications chip recognizes the opening and closing flags and passes
the address, control, and data (including PID) fields to the software. The FCS
field is a Frame Check Sequence computed by the transmitting chip and sent
with the frame. The receiving chip recomputes the FCS based on the data
received and rejects any frames in which the received FCS does not match the
computed FCS. There is virtually no chance of an undetected bad frame using
this method. This satisfies the level two task of bad data detection.
The communications chip used in the MFJ-TNC is a Zilog 8440 SIO operating
in conjunction with a two-chip "state machine" which is used to recover the
data clock. The transmitted data is encoded in NRZI form, which encodes a
"0" data bit as a transition in the encoded bit stream and a "1" data bit as no
transition. This, in combination with the "bit-stuffing" which ensures that no
more than five "1"s occur in a row except when FLAG bytes are being
transmitted, guarantees that a logic level transition occurs at least once every 5
bit times. These frequent transitions allow the receiver to synchronize its clock
with the transmitter. Other chips which are compatible with the SIO + "state
machine" are the Western Digital 1933/1935, the Intel 8273 (used on the
VADCG and Ashby TNCs) and the Zilog 8530 (used on the Xerox 820 FAD
adapter).
While the HDLC format supplied by the communications chips is used by the
AX.25 protocol, there are several other Layer Two concerns. These are
duplicate frame detection, connection and disconnection of the level two layers
on different TNCs, and buffer overrun avoidance. The AX.25 protocol solves
these problems as described below.

AX.25 Level Two

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PACKET PROTOCOL

AX.25 is based on the Balanced Link Access Procedure (LAPB) of the CCITT
X.25 standard. LAPB in turn conforms to the HDLC standard. Two
extensions are made to LAPB in AX.25. These are the extended address field,
and the unnumbered information (UI) frame. In LAPB, addresses are limited
to eight bits, while AX.25 uses from 112 to 560 bits, containing the originator's
call sign, the destination call sign and an optional list of one to eight digipeater
(simplex digital repeater) call signs.
The UI frame is used to send information bypassing the normal flow control
and acknowledgment protocol. The UI frame is not acknowledged but can be
transmitted at layer two without fear of disturbing higher layers. It is used for
beacon frames, for automatic identification packets, and for sending
information frames when the MFJ-TNC is not connected to another TNC,
e.g., CQ and QST activities.
The exact specifications for AX.25 are supplied in the ARRL publication
Amateur Packet-Radio Link-Layer Protocol, AX.25 Version 2.0. The TAPR
implementation adheres to this standard for AX.25 version 2.0. The
implementation of version 1.0 is almost identical to the TAPR TNC 1 version
of AX.25 protocol in software releases 3.x. This provides compatibility with
the majority of Amateur packet radio stations.
The following table lists the frame types used by AX.25 and describes their
purpose. This material is provided to give a general understanding of the
protocol, and is not intended to replace the published specification. The byte
fields are given as they appear in memory after data is received, i.e., the high
order bit is at the left and the low order bit is at the right. This is also the
format of the display provided by the TRACE command. Some texts,
including the AX.25 protocol specification, list the bits in the order in which
they are transmitted, which is low order bit first.
The control bytes are presented in hex with "x" used to indicate four bits which
depend on the acknowledge functions the packet is performing. Usually "x" is
a frame number. Frame numbers fit into three bits and are used to ensure that
frames are received in order and that no frames are missed. Since only three
bits are available, the frame number is counted module 8. This is why the
MAXFRAME parameter has a ceiling of 7: no more than seven frames can be
"in flight" (transmitted but unacknowledged) at one time. A short description
of the use of the frames is given after the table.

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MFJ-1270C/1274C MANUAL

Code
x1
x5
x9
03
0F
2F
43
63
87
even

Abbrv
RR
RNR
REJ
UI
DM
SABM
DISC
UA
FRMR
I

PACKET PROTOCOL

Frame Type
Receive Ready
Receive Not Ready
Reject
Unnumbered Information
Disconnected mode
Connect request
Disconnect request
Unnumbered Acknowledge
Frame reject
Any frame ending in an even number (including
$A, $C, and $E) is an information frame.

Table 10-1 AX.25 Control Codes
I
This and UI frames are the only frame types containing user data.The
control byte contains this frame's number and the number of the next frame
expected to be received from the other end of the link.
RR Usually used to acknowledge receipt of an I frame. The RR function can
also be performed by sending an I frame with an updated "expected next frame
number" field.
RNR

Used when the buffer space on the receiving side is full.

REJ Used to request retransmission of frames starting from "x". Missed
frames are detected by receiving a frame number different from that expected.
DM Sent in response to any frame received other than a connect request
(SABM) when the TNC is disconnected. Sent in response to an SABM
whenever the TNC is on the air but can't connect to the requesting user, e.g., if
the TNC is already connected to someone else or if CONOK is OFF.
SABM

Set Asynchronous Balanced Mode initiates a connect.

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DISC

PACKET PROTOCOL

Initiates a disconnect.

UA Sent to acknowledge receipt of an SABM or DISC.
FRMR Sent when an abnormal condition occurs, i.e., the control byte
received is undefined or not proper protocol at the time received. UI frames UI
An I frame without a frame number. It is not acknowledged.

Channel Use and Timing Functions
The following discussions mention timing parameters which are set by various
commands. These timing functions are also discussed in Chapter 5.
An important part of any packet radio protocol is the means by which many
stations make efficient use of an RF channel, achieving maximum throughput
with minimum interference. The basis for this time domain multiplexing is
Carrier-Sensed Multiple Access (CSMA) with collision detection and collision
avoidance.
CSMA means simply that (as every Amateur knows) no station will transmit if
the frequency is in use. The MFJ-TNC continually monitors for the presence
of an audio data carrier on frequency and transmits only if there is no carrier.
(The RF carrier is not normally detected; however, an input is available on the
MFJ-TNC radio interface connectors to allow such an input.) In order to
make detection of a busy channel more reliable, the MFJ-TNC sends an audio
signal (continuous flags) any time the transmitter is keyed and a packet is not
being sent, as during the transmitter keyup delay (TXDELAY), or while a slow
audio repeater is being keyed (AXDELAY).
By itself, CSMA is not enough to insure a minimum, or even low, interference
rate, due to the likelihood of simultaneous keyup by two or more stations. This
is where collision detection and collision avoidance come in. The MFJ-TNC
detects a collision by the absence of an ACK from the station it is sending to.
The receiving station does not acknowledge the frame that suffered the
collision, since either the FCS was incorrect or the packet was not heard.
There are other possible reasons for non-receipt of the packet, but the MFJTNC 's response is based on the assumption of a collision.

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PACKET PROTOCOL

After transmitting a packet, the MFJ-TNC waits a "reasonable" length of time
(FRACK) for an acknowledgment. "Reasonable" is determined by the link
activity, frame length, whether the packet is being digipeated, and other timerelated factors. If no ACK is received, the packet must be re-sent. If the
unACKed frame was lost due to a collision, the assumption is that there is at
least one other packet station out there that also lost a frame and will probably
have exactly the same criterion for deciding when to retry the transmission as
this station is using.
In order to avoid a second collision, the collision avoidance protocol calls for
the stations retrying transmissions to wait a random time interval after hearing
the frequency become clear before they key their transmitters. There must be
enough different random wait times to provide a reasonable chance of two or
more stations selecting different values. The difference between adjacent time
values must be similar to the keyup time delay of typical stations on the
frequency. This is the time lapse after a station keys its transmitter before other
stations detect its presence on the channel, and is a function of the keying
circuitry of the transmitter and the signal detection circuitry of the receiver.
We have chosen the random time to be a multiple (0-15) of the transmitting
station's keyup delay (TXDELAY). This is reasonable if one's own keyup
delay is similar to that of other stations on the channel.
One other factor must be taken into consideration in optimizing data
throughput. The currently implemented link protocols provide for relaying
(digipeating) of packets. The acknowledgment procedure for such packets is
that the relay station simply repeats packets without acknowledgment to the
sending station. The receiving station sends its ACK back through the same
digipeaters to the originating station. Since the digipeated packets are not
acknowledged to the digipeater, an unsuccessful transmission must be retried
from scratch by the originating station. In order to help alleviate the
congestion of the frequency that tends to result when digipeated packets suffer
collisions, the digipeater is given first shot at the frequency every time it
becomes clear. Other stations, instead of transmitting as soon as they hear the
channel clear, must wait a short time (DWAIT). This restriction applies to all
stations except the digipeater, which is permitted to transmit relayed packets
immediately. This prevents digipeated packets from suffering collisions except
on transmission by the originating station.
A special time delay (RESPTIME) is used as the minimum wait time prior to
transmitting acknowledgment frames, to prevent TNCs accepting data at high
speed from the asynchronous port from colliding with acknowledgment frames

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PACKET PROTOCOL

when fewer than MAXFRAME packets are outstanding. The receiving TNC
will wait long enough before sending the ACK so that it will hear the data
packet which would have caused the collision, thus avoiding a fairly frequent
source of delay in versions of AX.25 prior to 2.0.

Channel Flow Control
Flow control of data through the link is determined by the rate at which data is
being supplied to a sending TNC and accepted from a receiving TNC.
A TNC receiving data from the link will send an RNR when the next I frame
successfully received will not fit into the buffer for output to the serial port.
Whenever a TNC transmitting data received from the serial port over the link
runs out of temporary buffer space, the serial port will be halted by an XOFF
character or CTS signal. In the MFJ-TNC
implementation this happens
whenever there are 7 packets built and less than 210 characters left in the
buffer for input from the serial port.
When the TNC receiving data from the link clears out its buffers, it sends an
RR to the transmitting TNC. In order to guard against the possibility of the RR
being lost and the link becoming permanently locked, the transmitting TNC
will periodically re-transmit the packet that provoked the RNR. The receiving
TNC will continue to respond with RNR until it can accept the packet.

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MFJ-1270C/1274C MANUAL

APPENDIX A: RADIO HOOKUP

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APPENDIX A: RADIO HOOKUP

RADIO HOOKUP
MFGS. OR
RADIOS

CONNECTOR
TYPE

PTT To pin
3 of 1278

4 pin
5 pin
6 pin
8 Pin
HTs
HTs
"
"
"
4 pin
8 pin

MIC. AUDIO
To pin 1 of
1278
pin 1
Pin 1
Pin 1
Pin 1
Tip-Lg.
Ring-Lg.
"
"
" |
Pin 1
Pin 1

KENWOOD
"
"
"
TR-2500
TR-x600
TH-x1xx
TH-x15
TH-x5
ICOM
"
"
YAESU
"
FT-208
FT-x09
FT-x3
FT-727

HTs
4 pin
8 Pin
HTs
HTs*
HTs*
HTs*

Tip-Sm
Pin 2
Pin 8
Pin 1
Tip-Sm
"
"

Tip-Sm
Pin 3
Pin 6
Pin 3
Tip-Sm
"
"

Pin 2
Pin 2
Pin 2
Pin 2
Sleeve-Lg
Sleeve-Lg
"
"
"
Pin 2
Pin 5

RX AUDIO
To pin 4 of
1278
Speaker
Speaker
Speaker
Speaker
Tip-Sm.
Tip-Sm
"
"
"
Speaker
Speaker
or
pin 8
Tip-Lg
Speaker
Speaker
Pin 2
Tip-Lg
"
" |

GROUND
To pin 2 of
1278
Pin 3,4
Pin 4,5
Pin 6
Pin 7,8
Sleeve-Sm
Sleeve-Sm
"
"
"
Pin 4
Pin 6,7
Sleeves
Pin 1
Pin 7
Pin 4
Sleeves
"
"

Table: A-1 HOOKUP FOR SPECIFIC RADIOS

*:
Some ICOM and Yaesu HTs key the transmitter by completing the
ground connection on the microphone. If your HT is one that is noted in the
above chart, you must follow the instruction given in Chapter 3 of this
instruction manual.
NOTE: The radio connection information listed in the above chart is believed
to be accurate. However, you should CHECK the ACCURACY of this
information with the INSTRUCTION MANUAL of your radio. MFJ
Enterprises, Inc. is not responsible for any inaccuracy of information listed in
the above chart.

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APPENDIX B: CALIBRATION

MODEM CALIBRATION
The MFJ TNC is factory calibrated to operate to within factory guidelines. If it
becomes necessary to re-calibrate the modem, then the following procedure is
provided.

Modulator and Demodulator Frequency Calibration
Here we present two (2) Modulator and Demodulator calibration methods.
Method I requires test equipment as noted, where Method II does not require
test equipment.

Method I
HF Modem
Test equipment needed: Frequency Counter and probe and oscilloscope with
probe.
1.

Install push-on jumpers on JMP 4 and JMP 7.

2.

Verify a push-on jumper is installed on JMP 8.

3.

In the following procedure all frequencies are to be set to within +/- 2 HZ.

4.

Place the frequency probe at JMP 9 pin 1. This is the top pin.

5.

Place the oscilloscope probe on top pin of JMP 10.

6.

Set dip switch #6 ON.

7. Set one of the dip switches 1 thru 5 to the Computer Baud Rate which
appiles to the baud rate being used on the computer.
8.

Push the VHF/HF switch to the HF position.

9.

Initiate the calibration mode by typing:
CALIBRATE 

10. Now the modem must be keyed up. Do this by pressing the K key.
11. Check the voltage on pin 9 of U16. Press the SPACE BAR until this pin
indicates -5 VDC.
12. Adjust R106 to where the frequency counter indicates 2125 Hz +/- 2 Hz.
13. Press the SPACE BAR until pin 9 of U16 indicates +5 VDC.
14. Adjust R105 to where the frequency counter indicates 2295 Hz,+/- 2 Hz.
15. Press the D key.
16. Locate R212, which is near the front of the PC board by the tuning
indicator. Adjust R212 until the 10th led from the left is lit on the tuning
indicator. This enables proper signal tuning within the HF bands.
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APPENDIX B: CALIBRATION

VHF Modem
Test equipment needed: Frequency Counter and probe and oscilloscope with
probe.
1.

Install push-on jumpers on JMP 4 and JMP 7.

2.

Verify a push-on jumper is installed on JMP 8.

3.

In the following procedure all frequencies are to be set to within +/- 2 HZ.

4.

Place the frequency probe at JMP 9 pin 1. This is the top pin.

5.

Place the oscilloscope probe on top pin of JMP 10.

6.

Set dip switch #7 ON.

7. Set one of the dip switches 1 thru 5 to the Computer Baud Rate which
appiles to the baud rate being used on the computer.
8.

Push the VHF/HF switch to the VF position.

9.

Initiate the calibration mode by typing:
CALIBRATE 

10. Now the modem must be keyed up. Do this by pressing the K key.
11. Check the voltage on pin 9 of U16. Press the SPACE BAR until this pin
indicates -5 VDC.
12. Adjust R78 to where the frequency counter indicates 1200 Hz +/- 2 Hz.
13. Press the SPACE BAR until pin 9 of U16 indicates +5 VDC.
14. Adjust R77 to where the frequency counter indicates 2200 Hz,+/- 2 Hz.
15. Press the D key.
16. Set the TIME/DIV. scale on the scope to 1 MS/DIV and the VOLT/DIV
scale to 5 V/DIV. Connect the scope probe to the toppin of JMP 10.
17. Adjust R79 so that signal on the scope shows a 50% duty cyclesquare
wave. The square wave should be uniform in width ( i.e hightime is equal to
the low time ). The pulse duration of the high time and the low time is
approximately 2.4ms. The CON and STA LEDS may blink simutaneously.
18. Type Q to quit the calibration routine.

METHOD II
The below procedure needs no test equipment, and is very accurate if done
properly. Be sure to follow each step carefully. If any problems arise, please go
back and check the preceeding step, to make sure it worked.
This procedure is a three (3) step process. The three steps areas follows:
1.

Center the modulator tones over the required modem center frequency

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MFJ-1270C/1274C MANUAL

APPENDIX B: CALIBRATION

(Fc).
2.

Align the demodulator center frequency.

3.

Align the tuning indicator.

NOTE: ALL THREE STEPS SHOULD BE PERFORMED IN THE ABOVE
ORDER!
If they are not all done at the same time, or in the correct order, the modem
may not be receiving and transmitting on the same frequency, and the tuning
indicator may give false indications.

The third step, alignment of the tuning indicator, should only be used in
conjunction with alignment of the 300 baud 170 Hz shift demodulator.
The other AFSK modems available in the MFJ-TNC can be aligned using
exactly the same steps presented here but substituting the appropriate part
numbers for the adjustments. However, do NOT align the tuning indicator to
anything but the 300 baud 170 Hz shift HF packet modem.

It is important that the tuning indicator alignment be optimized for the 300
baud 170 Hz shift HF packet modem. It will indicate correctly for all other
modes when aligned for the HF packet modem.
As described elsewhere in this manual, the exact configuration of your radio's
filters and whether it has IF shift or not will determine the exact required center
frequency for the modem. Once the required center frequency has been
determined, the modem calibration can be carried out.
NOTE: It is essential that the modulator tones be properly aligned FIRST as
they will be used to align the demodulator center frequency.
Set the modulator tones to Fc MINUS 1/2 of the shift for the low tone and Fc
PLUS 1/2 of the shift for the high tone. For the 170 Hz shift 300 baud modem
used for HF packet this would be Fc + 100 Hz for the high tone and Fc - 100 Hz
for the low tone.

Set Modulator Tones Using Built-in Calibration Software
1. Make sure that the modem and TNC are both configured for 170 Hz shift
300 baud operation.
2.

Place a push on jumper at JMP 4 and JMP 7.

3.

Verify push-on jumpers at JMP8 and JMP 9 pins 1&2.

4.

Type "CALSET n ". Where n is a number determined by:
n = INT [ 525000 / F(low) ] + 1
This tells the CPU what tone frequency you are trying to achieve.

A table of CALSET numbers to use for the various "standard" modem
tone frequencies will be included at the end of this procedure.

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MFJ-1270C/1274C MANUAL

APPENDIX B: CALIBRATION

5. Command the MFJ-TNC into calibrate mode by typing "CALI followed
by a ".
6.

Command the MFJ-TNC to key the modem by typing "K".

7. Select the low tone by pressing the space bar until a voltmeter connected
to U16, pin 9 reads - 5 volts.
8. Adjust R106 carefully until both the "CON" and "STA" LEDs on the front
panel of the TNC are lit. One of the leds may filcker slightly. This is normal.
9. Type a "Q". This exits the MFJ-TNC from calibrate mode to ommand
mode.
10. Type "CALSET n ". Where n is a number determined by:
n = INT [ 525000 / F(high) ] + 1
11. Command the MFJ-TNC into calibrate mode by typing "CAL ".
12. Command the MFJ-TNC to key the modem by typing "K".

13. Select the high tone by pressing the space bar until a voltmeter connected
to U16, pin 9 reads + 5 volts.
14. Adjust R105 carefully until both the "CON" and "STA" LEDs on the front
panel of the MFJ-TNC are lit. One of the leds may flicker slightly. This is
normal.
15. Type a "Q". This exits the MFJ-TNC from calibrate mode to command
mode.

This completes the modulator tone alignment using the built in calibration
facility. If you had any problems with this section, then DO NOT go beyond
this point. If you do the calibration will be inaccurate. However, if all went
well, then you may proceed.
Now that the modulator tones have been properly centered over the intended
modem center frequency (Fc), now the demodulator center frequency will be
aligned.

Demodulator Center Frequency Alignment
1. Place push on jumpers at JMP 4 and JMP 7, if they are not already in
place.
2.

Verify a jumper is at JMP 9 pins 1 and 2 and JMP 8.

3. Type CALSET . Where n is a number determined by the following
equation:
n = INT (262,000 / f) +1
4.

Command the MFJ TNC into calibration mode by typing CAL 

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APPENDIX B: CALIBRATION

6. CAREFULLY adjust the appropriate control until the DCD LED on the
front panel is fully illuminated. Please refer to Appendix page___for the
proper control to adjust.
NOTE: The threshold control on the MFJ-TNC must be set to a position
which will allow the DCD circuit to function properly. A setting approximately
1/3 to 1/2 of the total range starting from maximum CCW should be adequate.
Continue to VERY CAREFULLY adjust R113 until the STA and CON LEDs
on the front panel either change state very slowly (alternate which one is lit) or
until both are simultaneously illuminated.
NOTE:This is a very critical adjustment. It is very unlikely that you will be
able to cause both LEDs to be turned on simultaneously, for longer than a very
brief instant. Just fine tune R113 very carefully, and notice the action between
the STA and CON leds. If they flash back and forth this is acceptable.
7. Return the MFJ-TNC to command mode by typing a "Q".

This completes demodulator center frequency alignment using the built in
calibration software. If there were any problems in the preceeding procedure,
then DO NOT go beyond this point. If you do the calibration will be inaccurate.
Now that the demodulator and modulator are properly aligned
to one another, the tuning indicator can be set for proper center indication.

Tuning Indicator Alignment
This procedure adjusts the tuning indicator so that it correctly indicates when a
signal is properly tuned in relation to the demodulator center frequency. In
order for the Tuning Indicator to be properly aligned the above calibration must
be done properly, otherwise you will align the Tuning Indicator improperly.
NOTE:The tuning indicator should ONLY be adjusted in reference to the 300
baud 200 Hz shift modem used for HF packet and RTTY. If adjusted for this
modem, It will indicate with sufficient accuracy for all other modes.
1. If you have not just finished aligning the modem as per the above
instructions, do so now. Otherwise you may be aligning the tuning indicator to
incorrect calibration settings.
2. Install push on jumpers at JMP 4 and JMP 7, if they are not still in place
from the modem alignment procedure.
3. Ensure that the jumpers on JMP9 and JMP16 are placed as stated in the
demodulator alignment section above.
4. Command the calibration routine to send 50 percent duty cycle square
wave data from the modulator by typing "RXCAL" .
5. While observing the LEDs in the tuning indicator, adjust R212 in the
tuning indicator area so that either the 10th or 11th led from the left (or both)
are illuminated.
8.

Return the MFJ-TNC to command mode by typing "Q".

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MFJ-1270C/1274C MANUAL
9.

APPENDIX B: CALIBRATION

Remove jumpers at JMP 4 and JMP 7.

This completes the tuning indicator alignment.
Now the modulator, demodulator, and tuning indicator are all aligned to the
same center frequency. If you notice that on the air reports suggest that you are
transmitting and receiving on significantly different frequencies after
successfully completing the above alignment procedure, it is possible that the
radio needs realignment. Many different transceivers for HF are capable of
being misaligned due to reference oscillator crystal aging or careless alignment
by amounts exceeding 500 Hz. RIT inadvertently left on can also cause hard to
detect problems in this area. Reliable HF packet communications requires that
the frequency error presented to the demodulator be below 30 Hz. If several
stations are to successfully share a single channel, transmitter / receiver offsets
larger than this will be intolerable.

MFJ-TNC Adjustment Location Map
This is a map of the physical locations of the adjustment potentiometers on the
MFJ-TNC circuit board. They are shown as they appear when looking down
on top of the board with the board oriented so that the rear panel connectors are
to the left. Information in the boxes is organized as shown below.
R78
1200

VP L VHF Low Tone
438
Modulator

R77
2200

VP H VHF High Tone
240
Modulator

R106
2125

HP L HF Low Tone
247
Modulator

R105
2295

HP H HF High Tone
229
Modulator

R79
VP
CALSET 8

VHF Demodulator

R113
HP
CALSET 32

HF Demodulator

NOTE: Separate procedure required to do alignment of CW demodulator
center frequency.
NOTE: CW receive through a narrow filter for HF CW operation will require
the CW demodulator center frequency to be selected to align with the radio's
filter passband. MCW operation on VHF FM will require that both stations
have both the modulator tone and demodulator center frequency to the same
frequency.

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MFJ-1270C/1274C MANUAL

APPENDIX B: CALIBRATION

Calset Values for Various Modulator Tone frequencies
Tone

CALSET #

Adjust

Modem / Remarks

2125

247

R106

2295

229

R105

HF Packet
Fc = 2210 Hz
170 Hz shift

1300

404

R78

2100

250

R77

1200

438

R78

2200

240

R77

Packet / 1000 Hz shift standard.
Too wide to fit comfortably
through SSB filters for linear
mode 1200 baud use

2125
2975

248
177

R106
R105

Fc = 2550 Hz
850 Hz shift

2178
2263

242
233

R106
R105

Fc = 2220 Hz
85 Hz shift.

Packet / Fc = 1700 Hz, 800 Hz
shift. CCITT V.23 std., preferable
for HF 1200 baud, works
well on VHF FM too.

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MFJ-1270C/1274C MANUAL

APPENDIX C: AUDIO OUTPUT

AUDIO OUTPUT CALIBRATION
The transmit audio output levels of MFJ-TNC Radio Port is factory set to 250
mV. You may find it necessary to set the output levels differently to match your
radio specifications, then you should follow the procedure given in this
appendix.
Transmit audio adjustment is accessible from the outside thru screw driver
adjustment holes on the left side of the MFJ-TNC. It is not necessary to remove
the cover.
Most often audio output level of the MFJ-TNC can be set simply by monitoring
the transmitting audio with a connecting station. However, if you require a
more precise setting or making the adjustment without an on-the-air test, then
use the procedure given here.

Audio Output Level Adjustment Procedure
1.

After the cmd: prompt sign, set the MFJ-TNC to VHF packet mode
by setting S1 to the VHF (IN) position.

2.

Set dip switch #7 on SW3 to the ON position. Set the correct
terminal baud rate on SW3 according to the baud rate you are
running on you computer or terminal. A list of terminal baud rates
available is shown below:
DIP SWITCH #
1
2
3
4
5

BAUD RATE
300/19.2K
1200
2400
4800
9600

3.

Place a push on jumper at JMP4 and JMP7.

4.

Enter:
CALI
should illuminate.

5.

Place the oscilloscope probe at JMP7.

6.

Signal on the scope will be approximately 2.5 volts p-p.

7.

Verify that the voltage on pin 9 of U16 is -5 Vdc. If it is +5 Vdc
instead of -5 Vdc, push the space bar. The voltage should alternate
between +5 Vdc and -5 Vdc each time the space bar is pressed. Set
this point to -5 Vdc.

8.

Move the probe to J9 pin 1 (TX audio). Adjust R157 for a signal of
100 mV p-p as shown on the scope. Or set it to a level recommended
by your radio instruction manual.

9.

Move the probe to J9 pin 4 (RX audio). The signal should be
approximately 1 V p-p.



Press the "K" key.

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The PTT LED

MFJ-1270C/1274C MANUAL

APPENDIX C: AUDIO OUTPUT

10. Press the space bar and again measure the peak to peak voltage at J9
pin 4.The audio level should not change.(Both mark and space audio
should be at the same level.)
11. Remove the jumpers from JMP 4 and JMP7.
12. Switch SW1 to the OFF position.

Page 245

MFJ-1270C/1274C MANUAL

APPENDIX D: ALIGNMENT

HF RADIO ALIGNMENT
If you have determined that it is necessary to realign the MFJ-TNC modem
center frequency to your radio filter center frequency, one of the following 2
methods should be used to make the radio filter center frequency (Fc)
determination. Both methods require access to a frequency counter capable of
measuring audio frequencies to a resolution of 1 Hz. Almost any frequency
counter should be capable of this.

First method: NOISE AVERAGE FREQUENCY
This method also requires an active noise source like a receiver noise bridge.
There are several suitable units available for this purpose.
1.

Set the receiver to LSB mode with the 500 Hz filter selected.

2. Connect the noise source to the receiver input. Make sure there is no
antenna connected to the system and that the receiver is tuned to a frequency
which is free of coherent internally generated signals (birdies).
3. Set the noise source output for a reading of approximately S-9 on the
receiver S meter.
4.

Connect the counter to the receiver audio output

5. Adjust the receiver output level for enough audio to reliably trigger the
counter.
6. Make sure the radio's IF shift control, if one is present, is in its proper
position (centered or on detente).
7. Record the frequency indicated by the counter. The counter should
indicate the average frequency of the noise spectrum passed by the filter in the
receiver and translated to audio by the product detector. This will be the
frequency used for the modem center frequency (Fc).
NOTE: If the counter is a phase locked loop (PLL) based prescaling type, its
PLL may not lock properly to the noise signal. If this is the case, use method 2
below. If your counter can resolve 1 Hz with a counting gate time of less than 1
second, it is a PLL prescaling counter.

Second method: FILTER SKIRT AVERAGE FREQUENCY
1.

Set the receiver to LSB mode with the 500 Hz filter selected.

2. Make sure the radio's IF shift control, if one is present, is in its proper
position (centered or on detente).
3. Using either a signal generator or a stable, relatively strong carrier from
an AM broadcast transmission (preferably ground wave signal), tune the
receiver so that the carrier falls near the center of the filter passband. Choose a
signal level near S-9 for this test. If your rig has a built in calibration
oscillator, this is a good source for this signal.
4. Slowly and carefully tune the receiver so that the tone frequency is
decreasing.
5. Find the point where the signal is reduced by 1 S-UNIT from the peak
value reached near the center of the filter passband.

Page 246

MFJ-1270C/1274C MANUAL

APPENDIX D: ALIGNMENT

6. Measure this tone frequency with the counter. Record this value as
F(low).
7. Slowly and carefully tune the receiver so that the tone frequency is
increasing.
8. Find the point where the signal is reduced by 1 S-UNIT from the peak
value reached near the center of the filter passband.
9. Measure this tone frequency with the counter. Record this value as
F(high).
10. Calculate the required modem center frequency as:
Fc = [F(low)+F(high)]/2
Once the required center frequency has been determined, the modem
calibration can be carried out.
NOTE: It is essential that the modulator tones be properly aligned FIRST as
they will be used to align the demodulator center frequency.
Set the modulator tones to Fc MINUS 100 Hz for the low tone and Fc PLUS
100 Hz for the high tone using the procedure given in the owners manual.
Align the demodulator to the modulator tones using the built in demodulator
alignment facility invoked with the RXCAL command described Appendix B
ofthismanual.

Page 247

MFJ-1270C/1274C MANUAL

APPENDIX E: 2400 MODEM

MFJ-TNC 2400 PACKET OPERATION
If your MFJ-TNC does not have the 2400 modem, an optional modem (MFJ2400) can be purchased and installed. Installation is simple; your MFJ-TNC is
equipped with all connectors necessary to make this installation without
modification or soldering. If you have the MFJ-1270CT or the MFJ-1274CT
the 2400 modem is already installed inside the unit.
With the 2400 modem installed, your MFJ-TNC is capable of operating 300,
1200 or 2400 baud packet. The 300 baud and 1200 baud packet modes are not
affected by the installation of the 2400 modem.
The addition of the 2400 modem feature will in no way require any internal
modification to your transceiver.

2400 Packet Operation Setup
All default parameters set for 1200 packet operation can be used for the 2400
operation. 2400 operation needs no unusual setup or parameter changes.
There are however, some changes that can be made later to the MFJ-TNC
parameters which will enable you to improve the speed of the throughput
performance of the 2400 operation. The "honing" of the parameters may not
seem like much, but we have found that at 2400, the MFJ-TNC seems to be
more responsive to the TXDELAY, DWAIT, RESPONSE and SLOTTIMES.
When using direct connects and good paths, the MAXFRAME and PACLEN
commands can be increased to allow larger packets to be moved during each
transmission. When returning to the active thru-put frequencies, these two
commands should be reduced to their original settings. You may find that if
you were using a TXD of 50, then a TXD of 40 will now perform better. The
DWAIT can be shortened or lengthened to suit the AGC recovery time of your
radio. For instance, if you have been running the DWAIT of 16, it may now
perform better at DWAIT of 12 or even 10. The FRACK will appear to
exercise more at 2400.
2400 really shows its place in the packet world when used to pass large ASCII,
BINARY and PICTURE files. It is always good to use clear frequency and/or
use direct connects to the target station rather than going thru a node or
digipeater. The reason is obvious. There are few 2400 nodes at the present
time. However, it should be pointed out that implementation of a 2400 node is
just as easy as building and using a 1200 node.
To select 2400 baud packet operation, set dip switch #8 ON at SW3.
The dip swiches 6 ,7, and 8 on SW3 will set as follows for 2400 baud
operation:
6
7
8
OFF OFF ON
The MFJ-TNC will be set to 2400 packet operation. The TURBO LED will
light. Note that if your MFJ- TNC is not equipped with the 2400 modem, the
TURBO LED will not function and you will not be able to operate 2400
packet.

B. Receive Audio Setting

Page 248

MFJ-1270C/1274C MANUAL

APPENDIX E: 2400 MODEM

The MFJ 2400 modem employs automatic gain control (AGC) for its receive
audio. The receive audio level is pre-set for proper 2400 operation; no
adjustment is necessary in most cases. If you set the receive audio of your
radio properly for 1200 operation, then it will be suitable for the 2400 operation
also. No adjustment for the receiver audio on the 2400 modem board is needed.

C. Transmit Audio Setting
Transmit audio on the 2400 board is set by adjusting R38 (next to T2) on the
2400 modem board. Transmit audio for the 1278BT is pre-set at the factory to
match the audio level of the 1200 modem on the MFJ-TNC mother board.
Once the 1200 and the 2400 transmit audio are set to the same level, then you
may adjust the audio level going into your radio by using the "Transmit Audio"
controls on the left side of the MFJ-TNC. Note that these controls set the
transmit audio levels for all the operation modes of the MFJ-TNC , including
the 2400 packet operation.
When adjusting the transmit audio level please note that the range of R38 on
the 2400 board is pre-set by CN-6 header. The shorting jumper on CN-6
header sets range as follows:

CN-6 Jumper
Position
no jumper
1 & 2 (default)
2&3

Transmit Audio Range
(no load)
50 mV - 60 mV p-p
100 mV - 200 mV p-p
250 mV - 3 V p-p

Page 249

MFJ-1270C/1274C MANUAL

APPENDIX F: JUMPERS

JUMPER FUNCTIONS AND LOCATIONS
The MFJ-TNC mother board has many jumper connectors. Each jumper
connector has a special function. The Jumper Function chart in this appendix
will help in identifying each jumper function. Figure G-1 will help in locating
the jumper connectors easily.
For normal operation a shorting jumper must be placed on the following
connectors: JMP 5; JMP 8; JMP 9 pins 2,3; JMP 13; JMP 18 pins 1,2; JMP 15
pins 2,3; JMP 26 pins 1,2. Also on the modem disconnect header J4 the
following pins need jumpers pins 1,2 11,12 13,14 17,18.

Table G-1: Jumper Function
Jumper #

Position

Function

JMP1

Pin 1 & 2
Pin 2 & 3
OFF (default)
Pin 1 & 2 (default)
Pin 2 & 3
ON
OFF (default)
ON (default)
OFF
ON
OFF (default)
ON (default)
OFF
Pin 1 & 2
Pin 2 & 3 (default)
ON
OFF (default)
LEFT
RIGHT (default)
ON (default)
OFF
Pin 1 & 2 (default)
Pin 2&3

!DCD (RS-232C) stays on
!DCD (RS-232C) stays off
!DCD reflects connect status
4.92 MHz CPU clock
2.46 MHz CPU clock
disable Tx watch-dog
enable Tx watch-dog
Lithium battery connected
Lithium battery disconnected
analog loopback mode
normal modem operation
demodulator enabled
demodulator calibrate
calibrate U16 tones
normal modem operation
digital loopback mode
normal modem operation
transmit data NRZ NEED PIN #
transmit data NRZI
TTL, RTS enable
TTL, RTS disable
256K firmware EPROM
512K bit firmware EPROM

JMP2
JMP4
JMP5
JMP7
JMP8
JMP9
JMP10
JMP11
JMP13
JMP15

Page 250

MFJ-1270C/1274C MANUAL

APPENDIX F: JUMPERS

Table G-1: Jumper Functions (Cont.)
Jumper#

Position

Function

JMP17

Pin1&2
Pin 2 & 3(default)
Pin 1 & 2(default)

2400 baud ext. modem clock
9600 baud ext. modem clock
Enable 19.2K baud termial
Disable 300 baud terminal
Enable 300 baud termial
Disable 19.2K baud terminal
Enable 32K mailbox RAM
Enable 128K mailbox RAM
Enable 512K mailbox RAM
512K mailbox RAM installed
32K or 128K mailbox RAM
Enable memory RESET
(default) Normal operation
Normal +5Vb bbRAM operation
Real-time clock installed
Normal SW3 Operation
Baud Rate Switch SW3 Bypass
TX audio has flat response
TX audio 6db/oct pre-emphasized
TX audio loopback to PTT for
Radio Port J9
Analog audio loopback for Radio
Port J9
Speaker Transmit Tone Enable
SpeakerTransmit Tone Disable
Speaker Receive Tone Enable
Speaker Receive Tone Disable
Speaker Connect Tone Enable
Speaker Connect Tone Disable

JMP18

Pin 2 & 3
JMP19

JMP20
JMP23*
JMP26**
JMP27
JMPJ
JMPL
JMPR
JMPX
JMPY
JMPZ

Outside pair(default)
Middle pair
Inside pair
ON
OFF(default)
ON
OFF
Pin 1&2 (default)
Pin 2&3
Pins 1&2 (Default)
Pins 2&3
ON
OFF(default)
ON
OFF(default)
ON
OFF(default)
ON(default)
OFF
ON(default)
OFF
ON(default)
OFF

*
When JMP23 is shorted, it will RESET the MFJ-TNC. This means that
all parameters will be reset to the default values. This is the same as removing
the bbRAM battery except it is much quicker. DO NOT SHORT THIS
JUMPER MORE THAN A COUPLE OF SECONDS, OTHERWISE
BATTERY DAMAGE COULD RESULT!!
** MFJ offers an optional Real-time clock module (MFJ-43) that can be
installed on the MFJ-TNC mother board. This clock keep the MFJ-TNC clock
running all the time. You will not have to reset the clock everytime you turn
the MFJ-TNC on.

Page 251

MFJ-1270C/1274C MANUAL

APPENDIX F: JUMPERS

Fig. G-1: Jumper Connector Location

Page 252

MFJ-1270C/1274C MANUAL

APPENDIX G: SUMMARY

COMMAND SUMMARY
Command

Parameter

Default

Mode

Function

Page

8BITCONV
ABORT
ACKPRIORITY

ON|OFF
-ON|OFF

on
I-command
on

Packet
M-Packet
Packet

6-5
6-6
6-7

ACKTIME

n

14

Packet

ANSWRQRA
AUTOLF
AWLEN

ON|OFF
ON|OFF
n

on
on
8

Packet
Packet
All

AX25L2V2

ON|OFF

on

Packet

AXDELAY
AXHANG
BBSMSGS

n
n
ON|OFF

0
0
off

Packet
Packet
Packet

BEACON
BKONDEL

n
ON|OFF

0
on

Packet
Packet

BLP
BTEXT
BUDLIST

ON|OFF
text
ON|OFF

on
blank
off

Packet
Packet
Packet

CALIBRA

--

I command

All

CANLINE

n

$18 (^x)

Packet

CANPAC

n

$19 (^Y)

Packet

CBELL

ON|OFF

off

Packet

CHAT

--

I-command

M-Packet

CHECK
CHECKV1

n
ON|OFF

30
off

Packet
Packet

CONPERM
CMDTIME
CMSG

ON|OFF
n
ON|OFF

off
1
off

Packet
Packet
Packet

CMSGDISC

ON|OFF

off

Packet

COMMAND

n

$03 (^C)

All

CONMODE

C|T

C

Packet

CONNECT

C1|Cx

none

Packet

CONOK

ON|OFF

on

Packet

CONSTAMP

ON|OFF

CONVERS
CPACTIME

-ON|OFF

I-command
off

All
Packet

CR

ON|OFF

on

Packet

CTEXT

text

blank

Packet

CSTATUS
DAYTIME

-D/T

I-command
none

Packet
Packet

Enables transmission of 8 bit data in converse mode
Allows SYSOP to force a disconnect on the Mailbox link
Permits an acknowledging TNC to transmit without
regard to slotting delay
Controls a delay that occurs whenever any packets that
have been received are not addressed to that unit
Set MFJ TNC to polls all TNCswithin range.
Determines the way the characters are displayed.
Defines the word length used by the MFJ TNC 's RS-232
port.
Determines the use of AX.25 Level 2 Ver. 2 or Ver. 1
Protocol.
Sets the voice repeater keyup delay in 10 ms intervals.
Sets the voice repeater hang time in 100 ms intervals.
Controls the display of certain messages incommand and
CONVERS mode
Sets the timing for an automatic transmission of a packet.
Determines the way the screen is updated when a
character is deleted in the command mode.
Allows Host Mode operation
Specifies the text of the beacon packet.
Determines if the packets listed in LCALLS are to be
displayed.
Used to transfer the control to the modem calibration
routine.
Changes the cancel-line input editing command
character.
Changes the cancel-packet inputediting command
character.
Sends bell tone to computer or terminal speaker when a
packet connection is made.
Allows SYSOP to break onto the mailbox's connected
link.
Sets a connection timeout.
Enables the automatic idle-link-dis- connect feature for
AX.25 L2V1 connections.
Allows a connection to become 6-30 permanent.
Sets the transparent mode timeout value.
Enable a message to be transmitted whenever there is a
connection made.
Controls whether the MFJ TNC will initiate a
disconnect sequence after it is connected to.
Sets the character used to enter the command mode from
CONVERS mode.
Sets the MFJ TNC to enter the transparent mode or
converse mode automatically.
Issues a connect from the command mode to another
packet station.
Determines the action taken by the MFJ TNC when it
receives a connect request.
PacketEnables the time stamping when a disconnect
occurs.
Forces the MFJ TNC to enter the converse mode.
Enables the automatic transmission of packets in the
converse mode.
Causes the MFJ TNC to send a every time a new
line character is sent.
Determines the packet text to be sent when a connect is
made.
Shows streams identifier and link state of all streams.
Sets the time and date used by the MFJ TNC

off

Page 253

6-7
6-9
6-13
6-14
6-15
6-16
6-17
6-18
6-19
6-20
6-21
6-22
6-23
6-24
6-26
6-27
6-28
6-29
6-29
6-30

6-31
6-32
6-32
6-33
6-34
6-35
6-36
6-37
6-37
6-38
6-39
6-40
6-39
6-43

MFJ-1270C/1274C MANUAL

APPENDIX G: SUMMARY

COMMAND

PARAMETE
R

DEFAUL
T

MODE

FUNCTION

PAGE

DAYUSA
DEADTIME

ON|OFF
nnn

on
33(330Ms)

Packet
Packet

6-44
6-45

DELETE
DEFLTDLC
DIGIPEAT
DISCONNE
DISPLAY.

ON|OFF
0-254
ON|OFF
---

off
254
on
I-command
class

Packet
Host
Packet
Packet
Packet

DWAIT
ECHO

n
ON|OFF

33
on

Packet
All

ESCAPE

ON|OFF

off

Packet

FIRMRNR
FLOW
FORWARD

ON|OFF
ON|OFF
--

on
on
I-command

FRACK
FULLDUP
HEADERLN
HEALLED
HID

n
ON|OFF
ON|OFF
ON|OFF
ON|OFF

3
off
off
off
off

Packet
Packet
Packet
Mailbox
Packet
Packet
Packet
Packet
Packet

Determines the display format for the time and date.
Determines the basic time interval used by the
slotting procedure.
Changes the input editing command.
Sets default DLC number for Host Mode
Allows your station to be used as a digipeater
Used to disconnect a connected station in packet
Used to list all the commands the MFJ TNC
acknowledges
Used to avoid collisions with digipeating
Allows the MFJ TNC to transmit back to you
everything that you type in all mode of operation.
Specifies the character which will be output when an
 character is to be sent
Controls the handling of busy states by MFJ TNC.
Sets type-in flow control to the terminal
Mail forwading to the destination bbs.

6-60
6-60
6-61
6-62
6-62

ID

--

I-command

Packet

KILONFWD

ON|OFF

off

M-Packet

KISS

ON|OFF

off

Packet

LCALLS

call

none

Packet

Sets the time interval between retries.
Allows communication in full duplex.
Affects the display format of monitored packets.
Redefines the function of the STA and CON LEDs.
Controls the sending of identification packets by the
MFJ TNC.
Sends a special identification packet to be sent in
packet.
Determines whether or not the MFJ TNC deletes a
message after it has been forwarded.
Allows the MFJ TNC to works as a modem for
special programs such as TCP/IP.
Used in conjunction with BUDLIST, allows
selective monitoring of other packets.

Page 254

6-46
6-47
6-48
6-49
6-50
6-53
6-55
6-56
6-58
6-59
6-59

6-63
6-63
6-64
6-65

MFJ-1270C/1274C MANUAL

APPENDIX G: SUMMARY

COMMAND

PARAMETER

DEFAULT

MODE

FUNCTION

PAGE

LCSTREAM

ON|OFF

on

Packet

6-65

LCOK

ON|OFF

on

packet

LFADD

ON|OFF

off

packet

LFIGNORE
MAILBOX
MAILLED

ON|OFF
ON|OFF
ON|OFF

off
on
on

Packet
Packet
Packet

MALL
MAXFRAME

ON|OFF
n

on
4

Packet
Packet

MCOM

ON|OFF

off

Packet

MCON

ON|OFF

off

Packet

MCTEXT

text

blank

Packet

MFILTER

n1-n4

$00

M-Packet

MHCLEAR
MHEARD
MYDLCNUM
MNONAX25
MNONPRIN

--0-254
ON|OFF
ON|OFF

I-command
I-command
0
off
on

Packet
Packet
Host
Packet
Packet

MONITOR

ON|OFF

on

Packet

MRPT
MSTAMP
MTIMEOUT

ON|OFF
ON|OFF
0-250

on
off
30

Packet
Packet
M-Packet

MYCALL
MYALIAS

call
call-n

nocall
blank

Packet
Packet

MYHIERAD

nnnn

text

M-Packet

MYMCALL
NEWMODE

call
ON|OFF

nocall
off

M-Packet
Packet

NODEFORW

--

I-command

M-Packet

NODEPATH

--

I-command

M-Packet

NOMODE

ON|OFF

off

Packet

NUCR

ON|OFF

off

Packet

NULF

ON|OFF

off

Packet

NULLS

n

0

Packet

PACLEN

n

128

Packet

PACTIME

n

10

Packet

PARITY

n

0

Packet

Allows MFJ TNC to understand lower case characters
as upper case after the streamswitch is entered.
Determines whether the lower or upper case characters
are set.
Enables the MFJ TNC to go to the next line when a
 character is received.
Line feeds are ignored except in transparent mode.
Enables the personal mailbox.
Controls the STA/MAIL LED. Flashes when mail is
presence.
Determines the class of packets which are monitored.
Sets the upper limit for the outstanding packets that
can occur at one time.
Enables monitoring of connected and disconnected
packet when monitor is on.
Allows the monitoring of otherpackets while connected
to another station
Allows storing of text (messages) to be stored for
mailbox. Text is sent when mailbox is connected
Allows you to eliminate certain characters from
received packets.
Clears the MHEARD list.
A list of all packet monitored.
Sets the DLC number for Host Mode
Allows MFJ TNC to monitor non AX.25 packet.
Determines whether monitored packets containing
non-printable characters are monitored or discarded
Enables packets that are not6-78 addressed to you to be
displayed.
Affects the way monitored packets are displayed.
Enables the time stamping of monitored packets
Mailbox connect will timeout after a time set by this
command.
Sets the callsign of the MFJ TNC
Specifies an alternate callsign for use as a digipeater
only.
Sets the heiarcal address text sent by a Mailbox
forward.
Dedicated mailbox callsign.
Selects the way the MFJ TNC behaves when
connections are made and broken.
Similar to Forward command but with callsign+ up to 8
vias.
Commands connected node by Nodeflow to link with
the receiving BBS.
Determines if the MFJ TNC will switch manually or
automatically to command mode.
Causes transmission of  characters, producing a
delay following any  sent to the terminal.
Same as NUCR, instead of  it sends a delay after a
.
Used in conjunction with NUCR and NULF, and
specifies how many  characters are sent.
Determines the number of characters it takes to
automatically transmit a packet.
Determines the length of time between transmit and
receive.
Sets the parity mode for terminal or computer data
transfer.

Page 255

6-66
6-66
6-67
6-68
6-69
6-70
6-72
6-73
6-74
6-74
6-75
6-76
6-76
6-76
6-77
6-77

6-79
6-80
6-80
6-82
6-82
6-83
6-83
6-86
6-87
6-87
6-88
6-88
6-89
6-89
6-90
6-91
6-91

MFJ-1270C/1274C MANUAL

APPENDIX G: SUMMARY

Commands

Parameters

Default

Mode

Function

Page

PASS

n

$16 (^V)

Packet

6-92

PASSALL

ON|OFF

off

Packet

RECONNECT

call 1-9

I-command

Packet

REMSYSOP

call0-15

blank

M-Packet

RESTART

--

I-command

Packet

REDISPLA

n

$12 (^R)

All

RESET

--

I-command

All

RESPTIME

n

0

Packet

RETRY

n

10

Packet

REVFLIM
RXBLOCK

call-n
ON|OFF

blank
off

M-Packet
Packet

RXCAL

--

I-command

All

RVFALWAY

ON|OFF

on

M-Packet

SCREENLN
SENDPAC

n
n

0
$0D (CR)

All
Packet

SLOTS

nn

3

Packet

START
STOP
STREAMCA

n
n
ON|OFF

$11 (^Q)
$13 (^S)
off

All
All
Packet

STREAMDB

ON|OFF

off

Packet

STREAMSW

n

$7C (|)

Packet

SYSOP

--

I-command

Packet

TIMEDCMD

text

blank

M-Packet

TIMEDMIN
TRACE
TRANS
TRFLOW
TRIES

n
ON|OFF
-ON|OFF
n

60
off
I-command
off
none

M-Packet
Packet
Packet
Packet
Packet

TXDIDDLE

ON|OFF

off

Packet

TXDELAY

n

33

Packet

TXDELAYC

n

2

Packet

TXFLOW

ON|OFF

off

All

TXTMO

n (0-65535)

0

Packet

Selects the ASCII character used for the "pass" input
editing character.
Causes the MFJ TNC to display packets received
with invalid CRC fields.
Used to change the path through which you are
currently connected to a station.
Permits the SYSOP to perform sysop functions
remotely.
Re-initializes the MFJ TNC using the stored
parameters.
Used to change the redisplay-line input editing
character.
Resets all parameters to their default values and
reinitiates the unit.
Sets the minimum delay that is imposed on any
acknowledging packets.
Allows retransmission of frames that are not
acknowledged.
Callsigns of BBS to enable reverse-forwards.
Determines whether the information will be sent in
standard or block format.
Generates test signals that are used by the internal
tuning software to align the demodulator circuit.
Initiates forwards and reverse of all forwardable
messages
Used to properly format terminal output.
Selects the character that will force a packet to be
sent in CONVERSE mode
Determines how many sides are on the slot time
dice.
Selects the user restart character
Selects the user stop character.
Used to enable the display of the connected to
station after the stream identifier.
Used to display received STREAMSWITCH
characters by "doubling" them
Selects the character used by both the MFJ TNC
and the user to select a new "stream".
Enables the MAILBOX systems operator to enter in
messages to the BBS system/bbs.
Text string in this command is executed at a time
pre-set by Timedmin command.
Set the time for Timedcmd command.
Enables the debugging protocol function.
Transparent mode.
Enables and disables the software flow control.
Retrieves the count of "tries" on the currently
selected input stream.
Invokes efficient key up technique in transmitted
packet to increase throughput.
Tells the MFJ TNC how long to wait after keying
up the transmitter before sending data.
Controls a new timer that runs after the regular
TXDELAY time has expired
Enables the software flow control for the transparent
mode.
A health counter that registers the number of packet
timeout/recovery events that have occurred sine the
MFJ TNC was powered up

Page 256

6-93
6-100
6-101
6-101
6-101
6-102
6-103
6-103
6-104
6-105
6-107
6-109
6-109
6-110
6-112
6-114
6-115
6-116
6-117
6-118
6-118
6-118
6-119
6-120
6-121
6-121
6-122
6-125
6-127
6-128
6-129
6-129

MFJ-1270C/1274C MANUAL

APPENDIX G: SUMMARY

Commands

Parameters

Default

Mode

Function

Page

TXUIFRAME

ON|OFF

on

Packet

6-130

UNPROTO

call1

CQ

Packet

USERS

n

1

Packet

XFLOW
XMITOK
XOFF
XON

ON|OFF
ON|OFF
n
n

on
on
$13 (^S)
$11 (^Q)

All
Packet
All
All

Used to tell the MFJ TNC what to do with
the unconnected information left in its
buffer.
Sets the digipeat and destination address
fields of packets sent in the unconnected
mode.
Controls the manner in which the incoming
connect requests are handled
Enables the flow control.
Enables the transmit function.
Selects the MFJ TNC stop character
Selects the MFJ TNC restart character.

Page 257

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6-131
6-133
6-134
6-134
6-135

MFJ-1270C/1274C MANUAL

Chapter 16 Page 29

INDEX



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