MFJ MFJ-1270X User manual

MFJ
TNC-X Packet Controller
Model MFJ-1270X
INSTRUCTION MANUAL
CAUTION: Read All Instructions Before Operating Equipment
MFJ ENTERPRISES, INC.
300 Industrial Park Road
Starkville, MS 39759 USA
Tel: [phone] Fax: [phone]
VERSION 1A COPYRIGHT © 2010 MFJ ENTERPRISES, INC.

MFJ-1270X Instruction Manual TNC-X Packet Controller
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DISCLAIMER
Information in this manual is designed for user purposes only and is not intended to supersede in-
formation contained in customer regulations, technical manuals/documents, positional handbooks,
or other official publications. The copy of this manual provided to the customer will not be updated
to reflect current data.
Customers using this manual should report errors or omissions, recommendations for improve-
ments, or other comments to MFJ Enterprises, 300 Industrial Park Road, Starkville, MS 39759.
Phone: [phone]; FAX: [phone]. Business hours: M-F 8-4:30 CST.

MFJ-1270X Instruction Manual TNC-X Packet Controller
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MFJ-1270X TNC-X Packet Contoller
For VHF Packet and APRS
Introduction
Thank you for purchasing the MFJ-1270X TNC-X Packet Controller. The MFJ-1270X is a new Ter-
minal Node Controller design based on the Chepponis/Karn KISS protocol. It is implemented using
a Microchip PIC 16F628A microcontroller, a CML MX614 Bell 202 modem chip, an 8K Ramtron
FRAM, a MAX232A level converter chip, and an op-amp which provides active audio filtering for
the modem. From the beginning, this TNC was designed to be small, inexpensive, have low power
consumption, and expandable.
The MFJ-1270X features an on-board USB port. The USB port was added because the design
took into consideration that computers these days lack the old style RS-232 serial ports. There is
also an 8-pin expansion header that allows the addition of "daughter boards". Power is provided to
the daughter board through the expansion header. In addition, signals that would otherwise go to or
from a host PC can be intercepted by the daughter board at the TTL level and processed. The I/O
on the expansion header speaks "KISS" so that any daughter board only has to send and receive
data packaged in KISS format to access the core module. This makes the development of daugh-
ter boards fairly simple and inexpensive. For example, daughter boards are now available that can
turn the MFJ-1270X into either of two types of digipeaters, or into a stand alone APRS Tracker.
In addition, the expansion header provides access to a second on-board serial port. The X-Track
daughter board, for example, uses this port to receive data from a GPS receiver. The data is then
processed and formed into packets and an APRS beacon is sent. Even without daughter boards
the MFJ-1270X works as a fully functional stand alone KISS mode TNC.
The idea behind the expansion options was to provide a platform that would allow additional func-
tionality to be added to the unit with the investment of very little design time and very few parts.
Power Requirements
IMPORTANT: DO NOT PLUG IN THE 8-15 VDC POWER SUPPLY AND THE 9-VOLT BATTERY
AT THE SAME TIME
The power requirements of the MFJ-1270X are very minimal due to the low power consumption of
the design. Using an 8-15 volt DC power supply capable of 200-300 mA is well within the consump-
tion specifications. There is also a 9-volt battery snap provided for a 9-volt battery. This makes the
TNC more portable for campers and backpackers.
IMPORTANT: DO NOT PLUG IN THE 8-15 VDC POWER SUPPLY AND THE 9-VOLT BATTERY
AT THE SAME TIME
Terminal Speed
The MFJ-1270X supports only 4 terminal speeds. Jumpers JP1 and JP2 determine the speed
strictly for the link between the TNC and the computer. The following settings are allowed:
JP1 JP2 Port Speed (Baud rate)
On
On
Off
Off
On
Off
On
Off
1200 (Default Speed)
4800
9600
19200

MFJ-1270X Instruction Manual TNC-X Packet Controller
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Note that the terminal speed setting does not affect the speed to transmit data. The out-going or
transmit speed is always 1200 baud. Note also that if you set this baud rate faster than 1200 baud,
it is possible for data to be fed into the modem faster than it can transmit it over the air. This may
eventually result in the transmit buffer filling up.
Setup If You Are Using USB
If you have elected to use the USB port to provide data communications to your PC, you should be-
gin by acquiring and installing the drivers for the PC and operating system that you are using. The
driver you need is a Virtual COM Port (VCP) driver. It will make the TNC appear as an additional
com port on your computer so that you can use any packet radio software that supports a KISS
TNC connected to a standard serial port.
If you use the USB port, do not supply any power to the TNC through the power jack.. The USB
buss can supply the rather limited power requirements for the TNC. If you are using the USB op-
tion, set the board jumpers as follows:
JP3 On the left two pins (toward C24).
JP4 Connect the center pin to the pin that is closest to the center of the board.
JP5 Jumper pins 1 and 2 (the end closest to Q1) and pins 3 and 4, unless you are using
a daughter board.
Setup If You Are Using the TNCs Serial Port
If you plan to connect the TNC to a standard computer serial port, set up the jumpers as follows:
JP3 On the right two pins (toward U5)
JP4 Connect the center pin to the pin closest to C22.
JP5 Jumper pins 1 and 2 (the end closest to Q1) and pins 3 and 4 unless you are using a
daughter board.
If you are using the on-board serial port, you must supply power to the TNC. This can be done in
one of two ways. There is a coaxial power jack on the board that can be used to receive anything
from 8 to 15 volts DC. Alternatively you can connect a 9-volt battery to the location marked BAT.
Aux 232
An auxiliary serial port using a MAX232 level converter. Main purpose is for GPS input for the X-
Track daughter board.
Serial Port
A standard DB 9-pin RS-232C serial port.
USB Port
A standard USB port for computers that lack the old style RS-232 serial ports.
Power 12VDC
A coaxial power jack for main power input. Center pin is positive and sleeve is negative.
RADIO
A 5-pin DIN connector used to interface the radio to the TNC.

MFJ-1270X Instruction Manual TNC-X Packet Controller
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POWER:
Indicates the MFJ-1270X has power supply voltage supplied.
RECEIVE DCD:
Indicates the MFJ-1270X is receiving a data packet signal from the radio.
TRANSMIT PTT:
Indicates that the MFJ-1270X is transmitting data signal from the radio.
Radio Setup
The radio connections are made via a 5-pin DIN chassis mounted connector. The connector is
shown below:
Back View of Connector
Radio Port Connections
These are the radio port pins and their respective functions. Match the proper pin and its function
to the same pin and function on your radio.
Pin 1
Microphone Audio: Supplies audio from the TNC to your radio.
Pin 2
Ground: Common connection for audio and PTT common.
Pin 3
Push-to-Talk: Allows the TNC to key your transmitter to transmit.
Pin 4
Receive Audio: Supplies audio from the radio to the TNC.
Pin 5
No Connection

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Troubleshooting
The MFJ-1270X is designed to give years of service. However, as with all things sometimes prob-
lems do come up and need to be taken care of. Here are a few troubleshooting tips in the event
that something does go wrong.
Voltage Supply
If the supply voltage is suspect this must be corrected first. The first thing to do is to check the main
voltage supply to the TNC. Do this using a DC voltmeter capable of measuring +5 volts DC. The
main supply voltage to the TNC must be at least 7 to 8 volts DC. The TNC uses a 78L05 voltage
regulator. The voltage regulator needs to see a voltage at least 2 volts greater than the regulation
voltage. If the main supply voltage is not 2 volts greater than +5 volts, then the regulator will not
work, thus not having a +5 volt DC output. To check this, do the following:
1. Set your voltmeter to read +5 volts DC.
2. Remove the main supply from the TNC. Check the voltage at the connector that plugs into the
TNC. The voltmeter should indicate +5 ±.5 volts DC. If the reading is lower, then check the
main power source. If the reading is good, then move on to step #3.
3. With the main power still removed from the TNC, carefully remove all IC chips from the TNC.
4. Reconnect the main power source into the TNC and re-check the +5 volts DC.
5. If you are using the computer’s USB port to supply voltage to the TNC, measure the voltage be-
tween ground and the right pin on JP4 or the right pin if you use power jack. It should be ap-
proximately +5 volts DC. If not, then we strongly recommend returning the TNC for service. If
the voltage is good, then move on to the next section,
Testing for Defective IC Chips
If you are reading this section, it means that you have determined that your TNC has a defective IC
chip. The procedure for checking for a defective IC is not complicated, but you should follow the
procedure carefully. If you do not follow the procedure carefully you can and probably will damage
an otherwise good IC and/or the TNC…so please be very careful.
1. Remove power from the TNC, either by removing the main supply at the power jack or the USB
port cable.
2. Carefully remove all IC chips from the TNC. Make note as to the orientation of each IC in their
respective IC sockets and which sockets the ICs came out of. Be careful not to bend any of the
pins of the ICs. IMPORTANT!!
3. Carefully re-insert one IC at a time into its respective socket and recheck the +5 volts DC. If
any IC causes the +5 volts DC to drop, then the IC that causes the voltage drop is your defec-
tive part. Be sure to check all IC chips, because you could have more than one defective part.
Call the MFJ Service Dept. for a replacement part.
Testing Receive
Hook up a receiver audio source to the receive pins on the board (or the mono jack if you are using
the enclosure). Make sure audio goes to the positive pin. Make sure the squelch is left open. When
a data packet is received, you should see the yellow LED light briefly and go out. Even when no
data is being received it is normal for the yellow LED to flicker. However, it should come solidly on
when a packet is received. Assuming that this checks out, run a serial program of some kind on
your PC, set the baud rate to whatever baud rate you specified with JP1 and JP2. Confirm that you
are receiving data (note, this will be raw KISS frames so much of it may look like garbage, but you
should see some recognizable data). Note that if you are using the USB option, you must the USB
drivers loaded on your computer.

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If you do not see the yellow light come on, first confirm that audio is getting to the TNC (a scope or
a small headphone may be useful for this). If it is, verify that audio is coming out of Pin 6 of U4. As-
suming this is working, if you have a scope or frequency counter, measure the frequency on Pin 1
of U1. It should read about 3.57 MHz. While you are at it, check Pin 16 of U3. It should read about
20 MHz. If at any point you don’t get the measurement you expect, carefully check the solder joints
in that part of the board. If the yellow light comes on but you see no data on your PC, start at Pin 8
of U3 and trace the data signal to header Pin 1, to header Pin 2 and on to Pin 10 of U5. It should
come out at Pin 7 of U5.
Next check out the transmit chain. The TXDelay is set by R13. Start by setting it at about halfway
(which will correspond to a TXDelay of about 240 ms (or a setting of 25 on most TNC’s). At this
point you need to be running a program on your PC that supports KISS mode. The TNC-X web-
page (www.tnc-x.com/documentation.htm) has a program called TXTest, which is a very simple
program that can be used to test your transmit chain.
When you transmit a packet, you should see the red LED come on briefly. Hook the transmit audio
and PTT up to a radio and try transmitting. R12 is used to adjust the transmit level. If you don’t
have a means of measuring the deviation precisely, monitor your signal on a receiver and slowly in-
crease R12 until you hear no further increase in volume on the receiver. Then back it off a bit. Even
if the TNC is not connected to a radio, you should see the red light come on when you transmit da-
ta via the TNC.
Many people use TNC-X for APRS applications. There are many good software programs available
for this application (WinAPRS, UI-View for Windows, for example). For a general purpose TNC pro-
gram that supports KISS, you might want to take a look at WinTNC. It has recently been revised so
that it works under Windows XP, as well as older versions of Windows. If you want to use AGWPE,
there is a link on the TNC-X webpage that contains detailed instructions.
If you have any problems with any of this, please contact MFJ Technical Services at the phone
number in the warranty instructions.
Figure 1: MFJ-1270X Parts Layout

MFJ-1270X Instruction Manual TNC-X Packet Controller
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Technical Assistance
If you have any problem with this unit first check the appropriate section of this manual. If the man-
ual does not reference your problem or your problem is not solved by reading the manual you may
call MFJ Technical Service at 662-323-0549 or the MFJ Factory at 662-323-5869. You will be best
helped if you have your unit, manual and all information on your station handy so you can answer
any questions the technicians may ask.
You can also send questions by mail to MFJ Enterprises, Inc., 300 Industrial Park Road, Starkville,
MS 39759; by Facsimile to 662-323-6551; or by email to [e-mail]. Send a
complete description of your problem, an explanation of exactly how you are using your unit, and a
complete description of your station.
Figure 2: MFJ-1270X Schematic

MFJ-1270X Instruction Manual TNC-X Packet Controller
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PARTS LIST FOR MFJ-1270X
CAPACITORS
PART NO. DESCRIPTION
C1 10 µF Electrolytic
C3 100 pF Disk Ceramic; (Marked 101J)
C2, C4, C5, C6, C11, C14, C15, C16, C17, C18, C19,
C20, C26
.01 µF Multilayer
C21, C22, C23, C25 .1µF Multilayer
C7, C8 .01.F Polypropylene (red/yellowblock)
C9, C10 18 pF Disk Ceramic (Marked 18J)
C12, C13 22 pF Disk Ceramic (Marked 22J)
C24 4.7 µF Electrolytic
RESISTORS (Note: There is no R5, R6 or R7)
PART NO. DESCRIPTION
R1-R3 100 kΩ(brown-black-yellow)
R8 24.9 kΩ, 1% (red-yellow-white-red-brown)
R9 9.31 kΩ, 1% (white-orange-brown- brownbrown)
R10 18.7 kΩ, 1% (brown-grey-purple-red-brown)
R11, R14, R16, R18, R20 10 kΩ, (brown-black-orange)
R12, R13 10 kΩHorizontal Trimpot (Marked 103)
R4, R15, R17, R19 1 kΩ(brown-black-red)
DIODES
PART NO. DESCRIPTION
D1 Green LED
D2 1N4001
D4 Red LED
D5 Yellow LED
HEADERS and JUMPERS
PART NO. DESCRIPTION
JP1, JP2 2-Pin Header
JP3. JP4 3-Pin Header
JP5 8-Pin Header
6 Small jumpers for JP1-JP5

MFJ-1270X Instruction Manual TNC-X Packet Controller
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OTHER COMPONENTS
PART NO. DESCRIPTION
X1 3.57 MHz Crystal (maybe marked A035)
X2 20 MHz. Crystal (maybe marked A200)
Q1 2N2222 or equivalent
IC1 FT232RL USB Interface Chip
U1 CML 614 Modem Chip
U2 FM25640 FRAM Memory Chip
U3 PIC16F628A or PIC16F648A
U4 MPC6023 Op Amp
U5 HIN232A
U6 78L05 Voltage Regulator
F09 DB9 Female PC mount Connector
J1 Coaxial Power Connector (Center Pin is Positive)
USB USB Female PC Mount Connector
L1 Ferrite Bead
Radio Port 5-Pin DIN Chassis Mount Connector
AUX 232 2.5mm Stereo Chassis Mount Connector
NOTE: Use IC sockets for U1-U5.

MFJ-1270X Instruction Manual TNC-X Packet Controller
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LIMITED 12 MONTH WARRANTY
MFJ Enterprises, Inc. warrants to the original owner of this product, if manufactured by MFJ Enter-
prises, Inc. and purchased from an authorized dealer or directly from MFJ Enterprises, Inc. to be
free from defects in material and workmanship for a period of 12 months from date of purchase pro-
vided the following terms of this warranty are satisfied.
1. The purchaser must retain the dated proof-of-purchase (bill of sale, canceled check, credit card
or money order receipt, etc.) describing the product to establish the validity of the warranty
claim and submit the original or machine reproduction of such proof of purchase to MFJ Enter-
prises, Inc. at the time of warranty service. MFJ Enterprises, Inc. shall have the discretion to
deny warranty without dated proof-of-purchase. Any evidence of alteration, erasure, or forgery
shall be cause to void any and all warranty terms immediately.
2. MFJ Enterprises, Inc. agrees to repair or replace at MFJ's option without charge to the original
owner any defective product under warrantee provided the product is returned postage prepaid
to MFJ Enterprises, Inc. with a personal check, cashiers check, or money order for $10.00 cov-
ering postage and handling.
3. This warranty is NOT void for owners who attempt to repair defective units. Technicalconsulta-
tion is available by calling the Service Department at 662-323-0549 or the MFJ Factory at 662-
323-5869.
4. This warranty does not apply to kits sold by or manufactured by MFJ Enterprises, Inc.
5. Wired and tested PC board products are covered by this warranty provided only the wired and
tested PC board product is returned. Wired and tested PC boards installed in the owner's cabi-
net or connected to switches, jacks, or cables, etc. sent to MFJ Enterprises, Inc. will be re-
turned at the owner's expense unrepaired.
6. Under no circumstances is MFJ Enterprises, Inc. liable for consequential damages to person or
property by the use of any MFJ products.
7. Out-of-Warranty Service: MFJ Enterprises, Inc. will repair any out-of-warranty product provided
the unit is shipped prepaid. All repaired units will be shipped COD to the owner. Repair charges
will be added to the COD fee unless other arrangements are made.
8. This warranty is given in lieu of any other warranty expressed or implied.
9. MFJ Enterprises, Inc. reserves the right to make changes or improvements in design or manu-
facture without incurring any obligation to install such changes upon any of the products previ-
ously manufactured.
10. All MFJ products to be serviced in-warranty or out-of-warranty should be addressed to:
MFJ Enterprises, Inc.
300 Industrial Park Road
Starkville, Mississippi 39759 USA
and must be accompanied by a letter describing the problem in detail along with a copy of your
dated proof-of-purchase.
11. This warranty gives you specific rights, and you may also have other rights which vary from
state to state.