KAM MFJ-1272B User manual
MFJ-1272B TNC/Microphone Switch
Introduction
Thank you for purchasing the MFJ-1272B TNC/MIC Switch. This switch is
designed to allow simultaneous connection of both your microphone and your TNC
to the radio.
The MFJ-1272B microphone switches were designed to be used with any radio that
has a standard, round, 8-pin microphone connector. Because many TNCs have
different connectors, MFJ offers 5 models:
MFJ Model Number TNC and Multimodes
MFJ-1272B All MFJ TNCs, TAPR TNC II clones, and PK-12/96/900
MFJ-1272BX PK-232
MFJ-1272BYV KAM® VHF port, KPC-2, KPC-3
MFJ-1272BYH KAM HF port
MFJ-1272BZ PK-88
For circuit board revisions, refer to page 11.
CAUTION
Always check your radio's owner's manual to see if there is a voltage on one of the
pins of the microphone before hooking up the microphone switch. You could
damage your radio by connecting the PTT line to a voltage source. Do not connect
any pin labeled as a voltage source to PTT !
WARNING: MFJ Enterprises, Inc. is not responsible for damaged radios or
associated equipment. It is your responsibility to make sure your
connections will not damage the radio.
KAM is a registered trademark of Kantronics Company, Inc.
MFJ-1272B Instruction Manual
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Installation
Before you install the MFJ-1272B TNC/MIC switch, you must set it up for your
particular radio. The MFJ-1272B comes pre-wired from the factory for Kenwood
and Alinco radios without RECEIVE AUDIO on the microphone jack. If you have
one of these radios, the TNC/MIC switch is ready to use. If you have a Kenwood or
Alinco radio with RECEIVE AUDIO on the microphone jack, or if your radio is not a
Kenwood or Alinco refer to the configuration section. We have given a few
diagrams for placing the internal jumpers for a few popular radios on Page 6.
Configuration
If you must configure the TNC/MIC switch for your radio, please follow this
procedure.
1. Remove the two screws and top cover of the MFJ-1272B.
2. Look at the writing on the unit's pc board. Please refer to Tables 1 thru 6 as
to where to place the jumpers in relation to the pinouts on your radio. Consult
your radio's manual and the definitions below to match signals.
Audio Out:
Audio to the from either the TNC or radio MICROPHONE.
PTT:
This is the Push to talk signal from either the TNC or radio microphone.
Receive:
Audio from the radio to the TNC. Please refer to the External Audio section
on the following page, if you use external audio make no connection here.
Audio In:
Audio from mic (same # as Audio Out)
Ground:
This is the system ground on radio's mic connector. Some radios have two
ground pins, MICROPHONE GROUND and GROUND. The microphone
ground should not be used, due to the possibility of introducing "hum" into the
system.Always use the pin labeled ground.
Throughs:
Connect all pins here except MICROPHONE AUDIO.
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(unlabled)
if you use external audio do not connect the radio pins for Receive
3. Header HD3 controls the RECEIVE AUDIO to the EXTERNAL SPEAKER.
Place a push-on jumper on pins 2 and 3 if you want the external speaker "on"
all of the time. Place the jumper on pins 1 and 2 if you want the external
speaker "off" when using the TNC. Most people prefer not to hear audio
during packet.
4. Replace the top and screws.
External Audio
If your radio does not have RECEIVE AUDIO on the microphone, then we suggest
the use of an inter-connecting to supply RECEIVE AUDIO to the TNC/MIC switch.
You would connect a cable from an external speaker or headphones jack on your
radio to the AUDIO IN jack of the TNC/MIC switch. Therefore, no jumper
connection should be made for Receive on the pc board.
Using the method above for connecting RECEIVE AUDIO to the TNC/MIC switch,
will cut off the internal speaker inside the radio. In this case, you must connect an
external speaker to the EXT. SPEAKER jack on the TNC/MIC switch. Otherwise,
you will not be able to hear any signals at all from your radio.
Jumper Configuration
Because there are so many different radio configurations, we have tried to make
the MFJ-1272B as versatile as possible. With the MFJ-1272B you can virtually
connect any radio pin to just about any TNC pin, just by configuring the jumpers
properly. The following tables will show how to set the jumpers, depending on the
TNC functions versus the MIC pins of a particular radio. Be sure to follow the
tables closely with your radio manual, to verify that you are not shorting any
microphone voltages or any other microphone signals to GROUND !
MFJ-1272B Instruction Manual
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Receive Audio Connections
Table 1 below shows where you would place a jumper if your radio had RECEIVE
AUDIO on one of the microphone pins. For example, if your radio had RECEIVE
AUDIO on pin 3 on a Kenwood microphone, you would place a jumper on position,
R3A in the RECEIVE section of header HD1. If your radio does not have RECEIVE
AUDIO on one of the microphone pins, then do not place a jumper in the RECEIVE
section of header HD1.
Radio MIC Pin MFJ-1272B
Header Place a jumper on:
1HD1 RECEIVE--R1A
2HD1 RECEIVE--R2A
3HD1 RECIEVE--R3A
4HD1 RECEIVE--R4A
5HD1 RECEIVE--R5A
6HD1 RECEIVE--R6A
7HD1 RECEIVE--R7A
8HD1 RECEIVE--R8A
Table 1
*Refer to External Audio, page 3
PTT (Push-to-Talk) Connections
Table 2 below shows where you would place a jumper, depending on what
microphone pin is designated PTT. For example, if PTT is designated as being pin
4 on a Kenwood microphone, then you would place a jumper on position R4B in the
PTT section of header HD1.
Radio MIC Pin MFJ-1272B
Header Place a jumper on:
1HD1 PTT--R1B
2HD1 PTT--R2B
3HD1 PTT--R3B
4HD1 PTT--R4B
5HD1 PTT--R5B
6HD1 PTT--R6B
7HD1 PTT--R7B
8HD1 PTT--R8B
Table 2
MFJ-1272B Instruction Manual
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Audio Out Connection
Table 3 below shows where you would place a jumper, depending on what
microphone pin is designated MICROPHONE AUDIO. The microphone pin,
designated MICROPHONE AUDIO, is the where the transmit audio from the TNC
comes into the radio. For example, if MICROPHONE AUDIO is designated pin 1
on a Kenwood microphone, then you would place a jumper on position R1C in the
AUDIO OUT section of header HD1.
Radio MIC Pin MFJ-1272B
Header Place a jumper on:
1HD1 AUDIO OUT--R1C
2HD1 AUDIO OUT--R2C
3HD1 AUDIO OUT--R3C
4HD1 AUDIO OUT--R4C
5HD1 AUDIO OUT--R5C
6HD1 AUDIO OUT--R6C
7HD1 AUDIO OUT--R7C
8HD1 AUDIO OUT--R8C
Table 3
Ground Connections
Table 4 below shows where you place a jumper, depending on what microphone
pin is designated GROUND. For example, if GROUND is designated as being pin
7 on a Kenwood microphone, then you would place a jumper on position R7D in the
GROUND section of header HD2.
Radio MIC Pin MFJ-1272B
Header Place a jumper on:
1HD2 GROUND--R1D
2HD2 GROUND--R2D
3HD2 GROUND--R3D
4HD2 GROUND--R4D
5HD2 GROUND--R5D
6HD2 GROUND--R6D
7HD2 GROUND--R7D
8HD2 GROUND--R8D
Table 4
Most radios have two ground pins on the microphone, GROUND and
MICROPHONE GROUND. Be sure to use the pin designated as ground, not
microphone ground, when making your jumper connections. The use of the
microphone ground could introduce audio hum in the system.
MFJ-1272B Instruction Manual
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Through Connections
Table 5 below shows where you would place a jumper, depending on the
microphone pin functions that are not to be switched by the MFJ-1272B.
Microphone pins designated, +V, UP and DOWN, are radio functions that are not
needed by the TNC, but are needed for normal microphone operations. For
example, if on a Kenwood microphone pin 3 is designated as being UP, which
would be for increasing your frequency readout on the radio, then you would place
a jumper on position, R3E-M3A on header HD2.
Radio MIC Pin MFJ-1272B
Header Place a jumper on:
1HD2 R1E--M1A
2HD2 R2E--M2A
3HD2 R3E--M3A
4HD2 R4E--M4A
5HD2 R5E--M5A
6HD2 R6E--M6A
7HD2 R7E--M7A
8HD2 R8E--M8A
Table 5
Mic Audio Connections
Table 6 below shows where you place a jumper, depending on what microphone
pin is designated MICROPHONE AUDIO. For example, if MICROPHONE AUDIO
is designated as being pin 5 on a Kenwood microphone, then you would place a
jumper on position, M5B in the AUDIO IN section of header HD2.
Radio MIC Pin MFJ-1272B
Header Place a jumper on:
1HD2 AUDIO IN--M1B
2HD2 AUDIO IN--M2B
3HD2 AUDIO IN--M3B
4HD2 AUDIO IN--M4B
5HD2 AUDIO IN--M5B
6HD2 AUDIO IN--M6B
7HD2 AUDIO IN--M7B
8HD2 AUDIO IN--M8B
Table 6
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Jumper positions for specific radios:
MFJ-1272B Instruction Manual
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Jumper positions for specific radios:
MFJ-1272B Instruction Manual
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Connections
Connection of the MFJ-1272B is very simple.
1. Connect your radio's microphone to the microphone connector on the front
panel of the MFJ-1272B. Be careful not to bend any of the microphone
connector pins. If the microphone plug does not insert easily, then do not
force it. Find out what the problem is. Tighten the threaded portion of the
microphone securely.
2. Connect the 8-pin MIC plug which exits the rear of the MFJ-1272B, to the
microphone connector on the radio. Be careful not to bend any of the
microphone connector pins. If the microphone plug does not insert easily,
then do not force it. Find out what the problem is. Tighten the threaded
portion of the microphone securely.
3. Connect the TNC cable which exits the rear of the MFJ-1272B, to the TNC.
External Receive Audio Connection
If you have a radio without RECEIVE AUDIO on the microphone connector, you will
need to perform steps 4 and 5.
4. Connect a cable from the headphones or speaker out jack of the radio to the
AUDIO IN jack of the MFJ-1272B. The AUDIO IN jack on the TNC/MIC
switch requires an RCA male phono plug.
5. Connect a speaker to the EXT. SPKR. jack on the back of the MFJ-1272B.
The EXT. SPKR. jack requires a 3.5mm mono plug, with the tip being positive
and the sleeve being ground.
MFJ-1272B Instruction Manual
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Technical Assistance
If you have any problem with this unit first check the appropriate section of this manual.
If the manual does not reference your problem or your problem is not solved by reading
the manual you may call MFJ Technical Service at 601-323-0549 or the MFJ Factory at
601-323-5869. 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 FAX to 601-323-6551; through Compuserve at
your problem, an explanation of exactly how you are using your unit, and a complete
description of your station.
Our goal is to provide you, the customer, with the best technical assistance we
can, and to see that it is as accurate as possible.
MFJ-1272B Instruction Manual
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Circuit Board Revisions
Note: This manual is written for the Revision 9 circuit board, pictured on the
right. The only difference between revisions 8 and 9 is the pin labeling
of the connectors HD1 and HD2. If your board is revision 8, please
refer to the labeling of the revision 9 board.
MFJ-1272B Instruction Manual
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Schematic
This manual suits for next models
4
