MFJ MFJ-1272M, MFJ-1272MX, MFJ-1272MYV, MFJ-1272MZ User Manual
MFJ-1272M TNC/MICROPHONE SWITCH
Introduction
Thank you for purchasing the MFJ-1272M TNC/MIC Switch.
The MFJ-1272M is designed to allow simultaneous
connection of both your microphone and your TNC to the
radio.
The MFJ-1272M microphone switches were designed to be
used with any radio that has an 8-pin, RJ-45 modular
microphone connector. Because many TNCs have different
connectors, MFJ offers 5 models:
MFJ Model# TNC and Multimodes
MFJ-1272M All MFJ TNCs, TAPR TNC-2 clones, and PK12/96/900
MFJ-1272MX PK-232
MFJ-1272MYV KAM® VHF port, KPC-9612, KPC-2, KPC-3
MFJ-1272MYH KAM® HF port
MFJ-1272MZ PK-88
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.
damaged radios or associated equipment. It is
your responsibility
connections will not damage the radio.
is not responsible
to make sure your
for
MFJ-1272M Instruction Manual
KAM® is a registered trademark of Kantronics Company, Inc.
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MFJ-1272M Instruction Manual
Installation
Before you install the MFJ-1272M TNC/MIC switch, you
must set it up for your particular radio. The MFJ1272M comes pre-wired from the factory for Kenwood
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 radio with RECEIVE
AUDIO on the microphone jack, or if your radio is not a
Kenwood, refer to the configuration section. We have
given a few diagrams for placing the internal jumpers
for a few popular radios on Page 8.
The MFJ-1272MYH model comes pre-wired and ready to use
with the HF port on the Kantronics KAM and Icom IC-
706. The jumpers are setup for the IC-706 with RECEIVE
AUDIO on pin 3 of the microphone plug.
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 MFJ1272M.
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 you radio.
Consult your radio's manual and the definitions
below to match signals.
Audio Out:
Audio to the radio from either the TNC or radio
MICROPHONE.
PTT:
This is the Push-to-talk signal from either the TNC
or radio Microphone.
Receive Audio:
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MFJ-1272M Instruction Manual
Audio from the radio to the TNC. Please refer to
External Audio
the
section on the following page.
If you use external audio make no connection here.
MIC Audio:
Audio from mic (same # as
Ground:
Audio Out
)
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.
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MFJ-1272M Instruction Manual
Throughs:
Connect all pins here except MICROPHONE AUDIO.
(unlabeled)
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., or 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. Set
this jumper to the positions desired, according to
your own preference.
4. Replace the top and screws.
External Audio
If your radio does not have RECEIVE AUDIO on the
microphone, we suggest the use of an interconnecting
cable to supply RECEIVE AUDIO to the TNC/MIC switch.
You would connect the 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-1272M as
versatile as possible. With the MFJ-1272M you can
virtually connect any radio pin to just about any TNC
pin, just by configuring the jumpers properly. The
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MFJ-1272M Instruction Manual
following tables will show how to set the jumpers,
depending on the TNC functions versus the MIC pins of
your particular radio. Be sure to follow the tables
closely, with your radio manual close at hand, to
verify that you are not shorting any microphone
voltages or any other microphone signals to GROUND !
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