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Introduction
Thank you for purchasing the MFJ-1272B TNC/MIC Switch.
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
MFJ-1272B
MFJ-1272BX
MFJ-1272BYV
MFJ-1272BYH
MFJ-1272BZ
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.
MFJ-1272B TNC/Microphone Switch
TNC and Multimodes
All MFJ TNCs, TAPR TNC II clones, and PK-12/96/900
PK-232
KAM® VHF port, KPC-2, KPC-3
KAM HF port
PK-88
KAM is a registered trademark of Kantronics Company, Inc.
This switch is
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Summary of Contents for KAM MFJ-1272B
- Page 1 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:...
- Page 2 MFJ-1272B Instruction Manual 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.
- Page 3 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.
- Page 4 MFJ-1272B Instruction Manual 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.
- Page 5 MFJ-1272B Instruction Manual 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.
- Page 6 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.
- Page 7 MFJ-1272B Instruction Manual Jumper positions for specific radios:...
- Page 8 MFJ-1272B Instruction Manual Jumper positions for specific radios:...
- Page 9 Find out what the problem is. Tighten the threaded portion of the microphone securely. 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.
- Page 10 MFJ-1272B Instruction Manual 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...
- Page 11 MFJ-1272B Instruction Manual 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...
- Page 12 MFJ-1272B Instruction Manual Schematic...