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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 MFJ-1272M 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
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.
Remove the two screws and top cover of the MFJ-1272M.
1.
Look at the writing on the unit's pc board. Please refer to Tables 1 thru 6 as to
2.
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:
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.
MIC Audio:
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.
ground should not be used, due to the possibility of introducing "hum" into the
system. Always use the pin labeled ground.
2
®
and Icom IC-706. The jumpers are setup for the IC-706 with
The microphone
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