MFJ MFJ-1272M 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 PK-12/96/900
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. 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.

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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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 MFJ-1272M.
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:
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. 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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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 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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Receive Audio Connections
Table 1 below shows where you would place a jumper if your radio has RECEIVE
AUDIO on one of the microphone pins. For example, if your radio has 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-1272M Header Jumper Placement for Kenwood & Yaesu Jumper Placement for Icom & Radio Shack
1HD1 RECEIVE--R1A RECEIVE--R8A
2HD1 RECEIVE--R2A RECEIVE--R7A
3HD1 RECEIVE--R3A RECEIVE--R6A
4HD1 RECEIVE--R4A RECEIVE--R5A
5HD1 RECEIVE--R5A RECEIVE--R4A
6HD1 RECEIVE--R6A RECEIVE--R3A
7HD1 RECEIVE--R7A RECEIVE--R2A
8HD1 RECEIVE--R8A RECEIVE--R1A
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-1272M Header Jumper Placement for Kenwood & Yaesu Jumper Placement for Icom & Radio Shack
1HD1 PTT--R1B PTT--R8B
2HD1 PTT--R2B PTT--R7B
3HD1 PTT--R3B PTT--R6B
4HD1 PTT--R4B PTT--R5B
5HD1 PTT--R5B PTT--R4B
6HD1 PTT--R6B PTT--R3B
7HD1 PTT--R7B PTT--R2B
8HD1 PTT--R8B PTT--R1B
Table 2

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Audio Out Connections
Table 3 below shows where you would place a jumper, depending on what
microphone pin is designated MIC. The microphone designated MIC, is the pin
that the transmit audio from the TNC comes into the radio. For example, if MIC is
designated as being 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-1272M Header Jumper Placement for Kenwood & Yaesu Jumper Placement for Icom & Radio Shack
1HD1 AUDIO OUT--R1C AUDIO OUT--R8C
2HD1 AUDIO OUT--R2C AUDIO OUT--R7C
3HD1 AUDIO OUT--R3C AUDIO OUT--R6C
4HD1 AUDIO OUT--R4C AUDIO OUT--R5C
5HD1 AUDIO OUT--R5C AUDIO OUT--R4C
6HD1 AUDIO OUT--R6C AUDIO OUT--R3C
7HD1 AUDIO OUT--R7C AUDIO OUT--R2C
8HD1 AUDIO OUT--R8C AUDIO OUT--R1C
Table 3
Ground Connections
Table 4 below shows where you would 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-1272M Header Jumper Placement for Kenwood & Yaesu Jumper Placement for Icom & Radio Shack
1HD2 GROUND--R1D GROUND--R8D
2HD2 GROUND--R2D GROUND--R7D
3HD2 GROUND--R3D GROUND--R6D
4HD2 GROUND--R4D GROUND--R5D
5HD2 GROUND--R5D GROUND--R4D
6HD2 GROUND--R6D GROUND--R3D
7HD2 GROUND--R7D GROUND--R2D
8HD2 GROUND--R8D GROUND--R1D
Tabel 4
Always use the MIC pin designated as GROUND (not mic ground). The use of
MIC GROUND could result in audio "hum" in the system.

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Through Connections
Table 5 below shows where you would place jumpers, depending on the
microphone pin functions that are not to be switched by the MFJ-1272M.
Microphone pins designated, +V, UP, DWN, 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 the HD2 header position on the MFJ-1272M PC board labeled R3E-
M3A.
Radio MIC
Pin MFJ-1272M Header Jumper Placement for Kenwood & Yaesu Jumper Placement for Icom & Radio Shack
1HD2 R1E - M1A R8E - M8A
2HD2 R2E - M2A R7E - M7A
3HD2 R3E - M3A R6E - M6A
4HD2 R4E - M4A R5E - M5A
5HD2 R5E - M5A R4E - M4A
6HD2 R6E - M6A R3E - M3A
7HD2 R7E - M7A R2E - M2A
8HD2 R8E - M8A R1E - M1A
Table 5
Mic Audio Connections
Table 6 below shows where you would place a jumper, depending on what
microphone pin is designated, MIC AUDIO. For example, if on a Kenwood, MIC
AUDIO is designated as being pin 5 of the microphone, then you would place a
jumper on position M5B in the AUDIO IN section of header HD2.
Radio MIC
Pin MFJ-1272M Header Jumper Placement for Kenwood & Yaesu Jumper Placement for Icom & Radio Shack
1HD2 AUDIO IN--M1B AUDIO IN--M8B
2HD2 AUDIO IN--M2B AUDIO IN--M7B
3HD2 AUDIO IN--M3B AUDIO IN--M6B
4HD2 AUDIO IN--M4B AUDIO IN--M5B
5HD2 AUDIO IN--M5B AUDIO IN--M4B
6HD2 AUDIO IN--M6B AUDIO IN--M3B
7HD2 AUDIO IN--M7B AUDIO IN--M2B
8HD2 AUDIO IN--M8B AUDIO IN--M1B
Table 6
*Refer to External Audio, page 3

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The jumper listings on the previous tables do not always hold true for all Kenwood,
Yaesu, Icom and Radio Shack transceivers. The best way to setup the MFJ-
1272M correctly, is to have your transceiver manual handy at the time of setup.
Having your transceiver manual handy will ensure that you setup the MFJ-1272M
properly, by making the right connections the first time.
If you find yourself in need of technical help, please refer to the Technical
Assistance section of this manual. Please have all necessary notes and data
ready, so we can provide you with the best possible service at the time of your call.
Note: Jumper positions for specific radios are detailed on page 8.
Note: The FT-2400H and FT-2500H are the only Yaesu VHF transceivers that
are compatible with the MFJ-1272M. All others, such as the FT-3000, FT-
8000, and FT-8500, use data ports for packet data.

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Jumper Placement Diagrams for specific radios

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Other Notes
All of the jumper designations and wiring on the MFJ-1272M come setup for Yaesu
and Kenwood transceivers. So, if your RECEIVE AUDIO is on pin 3 of your
Kenwood microphone, then you would place a jumper on R3A in the RECEIVE
section of HD1. You may need to change the installed jumpers for the radio you
are trying to use. The MFJ-1272M is compatible with the the Yaesu FT-2400H and
FT-2500H. All other Yaesu transceivers will either be the standard round 8-pin
screw-on type, or in the case of the FT-3000, FT-8000 and FT-8500, all packet
data is taken in and out through the DATA PORT in the back of the radio. In this
case, the MFJ-1272M is totally incompatible.
If you want to use the MFJ-1272M with an Icom or Radio Shack transceiver, then
all jumper designations need to be thought of in reverse order. This is due to the
numbering scheme on the Radio Shack and Icom microphones. So if your
RECEIVE AUDIO is on pin 3 of your Icom microphone, then you would place a
jumper on R6A in the RECEIVE section of HD1.
The MIC pins on the Radio Shack and Icom radios are numbered 1 through 8, from
left to right. Whereas, the Yaesu and Kenwood radio MIC pins are numbered 1
through 8, from right to left. The only Yaesu transceivers that are compatible with
this unit are the FT-2400 and FT-2500. All other Yaesu transceivers, such as the
FT-3000, FT-8000, and FT-8500, use data ports, which are located in the back of
the radios for all packet type communications.

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This means that the labels on the MFJ-1272M printed circuit board are backwards
for the Icom radios, such as the IC-2340, IC-2350, IC-281H, IC-2000H, and IC-706.
This also holds true for the Radio Shack HTX-212 VHF transceiver.
For example, MIC audio is designated as pin 6 in the ICOM IC-2340 manual, but
on our MFJ-1272M board it is pin 3, so R3C and M3B have jumper clips on them.
All other pin designations for the Icom and Radio Shack radios are also backwards.
Connections
Connection of the MFJ-1272M is very simple.
1. Connect your radio's microphone to the microphone connector on the front
panel of the MFJ-1272M. Make sure that that you hear a “click” when the
microphone snaps into place.
2. Connect the gray, 8-pin MIC plug, which exits the rear of the MFJ-1272M out
of the TO RADIO slot, to the microphone jack on the radio.
3. Connect the TNC cable, which exits the rear of the MFJ-1272M out of the TO
TNC slot, 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 MFJ-1272M. 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-1272M.
The EXT. SPKR jack requires a 3.5mm mono plug, with the tip being positive
and the sleeve ground.