Modifications for the Kenwood TM-241

TM-241A RX/TX mods


This mod is only intended for experimental applications only! Know what freq you are on and don't use this mod if you are not for sure.

The TM-421a is capable of transmitting from 136 to 174 MHz when the following modification is performed. The transmitter specifications will vary from published in-band specifications.
  1. Remove the top and bottom covers from the transciever.
  2. Remove the knobs from the front panel.
  3. Remove the nut from the mic jack and the nut from the channel selector switch.
  4. Remove the 4 screws that secure the front panel to the body of the transceiver.
  5. Pull the front panel off the transceiver to expose the Control board.
  6. Remove the 3 screws from the Control board. Gently pull the board off the transceiver.
  7. Cut the GREEN jumper wire on the Control board.
  8. Install an MA141A chip diode or 1N914 diode as D209 on the Control Board.
  9. Reassemble the transceiver by reversing steps 1 - 6.
  10. Reset the microprocessor by holding in the MR key as power is turned on.
+-------------------------------------------------------------------------+
|                            D209                                         |
|                         +-+     +-----+                                 |
|                         ||- |--|+---+                                 |
|                               | |                                     |
|                               | |                                     |
|                            | |  | |                                     |
|                            | |  +-+                                     |
|  +-----------------------+              +-------------------------+   |
|  | [] [] [] [] [] [] []  |    --+       | [] [] [] [] [] [] [] [] |   |
|  +-----------------------+    ---+       +-------------------------+   |
|                                                                         |
|                                                                         |
+-------------------------------------------------------------------------+


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