Modifications for the Kenwood TM-2570

TM-2530/2550/2570 MARS/CAP

The TM-2500 series radios may be easily modified for use on MARS/CAP frequencies from 141-150.995 MHz.

Locate the control unit (X54-1860-XX) on the bottom of the radio. This is the same board that the TU-7, and or MU-1 are mounted on. Just to the left of IC3 you will find a row of diodes. Cut diodes D8, and D11. After the diodes have been cut you will have to "reset" the microprocessor.
Microprocessor Reset.
  1. Press and hold the [PS] key.
  2. Turn ON the power switch.
  3. Release the [PS] key.
All of your programmed data such as memory channel data, DCL data, and Phone number data will be erased and you will have to reprogram them. If the radio is not reset, it will not recognize that you have cut the two diodes.
TM-2570 Low TX Power Output


Some owners of the TM-2570 have reportecd low transmitter power when the radio is used with an antenna having reasonably low VSWR (1.5:1)

  1. Remove the bottom cover on the heat sink.
  2. Ensure that C72 is installed correctly. (Refer to Service Manual)
  3. Squeeze the coils of L16 closer together.
  4. Make sure that C72 and L14 are as far away from each other as possible, move the capacitor, not the inductor.
  5. Readjust VR1-VR4, according to the instructions provided in the Service Manual. The protection circuit, VR4, should be adjusted for 8A at 146.000 Mhz rather than the values indicated in the Service manual. Change your service manual to reflect this value.
  6. Replace the bottom cover to complete the procedure.

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