How to Build a Motorola MTM800/MTM800E Programming Cable

The MTM800/MTM800E can be programmed using the accessory connector located at the backside of the radio. This connector is similar to those found on radios like the GM300 or the TM900 series. However, the Tetra radio’s accessory connector contains additional pins compared to these other models.

Caution! It’s not recommended for radio flashing, firmware upgrades, or downgrades, as the control head firmware cannot be flashed or realigned with the radio firmware version. Doing so may result in rendering the unit inoperable, commonly referred to as soft-bricking the unit.

To build a programming cable for the Motorola MTM800 or MTM800E you’ll need the following materials:

1. Classic USB  2,0  A to B cable (even a cheap mouse cable works, recommended a printer or good quality cable)
2. Bare accessory connector compatible with the radio (similar to those found on the GM300 or TM900 series radios)
3. Wire stripper
4. Soldering iron and solder
5. Heat shrink tubing (optional)
6. Multimeter (optional, for testing)

Please be aware that we are not responsible for any loss or damage to you or your equipment
that may occur during this process!

Here’s a step-by-step guide to wiring the cable:

1. Cut off the USB B  cconnector : Begin by cutting off the USB B side connector from the USB programming cable, leaving you with the exposed wires.

2. Identify the correct pins : Refer to the pinout provided in the service manual of the MTM800E radio. Pay close attention to the pin numbers and their corresponding functions. Focus on the following connections:
– Pin 6 (Accessory Connector) to Pin 13 (Radio)
– Pin 8 (Accessory Connector) to Ground (Radio)
– Pin 19 (Accessory Connector) to TXD (Radio)
– Pin 20 (Accessory Connector) to RXD (Radio)

 

3. Prepare the wires: Strip the insulation from the ends of the wires on both the USB programming cable and the bare accessory connector.

4. Solder the connections: Solder the wires from the new USB programming cable to the corresponding pins on the bare accessory connector according to the identified connections. Double-check the connections to ensure accuracy.

5. Insulate the connections (optional): If desired, cover the soldered connections with heat shrink tubing to provide insulation and protection.

6. Test the cable: If you have a multimeter, you can use it to verify the continuity of the connections between the USB programming cable and the bare accessory connector.

7. Secure the cable: Once you’ve confirmed that all connections are correct and functional, you can secure any loose wires and ensure the cable is properly assembled.

8. Final checks: Before using the cable for programming, perform a final visual inspection to ensure there are no exposed wires or solder joints.

   That’s it! You’ve now built a USB programming cable for the Motorola MTM800 or MTM800E radio using a common USB A to B programming cable and a bare accessory connector. Remember to follow safety precautions when soldering and handling electrical components.

  If you want to go further and make also a RS232 adapter for the cable or build a new RS232 not usb one, you can have a look on PE2KMW webpage where you can find a step by step instruction for that

* We do not provide programming software, licenses, additional information, or technical support beyond what is available through above published information!