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A36plus_mod

A modification guide for the Talkpod A36plus, enabling flat baseband input/output (so-called "9600 baud"). The stock firmware does not support flat baseband in/out, so it is required to flash the device with OpenRTX open-source alternative firmware.

Warning

This mod $${\color{orange}does \space not \space allow \space \space nor \space enable}$$ the radio to process or generate M17 on its own - an external modem is required. The proposed modification breaks both the RX and TX paths, meaning that it is $${\color{orange}no \space longer \space possible \space to \space use \space the \space radio's \space microphone \space and \space speaker}$$. The only baseband access is through the Kenwood connector.

The general idea

To access flat baseband, just connect two of the pins of the mod/demod IC with the Kenwood connector. Some parts have to be removed so that the signal is kept clean. Schematic_1 Schematic_2

Modification

  1. Remove (desolder) C4 and C148. Both capacitors are located close to the BK4819 chip at the back side of the board. Parts

  2. Remove (desolder) L43, R131 and C203. All of these parts are located close together near the Kenwood connector, at the back side of the PCB. Parts

  3. Remove (cut away) E15 (a 100uF THT electrolytic capacitor) and desolder the resistor parallel to it (R145, at the other side of the PCB).

  4. Connect pins 8 and 13 of the Beken IC with the Kenwood connector. Back_annotated

  5. Disconnect the MIC/SPK connector P3.

Modification overview

Front side of the mainboard Front

Back side of the mainboard Back

Flashing with OpenRTX

Linux

WIP.

Windows

Use the official flashing tool from Talkpod. A sample image can be found in the sample_firmware directory.