Tuesday, May 2, 2017

BITX40v3 Mod - add PTT sense

The newest version of the Raduino software supports RIT (Split) but requires a hardware mod to sense when the PTT is pressed. This is accomplished by adding a 10K resistor to the junction of C150, RV1 and the output of the 5V regulator. Since the 5V regulator is only powered during transmit, the Raduino can sense this voltage to determine if the PTT is pressed. The 10K resistor is connected to the black wire (A0) on the Raduino 8 pin connector.

The 10K resistor and wire can be soldered to the bottom of the BITX40 board to keep it out of the way. I used a small connector in the black wire leading to the Raduino to make it easy to remove the circuit board for further modifications. Some hot melt glue will keep the wire from moving around and breaking off the resistor lead from too much flexing.

73, AL - VE3RRD

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