Transistor (2N2222) connected to a PWM pin (e.g., Pin 8) to act as a switch for the radio. LCD (I2C): SDA to Pin 20, SCL to Pin 21.
Focusing on the Arduino Mega 2560 or Nano, which are the most common platforms for full-featured builds.
When using the K3NG code for a repacked hardware build, you must edit the keyer_features_and_options.h file. FEATURE_COMMAND_BUTTON Enable: FEATURE_POTENTIOMETER Disable: FEATURE_LCD_DISPLAY (to save space and power) Disable: FEATURE_MEMORIES (unless you add extra buttons) Pro-Tips for a Clean Repack
Remember that the "schematic" and the "code" must match. Before uploading, open keyer_pin_settings.h in the Arduino IDE and ensure the pin numbers in the code match your physical wiring. k3ng keyer schematic repack
You can connect push buttons to trigger pre-recorded messages. Pin A1 → Button → GND. Memory Button 2: Pin A2 → Button → GND. Memory Button 3: Pin A3 → Button → GND. USB Keyboard
Use a metal "mint tin" or aluminum project box to prevent RF interference from tripping the Arduino.
The Arduino generates a square wave for the audio sidetone, which sounds harsh without a basic low-pass filter. Transistor (2N2222) connected to a PWM pin (e
Ensure the pin numbers listed in your keyer_pin_settings.h match the Arduino Nano pin numbers detailed in the table above. PCB Layout and Construction Considerations
This is the most critical part of the schematic. You must interface the 5V Arduino logic with the (often higher voltage) keying line of your rig.
When you have found a reputable K3NG keyer schematic repack (often found in YouTube descriptions or hobbyist blogs), follow these steps: 1. Breadboard First When using the K3NG code for a repacked
A critical requirement for a schematic repack in the amateur radio context is RF filtering.
The entire circuit needs a clean 5V power source. If you're using a standard Arduino board, it has an on-board voltage regulator that allows you to power it from a 7-12V DC source via its Vin pin or the barrel jack. For a minimalist "chip-only" build (using just the AVR microcontroller), you would need to design an external 5V regulator circuit.
The paddle lines require hardware filtering to prevent RF energy from triggering false dits and dahs.