Summary of Morse Code Decoder
The article describes a Morse Code Decoder project that uses an electret microphone with a transistor amplifier serving as a bandpass filter, followed by an NE567 PLL tone detector to extract the Morse signal. The output is a digital pattern representing the dots and dashes, which is then processed by a PIC16F84 microcontroller. An LED indicator helps with tuning the receiver. This approach offers a robust alternative for decoding Morse code without complex devices, suitable for skilled listeners under varying signal conditions.
Parts used in the Morse Code Decoder:
- Electret microphone
- Transistor (for common emitter follower amplifier)
- Coupling capacitors
- Feedback capacitor
- NE567 Phase Lock Loop (PLL) tone detector/decoder
- PIC16F84 microcontroller
- LED (receiver tuning aid)
Morse code is used in telecommunication; it is a method of transmitting and receiving coded information. Each character (letter or numeral) is coded/represented by a unique sequence of dots and dashes. Compared to voice, Morse code is less sensitive to poor signal conditions, yet still comprehensible to humans without a decoding device, therefore, a useful alternative to synthesized speech for sending automated data to skilled listeners (radio operator) on a voice channel.
The project’s first part is composed of an electret microphone followed by a common emitter follower amplifier; this transistor amplifier also acts as a first level bandpass filter. Its band edges are determined by the size of the coupling capacitors, and the feedback capacitor between the transistor’s base and collector terminals. The next part of the project is the PLL (phase lock loop) tone detector/decoder NE567; its output is a one-zero pattern replicating the dots-and-dashes sequence of the received signal. This output drives both an input to the PIC16F84 microcontroller and an LED that is used as a receiver tuning aid.
For more detail: Morse Code Decoder
