Modulation Type
Sine Waves
Pulse Modulation
Simply turn on and off the sine wave. Based on the length of the sine wave, a Morse code (or other simple message) can be sent.
Amplitude Modulation
Vary the amplitude (peak-to-peak voltage) of the sine wave. Can be done by overlaying a person’s voice (low frequency) on the sine wave.
Frequency Modulation
Slight changes to the frequency of the sine wave to encode information.