________ Spectrum 01 ________
The picture shows the spectrum waveforms of the oscillator pair.
The user should set the distance of the frequencies between the oscillators about 5 to 6 kHz.
________ Spectrum 02 ________
The frequency of the oscillator drifts to the lower side by the moving hand toward the antenna.
The distance (between the output frequencies) decrease, the pitch of the de-modulated tone would be down.
When the frequencies turns almost the same, the beat sound would be stopped.
_____ Demodulator outputs _____
The difference of the frequencies are converted to the beat by the demodulator.
The microcontroller measures the time between the up-edges of the beat.