Strange as it seems, this circuit can transmit rf Amplitude modulated (AM) in approximately 600 Khz frequency for that he uses an integrated circuit as 555 oscillator. The audio enters the PIN number 5 of the integrated circuit 555 coming from an electret microphone, an integrated circuit converts the frequency modulated signal to a modulated amplitude and output is on pin 3, where an antenna can be placed directly on it or a coaxial cable.
