How do radio signals “carry” human voice exactly? How is signal modulation done exactly?
It is difficult to answer your question without knowing the level you are at. In the beginning the voice was used to control the amplitude of the radio signal (it’s strength), this was known as AM (amplitude modulation). This was surpassed (in terms of quality) by FM (frequency modulation – where the carrier frequency is deviated by the instantaneous level of the human voice). Modern systems now convert the voice to a stream of digital data and then this is transmitted (often) using a version of FM called PSK (phase-shift-keying), Many variants of this exist to pack more raw data into narrower bandwidths. As far as how modulation is done, this does vary. AM – typically the frequency source is passed into a modulator (a sort of voltage controlled amplifier, where the modulating voice signal controls the gain of the amplifier), this signal is then further amplified and transmitted. AM transmitters can be as simple as a single transistor. FM – typically the frequency source is modulated b
