In an AM transmitter, what does the modulation process involve?

The modulation process in an AM (Amplitude Modulation) transmitter specifically involves combining the modulating signal, often an audio signal, with the carrier signal, which is a higher frequency radio wave. This combination alters the amplitude of the carrier wave in accordance with the variations of the modulating signal.

When the modulating signal increases, the amplitude of the carrier wave also increases, and when the modulating signal decreases, the amplitude of the carrier wave diminishes correspondingly. This enables the transmission of audio information over long distances by effectively embedding the audio signal onto the radio frequency carrier wave.

The other choices involve aspects that are part of the overall radio transmission process but do not define the modulation aspect itself. Amplifying the RF signal and filtering unwanted frequencies are vital steps for enhancing and ensuring the clarity of the signal, but they do not constitute modulation. Generating new signal frequencies is also a critical aspect of signal processing, but it is not related to the modulation of an existing carrier signal. Hence, the key operation that signifies modulation in AM transmission is the combination of the modulating signal with the carrier signal.