What is the function of an AM transmitter?

The function of an AM transmitter primarily involves combining the modulating signal with the radio frequency (RF) signal. This process is known as amplitude modulation. In amplitude modulation, the amplitude of the RF carrier wave is varied in accordance with the amplitude of the modulating signal, which typically contains the information being transmitted, such as audio or data. This modulation allows the signal to be transmitted over long distances while being able to be demodulated by receivers that can extract the original information from the variations in amplitude.

This combining of signals is a crucial step in the transmission process, as it enables the effective transfer of information through the electromagnetic spectrum. The transmitted signal can then be picked up by receivers tuned to the correct frequency, where the original information can be retrieved.

In contrast, the other options don't accurately represent the primary function of an AM transmitter. Suppressing interference relates more to signal processing techniques rather than the transmitter's core function. Varying the frequency of the signal pertains more to frequency modulation (FM) rather than amplitude modulation. Filtering audio signals is a part of processing the signal but does not define the primary role of an AM transmitter. Thus, combining the modulating signal with the RF signal is the essential correct function.