For RF communications, "modulation" is best defined as?

Modulation is a fundamental concept in radio communications that refers to the process of varying a carrier wave in order to transfer data. It involves superimposing information onto a radio carrier frequency, which allows the transmission of voice, music, or data over the airwaves. This process is essential because raw radio signals cannot effectively convey the intended information in their unmodulated state.

When modulation occurs, various characteristics of the carrier wave—such as amplitude, frequency, or phase—are altered in accordance with the information being sent. This transformation allows the signal to be efficiently transmitted over large distances and makes it less susceptible to interference and noise.

In contrast, options like using a single carrier frequency at the proper power level or setting up the transceiver with the correct bandwidth deal with other aspects of communication setup but do not define the modulation process itself. The combination of received frequency and oscillator frequency in the mixer pertains to signal processing but is more specific to the demodulation phase. Thus, the correct definition encapsulates the core idea of encoding information onto a carrier for effective RF communications, which is precisely what modulation achieves.