In radio communication, what is modulation?

Modulation is the fundamental technique used in radio communication to enable the transmission of information. It involves varying a carrier signal's characteristics, such as its amplitude, frequency, or phase, to encode information onto the signal. This process is essential because it allows various types of signals, such as voice, data, or video, to be transmitted over radio waves effectively.

By modifying the carrier signal, modulation makes it possible to transmit information across different frequencies without interference. This variation helps in distinguishing the signal from noise and allows the receiver to decode the information accurately. Modulation is what enables single frequencies to carry multiple signals simultaneously, facilitating efficient use of bandwidth.

The other options describe processes associated with radio communications but do not encompass the full definition of modulation itself. For instance, increasing signal amplitude is just one aspect of amplitude modulation, but it does not represent modulation in a broader sense. Similarly, enhancing audio clarity relates more to signal processing techniques rather than the core concept of modulation. As for regulating frequency stability, while important in maintaining signal integrity, it does not directly address the process of encoding information within a carrier signal. Therefore, the definition that encapsulates modulation accurately and comprehensively is that it refers to varying a carrier signal to transmit information.