In communication systems, what does modulation specifically refer to?

• A. Changing signal amplitude
• B. Changing frequency
• C. Combining voice with carrier signal
• D. Amplifying weak signals

Answer: (C)

Modulation specifically refers to the process of modifying a carrier signal to encode information, such as voice, data, or video. This process involves altering certain characteristics of the carrier wave, like its amplitude, frequency, or phase, to represent the information being transmitted. In amateur radio and communication systems, modulation allows the transmission of audio or data signals over a variety of frequencies and through different media.

When voice signals are combined with a carrier signal during modulation, this enables the audio signal to be transmitted effectively over radio waves. The carrier wave is a high-frequency signal, and by modulating it with the voice signal, the information can be transmitted over the airwaves to a receiver where it can be demodulated back into its original form. The process of modulation is essential because it facilitates efficient transmission over long distances and makes the signals less susceptible to noise and interference.

The other options relate to changes in the signal but do not encapsulate the broader definition of modulation as the process of embedding information into a carrier signal. For instance, changing signal amplitude or frequency can be aspects of modulation, but modulation itself encompasses a wider range of methods and is specifically about encoding information onto a carrier wave.