In an AM broadcast signal using voice, how is the carrier modified?

In an AM (Amplitude Modulation) broadcast signal, the carrier is modified primarily by varying its amplitude in relation to the audio signal being transmitted. This modulation creates sidebands that include both an upper and lower frequency version of the signal, which carry the actual audio information.

The correct answer pertains to the standard operation of AM broadcast signals, where the carrier is indeed modulated in amplitude to produce a signal that contains both sidebands. In this context, the option stating that amplitude varies and employs both sidebands without the carrier highlights a concept more applicable to specific forms of modulation, such as Single-Sideband (SSB) transmission. However, for conventional AM broadcasts, the carrier itself remains present and is an essential part of the broadcast signal.

Thus, the best way to conceptualize standard AM broadcasting is through the adjustment of carrier amplitude, which generates sidebands while still retaining the carrier component as a reference signal. This is foundational in AM broadcasting as it allows receivers to demodulate the signal accurately.

In AM, two sidebands are formed—the upper and lower sidebands—each carrying the same information. The presence of the carrier along with sidebands is crucial in traditional AM operation for proper transmission and reception of voice signals, making this a critical