In a radio receiver, what is the primary effect of a limiter on the demodulation process?

• A. It reduces amplitude variations to a fixed level, aiding consistent demodulation, especially for FM.
• B. It increases amplitude variations to improve detection.
• C. It filters out all frequencies except the carrier.
• D. It converts the signal to digital immediately.

Answer: (B)

Limiters are used to produce a constant-amplitude signal, which is crucial for FM demodulation. In FM, the information is carried by instantaneous frequency changes, not by how strong the signal is. By clipping the peaks and removing amplitude variations caused by AM or noise, the limiter ensures the demodulator responds mainly to frequency deviation. With a stable, fixed amplitude, the discriminator or demodulator can convert those frequency changes into the output signal reliably, even when the received signal level varies. This is not about increasing amplitude fluctuations, filtering away all non-carrier frequencies, or digitizing the signal.