What is the effect of multipath on radio reception, and how can it be mitigated?

• A. Multipath causes fading and interference; mitigate via proper antenna orientation, RF diversity, or using frequency hopping and equalization.
• B. Multipath enhances signal strength; mitigated by lowering power.
• C. Multipath only affects receive sensitivity in urban areas; nothing can mitigate.
• D. Multipath is negligible at all frequencies.

Answer: (A)

Multipath causes fading and interference because the signal reaches the receiver through multiple paths, each with its own delay and phase. When these copies combine, they can add constructively or destructively, so the received strength can rise or drop as the geometry changes with movement or the environment changes. The best way to address this is to use techniques that reduce or overcome those destructive effects: proper antenna orientation to favor a strong, direct path and minimize reflections; RF diversity by receiving through multiple pathways or antennas so at least one path stays strong even if another fades; and frequency hopping or changing channels so a fading condition on one frequency doesn’t lock in on the entire transmission. Equalization at the receiver can also counteract the distortion caused by multiple delayed copies. Multipath isn’t limited to urban areas, and it isn’t negligible at all frequencies, so these mitigation methods are practical and effective.