1999 Lexus LX 470 Owners Manual - Page 323

FM Fading and drifting stations - Generally, the effective range of FM is about 40 km (25 miles). Once outside this range, you may notice fading and drifting, which increase with the distance from the radio transmitter. They are often accompanied by distortion. Multi-path - FM signals are reflective, making it possible for two signals to reach your antenna at the same time. If this happens, the signals will cancel each other out, causing a momentary flutter or loss of reception. Static and fluttering - These occur when signals are blocked by buildings, trees, or other large objects. Increasing the bass level may reduce static and fluttering. Station swapping - If the FM signal you are listening to is interrupted or weakened, and there is another strong station nearby on the FM band, your radio may tune in the second station until the original signal can be picked up again. AM Fading - AM broadcasts are reflected by the upper atmosphere - especially at night. These reflected signals can interfere with those received directly from the radio station, causing the radio station to sound alternately strong and weak. Station interference - When a reflected signal and a signal received directly from a radio station are very nearly the same frequency, they can interfere with each other, making it difficult to hear the broadcast.