Fading and drifting FM range is limited to about 25 miles (40
km), except for some high power stations. If a vehicle is moving
away from the desired station's transmitter, the signal will
tend to fade and/ or drift. This condition is more prevalent
with FM than AM, and is often accompanied by distortion. Fading
and drifting can be minimized to a certain degree by careful
attention to fine tuning or selection of a stronger signal.
Static and fluttering When the line-of-sight link between a
transmitter and vehicle is blocked by large buildings or
mountains, the radio sound may be accompanied with static or
fluttering because of the characteristic of FM. In a similar
effect, a fluttering noise is sometimes heard when driving along
a tree-lined road. This static and fluttering can be reduced by
adjusting the tone control for greater bass response until the
disturbance has passed. Because of the reflecting
characteristics of FM, direct and reflected signals may reach
the antenna at the same time (multipath) and ca