This occurs because after the sun sets, AM signals more easily bounce off the Earth's atmosphere and skip off the ground. The result is that AM stations from hundreds of miles away may be heard at night that are not heard during the day. For reference, FM signals travel only 40-50 miles at any time of day. Students may recognize this fact from having tuned FM stations on car trips, and noticed them go out of range. They will also notice that some AM stations are more powerful than others and have greater range.
Stations often state their transmitting power in watts during station breaks.
Makes a copy of the log sheet on the blackboard. Then call on students and records their log sheet information, moving around the class, and skipping any duplications. Stations are also marked on the state and US wall maps. Disagreements about call signs, frequencies or locations can be checked in the WRTH reference book. Keep in mind that stations sometimes change ownership and their call signs.