exhibit demonstrates the basic elements of an AM radio: antenna, tuner,
rectifier, and speaker. A long white antenna wire drops down from the
roof of the exhibition hall to the exhibit. Visitors can turn a knob and
adjust the position of the plates of the capacitor, adjusting the resonant
frequency of the "tuner" to that of a local AM radio station.
Visitors are often surprised when they notice that the power for the sound
is picked up by the antenna from the power broadcast by the radio station.