How do aerials work?

Answer 1

There are two main types of electric car aerial; automatic and semi-automatic. Automatic ones raise or lower when the ignition and/or the radio is turned on. Semi-automatic ones have a selector switch on the dashboard. When either of the conditions shown above exist, a relay turns ON and passes power to a motor at the base of the aerial. The motor then raises the aerial until it reaches its upper position where a limit switch breaks the circuit. The relay remains in the ON position and the aerial remains in the raised position until the ignition and/or the radio is turned off. When the ignition and/or the radio is turned off, the relay goes into the OFF condition. Power now flows through a second circuit in the relay and also through a second circuit in the aerial motor to reverse the drive and lower the aerial until a second, lower limit switch is broken. The relay is a single-throw, double-pole unit. The aerial motor is a three-wire unit and often incorporates a circuit breaker.

Answer 2

They collect radio waves from the air and feed them to the radio.