Radio waves are magnetic energy generated by a transmitter, and are transmitted via antenna. The antenna on a vehicle picks up the magnetic energy from the radio waves and sends it to the car's radio receiver, which in turn, isolates and amplifies the radio waves,in order to be heard. The passage of the radio waves over the antenna's mast, produces minute electrical charges. Depending on the length and other details of the antenna's design, particular radio wavelengths, are captured more easily than others. The design of a car's radio antenna takes into account the differing frequencies of the AM and FM bands,in order to provide good reception with either.
Electrically Operated and Activated Antennas
A car power radio antenna operates by electronic control. Most power antennas are designed to switch on when the vehicle ignition is turned on. When a key is inserted into the ignition switch and turned to the "On" position, electricity from the battery reaches the car's accessories, including that of the power antenna, and they are turned on, or activated. When a vehicle's accessories are turned off, the power antenna collapses and resides in a special compartment, or housing, located on the fender wall. This is a safety feature designed to protect the antenna from breakage or damage when not in use.
Power Antennas Function
When power is turned on at the ignition switch, the power antenna is activated, and it rises up out of its compartment and extends to its full height. In this position, the power antenna is fully functional and receiving radio signals.
Power Antenna Motor Operation
All power antennas operate by way of a small motor housed directly beneath the antenna housing in the car fender. A power antenna motor, which is basically a cylindrical rotor that spins, is the part that becomes energized when the car ignition switch is turned on. This motor propels the antenna up out of its housing upon activation, and it also collapses the antenna when the ignition switch is turned off.
Internal car antennas sit inside the trunk, dashboard or the windshield of a car. Internal antennas receive better protection from weather and accidental damage, but their reception generally isn't as clear as external or satellite antennas. Installing the antenna inside the car or using an antenna with a built-in amplifier may help reception performance.
External antennas, made of metal or fiberglass, are typically installed near the hood or trunk of the car. External antennas receive better reception but are more susceptible to breakage or weather damage. External antennas sometimes come with retractors that pull the antenna into the car to protect it when not in use, see power antennas.
Satellite antennas are the newest type of antenna used in automobiles as of 2012. The installer mounts a radio dock in the front near the windshield or in the dashboard, then wires the radio through the back or side of the car to a small magnetic antenna on the roof of the car. Satellite radio offers superior sound quality but requires a paid subscription, unlike free terrestrial stations.
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