What is an aerial/what does it do?

An aerial, also known as an antenna, is an electrical appliance, in the form of a metal rod, which receives radio waves so that driver and passengers can listen to the radio when travelling in the car. 

Getting into the details of an aerial

An aerial is a simple yet clever and useful piece of equipment. Radio waves are transmitted from a radio station and travel at the speed of light, dispatching the radio programme as they travel. The metal aerial in a car, captures these radio waves as they fly through the air, causing the radio waves to flow through the aerial. The action of the radio waves flowing through the metal aerial causes electrons to move backwards and forwards which creates an electric current. This current or signal is taken from the aerial to the radio inside the car where it is changed back into amplified sound, enabling the people travelling in the car to hear the radio programme being transmitted. In essence, an aerial captures radio waves and changes them into electrical signals which are then changed back into sound, by the electronic components inside the radio. The radio in the car is fitted with an electronic circuit which cleverly picks up the exact programme/station that has been selected by the user when they tune the radio in, from all the other programmes that are being broadcast across the airwaves.

The aerial is connected to the car stereo/radio receiver by an aerial cable which houses the conductor needed to receive radio reception, and is essentially an extension of the center conductor inside the aerial cable.

Aerials are usually mounted onto the outside of the car but some cars have an aerial mounted internally. Internal aerials are usually fixed to the dashboard of the car. 

Usually new cars are fitted, by the manufacturer, with a standard and often basic radio aerial. There are various types of aerials available should you wish or need to replace the factory fitted  aerial. There are manual aerials (retractable and non retractable) including pillar mounted and roof mounted; electric aerials, which can be extended fully or retracted back into the body of the car, which is a useful function making it less likely to be damaged by corrosion due to the weather or broken off accidentally; and satellite aerials, which tend to be more expensive but the quality and reliability of reception is of a high standard. There is also an aerial sat nav which is used to receive a signal and send this to the sat nav. Each type of aerial has it's benefits, so it's a good idea to give it some careful consideration before deciding which type of replacement aerial is right for your car, making sure it is compatible with your car, though it is possible to buy an aerial adapter if needs be.

What if something goes wrong with the aerial?

Aerials can, of course, suffer damage or become misaligned, or simply over a long period of use can stop working properly.  Aerials are prone to rust from being exposed to all weather conditions and can also be snapped off accidentally, particularly the non retractable type. If the aerial is still intact but you are experiencing poor reception and sound quality is getting worse over time, then this is a sign that you need to replace the car aerial. It is possible that you will still be able to receive FM radio when the aerial has stopped working but if the car stereo is unable to pick up a signal on the AM frequency then it is very likely the aerial is broken and  you will need to buy a new one.  It is important to make sure the replacement aerial is compatible with the make and model of car and that consideration is given to which type of aerial you would like to buy.