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By: Ikedi Ani-okoye.

Introduction to antennas

An electrical device designed to receive and transmit electromagnetic waves is called an antenna. Antennas are commonly used in radio, television broadcasting, cell phones, radar and other systems involving the use of electromagnetic waves.

Since electromagnetic waves can pass thru any medium at a certain frequency, this simply means that antennas can work not only in air but also under water and even thru solid ground. An antenna is also defined as an arrangement of conductors that generate electromagnetic field as a reaction to applied alternating electrical current or induce an alternating current between its terminals when placed in an electromagnetic field.

Types of Antenna

There are two basic types of antennas. The omni-directional antenna radiates electromagnetic signal equally in the three dimensional plane while the directional antenna radiates the signal more in one direction. Adding conducting elements such as a rod or a coil and varying their spacing, direction and length can create a specific antenna with specific properties.

By connecting several antennas to a common source, it becomes an antenna array that has a directive radiation pattern. The conductive means for conveying signal energy between the active antenna and the source is called antenna lead-in while the components between an amplifier and the active antenna is called antenna feed.

Antennas on a vehicle

Not all locations on the sheet metal will work the same and you may have to do some trial and error. Antennas work different on each vehicle since the sheet metal is different on each vehicle.

This difference changes the reflection points and other antenna properties, which does not make for a cut and dry solution. The roof will mostly work the best since there are no obstructions between the antenna and the satellite. Placing the antenna on the trunk lid may also work well provided the length of the cable is long enough.

How the antenna works

In order for an antenna to work it has to radiate. Your antenna, whether TV or radio has what is called free electrons running through it. It is these free electrons that vibrate. The question becomes, how do these free electrons vibrate and what causes them to vibrate?

Well, in real life it takes an electric field to move an electron. If you take an isolated straight dipole, the power comes from the combined fields of all the charged particles, both positive and negative, in the antenna. We'll call this field the antenna's coulomb field.

CONCLUSION

What ultimately happens with all these fields that makes it so that your TV or radio picks up signals through your antenna is this. The free electrons moving through your antenna are moving at their maximum speed. Even though CB isn't as popular with homeowners as it was 30 years ago, you can still see these bad boys on roof tops if you look close enough. Just make sure you stop the car first before taking a look.