Antenna



An antenna is a device used to transmit and receive electromagnetic waves, such as radio waves and microwaves. Antennas are found in a great variety of communication devices, including radios and television sets, weather radar systems, satellite communications systems, and radio astronomy research centers.

Your local radio station uses an antenna to transmit the programs it broadcasts. Words that are spoken or music that is played within the station are converted to electrical signals. These signals are then transmitted to an antenna in the form of an electric current. Electrons inside the antenna vibrate back and forth with the same frequency as the incoming

The antenna for a Doppler weather radar site. Doppler radar can be used to detect various weather conditions. (Reproduced by permission of The Stock Market.)
The antenna for a Doppler weather radar site. Doppler radar can be used to detect various weather conditions. (Reproduced by permission of
The Stock Market
.)

electric current. The vibration is characteristic of the sounds produced within the station. As these electrons vibrate, they create an electromagnetic wave in the air around the antenna. That wave spreads out and travels in all directions from the antenna. The frequency of the wave is the same as the frequency of the electron vibration in the antenna and of the sounds spoken in the station.

An antenna placed in the path of these waves reverses the above process. Electromagnetic waves in the air cause electrons in the receiving antenna to begin vibrating. The frequency of vibration is the same in the receiving antenna as it is in the wave. The vibrating electrons are converted into an electrical current, which travels into your radio receiver and is converted back into sound.

Antennas come in all sizes and shapes, from the tiny units found in miniature transistor radios to the massive structures used to transmit messages to and receive messages from outer space.

[ See also Microwave communication ; Radar ; Radio ]



Also read article about Antenna from Wikipedia

User Contributions:

1
piyush mishra
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Mar 31, 2008 @ 6:06 am
i want to know how generate electromagnetic wave in air through antena? nice article.

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