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Dipole antenna facts for kids

Kids Encyclopedia Facts

A dipole antenna is a very common and important type of radio antenna. It is often used by itself to send or receive radio signals. It also forms a key part of many other antenna designs, acting as the main part that sends out or picks up radio waves.

What is a Dipole Antenna?

A dipole antenna is made of two straight pieces of metal, like wires or rods. When a radio signal (which is an electric current) flows into these pieces, it creates electromagnetic waves, also known as radio waves. These waves then travel through the air.

To work best, a dipole antenna is usually cut to a special length. This length is chosen so the antenna "resonates" with the radio signal. For most dipole antennas, this special length is about half the wavelength of the radio signal it's designed for.

How Long Should a Dipole Antenna Be?

Tv with antenna
A dipole antenna ("rabbit ears") on top of a television

The length of a dipole antenna is super important because it decides which frequency (or channel) the antenna will work best on. The antenna needs to be an "electrical half wavelength" or a multiple of that.

This "electrical" length is a bit different from the actual wavelength of a radio signal traveling through the air. This is because the metal of the antenna affects the speed of the signal slightly. So, an antenna will be a little bit shorter than what you might calculate for a wave in open air.

To find the right length for a half-wave dipole, you first calculate the half-wavelength for the signal in air. Then, you multiply this number by a special factor, usually between 0.96 and 0.98. This factor depends on things like how thick the wire or tube used for the antenna is compared to its length.

Common Uses of Dipole Antennas

Dipole antennas are used in many everyday devices. You might have seen them as "rabbit ears" on older television sets. They are also popular for shortwave radio antennas, which people use to listen to radio stations from far away. Many whip antennas, like those on cars, are also types of dipole antennas.

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See also

Kids robot.svg In Spanish: Dipolo (antena) para niños

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