Dipole antenna

Definition

A dipole antenna is a radio antenna that can be made by connecting a pair of conductive elements, such as metal rods, to a transmitter or receiver. It is the simplest and most widely used type of antenna in electromagnetic wave propagation.

5 Must Know Facts For Your Next Test

1. The length of each arm of a dipole antenna is typically equal to one-quarter of the wavelength of the signal it is designed to transmit or receive.
2. Dipole antennas have a figure-eight radiation pattern in free space, providing maximum radiation perpendicular to the axis of the antenna.
3. The impedance at the center feed point of a resonant half-wave dipole antenna in free space is approximately 73 ohms.
4. Dipole antennas are used for both transmitting and receiving electromagnetic waves across various frequency bands, including HF, VHF, and UHF.
5. The effective height and orientation of a dipole antenna significantly affect its radiation pattern and efficiency.

Review Questions

• What is the typical length of each arm in a dipole antenna relative to the wavelength?
• Describe the radiation pattern associated with a dipole antenna in free space.
• What is the approximate impedance at the center feed point of a resonant half-wave dipole antenna?

Related terms

Electromagnetic Wave: A wave composed of oscillating electric and magnetic fields that propagate through space.

Wavelength:

The distance between successive crests or troughs in a wave, typically measured in meters for electromagnetic waves.

Impedance:

$$Z = R + jX$$ where \( Z \) is impedance, \( R \) is resistance, and \( X \) is reactance; describes how much an object resists current flow when voltage is applied.