Half-wave antenna

Definition

A half-wave antenna is a type of dipole antenna with a length equal to half the wavelength of the frequency it is designed to transmit or receive. It is widely used because of its simplicity and efficient radiation properties.

5 Must Know Facts For Your Next Test

1. The length of a half-wave antenna is calculated using $L = \frac{\lambda}{2}$, where $\lambda$ is the wavelength of the signal.
2. It has a high radiation efficiency and provides optimal performance when placed at least half a wavelength above the ground.
3. The impedance at the feed point of a center-fed half-wave antenna is approximately 73 ohms.
4. Half-wave antennas are commonly used in radio broadcasting and amateur radio due to their simplicity and effectiveness.
5. The radiation pattern of a half-wave antenna is doughnut-shaped, with maximum radiation perpendicular to the axis of the antenna.

Review Questions

• What formula is used to determine the length of a half-wave antenna?
• Why is it important for a half-wave antenna to be placed at least half a wavelength above the ground?
• What is the typical impedance characteristic of a center-fed half-wave antenna?

Related terms

Wavelength:

The distance between successive crests of a wave, typically measured in meters.

Dipole Antenna: An antenna consisting of two conductive elements such as metal rods or wires that are usually bilaterally symmetrical.

Radiation Pattern: A graphical representation showing how an antenna radiates energy into space in various directions.