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Dipole Antenna Basics

Appearing in different forms, such as a metallic rod, wire or loop, antennas receive or emit electromagnetic radiation. Some antennas increase radiation in certain directions, while others suppress it in other directions. Radio transmitting and receiving represents the most common use of dipole antennas. If you want an affordable antenna that you can build yourself, the simplicity of the dipole antenna may attract your attention.

Structure
- Since "dipole" means two poles, a dipole antenna has a basic structure of two straight wires or "arms" which it needs in order to radiate electromagnetic waves. You only need a few pieces of wire to make a simple dipole antenna, which works effectively for short-wave radio bands, for instance. How much the dipole radiates depends on the amount of radio frequency current the dipole antenna receives. The dipole does not need a "ground" in order to operate. Ground represents the connection between Earth and an electrical conductor.
Power
- Dipole antennas receive power through a feeder, which transfers it to or from the antenna. They need current and voltage in order to transmit the power, and these levels vary along the length of the antenna. For example, the middle of the antenna has a low voltage, which reaches a maximum level at the antenna ends. The current reaches its maximum at the middle of the antenna.
Half-Wave Dipole
- The linear, half-wavelength dipole antenna is the most common form of dipole antenna. The electrical length of this dipole is half a wavelength. Each wire has the same length. Each section of this dipole antenna has a length of a quarter wavelength.
Inverted V
- The inverted V-shaped dipole looks just like an upside-down "V." The inverted V has element ends reaching toward the ground, making this antenna more convenient to set up than other antennas. You must keep the inverted V at 120 degrees or more; otherwise, this antenna's performance will suffer.

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