Helical antenna

Common card · No. 461095

A helical antenna is an antenna consisting of one or more conducting wires wound in the form of a helix. A helical antenna made of one helical wire, the most common type, is called monofilar, while antennas with two or four wires in a helix are called bifilar, or quadrifilar, respectively. In most cases, directional helical antennas are mounted over a ground plane, while omnidirectional designs may not be. The feed line is connected between the bottom of the helix and the ground plane. Helical antennas can operate in one of two principal modes: normal or axial. In the normal mode or broadside helical antenna, the diameter and the pitch of the aerial are small compared with the wavelength. The antenna acts similarly to an electrically short dipole or monopole, equivalent to a ⁠1/4⁠ wave vertical and the radiation pattern, similar to these antennas is omnidirectional, with maximum radiation at right angles to the helix axis. For monofilar designs the radiation is linearly polarized parallel...

Read on Wikipedia · Image Kingbastard, CC BY-SA 3.0