The AH-218 is a circular polarization helix antenna. It has a directional radiation pattern and an invariable gain along its frequency range.
The most common application is the reception from ENG links, where the circular polarization allows the reduction of the multipath effect. Besides, it is also used in point-to-point links, where the distance to cover is not very long. These are compact and lightweight antennas, with a beamwidth which allows an easy steering of the antenna.