Helical antenna - Definition and Overview

A helical antenna is an antenna with a circular polarization. These antennas are best suited for space communication, where the orientation of the sender and receiver cannot be easily controlled, or where the polarization of the signal may change.

Helical antennas can have either a clockwise (right-handed) or counter-clockwise (left-handed) polarization. Helical antennas can receive signals with any type of polarization, such as horizontal or vertical polarization, but clockwise polarized antennas suffer a severe gain loss when receiving counter-clockwise signals, and vice versa.

Helical antennas are made of a single driven element which is coiled in a spiral, or helix. The direction of the coil determines its polarization, while the space between the coils and the diameter of the coils determine its wavelength. The length of the coil determines how directional the antenna will be and its gain; longer antennas will be more sensitive in the direction in which they point. A reflector is almost always used to increase the sensitivity, or gain, in one direction (away from the reflector).

See also

• Telstar (article includes image of a helical antenna)