A helical antenna is a type of antenna that is considered to be a hybrid of a loop antenna and a dipole antenna. It has a conducting wire that is wound in the form of a helix shape as shown in the below figure. Helical antennas operate over wide bandwidths compared to other types of RF antennas. They appear as one or more springs or helixes, and are mounted over a ground plane. The feed line, which carries the electromagnetic signal, is connected between the bottom of the helix and the ground plane. Helical antennas operate in 3 different modes – normal mode, axial mode, and conical mode, and each mode exhibits different radiation patterns. Since these antennas are helical in geometry, they emit electromagnetic waves with circular polarization.

This circular polarization enables receiving antennas to receive signals in both horizontal and vertical directions in space, resulting in greater reception. Helical antennas are ideal for satellite and space probe communications, VHF signal transmission and reception, telemetry links, and radio astronomy.

Design Parameters of a Helical Antenna:

Antenna Gain:

Where,

 is the number of turns of helix, and

 is the space between the coils

Diameter:

Where,

 is the wavelength of the electromagnetic signal

Half Power Beamwidth (HPBW):

Where,

 is the circumference of the helix.

 for normal mode

 for axial mode, and

 for conical mode.

Beamwidth First Nulls:

Effective Aperture of the Antenna:

Upon entering the wavelength, number of turns, and spacing between coils, this helical antenna design calculator easily calculates the gain, diameter, half power beamwidth, beamwidth first nulls, and effective aperture of the helical antenna.