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A helical antenna is an antenna consisting of a conductive wire coiled in the form of a helix. In most cases, the helical antennas are mounted on a ground plane. The power line is connected between the bottom of the propeller and the ground plane. Helical antennas can operate in one of two main modes: normal mode or axial mode.

In normal mode or helical antenna on the side, the diameter and pitch of the antenna are small compared to the wavelength. The antenna acts similarly to an electrically short dipole or monopole, and the radiation pattern similar to these antennas is omnidirectional, with maximum radiation at right angles to the axis of the propeller. The radiation is linearly polarized parallel to the axis of the propeller. They are used for compact antennas for portable and mobile bidirectional radios, and for UHF television broadcast antennas.

In the axial mode or helical antenna of fire end, the diameter and pitch of the propeller are comparable to a wavelength. The antenna acts as a directional antenna that radiates a beam from the ends of the propeller, along the axis of the antenna. Radiated circularly polarized radio waves. These are used for satellite communication.

If the helix's circumference is significantly less than a wavelength and its pitch (axial distance between successive turns) is significantly less than a quarter wavelength, the antenna is called a normal-mode helix. The antenna acts similarly to a mono-polar antenna, with an omnidirectional radiation pattern, radiating equal power in all directions perpendicular to the antenna axis. However, because of the added inductance by the helical form, the antenna acts as an inductively charged monopoly; at its resonant frequency is shorter than a quarter wavelength. Thus, normal mode propellers can be used as electrically short mono-poles, an alternative to center or base loaded whip antennas, in applications where a full-sized quarter-wave mono-pole would be too large. As with other electrically short antennas, the gain, and therefore the range of communication, of the propeller will be less than that of a full-size antenna. Its compact size makes "helical" antennas useful for mobile and portable communications equipment in the HF, VHF and UHF bands.