# In which conditions can a helical antenna operate in axial mode?

## In which conditions can a helical antenna operate in axial mode?

The dimensions of the helix are determined by the wavelength λ of the radio waves used, which depends on the frequency. In order to operate in axial-mode, the circumference should be equal to the wavelength.

## What is the polarization of helical antenna in axial mode?

In axial mode of radiation, the radiation is in the end-fire direction along the helical axis and the waves are circularly or nearly circularly polarized. This mode of operation is obtained by raising the circumference to the order of one wavelength (λ) and spacing of approximately λ/4.

Is a helical antenna directional?

In the axial mode or end-fire helix, the dimensions of the helix are comparable to a wavelength. The antenna functions as a directional antenna radiating a beam off the ends of the helix, along the antenna’s axis. It radiates circularly polarised radio waves.

How is the radiation pattern of a helical antenna obtained?

In normal mode of radiation, the radiation field is normal to the helix axis. The radiated waves are circularly polarized. This mode of radiation is obtained if the dimensions of helix are small compared to the wavelength. The radiation pattern of this helical antenna is a combination of short dipole and loop antenna.

### What are the benefits of a helix antenna?

These helix antennas are referred to as axial-mode helical antennas. The benefits of this helix antenna is it has a wide bandwidth, is easily constructed, has a real input impedance, and can produce circularly polarized fields. The basic geometry of the helix antenna shown in Figure 1. Figure 1. Geometry of Helical Antenna.

### How is the axial mode of radiation obtained?

In axial mode of radiation, the radiation is in the end-fire direction along the helical axis and the waves are circularly or nearly circularly polarized. This mode of operation is obtained by raising the circumference to the order of one wavelength (λ) and spacing of approximately λ/4.

How is the radiation field normal to the helix axis?

In normal mode of radiation, the radiation field is normal to the helix axis. The radiated waves are circularly polarized. This mode of radiation is obtained if the dimensions of helix are small compared to the wavelength.