Helical Antenna: Advantages and Disadvantages

This page explores the advantages and disadvantages of helical antennas. It covers the benefits and drawbacks of using helical antennas, along with a basic introduction to what they are.

What is a Helical Antenna?

Introduction: A helical antenna utilizes a helix-shaped radiating element. These antennas are commonly used at VHF and UHF frequencies where circular polarization is desired.

The helix is typically supported by a ground plane, as illustrated below:

Helical antennas support two primary modes of radiation:

• Normal Mode: Radiation is perpendicular to the axis of the helix.
• Axial Mode: Radiation occurs in the axial direction (along the helix’s axis).

A helical antenna with circular polarization can effectively receive both horizontally and vertically polarized waves.

Applications of Helical Antennas

Helical antennas find use in various applications:

• Transmission and reception of VHF signals through the ionosphere.
• Satellite communications and radiometry applications.
• Communication between the Earth and the Moon.

Advantages (Benefits) of Helical Antennas

Here are the key advantages of using a helical antenna:

• Simple Design: Helical antennas are relatively straightforward to design and manufacture.
• Polarization Compatibility: Due to their circular polarization, they can effectively receive signals from both horizontal and vertical polarized antennas.
• Broadband Applications: They offer a wider bandwidth, making them suitable for broadband applications.
• HF/VHF Usage: Can be used for transmission and reception at HF/VHF frequencies.
• High Directivity: They offer higher directivity, focusing the signal in a specific direction.
• Robust Construction: Helical antennas are generally robust and durable.

Disadvantages (Drawbacks) of Helical Antennas

Despite their advantages, helical antennas also have some drawbacks:

• Large Size: They tend to be large, requiring more space for installation.
• Decreased Efficiency with More Turns: As the number of turns increases, the efficiency decreases. Maximum efficiency (around 80%) is typically achieved with 3 to 4 turns.
• Higher Cost: They can be more expensive compared to some other antenna types.