Turnstile Antenna: Advantages and Disadvantages

This page explores the pros and cons of turnstile antennas, covering the basics of their operation and applications.

What is a Turnstile Antenna?

A turnstile antenna is a type of array antenna typically operating in the 30MHz to 3GHz frequency range. To increase directivity, multiple turnstile antennas are often combined.

These antennas can operate in different modes, most commonly:

• Normal Mode: Radiates horizontally polarized waves.
• Axial Mode: Radiates circularly polarized waves.

Turnstile antennas find applications in various fields, including:

• VHF communications
• FM broadcasting
• Military communications
• Satellite communications

Double turnstile antenna

The image above shows a double turnstile antenna. It consists of two dipoles positioned at right angles to each other. One dipole is connected to a 90-degree phasing cable for quadrature connection. Depending on specific requirements, additional sets of dipoles can be added. The mast is typically made of insulating materials like PVC pipe or wooden dowels.

Benefits or Advantages of Turnstile Antennas

Here are some key advantages of using a turnstile antenna:

• Simple Construction: Relatively easy to build, as it primarily uses two linear dipoles.
• Higher Gain: When multiple turnstile antennas are stacked, they provide significant gain. A good example is the Super-turnstile antenna.
• Improved Directivity: Offers better directional control of the signal.

Drawbacks or Disadvantages of Turnstile Antennas

Despite their benefits, turnstile antennas also have some limitations:

• Poor Horizon Performance: Performance is not ideal near the horizon.
• Image Quality Limitations: Optimal image quality is generally limited to a +/-30-degree field of view about the vertical.
• Radiation Power Loss: The radiation power is approximately 3 dB less compared to the maximum radiation of a λ/2 dipole transmitting the same amount of power.