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4-square Antenna

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A 4-square antenna is a type of directional antenna array commonly used in amateur radio, particularly for low-frequency (LF) and high-frequency (HF) communications. It consists of four vertical antennas arranged in a square configuration, with each antenna oriented in a different direction (north, south, east, and west). This design allows for effective radiation patterns and excellent performance in specific directions.

Key Characteristics of a 4-Square Antenna:

  1. Design:
    • The 4-square antenna consists of four vertical elements, typically quarter-wave vertical antennas, arranged at the corners of a square. The elements are usually fed with a common feed line.
    • The spacing between the elements is typically around one-quarter wavelength at the operating frequency.
  2. Radiation Pattern:
    • The 4-square antenna produces a highly directional radiation pattern, with the main lobe directed toward the desired communication direction. By adjusting the phase of the feed to each element, the antenna can be made to favor specific directions while minimizing radiation in others.
  3. Impedance:
    • The feed point impedance of a 4-square antenna is typically around 50 ohms, making it compatible with most common radio equipment.
  4. Phasing Network:
    • A phasing network is often used to control the phase relationship between the elements, allowing the operator to switch the antenna’s directionality. This can be done using a switch or relay system.

Advantages:

  1. High Gain:
    • The 4-square antenna provides significant gain compared to single vertical antennas, making it effective for long-distance (DX) communications.
  2. Directional Control:
    • The ability to switch the direction of the antenna allows operators to focus on specific stations or areas, improving signal quality and reducing interference.
  3. Low Angle Radiation:
    • The design of the 4-square antenna typically results in low-angle radiation, which is advantageous for long-distance communications, especially on HF bands.
  4. Compact Design:
    • While it requires some space, the 4-square antenna can be more compact than other high-gain directional antennas, such as Yagi arrays.

Disadvantages:

  1. Space Requirement:
    • Although more compact than some other arrays, a 4-square antenna still requires a reasonable amount of space for installation, especially to maintain proper spacing between elements.
  2. Complexity:
    • The design and construction of a 4-square antenna can be more complex than simpler antennas, particularly in terms of the phasing network and feed system.
  3. Ground Dependence:
    • The performance of a 4-square antenna can be affected by ground conditions, requiring a good ground plane or radial system for optimal operation.

Applications:

The 4-square antenna is commonly used in amateur radio for various applications, including:

  • DXing: Long-distance communication on HF bands.
  • Contesting: Providing a competitive edge in radio contests by allowing quick direction switching.
  • Field Operations: Portable operations where a compact, effective antenna is needed.

In summary, the 4-square antenna is a highly effective directional antenna array that offers high gain, directional control, and low-angle radiation, making it a popular choice for amateur radio operators engaged in long-distance communications.