Aviation Antennas: Types, Patterns, and Use

062-01-02Pablo Asensio Martínez2026-04-012 min

Antennas are devices that allow the transition between a guided electric current and an electromagnetic wave in free space.

Basic Principles

  • Transmission: Electric current is converted into electromagnetic waves.
  • Reception: Electromagnetic waves induce an electric current in the antenna.
  • Reciprocity: The characteristics of an antenna (gain, radiation pattern) are identical for both transmitting and receiving.

Polarization

Polarization is defined by the orientation of the electric field (E) of the wave with respect to the direction of propagation.

  • Linear: The electric field oscillates in a single plane (Vertical or Horizontal). For optimal reception, the receiving antenna must have the same polarization as the transmitting one.
  • Circular: The electric field rotates as the wave advances. Used in weather radars to reduce rain "clutter" (echoes), as water droplets reverse the direction of rotation when reflecting the signal.
  • Elliptical: A general combination of the above.

Types of Antennas

  1. Dipole: The most basic form. Used in VOR and VHF communications.
  2. Loop Antenna: Used in older ADF receivers. It is directional and detects the source of the signal by seeking the "null" (minimum signal).
  3. Parabolic Antenna: Uses a curved reflector to focus energy into a narrow beam. High directivity and gain. Used in older radars.
  4. Slotted Planar Array: Flat antenna with slots, used in modern weather radars. It is more efficient, lighter, and aerodynamic than the parabolic, producing a beam with fewer side lobes.
  5. Helical Antenna: Can be directional or omnidirectional. Often used for circular polarization.
  6. Adcock Antenna: Array of vertical dipoles used in VDF (VHF Direction Finding) ground stations to determine the direction of an aircraft.

Location and Shadowing

The location of antennas on the aircraft is critical to avoid signal blocking by the aircraft's own structure (wings, fuselage, empennage).

  • Communications and Ground Navigation Antennas (VOR, DME, ADF): Generally located on the bottom of the fuselage to have line of sight with ground stations.
  • Satellite Antennas (GNSS/GPS): Must be located on the top of the fuselage to have a direct view of the sky and satellites.
  • Glide Slope Antenna: Generally located in the nose of the aircraft or behind the radome.

Note: During turns, the wing can block the signal between the antenna and the ground station/satellite, causing temporary signal loss.

Weather Radar

Airborne weather radars typically operate in the X-Band (8-12 GHz), with a wavelength of approx. 3 cm. They require highly directional antennas (narrow beam) to accurately locate storms.