Turnstile antenna

An axial-mode turnstile antenna for 136-137 MHz to receive data from weather satellites, consisting of a pair of driven crossed dipoles above a pair passive crossed dipoles serving as a reflector.
High gain axial mode Yagi turnstile array used to communicate with weather satellites on 136-137 MHz at Redu, Belgium. Each of the 6 components of the array consists of two 9-element Yagi antennas mounted on the same axis at right angles and fed in quadrature to radiate a narrow beam of circularly polarized radio waves

A turnstile antenna, or crossed-dipole antenna,[1] is a radio antenna consisting of a set of two identical dipole antennas mounted at right angles to each other and fed in phase quadrature; the two currents applied to the dipoles are 90° out of phase.[2][3] The name reflects the notion the antenna looks like a turnstile when mounted horizontally. The antenna can be used in two possible modes. In normal mode the antenna radiates horizontally polarized radio waves perpendicular to its axis. In axial mode the antenna radiates circularly polarized radiation along its axis.

Specialized normal mode turnstile antennas called superturnstile or batwing antennas are used as television broadcasting antennas. Axial mode turnstiles are widely used for satellite ground station antennas in the VHF and UHF bands, as circular polarization is often used for satellite communication since it is not sensitive to the orientation of the satellite antenna in space.

  1. ^ Milligan, Thomas (2005). "5 - Dipoles, Slots and Loops". Modern Antenna Design (2nd ed.). Hoboken, New Jersey: John Wiley & Sons, Inc. pp. 231–237. ISBN 978-0-471-45776-3.
  2. ^ Brown, George. "US Patent 2086976". Antenna system. Retrieved 14 January 2014. filed: September 20, 1935; granted: July 13, 1937
  3. ^ Kraus, John (1988). "16: Antennas for Special Applications: Feeding Applications". Antennas (2nd ed.). McGraw-Hill, Inc. pp. 726–729. ISBN 0-07-035422-7.