What is a Super-Turnstile or Batwing Antenna?

A Super-Turnstile Antenna or Batwing Antenna is a specialized type of crossed dipole antenna where two pairs of identical batwing-shaped elements are mounted vertically at right angle around a common mast. The two dipoles are fed 90 degrees out of phase to generate an omnidirectional pattern. This antenna radiates horizontally polarized radiation in the horizontal plane. The super turnstile allows complete frequency coverage of the VHF/UHF commercial broadcast bands using a single antenna. Each group of four elements at a single level is referred to as a bay. The figure below shows a one-bay and a four-bay super turnstile antenna.

To reduce power radiated in the unwanted axial directions, multiple bays are fed in phase and are stacked vertically with a spacing of approximately one wavelength in order to create a collinear array. An omnidirectional radiation pattern is generated with increased horizontal gain, suitable for terrestrial broadcasting. 

The advantage of the “batwing” design for television broadcasting is that it has a wide bandwidth. This makes the antenna design suitable for broadcasters who wish to use a single antenna to transmit multiple television signals and thus made the batwing the preferred antenna for low-band TV stations. It was the first widely used television broadcasting antenna.