A batwing or super turnstile antenna is a type of broadcasting antenna used at VHF and UHF frequencies, named for its distinctive shape which resembles a bat wing or

bow tie The bow tie is a type of necktie. A modern bow tie is tied using a common shoelace knot, which is also called the bow knot for that reason. It consists of a ribbon of fabric tied around the collar of a shirt in a symmetrical manner so that t ...

. Stacked arrays of batwing antennas are used as

television broadcasting A television network or television broadcaster is a telecommunications network for distribution of television program content, where a central operation provides programming to many television stations or pay television providers. Until the mid- ...

antennas due to their

omnidirectional Omnidirectional refers to the notion of existing in every direction. Omnidirectional devices include: * Omnidirectional antenna, an antenna that radiates equally in all directions * VHF omnidirectional range, a type of radio navigation system for ...

characteristics. Batwing antennas generate a horizontally polarized signal. The advantage of the "batwing" design for television broadcasting is that it has a wide

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

. It was the first widely used television broadcasting antenna.

Design and characteristics

Batwing antennas are a specialized type of crossed dipole antenna, a variant of the

turnstile antenna A turnstile antenna, or crossed-dipole antenna, 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 ph ...

. Two pairs of identical vertical batwing-shaped elements are mounted at right angles around a common mast. Element “wings” on opposite sides are fed as a dipole. To generate an omnidirectional pattern, the two dipoles are fed 90°

out of phase In physics and mathematics, the phase of a periodic function F of some real variable t (such as time) is an angle-like quantity representing the fraction of the cycle covered up to t. It is denoted \phi(t) and expressed in such a scale that it ...

. The antenna radiates horizontally polarized radiation in the horizontal plane. Each group of four elements at a single level is referred to as a ''bay''. The

radiation pattern In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: “A ...

is close to omnidirectional but has four small lobes (maxima) in the directions of the four elements. To reduce power radiated in the unwanted axial directions, in broadcast applications multiple bays fed in phase are stacked vertically with a spacing of approximately one

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...

, to create a collinear array. This generates an omnidirectional radiation pattern with increased horizontal gain (more of the energy radiated in horizontal directions and less into the sky or down at the earth), suitable for terrestrial broadcasting. The "batwing" shape of the elements is used because it gives the antenna a wide

of approximately 20% of operating frequency at a

VSWR In radio engineering and telecommunications, standing wave ratio (SWR) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide. Impedance mismatches result in standing waves along the transmi ...

of 1.1:1. 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 lowband TV stations (channels 2–6) in the early days of broadcast television.

References

Sources

* * * * Antennas (radio) Radio electronics Radio frequency antenna types {{radio-comm-stub

Design and characteristics

See also

References

Sources