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Array of four axial-mode helical antennas used as a satellite tracking-acquisition antenna, Pleumeur-Bodou, FranceAxial-mode helical antenna:
(B) Central support,
(C) Coaxial cable feedline,
(E) Insulating supports for the helix,
(R) Reflector ground plane,
(S) Helical radiating wire
A helical antenna is an antenna consisting of one or more conducting wires wound in the form of a helix. A helical antenna made of one helical wire, the most common type, is called monofilar, while antennas with two or four wires in a helix are called bifilar, or quadrifilar, respectively.
In most cases, directional helical antennas are mounted over a ground plane, while omnidirectional designs may not be. The feed line is connected between the bottom of the helix and the ground plane. Helical antennas can operate in one of two principal modes: normal or axial.
In the normal mode or broadside helical antenna, the diameter and the pitch of the aerial are small compared with the wavelength. The antenna acts similarly to an electrically short dipole or monopole, equivalent to a 1/4 wave vertical and the radiation pattern,[citation needed] similar to these antennas is omnidirectional, with maximum radiation at right angles to the helix axis. For monofilar designs the radiation is linearly polarized parallel to the helix axis. These are used for compact antennas for portable hand held as well as mobile vehicle mount two-way radios, and in larger scale for UHF television broadcasting antennas. In bifilar or quadrifilar implementations, broadside circularly polarized radiation can be realized.
In the axial mode or end-fire helical antenna, the diameter and pitch of the helix are comparable to a wavelength. The antenna functions as a directional antenna radiating a beam off the ends of the helix, along the antenna's axis. It radiates circularly polarized radio waves. These are used for satellite communication. Axial mode operation was discovered by physicist John D. Kraus[1]
^Kraus, J.D. (March 1949). "The Helical Antenna". Proceedings of the I.R.E. 37 (3): 263–272. doi:10.1109/JRPROC.1949.231279.
A helicalantenna is an antenna consisting of one or more conducting wires wound in the form of a helix. A helicalantenna made of one helical wire, the...
waves as in resonant antennas. All except the helicalantenna have linear polarization. Unidirectional traveling-wave antennas are terminated by a resistor...
An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves...
The Moxon antenna or Moxon rectangle is a simple and mechanically rugged two-element parasitic array, single-frequency antenna. It takes its name from...
jacket to protect the antenna. The rubber ducky antenna is a form of normal-mode helicalantenna. Electrically short antennas like the rubber ducky are...
radio – a planar helicalantenna – or a separate, rotatable, furniture-sized rack looped with wire – a frame antenna. Ferrite loop antennas are made by winding...
this antenna in 1946. It is very popular in the United States. The antenna can be erected as horizontal dipole, as sloper, or an inverted-V antenna. With...
S. patent 3,278,937, "Antenna near field coupling system". 1966. Van Voorhies, U.S. patent 6,218,998, "Toroidal helicalantenna" Gene Koonce, U.S. patent...
distinction arises solely from different desirable radiation patterns of the antennas (near vertical for NVIS, near horizontal for conventional long-range skywave...
Electromagnetics Code, or NEC, is a popular antenna modeling computer program for wire and surface antennas. It was originally written in FORTRAN during...
the dipole antenna or 37.5 ohms. Common types of monopole antenna are whip rubber ducky helical random wire umbrella inverted-L and T-antenna folded unipole...
3 inches) wide. Lunokhod 1 was equipped with a cone-shaped antenna, a highly directional helicalantenna, four television cameras, and special extendable devices...
high definition meant a line standard greater than 240 lines. helicalantenna A radio antenna with one or more conductive wires, wound up in the shape of...
via the adjacent array of larger box-shaped cavities. The prominent helicalantenna received telecommands from a ground station. Launched by NASA aboard...
The Sloper Antenna is a slanted Dipole antenna. While horizontal dipoles required two large support masts, this antenna type only needs one large mast...
wheels. Lunokhod 1 was equipped with a cone-shaped antenna, a highly directional helicalantenna, four teleray spectrometer, an x-ray telescope, cosmic-ray...
independently-powered wheels. They were equipped with a cone-shaped antenna, a highly directional helicalantenna, television cameras, and special extendable devices...
following antennas are usually employed: Dipole antennas, short antennas, parabolic and other reflector antennas, horn antennas, periscope antennas, helical antennas...
resonant load frequencies have negligible amplitudes. The effectiveness of helical strakes for reducing vortex induced vibration was discovered in 1957 by...
Dublin, Ireland Hybrid helical spiral staircase in a former London City Hall The term "helical stair" has many synonyms:: 53 The helical stair is also called...
the antenna is symmetrical about an axis (as is the case in dipole, helical and some parabolic antennas) a unique graph is sufficient. Each antenna supplier/user...
subpackage which usually carried one or two of the experiments and the antenna gimbal assembly. On Apollo 12, 13, and 14, the second subpackage also stored...
including a five-element UHF bifilar helicalantenna array, two X band horn antennas, and a biconical antenna for telemetry and control. The UHF transponder...
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