Antennas

An antenna is a transducer designed to transmit or receive radio waves which are a class of electromagnetic waves. In other words, antennas convert radio frequency electrical currents into electromagnetic waves and vice versa. more...

Home
Accessories, Parts
Accessory Bundles, Packages
Antennas
Audiovox
Kyocera, Qualcomm
LG, Touchpoint
Motorola
i Series, Nextel, i730, i80
Mixed Lots
Other Series
Startac
T720, T722, T730, T Series
V60, V300, V500, V Series
Nokia
Other Brands
Samsung
a460, a500, a Series
e105, e315, e713, e Series
i Series, i500, i600, i700
n200, n400, n Series
Other Series
r210, r225, r Series
s100, s105, s Series
x426, x427, x450, x Series
Sanyo
Batteries
Belt Clips, Holsters
Camera Attachments
Car Kits & Car Chargers
Cases, Pouches
Cradles, Cradle Chargers
Data Cables
Faceplates, Housings
Headsets-Corded
Keyboards
Keypads
LCD Screens
Manuals, User Guides
Memory Cards
Modems
Mounts, Holders
Other Accessories
Ringtones & Wallpaper
Screen Protectors
Software
Speakerphones
Straps & Charms
Styluses
Tools, Screwdrivers
Travel Chargers, Wall...
Unlocking Kits, Services
Bluetooth Wireless...
Cell Phones
PDAs & Pocket PCs
Phone & SIM Cards
Smartphones
Wholesale & Large Lots

Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless LAN, radar, and space exploration. Antennas usually work in air or outer space, but can also be operated under water or even through soil and rock at certain frequencies for short distances.

Physically, an antenna is an arrangement of conductors that generate a radiating electromagnetic field in response to an applied alternating voltage and the associated alternating electric current, or can be placed in an electromagnetic field so that the field will induce an alternating current in the antenna and a voltage between its terminals. Some antenna devices (parabola, horn antenna) just adapt the free space to another type of antenna.

Thomas Edison used antennas by 1885. Edison patented his system in U.S. Patent 465,971 . Antennas were also used in 1888 by Heinrich Hertz (1857-1894) to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed the emitter dipole in the focal point of a parabolic reflector. He published his work and installation drawings in Annalen der Physik und Chemie (vol. 36, 1889).

Terminology

The words antenna (plural: antennas) and "aerial" are used interchangeably; but usually a rigid metallic structure is termed an antenna and a wire format is called an aerial. The origin of the word antenna relative to wireless apparatus is attributed to Guglielmo Marconi. In 1895, while testing early radio apparatus in the Swiss Alps at Salvan, Switzerland in the Mont Blanc region, Marconi experimented with early wireless equipment. A 2.5 meter long pole, along which was carried a wire, was used as a radiating and receiving aerial element. In Italian a tent pole is known as l'antenna centrale, and the pole with a wire alongside it used as an aerial was simply called l'antenna. Until then wireless radiating transmitting and receiving elements were known simply as aerials or terminals. Marconi's use of the word antenna (Italian for pole) would become a popular term for what today is uniformly known as the antenna.

A Hertzian antenna is a set of terminals that does not require the presence of a ground for its operation (versus a Tesla antenna which is grounded ). A loaded antenna is an active antenna having an elongated portion of appreciable electrical length and having additional inductance or capacitance directly in series or shunt with the elongated portion so as to modify the standing wave pattern existing along the portion or to change the effective electrical length of the portion. An antenna grounding structure is a structure for establishing a reference potential level for operating the active antenna. It can be any structure closely associated with (or acting as) the ground which is connected to the terminal of the signal receiver or source opposing the active antenna terminal, (i.e., the signal receiver or source is interposed between the active antenna and this structure).

Read more at Wikipedia.org