Whip antenna

A whip antenna is an antenna consisting of a straight flexible wire or rod. The bottom end of the whip is connected to the radio receiver or transmitter. The antenna is designed to be flexible so that it does not easily break, and the name is derived from the whip-like motion that it exhibits when disturbed. Whip antennas for portable radios are often made of a series of interlocking telescoping metal tubes, so they can be retracted when not in use. Longer ones, made for mounting on vehicles and structures, are made of a flexible fiberglass rod around a wire core and can be up to 35 ft (10 m) long. The most common type is the quarter-wave whip, which is approximately one-quarter of a wavelength long. Whips are the most common type of monopole antenna, and are used in the HF, VHF and UHF radio bands. They are widely used as the antennas for hand-held radios, such as cell phones, cordless phones, walkie-talkies, FM radios, boom boxes, Wi-Fi enabled devices, and GPS receivers, and are attached to vehicles as the antennas for car radios and two-way radios for wheeled vehicles and for aircraft. Larger versions mounted on roofs and radio masts are used as base station antennas for police, fire, ambulance, taxi, and other vehicle dispatchers.

The whip antenna is a monopole antenna, and like a vertical dipole has an omnidirectional radiation pattern, radiating equal radio power in all azimuthal directions (perpendicular to the antenna's axis), with the radiated power falling off with elevation angle to zero on the antenna's axis. Whip antennas 1/4 wavelength long or less (the most common type) have a single main lobe, with field strength maximum in horizontal directions, falling monotonically to zero on the axis. Antennas longer than a quarter wavelength have patterns consisting of several conical "lobes"; with radiation maxima at several elevation angles; the longer the electrical length of the antenna, the more lobes the pattern has.

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