Whip antennaA whip antenna is an antenna consisting of a single straight flexible wire or rod, often mounted above some

type of conducting surface called a ground plane.[1] The bottom end of the whip is connected to the radio

receiver or transmitter. They are designed to be flexible so that they won't break off, and the name is derived

from their whip-like motion when disturbed. Often whip antennas for portable radios are made of a series of

interlocking telescoping metal tubes, so they can be retracted when not in use. They are the most common

type of monopole antenna. These antennas are widely used for hand-held radios such as cell phones, cordless

phones, walkie-talkies, FM radios, boom boxes, Wifi enabled devices, and GPS receivers, and also attached to

vehicles as the antennas for car radios and two way radios for police, fire and aircraft.

The whip antenna can be considered half of a dipole 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. Vertical

whip antennas are widely used for nondirectional radio communication on the surface of the Earth, where the

direction to the transmitter (or the receiver) is unknown or constantly changing, for example in portable FM

radio receivers, walkie-talkies, and two-way radios in vehicles. This is because they transmit (or receive)

equally well in all horizontal directions, while radiating little radio energy up into the sky where it is wasted.

Length

Whip antennas are normally designed as resonant antennas. Therefore the length of the whip antenna is

determined by the wavelength of the radio waves used. The most common length is one-quarter of the

wavelength, called a quarter-wave whip (although this type of antenna is often shortened by the use of a

loading coil; see Electrically short whips below). For example, the common quarter-wave whip antennas used

on FM radios in the USA are approximately 75 cm long, which is roughly one-quarter the length of radio waves

in the FM radio band, which are 2.78 to 3.41 meters long. Half-wave whip antennas are also common.

Whip antennas are very common in hand-held radios. This is a variation called aRubber Ducky antenna on a

handheld UHF CB  transciever.

Turnstile antennaA turnstile antenna is a set of two dipole antennas aligned at right angles to each other and fed 90 degrees

out-of-phase. The name reflects that the antenna looks like a turnstile when mounted horizontally. When

mounted horizontally the antenna is nearly omnidirectional on the horizontal plane. When mounted vertically

the antenna is directional to a right angle to its plane and iscircularly polarized. The turnstile antenna is often

used for communication satellites because, being circularly polarized, the polarization of the signal doesn't

rotate when the satellite rotates.

The principles of the turnstile antenna are also applicable to Yagi and Log-periodic antennas.

A random wire antenna (or long-wire antenna) is a radio frequency antenna consisting of a wire whose

length does not bear a relation to the wavelength of the radio waves used, but is typically chosen more for

convenience. This type of antenna sometimes is called the zig-zag antenna, as it may be strung back and

forth between trees just to get enough wire into the air. For example, an antenna for 3MHz might be 20 m

(66 ft) - 40 m (131 ft) long. Such antennas are usually not as effective as antennas whose length is

adjusted to resonate at the wavelength to be used. They are widely used as receiving antennas on

the long wave, medium wave, and short wavebands, as well as transmitting antennas on these bands for

small outdoor, temporary or emergency transmitting stations, as well as in situations where more

permanent antennas cannot be installed. Random wire antennas are a type of monopole antenna and the

other side of the receiver or transmitter antenna terminal must be connected to an earth ground.

Radiation pattern

The radiation pattern of a straight random wire antenna is unpredictable and depends on its electrical

length, it may have several lobes at angles to the antenna axis.[1] The radiation will drop off to zero on the

axis. A folded or zig-zag antenna will have an even more unpredictable pattern.

Construction

Usually, it consists of a long (at least one quarter wavelength) wire with one end connected to the radio

and the other in free space, arranged in any way most convenient for the space available. Ideally, it is a

straight wire strung as high as possible between trees or buildings, the ends insulated from supports

with strain insulators. Typically it is made from number 12 or 14 AWG (1.6 to 2.0 mm (0 in) diameter)

copperclad wire. Folding (to fit in space available) will reduce effectiveness and make theoretical analysis

extremely difficult. (The added length helps more than the folding typically hurts.)

If used for transmitting, a random wire antenna usually will also require an antenna tuner, as it has an

unpredictable impedance that varies with frequency.[2] One side of the output of the tuner is connected

directly to the antenna, without a transmission line, the other to a good earth ground. One-

quarter wavelength works best, and one half wavelength will work poorly with most tuners. [3][4] Since the

antenna is located very close to the transmitter, RF feedback can be an issue. RF feedback can be

minimized by selecting a wire length that causes the low feed-point impedance at a current loop to occur

at the transmitter.[2] Alternately, a remote tuner can be fed with feedline, and the tuner located on the

antenna.

Horn antenna

A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguideshaped like

a horn to direct the radio waves. Horns are widely used as antennas at UHF andmicrowave frequencies, above

300 MHz.[1] They are used as feeders (called feed horns) for larger antenna structures such as parabolic

antennas, as standard calibration antennas to measure thegain of other antennas, and as directive antennas

for such devices as radar guns, automatic door openers, and microwave radiometers.[2] Their advantages are

moderate directivity (gain), low SWR, broad bandwidth, and simple construction and adjustment.[3]

One of the first horn antennas was constructed in 1897 by Indian radio researcher Jagadish Chandra Bose in

his pioneering experiments with microwaves.[4] In the 1930s the first experimental research (Southworth and

Barrow, 1936) and theoretical analysis (Barrow and Chu, 1939) of horns as antennas was done.[5] The

development of radar in World War 2 stimulated horn research. The corrugated horn proposed by Kay in 1962

has become widely used as a feed horn for microwave antennas such as satellite dishes and radio telescopes.

[5]

An advantage of horn antennas is that since they don't have any resonant elements, they can operate over a

wide range of frequencies, a wide bandwidth. The useable bandwidth of horn antennas is typically of the order

of 10:1, and can be up to 20:1 (for example allowing it to operate from 1 GHz to 20 GHz).[1] The input

impedance is slowly-varying over this wide frequency range, allowing low VSWR over the bandwidth.[1]The gain

of horn antennas ranges up to 25 dBi, with 10 - 20 dBi being typical.[1]

Parabolic antenna

A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional

shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly

called a dish antenna or parabolic dish. The main advantage of a parabolic antenna is that it is

highly directive; it functions similarly to asearchlight or flashlight reflector to direct the radio waves in a narrow

beam, or receive radio waves from one particular direction only. Parabolic antennas have some of the

highest gains, that is they can produce the narrowest beam width angles, of any antenna type.[1] In order to

achieve narrow beamwidths, the parabolic reflector must be much larger than the wavelengthof the radio

waves used, so parabolic antennas are used in the high frequency part of theradio spectrum,

at UHF and microwave (SHF) frequencies, at which wavelengths are small enough that conveniently sized

dishes can be used.

Parabolic antennas are used as high-gain antennas for point-to-point communication, in applications such

as microwave relay links that carry telephone and television signals between nearby cities, wireless

WAN/LAN links for data communications, satellite and spacecraft communication antennas, and radio

telescopes. Their other large use is in radarantennas, which need to emit a narrow beam of radio waves to

locate objects like ships and airplanes. With the advent of home satellite television dishes, parabolic antennas

have become a ubiquitous feature of the modern landscape.

Patch antennaA patch antenna (also known as a rectangular microstrip antenna) is a type of radio antenna with a low profile,

which can be mounted on a flat surface. It consists of a flat rectangular sheet or "patch" of metal, mounted over

a larger sheet of metal called a ground plane. The assembly is usually contained inside a plastic radome, which

protects the antenna structure from damage. Patch antennas are simple to fabricate and easy to modify and

customize. They are the original type of microstrip antenna described by Howell[1]; the two metal sheets

together form a resonant piece of microstrip transmission line with a length of approximately one-

half wavelength of the radio waves. The radiation mechanism arises from discontinuities at each truncated

edge of the microstrip transmission line.[2] The radiation at the edges causes the antenna to act slightly larger

electrically than its physical dimensions, so in order for the antenna to be resonant, a length of microstrip

transmission line slightly shorter than one-half a wavelength at the frequency is used. A patch antenna is

usually constructed on adielectric substrate, using the same materials and lithography processes used to

make printed circuit boards.

Yagi-Uda AntennaA Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional antennaconsisting of a

driven element (typically a dipole or folded dipole) and additional parasitic elements(usually a so-

called reflector and one or more directors). The reflector element is slightly longer (typically 5% longer)

than the driven dipole, whereas the so-called directors are a little bit shorter. This design achieves a very

substantial increase in the antenna's directionality and gain compared to a simple dipole.[1]

Highly directional antennas such as the Yagi-Uda are commonly referred to as "beam antennas" due to

their high gain. However the Yagi-Uda design only achieves this high gain over a rather narrow

bandwidth, making it more useful for various communications bands (including amateur radio) but less

suitable for traditional radio and television broadcast bands. Amateur radiooperators ("hams") frequently

employ these for communication on HF, VHF, and UHF bands, often constructing such antennas

themselves ("homebrewing"), leading to a quantity of technical papers and software. Wideband antennas

used for VHF/UHF broadcast bands include the lower-gain log-periodic dipole array, which is often

confused with the Yagi-Uda array due to its superficially similar appearance. That design along with

other phased arrays have electrical connections on each element, whereas the Yagi-Uda design operates

on the basis of electromagnetic interaction between the "parasitic" elements and the one driven (dipole)

element.

The Yagi-Uda array was invented in 1926 by ShintaroUda of Tohoku Imperial University, Japan, with a

lesser role played by his colleagueHidetsuguYagi. However the "Yagi" name has become more familiar

with the name of Uda often omitted.

Marconi Antenna

The term "Marconi antenna" usually refers to a two part antenna consisting of a vertical portion and a "reflective" or "ground" portion. When constructed properly, it is very similar to a vertically oriented dipole, in that one element is "up" and the other "down". The reflective portion is not always a physical element, but often either natural earth ground (where the soil conductivity is sufficient) or ground "radials" - a set of wires along or just beneath the ground that act as the reflective portion. A Marconi antenna is an omni-directional (same transmit/receive in all directions) antenna that has good long distance characteristics on HF (high frequency) and MW (medium wave, or AM) frequencies. A Marconi is typically built with a 1/4 wavelength vertical element, and similar length radial(s). For

example, the full wavelength for 7MHz is about 133ft. A 1/4 wavelength vertical element (and each radial) would therefore be about 33.5ft. Most AM broadcast stations use some variation of a Marconi antenna. Since an AM station at 1050 on an AM dial is equal to 1.050MHz and therefore a wavelength of over 990ft, a 1/4 wavelength vertical element would be almost 223ft for that station! The antenna was originally made using telescopic fiber glass tubes and then covered with a copper film to make them look electrically like a huge copper tube. The antenna was made by a company located in London called Bantex Antennas. This company shut down and the team of engineer was take over and built a new company called Renair Antennae Ltd, they carried manufacturing these antennas for some years. These antennas were ordered from Marconi to be mount overseas mainly. They were real big monsters!

Discone antenna

A discone antenna is a version of a biconical antenna in which one of the cones is replaced by a disc. It is

usually mounted vertically, with the disc at the top and the cone beneath.

Omnidirectional, vertically polarized and exhibiting unity gain, it is exceptionally wideband, offering a frequency

range ratio of up to ~10:1. The radiation pattern in the horizontal plane is quite narrow, making

its sensitivity highest in the plane tangent to the Earth's surface.

Helical antenna

A helical antenna is an antenna consisting of a conducting wire wound in the form of a helix. In most cases,

helical antennas are mounted over a ground plane. 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 mode or axial mode.

In the normal mode or broadside helix, the dimensions of the helix (the diameter and the pitch) are small

compared with the wavelength. The antenna acts similarly to an electrically short dipole ormonopole, and

the radiation pattern, similar to these antennas is omnidirectional, with maximum radiation at right angles to the

helix axis. The radiation is linearly polarized parallel to the helix axis.

In the axial mode or end-fire helix, the dimensions 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.

Normal-mode helical

Radiating at 90 degrees from the axis of the helix this design is efficient as a practical reduced-length

radiator when compared with the operation of other types such as base-loaded, top-loaded or center-

loaded whips. They are typically used for applications where reduced size is a critical operational factor.

These simple and practical "Helicals" were primarily designed to replace very large antennas. Their

reduced size is therefore most suitable for Mobile and Portable High-frequency (HF) communications in

the 1 MHz to 30 MHz operating range.

A common form of normal-mode helical antenna is the Rubber Ducky antenna used in portable radios. The loading provided

by the helix allows the antenna to be shorter than its electrical length of a quarter-wavelength.

Usually wound in a linear "spiroidal" pattern (constant parallel spaced turns) providing consistent uniform

radiation as a reduced sized equivalent in respect to the standard 1/4 wave antenna. This concept was

proven practical by an Australian design.[citation needed]

An effect of this type of concertinaed 'reduced size 1/4 wave' is that the matching impedance is changed

from the nominal 50 ohms to between 25 to 35 ohms base impedance. This does not seem to be adverse

to operation or matching with a normal 50 ohm transmission line, provided the connecting feed is the

electrical equivalent of a 1/2 wave at the frequency of operation.

Another example of the type as used in mobile communications is "spaced constant turn" in which two or

more different linear windings are wound on a single former and spaced so as to provide an efficient

balance between capacitance and inductance for the radiating element at a particular resonant frequency.

Many examples of this type have been used extensively for 27 MHz CB radio with a wide variety of

designs originating in the US and Australia in the late 1960s. Multi-frequency versions with plug-in taps

have become the mainstay for multi-band Single-sideband modulation (SSB) HF communications.

Most examples were wound with copper wire using a fiberglass rod as a former. This flexible radiator is

then covered with heat-shrink tubingwhich provides a resilient and rugged waterproof covering for the

finished mobile antenna.

These popular designs are still in common use today (2010) and have been universally adapted as

standard FM receiving antennas for many factory produced motor vehicles as well as the existing basic

style of aftermarket HF and VHF mobile helical. The broadside helixes most common use is in the Rubber

Ducky antenna found on most portable VHF and UHF radios.

Axial-mode helical

End fire helical satellite communications antenna, Scott Air Force base, Illinois, USA. Satellite communication systems often

usecircularly polarized radio waves, because the satellite antenna may be oriented at any angle in space without affecting

the transmission, and axial mode (end fire) helical antennas are often used as the ground antenna.

In the axial mode, the helix dimensions are at or above the wavelength of operation. The antenna then

falls under the class of waveguide antennas, and produces radio waves with circular polarization.

The main lobes of the radiation pattern are along the axis of the helix, off both ends. Since in a directional

antenna only radiation in one direction is wanted, the other end of the helix is terminated in a flat metal

sheet or screen reflector to reflect the waves forward.

In radio transmission, circular polarization is often used where the relative orientation of the transmitting

and receiving antennas cannot be easily controlled, such as in animal tracking andspacecraft

communications, or where the polarization of the signal may change, so end-fire helical antennas are

frequently used for these applications. Since large helices are difficult to build and unwieldy to steer and

aim, the design is commonly employed only at higher frequencies, ranging from VHF up to microwave.

The helix in the antenna can twist in two possible directions: right-handed or left-handed, as defined by

the right hand rule. In an axial-mode helical antenna the direction of twist of the helix determines the

polarization of the radio waves: a left-handed helix radiates left-circularly-polarized radio waves, a right-

handed helix radiates right-circularly-polarized radio waves. Helical antennas can receive signals with any

type of linear polarization, such as horizontal or vertical polarization, but when receiving circularly

polarized signals the handedness of the receiving antenna must be the same as the transmitting antenna;

left-hand polarized antennas suffer a severe loss of gain when receiving right-circularly-polarized signals,

and vice versa.

The dimensions of the helix are determined by the wavelength λ of the radio waves used, which depends

on the frequency. In axial-mode operation, the spacing between the coils should be approximately one-

quarter of the wavelength (λ/4), and the diameter of the coils should be approximately the wavelength

divided by pi (λ/π). The length of the coil determines how directional the antenna will be as well as its

gain; longer antennas will be more sensitive in the direction in which they point.

Rhombic antenna

Rhombic antenna signal-gathering action compared to other end-fire, backfire and traveling-wave types.

A rhombic antenna is a broadband directional antenna co-invented by Edmond Bruce and HaraldFriis,

[1] mostly commonly used in HF (high frequency, also calledshortwave) ranges.

Technical Detail

It is named after its "rhombic" diamond shape, with each side typically at least onewavelength (λ) or

longer in length. Each vertex is supported by a pole, typically at least one wavelength high. A horizontal

rhombic antenna (picture below) radiates horizontally polarised waves. Its principal advantages over other

choices of antenna are its simplicity, high forward gain and the ability to operate over a wide range of

frequencies.

It is typically fed at one of the two sharper angles through a balanced transmission line. Less commonly, it

can be fed with coaxial cable through a balun transformer. The opposite end is either left open for bi-

directional use, or terminated at the opposite sharp angle with a non-inductive resistor. It is directional

towards the resistor end, so the termination end points towards the region of the world it is designed to

serve. Even when unterminated (bi-directional) the rhombic is not perfectly bi-directional. This is because

of losses in the system primarily caused by radiation, conductor resistance, and coupling to the lossy soil

below the antenna.

The rhombic antenna, like other horizontal antennas, can radiate at elevation angles close to the horizon

or at higher angles depending on its height above ground relative to the operating frequency and its

physical construction. Likewise, its beam can be narrow or broad, depending primarily on its length. A

proper combination of size, height, and operating frequency make it fit for medium or long range

communication.

A rhombic requires a large area of land — especially if several antennas are installed to serve a variety of

geographic regions at different distances or directions or to cover widely different frequencies. The

rhombic suffers from efficiency problems due to earth losses below the antenna, significant power-

wasting spurious lobes, termination losses, and the inability to maintain constant current along the length

of the conductors. Typical radiation efficiency is in the order of 40-50%. The low efficiency significantly

reduces gain for a given main lobe beamwidth when compared to other arrays of the same beamwidth.[2]

At the expense of system simplicity, it is possible to improve efficiency by recirculation of power wasted in

the termination resistance of unidirectional rhombics. Use of a recirculating termination system can move

efficiency into the 70-80% range by combining power that would have been wasted in the termination with

the transmitter power. Such systems bring a low-loss balanced line back from the termination end to the

feedpoint through a matching and phasing system. Energy that would otherwise dissipated in the

termination resistance is applied in-phase with the excitation.

Prior to WWII, the rhombic was one of the most popular point-to-point high frequency antenna arrays.

After WWII the rhombic largely fell out of favor for shortwave broadcast and point-to-point

communications work, being replaced by log periodics and curtain arrays. Larger log periodics provide

wider frequency coverage with comparable gain to rhombics. Distributed feed curtains or HRS curtain

arrays provided a cleaner pattern, ability to steer the pattern in elevation and azimuth, much higher

efficiency, and significantly higher gain in less space. However, rhombic antennas are used in cases

where the combination of high forward gain (despite the losses described above) and large operating

bandwidth cannot be achieved by other means.

The rhombic remains one of the least complex medium-gain options for sustained long distance

communications over point-to-point circuits. Rhombics also handle considerable transmitter power, since

they have essentially uniform voltage and current distribution. The rhombic's low cost, simplicity,

reliability, and ease of construction sometimes outweighs performance advantages offered by other more

complex arrays.[3][4][5]

NOTCH Antenna(electromagnetism) Microwave antenna in which the radiation pattern is determined by the size and shape of a notch or slot in a radiating surface. 

Cassegrain antenna

In telecommunications and radar, a Cassegrain antenna is a parabolic antenna in which the feed radiator is

mounted at or behind the surface of the concave main parabolic reflector dish and is aimed at a

smaller convex secondary reflector suspended in front of the primary reflector. The beam of radio waves from

the feed illuminates the secondary reflector, which reflects it back to the main reflector dish, which reflects it

forward again to form the desired beam.

This design is an alternative to the most common parabolic antenna design, called "front feed", in which

the feed antenna itself is mounted suspended in front of the dish at the focus. One advantage of the

Cassegrain design is that the feed antennas and associated waveguides and "front end" electronics can be

located on or behind the dish, rather than suspended in front where they block part of the outgoing beam.

[1] Therefore this design is used for antennas with bulky or complicated feeds, [1] such as satellite

communication ground antennas, radio telescopes, and the antennas on some communication satellites.

Another reason for using the Cassegrain design is that modifying the shape of the secondary reflector offers

additional possibilities for shaping the beam pattern of the antenna over what is possible with a simple

parabolic antenna.

Loop antenna

A loop antenna is a radio antenna consisting of a loop (or loops) of wire, tubing, or other electrical

conductor with its ends connected to a balanced transmission line. Within this physical description there are

two very distinct antenna designs: the small loop (or magnetic loop) with a size muchsmaller than a

wavelength, and the resonant loop antenna with a circumference approximately equal to the wavelength.

Small loops have a poor efficiency and are mainly used as receiving antennas at low frequencies. Except for

car radios, almost every AM broadcast receiver sold has such an antenna built inside of it or directly attached

to it. These antennas are also used for radio direction finding. A technically small loop, also known as a

magnetic loop, should have a circumference of one tenth of a wavelength or less. This is necessary to ensure a

constant current distribution round the loop. As the frequency or the size are increased, a standing wave starts

to develop in the current, and the antenna starts to have some of the characteristics of a folded dipole antenna

or a self-resonant loop.

Self-resonant loop antennas are larger. They are typically used at higher frequencies, especially VHF and UHF,

where their size is manageable. They can be viewed as a form of folded dipole and have somewhat similar

characteristics. The radiation efficiency is also high and similar to that of a dipole.

Biconical antenna

In radio systems, a biconical antenna is a broad-bandwith antenna made of two roughly conical conductive

objects, nearly touching at their points. [1] Biconical antennas are broadband dipole antennas, typically

exhibiting a bandwidth of 3 octaves or more.

The conical conductors need not be solid cones nor infinitely long. A simple conical monopole antenna is a wire

approximation of the solid biconical antenna and has increased bandwidth (over a simple monopole). Abowtie

antenna is simple broadband wire approximation in two dimensions of a biconic dipole antenna (used, for

example, for UHF television reception). A common variant is the Discone antenna, where one of the cones has

a vertex angle of 180 degrees (or is reduced to a plane).

The biconical antenna has a broad bandwidth because it is an example of a travelling wave structure; the

analysis for a theoretical infinite antenna resembles that of a transmission line. For an infinite antenna,

thecharacteristic impedance at the point of connection is a function of the cone angle only and is independent

of the frequency. Practical antennas have finite length and a definite resonant frequency. [1]

Biconical (or "Bicon") antennas are often used in electromagnetic interference (EMI) testing either for immunity

testing, or emissions testing. While the Bicon is very broadband, it exhibits poor efficiency at low frequencies,

resulting in low field strengths when compared to the input power. Log periodic dipole arrays, yagi-uda arrays,

and reverberation chambers have shown to achieve much higher field stregths for the power input than a

simple biconical antenna in an anechoic chamber.