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ANTENNASANTENNAS
A structure that is generally a metallic object, often a wire or group of wires, used to convert
high frequency signals into electromagnetic waves and vice
versa.
ANTENNA
A device whose function is to radiate
electromagnetic energy and/or
intercept electromagnetic
radiation
ANTENNA
Basic Consideration:
Maximum Power
Transfer
FIELDS OF AN ANTENNA
FIELDS OF AN ANTENNA
INDUCTION FIELDINDUCTION FIELD
Considered to extend out from the antenna
to a distance of D2/8λ
Near Field or Fresnel Region
RADIATION FIELDRADIATION FIELD
Considered to extend out from a distance of
2D2/λFar Field or
Fraunhoffer Region
TRANSITION ZONETRANSITION ZONEZone between the
two(2) regions
BASIC FORMULAS
ANTENNAS
T = 1/f
Where: T – time
F - frequency
λ = c/f
Where: λ – wavelength
F – frequency
C – velocity in free space
RADIATION PATTERN
ANTENNA PARAMETERS
A line drawn to join points in space which
have equal field intensity due to the
source.
RADIATION PATTERN
Major Lobe – the direction of maximum
radiationMinor Lobe – the
direction of minimum radiation
Null – the direction with radiation intensity
equal to zero.
a. Antenna a. Antenna heightheight
b. Power lossesb. Power losses
d. Thickness of the antenna d. Thickness of the antenna wirewire
RADIATION PATTERN
FACTORS WHICH DETERMINE THE RADIATION PATTERN OF
AN ANTENNA
c. Terminations at its c. Terminations at its endend
PRINCIPLE OF RECIPROCITYPRINCIPLE OF RECIPROCITY
The characteristics of antennas, such as impedance and radiation pattern are identical, regardless of use
for reception or transmission.
GENERAL CHARACTERISTICS OF ANTENNAS
ISOTROPIC ANTENNAISOTROPIC ANTENNA
An antenna that radiates uniformly in all directions in space
DIRECTIVE GAINDIRECTIVE GAIN
The ratio of the power density in a particular direction of one antenna to the power density that
would be radiated by an isotropic antenna.
HERTZIAN DIPOLE: 1.5 : 1 (1.76 dB)
HALF WAVE DIPOLE: 1.64 : 1 (2.15 dB)
GENERAL CHARACTERISTICS OF ANTENNAS
NOTESNOTES
The longer the antenna, the higher the directive gain
Non resonant antennas have higher directive gain than resonant antennas
GENERAL CHARACTERISTICS OF ANTENNAS
The directive gain of all practical antennas is greater than unity
DIRECTIVITY, DDIRECTIVITY, D
The gain in the direction of one of the major lobes in the antenna’s radiation pattern.
Maximum directive gain
GENERAL CHARACTERISTICS OF ANTENNAS
GENERAL CHARACTERISTICS OF ANTENNAS
POWER GAINPOWER GAIN
Overall gain considering losses and efficiency
Ap = %D
Where: % - antenna efficiency
D - directivity
ANTENNA RESISTANCEANTENNA RESISTANCE
The ratio of the applied voltage to the flowing current
AC resistance
GENERAL CHARACTERISTICS OF ANTENNAS
The ratio of the power radiated by the antenna to the square
1. RADIATION RESISTANCE, Rr1. RADIATION RESISTANCE, Rr
Antenna and ground resistance
Discharge or corona effects
GENERAL CHARACTERISTICS OF ANTENNAS
Losses in imperfect dielectric very near the antenna
Eddy current loss
2. LOSS RESISTANCE, Rd2. LOSS RESISTANCE, Rd
ANTENNA EFFICIENCYANTENNA EFFICIENCY
The ratio of the power radiated by the antenna to the power delivered at the
feedpointThe ratio of radiation resistance to the total
system resistance
GENERAL CHARACTERISTICS OF ANTENNAS
% = Rr / Rr + Rd
SAMPLE QUESTION
Ex. An antenna has a radiation resistance of 72 ohms, a loss resistance of 8 ohms, and a power gain of 16. What efficiency and directivity does it have.a. 90% and 17.78b. 10% and 160c. 90% and 160d. 10% and 17.78
REVIEW QUESTIONS
Ex. To produce a power density of 1 mw/m2 in a given direction, at a distance of 2 km, an antenna radiates a total of 180 w. An isotropic antenna would have to radiate 2400 w to produce the same power density at that distance. What, in dB, is the directive gain of the practical antenna?a. 11.25 dBb. 13.21 dBc. 10 dBd. 6 dB
EFFECTIVE EFFECTIVE RADIATED POWER RADIATED POWER
(ERP)(ERP)
The product of the power fed to an antenna and its power gain.
ERP = Total Radiated Power x Power Gain
The power radiated by an antenna in its favored direction, taking the gain of the antenna into
account as referenced to an isotropic radiator
EFFECTIVE EFFECTIVE ISOTROPIC RADIATED ISOTROPIC RADIATED
POWER (EIRP)POWER (EIRP)
GENERAL CHARACTERISTICS OF ANTENNAS
FRONT TO BACK RATIOFRONT TO BACK RATIO
Ratio of the power at the optimum direction of the antenna to that of the power 180
degrees from the optimum direction
The operating frequency range of an antenna
GENERAL CHARACTERISTICS OF ANTENNAS
BANDWIDTHBANDWIDTH
BEAMWIDTHBEAMWIDTH
Angular separation between two half power points in a major lobe of an
antenna radiation pattern
The degree of concentration of the antenna’s radiation
GENERAL CHARACTERISTICS OF ANTENNAS
POLARIZATIONPOLARIZATION
Space orientation of the waves that
the antenna radiates
The electric field vector is always parallel to the
antenna elements.
GENERAL CHARACTERISTICS OF ANTENNAS
FIELD STRENGTHFIELD STRENGTH
Radiated power per unit area
Is inversely proportional to the square of the distance from the
source.
GENERAL CHARACTERISTICS OF ANTENNAS
PHYSICAL PHYSICAL LENGTHLENGTH
Actual length of the antenna
λ/2 is the shortest length of a conductor which will resonate at
a given frequency
ANTENNA LENGTHS
L =λ/2; λ= c/f
ELECTRICAL LENGTHELECTRICAL LENGTH
Dependent upon the velocity coefficient or
velocity factor
The velocity factor is dependent upon the
ratio of the half wavelength to
conductor diameter
L = k λ
REVIEW QUESTIONS
EFFECTS OF GROUND ON EFFECTS OF GROUND ON ANTENNASANTENNAS
Whereas an ungrounded antenna with its image forms an antenna array, the bottom of the grounded
antenna is joined to the top of the image; the system acts as an antenna of double size.
GENERAL CHARACTERISTICS OF ANTENNAS
FUNCTIONS OF GROUNDFUNCTIONS OF GROUND
To help dissipate energy from lightning strikes
EFFECTS OF GROUND ON ANTENNAS
To provide safety in case something tries to energize the chassis of equipment with dangerous voltages
To provide a controlled RF return path for end-fed antennas
To provide a highly conductive path for induced radio-frequency currents or fields rather than having them flow in lossy
EFFECTS OF GROUND ON EFFECTS OF GROUND ON ANTENNASANTENNAS
Whereas an ungrounded antenna
with its image forms an antenna array, the
bottom of the grounded antenna is joined to the
top of the image; the system acts as an
antenna of double size.
EFFECTS OF GROUND ON ANTENNAS
GROUND SCREENGROUND SCREEN
A network of buried wires directly under the antenna, consisting of a large number of radials
extending from the base of the tower, like spokes on a wheel, and placed 15 and 30 cm
below the ground
GROUNDING SYSTEMS
COUNTERPOISECOUNTERPOISE
A substitute for ground screen in areas of low conductivity, i.e. rock,
mountains and antennas on top of
buildings
GROUNDING SYSTEMS
ANTENNA HEIGHTANTENNA HEIGHT
The actual antenna height should at least be /4, but where this is
not possible, the effective height should
correspond to /4.
EFFECTS OF ANTENNA HEIGHT
TOP LOADINGTOP LOADING
A good method of increasing radiation resistance by having a
horizontal portion at the top of the antenna
EFFECTS OF ANTENNA HEIGHT
Effect: to increase the current at the base of the antenna and to
make the current distribution more uniform
EFFECTIVE EFFECTIVE LENGTHLENGTH
Antennas behave as though (electrically) they were longer
than their physical length
EFFECTS OF ANTENNA HEIGHT
The result of physical antennas having finite thickness, instead of
being infinitely thin.
END EFFECTEND EFFECT
ANTENNA ANTENNA COUPLINGCOUPLING
A network composed of reactances and
transformers, which may be lumped or
distributed, to provide impedance matching
COUPLING NETWORK
To tune out the reactive component of the antenna
impedance
REASONS FOR REASONS FOR COUPLINGCOUPLING
To provide the transmitter with the correct value of
load resistance
To prevent illegal radiation of spurious
frequencies
ANTENNA COUPLERSANTENNA COUPLERS
COUPLING NETWORK
The antennas are coupled directly to their transmitters
Affords a wider reactance range, giving adequate harmonic
suppression
Used for balanced lines
Direct CouplerDirect Coupler
CouplerCoupler
Symmetrical Symmetrical CouplerCoupler
IMPEDANCE MATCHINGIMPEDANCE MATCHING
IMPEDANCE MATCHING
Accomplished by connecting the coax or twin lead to the stub
and sliding the connections up or down the stub until the proper
SWR is indicated by a meter connected in the
system.
Stub Stub MatchingMatching
ANTENNA COUPLERSANTENNA COUPLERS
IMPEDANCE MATCHING
Accomplished by spreading the ends of the feedline and
adjusting the spacing until
optimum performance is
reached.
Delta MatchingDelta Matching
ANTENNA COUPLERSANTENNA COUPLERS
IMPEDANCE MATCHING
A sliding clamp is included in the
assembly to permit fine tuning for
minimum SWR at the time of installation
Gamma MatchingGamma Matching
ANTENNA COUPLERSANTENNA COUPLERS
IMPEDANCE MATCHING
A section of transmission line
one quarter wavelength long placed between the load and the
line
Quarter Wave Quarter Wave MatchingMatching
BalunBalun
Used to connect an unbalanced (coaxial line)
to a balanced antenna
CURRENT FED (LOW Z FEED)CURRENT FED (LOW Z FEED)
An antenna is said to be current fed if it is fed at the point of current maximum
SELECTION OF FEEDPOINT
Includes all feed point impedances below 600
ohms
Ex. Center fed half wave dipole or Marconi
antenna
VOLTAGE FED (HIGH Z FEED)VOLTAGE FED (HIGH Z FEED)
An antenna is said to be voltage fed if it is fed at the point of voltage maximum
SELECTION OF FEEDPOINT
Includes all feed point impedances in excess of 600
ohmsEx. Center fed full
wave dipole
1. A polar diagram or graph representing field strengths or power densities at various angular positions relative to an antenna.
a. Venn Diagramb. Figure 8 patternc. Lissajous figured. Radiation Pattern
REVIEW QUESTIONS
2. Refers to the orientation of the electric field radiated from an antenna.
a. radiationb. polarizationc. beamwidthd. bandwidth
REVIEW QUESTIONS
3. Pertains to a wire structure placed below the antenna and erected above the ground which is a form of capacitive grounding system.
a. imageb. counterpoisec. antenna orientationd. polarization
REVIEW QUESTIONS
4. What is the technique used to electrically increase the antenna length?
a. loadingb. using image antennac. using antenna arraysd. increasing antenna height
REVIEW QUESTIONS
5. Antenna supported by insulators seems electrically longer than its physical length due to
a. imageb. reflectionc. end effectd. broadside effect
REVIEW QUESTIONS
6. The ratio of the power radiated by the antenna to the total input power.
a. power gainb. directive gainc. antenna efficiencyd. radiation efficiency
REVIEW QUESTIONS
The ratio of the front lobe power to the back lobe power
front to side ratiofront to back ratioback to front ratio
minor to major ratio
REVIEW QUESTIONS
5What is the length of an antenna operating at a frequency of 500 kHz?
500 m570 m600 m630 m
REVIEW QUESTIONS
The gain of a hertzian dipole with respect to an isotropic antenna
1.76 dB2.15 dB1.5 dB1.64 dB
REVIEW QUESTIONS
A half wave dipole antenna is capable of radiating 2000 watts and has a 2.15 dB gain over an
isotropic antenna. How much power must be delivered to the isotropic antenna to match the
field strength of the directional antenna?1640 watts3280 watts4300 watts3520 watts
REVIEW QUESTIONS
5. Calculate the beamwidth between nulls of a 1m paraboloid reflector used at 6GHz.
3.5˚7˚
1.75˚14˚
REVIEW QUESTIONS
An antenna has a radiation resistance of 72 ohms, a loss resistance of 8 ohms and a power gain of 16.
What efficiency and directivity does it have?90% and 17.7810% and 17.7890% and 14.410% and 14.4
REVIEW QUESTIONS
Device that converts high frequency current into electromagnetic waves.
antennaloudspeakermicrophone
lightning arrester
REVIEW QUESTIONS
An ungrounded antenna near the groundacts as a single antenna of twice the height
is unlikely to need a ground screenacts as an antenna array
must be horizontally polarized
REVIEW QUESTIONS
Top loading is sometimes used with an antenna in order to increase itseffective height
bandwidthbeamwidth
input capacitance
REVIEW QUESTIONS
Very low signal strength in antennaminor lobes
nullsantenna patterns
major lobes
REVIEW QUESTIONS
A horizontal antenna is ______ polarized.vertically
horizontallycentrallycircularly
REVIEW QUESTIONS
Which of the following improves antenna directivity?driven element
reflectordirector
parasitic element
REVIEW QUESTIONS
What is the front to back ratio of an antenna which radiates 500 watts in a northernly direction and
50 watts in a southernly direction?25000 dB
10 dB100 dB20 dB
REVIEW QUESTIONS
If a 4 kw antenna produces 50 uV/m in a receiving antenna, a 16 kw will produce
200 uV/m10 uV/m100 uV/m20 uV/m
REVIEW QUESTIONS
If the radiated power increases 10.89 times, the antenna current increases by
3.3 times6.6 times1.82 times
10.89 times
REVIEW QUESTIONS
Shortening effect of an antenna that makes it appear as if it were 5% longer
end effectflywheel effect
skin effectcapture effect
REVIEW QUESTIONS
A simple half wavelength antenna radiates the strongest signal
at 45 degrees to its axisparallel to its axis
at right angles to its axisat 60 degrees to its axis
REVIEW QUESTIONS
If an antenna is too short for the wavelength being used, the effective length can be increased by
addingcapacitance in seriesinductance in seriesresistance in parallelresistance in series
REVIEW QUESTIONS
Actual height of an antenna should be at least1λλ/2λ/4¾ λ
REVIEW QUESTIONS
The directivity pattern of an isotropic radiatorfigure 8a sphere
unidirectional cardioidparabola
REVIEW QUESTIONS
Where are the voltage nodes in a half wave antenna?
at the endsthree quarters of the way from the feedpoint
towards the endone half of the way from the feedpoint towards the
endat the feedpoint
REVIEW QUESTIONS
A Herts antenna is operating on a frequency of 2182 kHz and consists of a horizontal wire that is
hanged between two towers. What is the frequency of its third harmonic?
727 kHz6546 kHz436 kHz
6.546 kHz
REVIEW QUESTIONS
What is the gain of an antenna over a half wavelength dipole when it has 6 dB gain over an
isotropic radiator?6 dB
8.1 dB3.9 dB10 dB
REVIEW QUESTIONS
Top loading is sometimes used with an antenna in order to increase itseffective height
bandwidthbeamwidth
input capacitance
REVIEW QUESTIONS
Top loading is sometimes used with an antenna in order to increase itseffective height
bandwidthbeamwidth
input capacitance
REVIEW QUESTIONS
Top loading is sometimes used with an antenna in order to increase itseffective height
bandwidthbeamwidth
input capacitance
REVIEW QUESTIONS
Top loading is sometimes used with an antenna in order to increase itseffective height
bandwidthbeamwidth
input capacitance
REVIEW QUESTIONS
Top loading is sometimes used with an antenna in order to increase itseffective height
bandwidthbeamwidth
input capacitance
REVIEW QUESTIONS
Top loading is sometimes used with an antenna in order to increase itseffective height
bandwidthbeamwidth
input capacitance
REVIEW QUESTIONS
Top loading is sometimes used with an antenna in order to increase itseffective height
bandwidthbeamwidth
input capacitance
REVIEW QUESTIONS
BASIC ANTENNAS
a standard reference antenna , radiating equally in all directions,
so that the radiation pattern is spherical.
ISOTROPIC ANTENNAISOTROPIC ANTENNA
ELEMENTARY DOUBLETELEMENTARY DOUBLET
A theoretical antenna shorter than a wavelength used as a standard to
which all other antenna characteristics can be compared
FIELD STRENGTH OF AN ELEMENTARY DOUBLET
= 60 le I sin = 60 le I sin θθ / / λλrr
Where
– antenna length
r – antenna length
Le – antenna length
I – antenna current
θθ – angle of axis and point of maximum radiation
REVIEW QUESTIONS
An elementary doublet is 10 cm long. If the 10 MHz current flowing through it is 2 A, what is the field strength 20 km away from the doublet in a direction of maximum radiation?
a. Announceb. Broadcastc. Transmitd. Media
BASIC ANTENNAS
An antenna made up of two wires bent at 90
degrees to each other so as to be in the same line and signal is fed at
the center
DIPOLEDIPOLE
DIPOLE
BASIC ANTENNAS
HALF WAVE DIPOLEHALF WAVE DIPOLE
Length is λ/2 and radiation pattern is a toroid (bidirectional)
DIPOLE
VOLTAGE AND CURRENT CHARACTERISTICS
VOLTAGEVOLTAGE CURRENTCURRENT
TYPES OF ANTENNAS
NON-RESONANT ANTENNANON-RESONANT ANTENNA
One in which there are no standing waves
Radiation pattern is directional
Standing waves are suppressed by the use of a
correct termination to ensure that no power is reflected, so that only a forward travelling
wave will exist.
NON-RESONANT ANTENNAS
LONG WIRE ANTENNALONG WIRE ANTENNA
Lengths in the order of several wavelengths
When an antenna is 2 or more wavelengths long, it provides gain and a multilobe radiation pattern. When terminated at
one end, it becomes unidirectional.
RHOMBIC ANTENNARHOMBIC ANTENNA
Consists of non-resonant antenna elements arranged differently, i.e.
planar rhombus
ANTENNA ARRAY
Length of equal radiators = 2 to 8 ‘s
Angle of tilt: 40 to 75
Rt = 800 ohms
Rin = 650 to 700 ohms
RHOMBIC ANTENNARHOMBIC ANTENNA
Non-resonant antenna used for long distance sky wave
transmission or reception of horizontally polarized waves over distances from 200 to
over 3000 miles at frequencies from 4 to 22 MHz.
NON-RESONANT ANTENNA
TYPES OF TRANSMITTER
RESONANT ANTENNARESONANT ANTENNA
Standing waves exist, caused by the presence of both a
reflected traveling wave and the forward wave.
Antenna whose length is a multiple of /4’s
RESONANT ANTENNA
HERTZ ANTENNAHERTZ ANTENNA
An antenna system in which the ground is not an essential
part
Half Wave Dipole
Half wave antenna used for frequencies above 2 MHz
RESONANT ANTENNA
MARCONI ANTENNAMARCONI ANTENNA
Grounded Quarter Wavelength antenna
Vertical Monopole
Quarter Wavelength antenna used for frequencies below 2
MHz; ominirectional
ANTENNA ARRAYANTENNA ARRAY
A radiating system consisting of
individual radiators or elements placed close together so as
to be within each other’s induction
field
ANTENNA ARRAY
DRIVEN ELEMENTDRIVEN ELEMENT
Element of an array connected to the output of the transmitter
ANTENNA ARRAY
Radiation not directly connected to the output of the transmitter
PARASITIC PARASITIC ELEMENTELEMENT
Receives energy through the induction field of a driven
element
REFLECTORREFLECTOR
A parasitic element longer than the driven element and close to it
reduces signal strength in its own direction and increases it in the
opposite direction.
ANTENNA ARRAY
DIRECTORDIRECTOR
A parasitic element shorter than the driven one from which it
receives energy; tends to increase radiation in its own direction
BROADSIDE ARRAYBROADSIDE ARRAY
Simplest array which consists of a number of dipoles of equal size,
equally spaced along a straight line with all dipoles fed in the same phase
from the same source.
ANTENNA ARRAY
Typical antenna length: 2 to 10 ‘s
Typical spacing: /2 or /4
Number of elements: dozens
ENDFIRE ARRAYENDFIRE ARRAY
Physical arrangement is the same as that of the
broadside array
ANTENNA ARRAY
The magnitude of the current in each element is still the same as in every other element, there is now a phase difference between these currents.
TURNSTILE ARRAYTURNSTILE ARRAY
Consists of two horizontal, half wave antennas mounted at right angles to each
other
ANTENNA ARRAY
YAGI UDA ANTENNAYAGI UDA ANTENNA
An array consisting of a driven element and one or more parasitic elements arranged collinearly and
close together.
ANTENNA ARRAY
FOLDED DIPOLEFOLDED DIPOLE
Single antenna which consists of 2 elements, one is fed directly and the other
coupled conductively at the ends.
ANTENNA ARRAY
LOG PERIODIC ANTENNALOG PERIODIC ANTENNA
Main feature is frequency independence for both radiation resistance and pattern
ANTENNA ARRAY
Bandwidths of 10:1 are achievable with ease
Radiation patterns: uni and bidirectional
LOG PERIODIC ANTENNALOG PERIODIC ANTENNA
Main feature is frequency independence for both radiation resistance and pattern
ANTENNA ARRAY
PYRAMIDAL ANTENNAPYRAMIDAL ANTENNA
a type of log periodic antenna
ANTENNA ARRAY
It looks and works in much the same way that a
standard lp antenna works, with one big difference:
the two halves of the transmission line are
separated and positioned as a V, so each half of the
transmission line is in effect a single wire transmission line.
PARABOLIC ANTENNAPARABOLIC ANTENNA
UHF AND MICROWAVE ANTENNAS
Parabola – a plane curve defined as the locus of a point which
moves so that its distance from another point (called the focus) plus its distance from a straight
line (directrix) is constant.
Works on the principle of a parabola
PARABOLIC ANTENNAPARABOLIC ANTENNA
UHF AND MICROWAVE ANTENNAS
All waves coming from the source and reflected
by the parabola will travel in the same
distance by the time they reach the directrix,
no matter from what point on the parabola
they are reflected.
CASSEGRAIN ANTENNACASSEGRAIN ANTENNA
TYPES OF FEED
an antenna in which the radiator is mounted at or near the surface of a concave main reflector and is aimed at a convex secondary reflector slightly inside the focus of the main reflector.
BEAMWIDTHBEAMWIDTH
PROPERTIES OF PARABOLIC REFLECTOR
Ф = 70λ / D Ф0 = 2 Ф
Where:
Ф0 = beamwidth between nulls, degrees
Ф = beamwidth between half power points, degrees
λ = wavelength, meters
D= mouth diameter, meters
GAIN OF A PARABOLIC ANTENNAGAIN OF A PARABOLIC ANTENNA
PROPERTIES OF PARABOLIC REFLECTOR
Ap = 6 ( D/λ)2
Where:
Ap = Power Gain
λ = wavelength, meters
D= mouth diameter, meters
1. Calculate the beamwidth between nulls of a 2-meter paraboloid reflector used at 6 GHz. Also, calculate the gain of the paraboloid reflector.
REVIEW QUESTIONS
HORN ANTENNAHORN ANTENNA
Ideal as primary feed antenna for parabolic reflectors and
lenses
UHF AND MICROWAVE ANTENNAS
LENS LENS ANTENNAANTENNAUsed as a collimator of
frequencies in excess of 3 GHz
UHF AND MICROWAVE ANTENNAS
HELICAL ANTENNAHELICAL ANTENNA
A broadband VHF and UHF antenna which used when it is
desired to provide circular polarization characteristics
UHF AND MICROWAVE ANTENNAS
Consists of a loosely wound helix backed up by a ground plane,
which is simply a screen made of chicken wire
DISCONE ANTENNADISCONE ANTENNA
A combination of a disk and a cone in close proximity
UHF AND MICROWAVE ANTENNAS
Characterized by an enormous bandwidth for both input
impedance and radiation pattern
A constant angle, low gain antenna; omnidirectional
LOOP ANTENNALOOP ANTENNA
Used for direction finding, because they do not
radiate in a direction at right angles to the plane of
the loop
UHF AND MICROWAVE ANTENNAS
For portable domestic receivers
Circular or square shaped
PHASED ARRAYPHASED ARRAY
Group of antennas, connected to one transmitter or receiver, whose radiation beam can be adjusted electronically without physically moving parts; used
in radars.
RADAR ANTENNA
PHASED ARRAYPHASED ARRAY
Group of antennas, connected to one transmitter or receiver, whose radiation beam can be adjusted electronically without physically moving parts; used
in radars.
RADAR ANTENNA
WHIP ANTENNAWHIP ANTENNA
whip antenna is the most common example of a monopole antenna, an antenna with a single driven element and a ground plane.The whip antenna is a stiff but flexible wire mounted, usually vertically, with one
end adjacent to a ground plane..
RADAR ANTENNA
WHIP ANTENNAWHIP ANTENNA
whip antenna is the most common example of a monopole antenna, an antenna with a single driven element and a ground plane.The whip antenna is a stiff but flexible wire mounted, usually vertically, with one
end adjacent to a ground plane..
RADAR ANTENNA
POLEPOLE
Used to signify one piece of structure similar to the common telephone pole
ANTENNA SUPPORTING STRUCTURES
ANTENNA SUPPORTING STRUCTURES
Used to designate a structure made of metal or wood which may be
either in a form of a one piece or sectionalized structure
MASTMAST
TOWERTOWER
Applied to a very large, high structure, which in
most cases, is constructed of metal
ANTENNA SUPPORTING STRUCTURES
1. A non-resonant antenna that is capable of operating satisfactorily over a relatively wide bandwidth, making it ideally suited for HF transmission.
a. end-fire arrayb. rhombicc. broadside arrayd. log periodic
2.
REVIEW QUESTIONS
Antenna that is independent of their radiation resistance and radiation pattern to frequency. It has bandwidth ratios of 10:1
or greater.a. loop antenna
b. helicalc. Yagi Uda antennad. Log periodic antenna
REVIEW QUESTIONS
A half wave antennaHertz
MarconiParabolic
Vertical Monopole
REVIEW QUESTIONS
Antenna which is used very frequently but almost entirely as a reception antenna and is usually found at the back of table radios.
loop antennafolded antenna
rhombiclog periodic
REVIEW QUESTIONS
One of the special purpose antennas which has broadband VHF and UHF that is ideally suited for applications for which radiating circular
rather than horizontal or vertical polarized electromagnetic waves are required.
loop antennaphased arrayfolded dipole
helical
REVIEW QUESTIONS
What are the two types of antenna elements?driven and reflector
director and reflectorparasitic and directordriven and parasitic
REVIEW QUESTIONS
Which one of the following terms does not apply to the Yagi Uda array?
good bandwidthparasitic elements
folded dipolehigh gain
REVIEW QUESTIONS
Indicate the antenna that is not wideband.discone
folded dipolehelical
Marconi
REVIEW QUESTIONS
One of the following is not an omnidirectional antennahalfwave dipole
log periodic antennadisconbeMarconi
REVIEW QUESTIONS
One of the following consists of nonresonant antennasrhombic
folded dipoleend fire array
broadside array
REVIEW QUESTIONS
Which of the following is best excited from a waveguide?biconical
hornhelicaldiscone
REVIEW QUESTIONS
An antenna that is circularly polarizedparabolic reflector
Yagi UdaHelical
Circular loop
REVIEW QUESTIONS
What is the polarization of a discone antenna?vertical
horizontalcircularspiral
REVIEW QUESTIONS
When speaking of antennas, ____ is a section which would be a complete antenna by itself.
imagetop loading
bayquarterwave
REVIEW QUESTIONS
______ is an antenna with a number of half wave antennas in it.
antenna arraytower
omnidirectionalrhombic
REVIEW QUESTIONS
Which antenna radiates an omnidirectional pattern in the horizontal plane with vertical
polarization?MarconiDiscone
HornHelical
REVIEW QUESTIONS
An antenna with very high gain and very narrow beamwidth.
helicaldiscone
hornparabolic dish
REVIEW QUESTIONS
An open ended slot antennahelical
rhombicnotch
cassegrain
REVIEW QUESTIONS
Which antenna is properly terminated?MarconiRhombicDipole
Yagi Uda
REVIEW QUESTIONS
33. In a standard commercial TV broadcast, the picture carrier signal is located _____ above the lower end frequency of the channel.a. 0.75 MHzb. 0.25 MHzc. 4.2 MHzd. 1.25 MHz
34. Special effects and production switching are done by the a. CCUb. ENGc. SEGd. Sync Gen
REVIEW QUESTIONS
35. The hue 180 degrees out of phase with red isa. cyanb. yellowc. greend. Magenta
36. Greater peak to peak amplitude of the 3.58 MHz chrominance signal indicates morea. whiteb. yellowc. hued. saturation
What is the radiation characteristic of a dipole antenna?
omnidirectionalbidirectionalunidirectionalhemispherical
REVIEW QUESTIONS
An antenna with unity gain.rhombic
half wave dipoleisotropic
whip
REVIEW QUESTIONS
An antenna which is one tenth wavelength long.hertz antennaloop antenna
Marconi antennaElementary doublet
REVIEW QUESTIONS
What is the minimum number of turns a helical antenna must have?3456
REVIEW QUESTIONS
An antenna made up of a number of full wavelengths
elementary doubletlog periodiclong wire
whip
REVIEW QUESTIONS