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All Electronics & Telecommunication MCQs

Browse Electronics & Telecommunication Engineering MCQs with four options, hidden answers, concise explanations and references where available. Questions are organized in pages of up to 100 for focused practice.

Question 1002
Electromagnetic TheoryStanding Waves

A VSWR of 1 corresponds to?

  • APerfect matching with no reflection
  • BTotal reflection
  • CA reflection coefficient magnitude of 1
  • DInfinite attenuation
Report an error
Correct Answer: A. Perfect matching with no reflection
Explanation: VSWR=1 occurs only when |Γ|=0, corresponding to a matched condition.
Reference: Standard electromagnetic theory: standing waves
Question 1003
Electromagnetic TheoryPolarization

The polarization of an electromagnetic wave is specified by the behavior of its?

  • AElectric-field vector
  • BPropagation speed only
  • CMagnetic permeability only
  • DFrequency counter reading
Report an error
Correct Answer: A. Electric-field vector
Explanation: Wave polarization is conventionally defined by the locus and orientation of the electric-field vector at a fixed point.
Reference: Standard electromagnetic theory: polarization
Question 1006
Electromagnetic TheoryPolarization

Two orthogonal field components generally produce elliptical polarization when they have?

  • ASuitable unequal amplitudes and/or a phase difference other than the special linear/circular cases
  • BZero frequency only
  • CNo electric field
  • DOnly identical phase and identical direction
Report an error
Correct Answer: A. Suitable unequal amplitudes and/or a phase difference other than the special linear/circular cases
Explanation: Elliptical polarization is the general case for orthogonal components with relative amplitude and phase that do not reduce to linear or circular polarization.
Reference: Standard electromagnetic theory: polarization
Question 1008
Antenna & Wave PropagationAntenna Fundamentals

The primary function of a transmitting antenna is to convert?

  • AGuided electromagnetic energy into radiated electromagnetic waves
  • BDC power directly into mechanical energy
  • CSound waves into heat only
  • DDigital data into resistance
Report an error
Correct Answer: A. Guided electromagnetic energy into radiated electromagnetic waves
Explanation: A transmitting antenna couples guided RF energy from a transmission system into electromagnetic waves that propagate through space.
Reference: Standard antenna and wave propagation: antenna fundamentals
Question 1009
Antenna & Wave PropagationAntenna Fundamentals

A receiving antenna primarily converts incident electromagnetic waves into?

  • AElectrical signals available at its terminals
  • BMechanical rotation only
  • CDC resistance only
  • DOptical energy only
Report an error
Correct Answer: A. Electrical signals available at its terminals
Explanation: A receiving antenna intercepts electromagnetic energy and produces a corresponding electrical signal at its terminals.
Reference: Standard antenna and wave propagation: antenna fundamentals
Question 1010
Antenna & Wave PropagationRadiation Pattern

The radiation pattern of an antenna describes the variation of its radiation properties with?

  • ADirection in space
  • BSupply voltage only
  • CConductor resistance only
  • DTime of day
Report an error
Correct Answer: A. Direction in space
Explanation: An antenna radiation pattern shows how radiation intensity, field strength or related quantities vary with direction.
Reference: Standard antenna and wave propagation: radiation pattern
Question 1013
Antenna & Wave PropagationRadiation Pattern

A lobe other than the major lobe is generally called a?

  • AMinor lobe
  • BIsotropic lobe
  • CFeed lobe
  • DImpedance lobe
Report an error
Correct Answer: A. Minor lobe
Explanation: Side lobes and back lobes are collectively minor lobes because they are not the principal radiation lobe.
Reference: Standard antenna and wave propagation: radiation pattern
Question 1014
Antenna & Wave PropagationIsotropic Radiator

An isotropic radiator is a hypothetical antenna that radiates?

  • AEqually in all directions
  • BOnly along one axis
  • COnly in the horizontal plane
  • DNo power
Report an error
Correct Answer: A. Equally in all directions
Explanation: An isotropic radiator is an ideal reference source with uniform radiation intensity in every direction.
Reference: Standard antenna and wave propagation: isotropic radiator
Question 1015
Antenna & Wave PropagationDirectivity & Gain

The directivity of an isotropic radiator is?

  • A1 or 0 dBi
  • B2 or 3 dBi
  • C1.64 or 2.15 dBi
  • DInfinite
Report an error
Correct Answer: A. 1 or 0 dBi
Explanation: By definition, an isotropic radiator has directivity 1, corresponding to 0 dBi.
Reference: Standard antenna and wave propagation: directivity & gain
Question 1016
Antenna & Wave PropagationDirectivity & Gain

Antenna directivity is the ratio of radiation intensity in a specified direction to?

  • AAverage radiation intensity over all directions
  • BInput current only
  • COhmic resistance
  • DWavelength squared only
Report an error
Correct Answer: A. Average radiation intensity over all directions
Explanation: Directivity compares radiation intensity in a given direction, usually its maximum, with the average radiation intensity.
Reference: Standard antenna and wave propagation: directivity & gain
Question 1017
Antenna & Wave PropagationDirectivity & Gain

Antenna gain differs from directivity because gain also accounts for?

  • AAntenna efficiency
  • BOnly operating frequency
  • COnly polarization direction
  • DSpeed of light
Report an error
Correct Answer: A. Antenna efficiency
Explanation: Gain includes the effect of radiation efficiency, whereas directivity is based on the shape of the radiation pattern.
Reference: Standard antenna and wave propagation: directivity & gain
Question 1019
Antenna & Wave PropagationDirectivity & Gain

A power gain of 10 corresponds to approximately?

  • A3 dB
  • B10 dB
  • C20 dB
  • D100 dB
Report an error
Correct Answer: B. 10 dB
Explanation: Gain in decibels is 10log10(10)=10 dB.
Reference: Standard antenna and wave propagation: directivity & gain
Question 1022
Antenna & Wave PropagationBeamwidth

A narrower main beam generally indicates?

  • AHigher directivity
  • BLower directivity in every case
  • CZero gain
  • DNo radiation
Report an error
Correct Answer: A. Higher directivity
Explanation: Concentrating radiation into a narrower angular region generally increases antenna directivity.
Reference: Standard antenna and wave propagation: beamwidth
Question 1023
Antenna & Wave PropagationAntenna Resistance

Radiation resistance is a fictitious resistance that represents?

  • APower radiated by the antenna
  • BOnly conductor heating loss
  • CDielectric breakdown
  • DFeed-line reactance only
Report an error
Correct Answer: A. Power radiated by the antenna
Explanation: Radiation resistance is defined so that the power attributed to it equals the antenna's radiated power for the specified current convention.
Reference: Standard antenna and wave propagation: antenna resistance
Question 1024
Antenna & Wave PropagationAntenna Efficiency

Antenna radiation efficiency is commonly defined as radiated power divided by?

  • AAccepted input power
  • BIncident power density only
  • CReactive power only
  • DReflected power only
Report an error
Correct Answer: A. Accepted input power
Explanation: Radiation efficiency is the fraction of power accepted by the antenna that is actually radiated rather than dissipated as loss.
Reference: Standard antenna and wave propagation: antenna efficiency
Question 1026
Antenna & Wave PropagationAntenna Impedance

For maximum power transfer between a transmission line and an antenna at a single frequency, the antenna input impedance should ideally be?

  • AMatched to the line impedance
  • BZero
  • CInfinite
  • DPurely capacitive regardless of the line
Report an error
Correct Answer: A. Matched to the line impedance
Explanation: Impedance matching minimizes reflection and permits efficient transfer of power from the line to the antenna.
Reference: Standard antenna and wave propagation: antenna impedance
Question 1027
Antenna & Wave PropagationPolarization

The polarization of an antenna is normally defined by the polarization of the wave it?

  • ARadiates in a specified direction
  • BAbsorbs as heat only
  • CReflects from the ground only
  • DCarries inside a DC cable
Report an error
Correct Answer: A. Radiates in a specified direction
Explanation: Antenna polarization is described by the electric-field polarization of its radiated wave in the direction considered.
Reference: Standard antenna and wave propagation: polarization
Question 1028
Antenna & Wave PropagationDipole Antennas

A vertically oriented half-wave dipole ideally produces what polarization in its broadside direction?

  • AVertical linear polarization
  • BHorizontal linear polarization
  • CCircular polarization automatically
  • DUnpolarized radiation
Report an error
Correct Answer: A. Vertical linear polarization
Explanation: The electric field of a thin dipole is oriented parallel to the dipole axis, giving vertical linear polarization for a vertical dipole.
Reference: Standard antenna and wave propagation: dipole antennas
Question 1033
Antenna & Wave PropagationDipole Antennas

The radiation pattern of an ideal half-wave dipole has maximum radiation in directions?

  • AAlong the dipole axis
  • BPerpendicular to the dipole axis
  • COnly at 45 degrees to the axis
  • DEqually in every direction
Report an error
Correct Answer: B. Perpendicular to the dipole axis
Explanation: A thin half-wave dipole has maximum radiation broadside to its axis and nulls along the axis.
Reference: Standard antenna and wave propagation: dipole antennas
Question 1035
Antenna & Wave PropagationDipole Antennas

The directivity of a half-wave dipole is approximately?

  • A1 or 0 dBi
  • B1.64 or 2.15 dBi
  • C3.28 or 5.16 dBi
  • D10 or 10 dBi
Report an error
Correct Answer: B. 1.64 or 2.15 dBi
Explanation: A half-wave dipole has maximum directivity about 1.64, corresponding to approximately 2.15 dBi.
Reference: Standard antenna and wave propagation: dipole antennas
Question 1036
Antenna & Wave PropagationMonopole Antennas

The approximate directivity of a quarter-wave monopole over an ideal infinite conducting ground plane is?

  • A1 or 0 dBi
  • B1.64 or 2.15 dBi
  • C3.28 or 5.15 dBi
  • D10 or 10 dBi
Report an error
Correct Answer: C. 3.28 or 5.15 dBi
Explanation: An ideal quarter-wave monopole radiates into one hemisphere and has about twice the directivity of a half-wave dipole, approximately 3.28 or 5.15 dBi.
Reference: Standard antenna and wave propagation: monopole antennas
Question 1037
Antenna & Wave PropagationEffective Aperture

For a receiving antenna, effective aperture Ae and gain G are related by?

  • AAe = G lambda²/(4 pi)
  • BAe = 4 pi G/lambda²
  • CAe = G/(4 pi lambda²)
  • DAe = lambda/(4 pi G)
Report an error
Correct Answer: A. Ae = G lambda²/(4 pi)
Explanation: For a matched receiving antenna, effective aperture is related to gain by Ae=Gλ²/(4π).
Reference: Standard antenna and wave propagation: effective aperture
Question 1039
Antenna & Wave PropagationFriis Transmission

The Friis free-space transmission equation is primarily used to estimate?

  • AReceived power between antennas in free-space far-field conditions
  • BConductor skin depth
  • CAntenna mechanical strength
  • DIonospheric critical frequency only
Report an error
Correct Answer: A. Received power between antennas in free-space far-field conditions
Explanation: The Friis equation relates transmitted power, antenna gains, wavelength and separation to received power under ideal free-space far-field conditions.
Reference: Standard antenna and wave propagation: friis transmission
Question 1040
Antenna & Wave PropagationFriis Transmission

In ideal free-space propagation, if the distance between transmitting and receiving antennas is doubled while all other factors remain unchanged, received power becomes?

  • ATwice
  • BHalf
  • COne-fourth
  • DOne-eighth
Report an error
Correct Answer: C. One-fourth
Explanation: The Friis equation gives received power proportional to 1/R², so doubling distance reduces received power to one-fourth.
Reference: Standard antenna and wave propagation: friis transmission
Question 1041
Antenna & Wave PropagationAntenna Arrays

An antenna array is formed by using?

  • AMultiple radiating elements arranged and excited to obtain a desired radiation pattern
  • BA single resistor only
  • COnly one isotropic point with no feed
  • DA capacitor bank with no radiators
Report an error
Correct Answer: A. Multiple radiating elements arranged and excited to obtain a desired radiation pattern
Explanation: Arrays combine fields from multiple antenna elements to shape beam direction, gain and sidelobe behavior.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1042
Antenna & Wave PropagationAntenna Arrays

In a broadside linear array, the principal maximum is ideally directed?

  • AAlong the array axis
  • BPerpendicular to the array axis
  • COnly toward the feed point
  • DRandomly
Report an error
Correct Answer: B. Perpendicular to the array axis
Explanation: A broadside array is phased so that its main beam is normal to the array axis.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1043
Antenna & Wave PropagationAntenna Arrays

In an end-fire array, the principal radiation is directed approximately?

  • AAlong the array axis
  • BPerpendicular to the array axis
  • COnly vertically regardless of orientation
  • DEqually in all directions
Report an error
Correct Answer: A. Along the array axis
Explanation: An end-fire array is phased to produce its main beam along the array axis.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1044
Antenna & Wave PropagationAntenna Arrays

The array factor of an antenna array primarily depends on element?

  • APositions and relative excitation amplitudes/phases
  • BConductor color
  • CMechanical weight only
  • DDielectric breakdown voltage only
Report an error
Correct Answer: A. Positions and relative excitation amplitudes/phases
Explanation: Array factor is determined by the geometry and relative complex excitation of the elements, separate from the individual element pattern.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1045
Antenna & Wave PropagationYagi-Uda Antenna

A Yagi-Uda antenna normally consists of a driven element together with?

  • AA reflector and one or more directors
  • BOnly a parabolic dish
  • COnly a horn aperture
  • DTwo identical ground planes with no parasitic elements
Report an error
Correct Answer: A. A reflector and one or more directors
Explanation: A typical Yagi-Uda uses one driven element, usually a dipole, plus a reflector and one or more parasitic directors.
Reference: Standard antenna and wave propagation: yagi-uda antenna
Question 1046
Antenna & Wave PropagationYagi-Uda Antenna

In a conventional Yagi-Uda antenna, the reflector is generally placed?

  • ABehind the driven element relative to the main radiation direction
  • BIn front of all directors
  • CAt the exact same position as the driven element
  • DOnly inside the feed cable
Report an error
Correct Answer: A. Behind the driven element relative to the main radiation direction
Explanation: The reflector is placed behind the driven element and helps reinforce radiation toward the directors.
Reference: Standard antenna and wave propagation: yagi-uda antenna
Question 1047
Antenna & Wave PropagationYagi-Uda Antenna

Adding suitably designed directors to a Yagi-Uda antenna generally tends to?

  • AIncrease directivity in the forward direction
  • BMake it perfectly isotropic
  • CEliminate all impedance
  • DForce radiation only backward
Report an error
Correct Answer: A. Increase directivity in the forward direction
Explanation: Directors concentrate radiation in the forward direction and can increase Yagi-Uda directivity.
Reference: Standard antenna and wave propagation: yagi-uda antenna
Question 1048
Antenna & Wave PropagationHorn Antenna

A horn antenna is commonly used at?

  • AMicrowave frequencies
  • BOnly audio frequencies
  • CDC only
  • DPower-line frequency only
Report an error
Correct Answer: A. Microwave frequencies
Explanation: Horn antennas are practical high-frequency aperture antennas widely used in microwave systems and as feeds for reflectors.
Reference: Standard antenna and wave propagation: horn antenna
Question 1049
Antenna & Wave PropagationHorn Antenna

A major purpose of gradually flaring a waveguide into a horn is to?

  • AProvide a smoother transition from waveguide to free space
  • BCreate a DC short circuit
  • CStop all radiation
  • DIncrease conductor resistance intentionally
Report an error
Correct Answer: A. Provide a smoother transition from waveguide to free space
Explanation: The flare provides a gradual impedance transition and a larger radiating aperture, improving radiation into free space.
Reference: Standard antenna and wave propagation: horn antenna
Question 1050
Antenna & Wave PropagationParabolic Reflector

A parabolic reflector antenna produces high directivity mainly because it?

  • AForms a large effective aperture and converts spherical wavefronts to approximately planar wavefronts
  • BRadiates equally in all directions
  • CUses only a resistive load
  • DHas zero physical aperture
Report an error
Correct Answer: A. Forms a large effective aperture and converts spherical wavefronts to approximately planar wavefronts
Explanation: With a feed near its focus, a paraboloid collimates radiation into a narrow beam, giving high gain/directivity.
Reference: Standard antenna and wave propagation: parabolic reflector
Question 1051
Antenna & Wave PropagationParabolic Reflector

For a parabolic reflector of fixed efficiency and wavelength, increasing the dish diameter generally?

  • AIncreases gain and narrows the beam
  • BDecreases gain and narrows the beam
  • CLeaves gain unchanged
  • DMakes the antenna isotropic
Report an error
Correct Answer: A. Increases gain and narrows the beam
Explanation: Reflector gain is approximately proportional to (D/lambda)², so a larger diameter gives higher gain and a narrower beam.
Reference: Standard antenna and wave propagation: parabolic reflector
Question 1053
Antenna & Wave PropagationWave Propagation

Ground-wave propagation is most useful at relatively?

  • ALow frequencies
  • BOnly optical frequencies
  • COnly millimeter-wave frequencies
  • DX-ray frequencies
Report an error
Correct Answer: A. Low frequencies
Explanation: Ground waves can follow Earth's surface effectively at lower frequencies, with losses increasing as frequency rises.
Reference: Standard antenna and wave propagation: wave propagation
Question 1054
Antenna & Wave PropagationSky-Wave Propagation

Sky-wave propagation relies mainly on refraction/return of radio waves by the?

  • AIonosphere
  • BTropospheric ground surface only
  • COcean floor
  • DTransmission-line dielectric
Report an error
Correct Answer: A. Ionosphere
Explanation: In sky-wave communication, ionized atmospheric layers can bend suitable radio waves back toward Earth.
Reference: Standard antenna and wave propagation: sky-wave propagation
Question 1055
Antenna & Wave PropagationSpace-Wave Propagation

Line-of-sight or space-wave propagation is especially important at?

  • AVHF and higher frequencies
  • BOnly very low frequency
  • CDC
  • DAudio frequency
Report an error
Correct Answer: A. VHF and higher frequencies
Explanation: At VHF, UHF and microwave frequencies, propagation is predominantly line-of-sight or space-wave because ionospheric return is generally not the normal mode.
Reference: Standard antenna and wave propagation: space-wave propagation
Question 1056
Antenna & Wave PropagationSpace-Wave Propagation

If transmitting and receiving antenna heights are increased, the radio line-of-sight range generally?

  • AIncreases
  • BDecreases to zero
  • CRemains exactly unchanged
  • DBecomes independent of Earth curvature
Report an error
Correct Answer: A. Increases
Explanation: Increasing antenna heights extends the geometric/radio horizon and therefore generally increases line-of-sight range.
Reference: Standard antenna and wave propagation: space-wave propagation
Question 1057
Antenna & Wave PropagationSpace-Wave Propagation

Which propagation mode is normally most appropriate for a terrestrial microwave point-to-point link?

  • ALine-of-sight space-wave propagation
  • BGround wave around the entire Earth
  • CIonospheric sky wave as the primary mode
  • DConduction through soil
Report an error
Correct Answer: A. Line-of-sight space-wave propagation
Explanation: Terrestrial microwave links generally use highly directional antennas and line-of-sight space-wave propagation.
Reference: Standard antenna and wave propagation: space-wave propagation
Question 1058
Antenna & Wave PropagationAntenna Pattern Parameters

The front-to-back ratio of a directional antenna compares radiation in the main-beam direction with radiation?

  • AIn the opposite direction
  • BAt the half-power point
  • CAt 90 degrees only
  • DAt the feed terminals
Report an error
Correct Answer: A. In the opposite direction
Explanation: Front-to-back ratio compares forward radiation with radiation approximately 180 degrees behind the main beam.
Reference: Standard antenna and wave propagation: antenna pattern parameters
Question 1062
Antenna & Wave PropagationParabolic Reflector

The approximate gain of a parabolic reflector is proportional to?

  • A(D/lambda)² times aperture efficiency
  • BD/lambda only
  • Clambda²/D
  • DD²lambda² only
Report an error
Correct Answer: A. (D/lambda)² times aperture efficiency
Explanation: A common reflector relation is G≈eta_a(pi D/lambda)², so gain scales with (D/lambda)² for fixed efficiency.
Reference: Standard antenna and wave propagation: parabolic reflector
Question 1065
Antenna & Wave PropagationAntenna Arrays

In a uniform linear array, increasing the number of similarly spaced elements while maintaining a comparable aperture arrangement generally tends to?

  • AIncrease directivity and narrow the main beam
  • BReduce directivity to zero
  • CMake all sidelobes disappear automatically
  • DMake element spacing irrelevant
Report an error
Correct Answer: A. Increase directivity and narrow the main beam
Explanation: More coherently combined elements generally provide a larger effective aperture, higher directivity and narrower main beam.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1067
Antenna & Wave PropagationAntenna Matching

A common purpose of impedance matching at an antenna feed is to reduce?

  • AReflected power
  • BRadiated power intentionally to zero
  • COperating wavelength
  • DSpeed of electromagnetic waves
Report an error
Correct Answer: A. Reflected power
Explanation: A good impedance match reduces the reflection coefficient and improves transfer of available power between feed line and antenna.
Reference: Standard antenna and wave propagation: antenna matching
Question 1069
Antenna & Wave PropagationIonospheric Propagation

The ionosphere is important to HF communication because it contains?

  • AIonized particles capable of refracting radio waves
  • BOnly neutral particles with no electromagnetic effect
  • CA perfect metallic mirror
  • DNo free electrons
Report an error
Correct Answer: A. Ionized particles capable of refracting radio waves
Explanation: Solar radiation ionizes portions of the upper atmosphere, producing electrons and ions that affect radio-wave propagation.
Reference: Standard antenna and wave propagation: ionospheric propagation
Question 1071
Antenna & Wave PropagationIonospheric Propagation

The D layer is particularly associated with significant absorption of?

  • ALower-HF and MF radio waves
  • BVisible light only
  • CAll microwave signals completely
  • DDC current
Report an error
Correct Answer: A. Lower-HF and MF radio waves
Explanation: Collisions in the lower ionosphere cause appreciable absorption, especially at lower radio frequencies.
Reference: Standard antenna and wave propagation: ionospheric propagation
Question 1072
Antenna & Wave PropagationIonospheric Propagation

During daytime, the F region commonly separates into?

  • AF1 and F2 layers
  • BD1 and D2 only
  • CE1 and E2 only
  • DTwo tropospheric layers
Report an error
Correct Answer: A. F1 and F2 layers
Explanation: Under daytime solar ionization, the F region is commonly described as F1 and F2; they tend to merge at night.
Reference: Standard antenna and wave propagation: ionospheric propagation
Question 1073
Antenna & Wave PropagationCritical Frequency

The critical frequency of an ionospheric layer is the highest frequency that is returned to Earth for?

  • AVertical incidence
  • BHorizontal incidence only
  • CAny angle without limit
  • DGround-wave propagation
Report an error
Correct Answer: A. Vertical incidence
Explanation: Critical frequency is defined for vertical incidence on a particular ionospheric layer.
Reference: Standard antenna and wave propagation: critical frequency
Question 1074
Antenna & Wave PropagationMUF

The maximum usable frequency (MUF) for a given ionospheric path is generally?

  • AAt least as high as the relevant critical frequency and depends on path geometry
  • BAlways zero
  • CAlways lower than every critical frequency
  • DIndependent of ionosphere and path
Report an error
Correct Answer: A. At least as high as the relevant critical frequency and depends on path geometry
Explanation: For oblique incidence, frequencies above the vertical-incidence critical frequency may be returned; MUF depends on layer conditions and geometry.
Reference: Standard antenna and wave propagation: muf
Question 1077
Antenna & Wave PropagationSkip Distance

Skip distance in sky-wave propagation is the minimum distance from the transmitter at which a wave of specified frequency is?

  • AReturned to Earth by the ionosphere
  • BAbsorbed completely by the antenna
  • CConverted to a ground current
  • DGuaranteed to have zero fading
Report an error
Correct Answer: A. Returned to Earth by the ionosphere
Explanation: Skip distance is the shortest ground distance at which a given sky wave returns to Earth under the prevailing ionospheric conditions.
Reference: Standard antenna and wave propagation: skip distance
Question 1079
Antenna & Wave PropagationIonospheric Propagation

Virtual height of an ionospheric layer is the apparent reflection height inferred by assuming the radio wave?

  • ATravels at the speed of light along an equivalent straight path
  • BStops at the ionosphere
  • CTravels through a metallic cable
  • DHas zero propagation time
Report an error
Correct Answer: A. Travels at the speed of light along an equivalent straight path
Explanation: Virtual height is derived from propagation delay using an equivalent straight-line path assumption and is not necessarily the true physical layer height.
Reference: Standard antenna and wave propagation: ionospheric propagation
Question 1083
Antenna & Wave PropagationGain Units

Antenna gain expressed in dBi is referenced to which ideal antenna?

  • AIsotropic radiator
  • BHalf-wave dipole
  • CQuarter-wave monopole
  • DSmall loop
Report an error
Correct Answer: A. Isotropic radiator
Explanation: dBi expresses antenna gain relative to an ideal isotropic radiator.
Reference: Standard antenna and wave propagation: gain units
Question 1084
Antenna & Wave PropagationGain Units

Antenna gain expressed in dBd is referenced to a?

  • AHalf-wave dipole
  • BIsotropic radiator
  • CParabolic reflector
  • DQuarter-wave transformer
Report an error
Correct Answer: A. Half-wave dipole
Explanation: dBd uses a half-wave dipole as the gain reference.
Reference: Standard antenna and wave propagation: gain units
Question 1085
Antenna & Wave PropagationGain Units

A gain of 0 dBd is approximately equal to?

  • A0 dBi
  • B1 dBi
  • C2.15 dBi
  • D3 dBi
Report an error
Correct Answer: C. 2.15 dBi
Explanation: An ideal half-wave dipole has approximately 2.15 dBi gain, so 0 dBd≈2.15 dBi.
Reference: Standard antenna and wave propagation: gain units
Question 1087
Antenna & Wave PropagationEIRP

Effective isotropic radiated power (EIRP) is the product of transmitter power delivered to the antenna and?

  • AAntenna gain relative to isotropic, including applicable feed losses when forming the link budget
  • BAntenna resistance only
  • COperating wavelength only
  • DReceiver sensitivity
Report an error
Correct Answer: A. Antenna gain relative to isotropic, including applicable feed losses when forming the link budget
Explanation: EIRP represents the equivalent power an isotropic radiator would need to produce the same power density in the direction of maximum antenna gain.
Reference: Standard antenna and wave propagation: eirp
Question 1092
Antenna & Wave PropagationLink Budget

A received power of 0 dBm corresponds to?

  • A1 mW
  • B10 mW
  • C100 mW
  • D1 W
Report an error
Correct Answer: A. 1 mW
Explanation: By definition, 0 dBm is 1 milliwatt.
Reference: Standard antenna and wave propagation: link budget
Question 1093
Antenna & Wave PropagationLink Budget

A received power of 30 dBm corresponds to?

  • A30 mW
  • B100 mW
  • C1 W
  • D30 W
Report an error
Correct Answer: C. 1 W
Explanation: 30 dBm=10^(30/10) mW=1000 mW=1 W.
Reference: Standard antenna and wave propagation: link budget
Question 1096
Antenna & Wave PropagationAntenna Noise

The equivalent noise temperature of an antenna is related primarily to?

  • ANoise power received from the environment through its radiation pattern
  • BIts DC resistance only
  • CIts mechanical temperature in every case only
  • DTransmitter output power
Report an error
Correct Answer: A. Noise power received from the environment through its radiation pattern
Explanation: Antenna noise temperature represents environmental noise collected by the antenna, weighted by its directional response.
Reference: Standard antenna and wave propagation: antenna noise
Question 1099
Antenna & Wave PropagationTropospheric Propagation

Tropospheric ducting can allow VHF/UHF/microwave signals to travel?

  • ABeyond the normal radio horizon
  • BOnly through underground conductors
  • COnly vertically upward
  • DOnly within an antenna feed line
Report an error
Correct Answer: A. Beyond the normal radio horizon
Explanation: Strong refractive-index gradients can trap radio waves in atmospheric ducts and extend propagation beyond the normal horizon.
Reference: Standard antenna and wave propagation: tropospheric propagation
Question 1100
Antenna & Wave PropagationTropospheric Propagation

Troposcatter communication relies on?

  • AScattering from irregularities in the troposphere
  • BReflection from the ionospheric F2 layer only
  • CConduction along Earth wires
  • DReflection from a parabolic feed itself
Report an error
Correct Answer: A. Scattering from irregularities in the troposphere
Explanation: Tropospheric scatter uses small-angle scattering from refractive-index irregularities to communicate beyond line of sight.
Reference: Standard antenna and wave propagation: tropospheric propagation