# Antenna and wave propagation MCQ with answers

**1) What is the wavelength of Super high frequency (SHF) especially used in Radar & satellite communication?**

**a.** 1 m – 10 m

**b.** 1 cm – 10 cm

**c.** 10 cm – 1 m

**d.** 0.1 cm – 1 cm

**ANSWER: 1 cm – 10 cm**

**2) Which among the following is an application of high frequency?**

**a.** SONAR

**b.** Subsurface communication

**c.** Radio navigation

**d.** Facsimile

**ANSWER: Facsimile**

**3) Wavefront is basically a locus of points acquiring similar _______**

**a.** Phase

**b.** Frequency

**c.** Amplitude

**d.** Wave equation

**ANSWER: Phase**

**4) In which kind of waveform is the phase velocity defined?**

**a.** Sinusoidal

**b.** Rectangular

**c.** Square

**d.** Triangular

**ANSWER: Sinusoidal**

**5) Which among the following is/are not present in free space?**

**a.** Solid bodies

**b.** Ionized particles

**c.** Interference of normal radiation & radio wave propagation

**d.** All of the above

**ANSWER: All of the above**

**6) Power density is basically termed as ________ power per unit area**

**a.** Reflected

**b.** Refracted

**c.** Radiated

**d.** Diffracted

**ANSWER: Radiated**

**7) If the path difference of two waves with single source traveling by different paths to arrive at the same point, is λ/2, what would be the phase difference between them?**

**a.** β x (λ/2)

**b.** β / (λ/2)

**c.** β + (λ/2)

**d.** β – (λ/2)

**ANSWER: β x (λ/2)**

**8) Which ionization layer exists during day time & usually vanishes at night due to highest recombination rate?**

**a.** D-region

**b.** Normal E-region

**c.** Sporadic E-region

**d.** Appleton region

**ANSWER: D-region**

**9) What is the possible range of height for the occurrence of sporadic E-region with respect to normal E-region?**

**a.** 20 km – 50 km

**b.** 45 km – 85 km

**c.** 90 km – 130 km

**d.** 140 km – 200 km

**ANSWER: 90 km – 130 km**

**10) F _{2} layer of appleton region acts as a significant reflecting medium for _____ frequency radio waves**

**a.** Low

**b.** Moderate

**c.** High

**d.** All of the above

**ANSWER: High**

**11) The knowledge of which parameter is sufficient for deriving the time varying electromagnetic field?**

**a.** Electric field intensity

**b.** Magnetic field intensity

**c.** Current density

**d.** Power density

**ANSWER: Current density**

**12) According to Webster’s dictionary, what is an antenna?**

**a.** Impedance matching device

**b.** Sensor of electromagnetic waves

**c.** Transducer between guided wave & free space wave

**d.** Metallic device for radiating or receiving radio waves

**ANSWER: Metallic device for radiating or receiving radio waves**

**13) Under which conditions of charge does the radiation occur through wire antenna?**

**a.** For a charge with no motion

**b.** For a charge moving with uniform velocity with straight & infinite wire

**c.** For a charge oscillating in time motion

**d.** All of the above

**ANSWER: For a charge oscillating in time motion**

**14) In a non-isotropic directional antenna, which radiating lobe axis makes an angle of 180° w.r.t. major beam of an antenna?**

**a.** Minor lobe

**b.** Side lobe

**c.** Back lobe

**d.** None of the above

**ANSWER: Back lobe**

**15) At which angles does the front to back ratio specify an antenna gain?**

**a.** 0° & 180°

**b.** 90° & 180°

**c.** 180° & 270°

**d.** 180° & 360°

**ANSWER: 0° & 180°**

**16) Which among the following defines the angular distance between two points on each side of major lobe especially when the radiation drops to zero?**

**a.** Half power beam width (HPBW)

**b.** First null beam width (FNBW)

**c.** Side lobe level (SLL)

**d.** Front to back ratio (FBR)

**ANSWER: First null beam width (FNBW)**

**17) If an observation point is closely located to the source, then the field is termed as ________**

**a.** Induced

**b.** Radiated

**c.** Reflected

**d.** Far-field

**ANSWER: Induced**

**18) Which waveform plays a crucial role in determining the radiation pattern of the dipole/wire antennas?**

**a.** Current

**b.** Voltage

**c.** Frequency

**d.** Phase

**ANSWER: Current**

**19) How are the infinitesimal dipoles represented in terms of antenna length and signal wavelength?**

**a.** l ≤ (λ /50)

**b.** (λ/50 ) < l ≤ (λ /10)

**c.** l = λ/2

**d.** None of the above

**ANSWER: l ≤ (λ /50)**

**20) In flared transmission line, the radiation phenomenon increases due to ________ in flaring**

**a.** Increase

**b.** Decrease

**c.** Stability

**d.** None of the above

**ANSWER: Increase**

**21) Which pattern is generated due to plotting of square of amplitude of an electric field?**

**a.** Field Pattern

**b.** Voltage Pattern

**c.** Power Pattern

**d.** All of the above

**ANSWER: Power Pattern**

**22) In an electrically small loops, the overall length of the loop is ______ one-tenth of a wavelength.**

**a.** Less than

**b.** Equal to

**c.** Greater than

**d.** None of the above

**ANSWER: Less than**

**23) On which factor/s do/does the radiation field of a small loop depend?**

**a.** Shape

**b.** Area

**c.** Both a and b

**d.** None of the above

**ANSWER: Area**

**24) From the radiation point of view, small loops are _________radiators**

**a.** Poor

**b.** Good

**c.** Better

**d.** Excellent

**ANSWER: Poor**

**25) According to the directivity of a small loop, which value of ‘θ’ contributes to achieve the maximum value of radiation intensity (U _{max})?**

**a.** 0°

**b.** 90°

**c.** 180°

**d.** 270°

**ANSWER: 90°**

**26) In which kind of array configuration, the element locations must deviate or adjust to some nonplaner surface like an aircraft or missile?**

**a.** Linear

**b.** Planer

**c.** Conformal

**d.** All of the above

**ANSWER: Conformal**

**27) What is the nature of radiation pattern of an isotropic antenna?**

**a.** Spherical

**b.** Dough-nut

**c.** Elliptical

**d.** Hyperbolic

**ANSWER: Spherical**

**28) In broadside array, all the elements in the array should have similar _______excitation along with similar amplitude excitation for maximum radiation.**

**a.** Phase

**b.** Frequency

**c.** Current

**d.** Voltage

**ANSWER: Phase**

**29) Which among the following is regarded as a condition of an ordinary endfire array?**

**a.** α < βd

**b.** α > βd

**c.** α = ±βd

**d.** α ≠ ±βd

**ANSWER: α = ±βd**

**30) Which mode of propagation is adopted in HF antennas?**

**a.** Ionospheric

**b.** Ground wave

**c.** Tropospheric

**d.** All of the above

**ANSWER: Ionospheric**

**31) For which band/s is the space wave propagation suitable over 30 MHz?**

**a.** VHF

**b.** SHF

**c.** UHF

**d.** All of the above

**ANSWER: All of the above**

**32) If the tower antenna is not grounded, which method of excitation is/are applicable for it?**

**a.** Series

**b.** Shunt

**c.** Both a and b

**d.** None of the above

**ANSWER: Series**

**33) In ungrounded antennas, if an excitation is applied directly across the base insulator, then on which factor/s would the voltage across the insulator depend?**

**a.** Power delivered to antenna

**b.** Power factor of impedance

**c.** Both a and b

**d.** None of the above

**ANSWER: Both a and b**

**34) Which among the following exhibits perpendicular nature in TEM wave?**

**a.**Electric field

**b.**Magnetic field

**c.**Direction of propagation

**d.**All of the above

**ANSWER: All of the above**

**35) Which equations are regarded as wave equations in frequency domain for lossless media?**

**a.** Maxwell’s

**b.** Lorentz

**c.** Helmholtz

**d.** Poisson’s

**ANSWER: Helmholtz**

**36) If the magnetic field component of a plane wave in a lossless dielectric is H = 50 sin (2π x 10 ^{6} t – 6x) a_{z}mA/m , what will be the wave velocity?**

**a.** 1.047 x 10^{6} m/s

**b.** 1.257 x 10^{6} m/s

**c.** 2.50 x 10^{6} m/s

**d.** 3 x 10^{6} m/s

**ANSWER: 1.047 x 10 ^{6} m/s**

**37) In an electrical circuit,which nature of impedance causes the current & voltages in phase?**

**a.** Reactive

**b.** Resistive

**c.** Capacitive

**d.** Inductive

**ANSWER: Resistive**

**38) Which type of ground wave travels over the earth surface by acquiring direct path through air from transmitting to receiving antennas?**

**a.** Surface wave

**b.** Space wave

**c.** Both a & b

**d.** None of the above

**ANSWER: Space wave**

**39) After which phenomenon/phenomena do the waves arrive at the receiving antenna in ionospheric propagation?**

**a.** Reflection or Scattering

**b.** Refraction

**c.** Defraction

**d.** All of the above

**ANSWER: Reflection or Scattering**

**40) By which name/s is an ionospheric propagation, also known as?**

**a.** Sea wave propagation

**b.** Ground wave propagation

**c.** Sky wave propagation

**d.** All of the above

**ANSWER: Sky wave propagation**

**41) According to Snell’s law in optics, if a ray travels from dense media to rarer media, what would be its direction w.r.t the normal?**

**a.** Towards

**b.** Away

**c.** Across

**d.** Beside

**ANSWER: Away**

**42) Which mechanism/s is/are likely to occur in mid-frequency operation corresponding to ionospheric region?**

**a.** Only Reflection

**b.** Only Refraction

**c.** Partial reflection & refraction

**d.** None of the above

**ANSWER: Partial reflection & refraction**

**43) Which among the following plays a primary role in generation of conduction current in an ionosphere due to presence of electric field?**

**a.** Ions

**b.** Motion of electrons

**c.** Neutral molecules

**d.** None of the above

**ANSWER: Motion of electrons**

**44) Which type of wire antennas are also known as dipoles?**

**a.** Linear

**b.** Loop

**c.** Helical

**d.** All of the above

**ANSWER: Linear**

**45) Which antennas are renowned as patch antennas especially adopted for space craft applications?**

**a.** Aperture

**b.** Microstrip

**c.** Array

**d.** Lens

**ANSWER: Microstrip**

**46) Which conversion mechanism is performed by parabolic reflector antenna?**

**a.** Plane to spherical wave

**b.** Spherical to plane wave

**c.** Both a and b

**d.** None of the above

**ANSWER: Spherical to plane wave**

**47) Which antenna radiating region/s has/have independent nature of angular field distribution over the distance from the antenna?**

**a.** Reactive near-field region

**b.** Fresnel region

**c.** Fraunhofer region

**d.** All of the above

**ANSWER: Fraunhofer region**

**48) Sterdian is a measurement unit of __________**

**a.** Point angle

**b.** Linear angle

**c.** Plane angle

**d.** Solid angle

**ANSWER: Solid angle**

**49) According to the geometry, how many sterdians are present in a full sphere?**

**a.** π/2

**b.** π

**c.** 2π

**d.** 4π

**ANSWER: 4π**

**50) The vector magnetic potential shows the inverse relationship with its ____**

**a.** Source

**b.** Distance of point from the source (R)

**c.** Both a and b

**d.** None of the above

**ANSWER: Distance of point from the source (R)**

**51) In retarded potentials, what factor of time delay is generally introduced in A & V equations?**

**a.** R + c

**b.** R – c

**c.** R/c

**d.** R x c

**ANSWER: R/c**

**52) In the solutions of inhomogeneous vector potential wave equation, which component exists if the source is at origin and the points are removed from the source (J _{z} = 0)?**

**a.** Inward

**b.** Outward

**c.** Both a and b

**d.** None of the above

**ANSWER: Outward**

**53) If a half-wave dipole operates at 300 MHz with λ = 0.5m & D _{0} = 1.643, what will be its effective area?**

**a.** 0.032 m^{2}

**b.** 0.047 m^{2}

**c.** 0.65 m^{2}

**d.** 0.99 m^{2}

**ANSWER: 0.032 m ^{2}**

**54) Dipole antenna is symmetrical in nature where the two ends are at equal potentials with respect to _____point**

**a.** Initial

**b.** Eventual

**c.** Mid

**d.** None of the above

**ANSWER: Mid**

**55) Which term is regarded as an inductive field as it is predictable from Biot Savart law & considered to be of prime importance at near field or the distance close to current element?**

**a.** 1/ r

**b.** 1/ r^{2}

**c.** 1/ r^{3}

**d.** 1/ r^{4}

**ANSWER: 1/ r ^{2}**

**56) What is the nature of current distribution over the small dipoles?**

**a.** Spherical

**b.** Rectangular

**c.** Triangular

**d.** Square

**ANSWER: Triangular**

**57) For receiving a particular frequency signal, which tuning component must be used by the loop to form a resonant circuit for tuning to that frequency?**

**a.** Capacitor

**b.** Inductor

**c.** Resistor

**d.** Gyrator

**ANSWER: Capacitor**

**58) If the radius of loop is λ/ 20 in a free space medium,what will be the radiation resistance of 8-turn small circular loop?**

**a.** 0.7883 Ω

**b.** 50.45 Ω

**c.** 123.17 Ω

**d.** 190.01 Ω

**ANSWER: 123.17 Ω**

**59) What is the far-field position of an electric short dipole?**

**a.** Along x-axis

**b.** Along y-axis

**c.** Along z-axis

**d.** Along xy plane

**ANSWER: Along z-axis**

**60) What would happen if the rms value of induced emf in loop acquires an angle θ = 90°?**

**a.** Wave is incident in direction of plane of the loop with induced maximum voltage

**b.** Wave is incident normal to plane of the loop with no induced voltage

**c.** Wave is incident in opposite direction of plane of the loop with minimum voltage

**d.** None of the above

**ANSWER: Wave is incident normal to plane of the loop with no induced voltage**

**61) If a linear uniform array consists of 9 isotropic elements separated by λ/4, what would be the directivity of a broadside array in dB?**

**a.** 6.53 dB

**b.** 7.99 dB

**c.** 8.55 dB

**d.** 9.02 dB

**ANSWER: 6.53 dB**

**62) If the elements of a binomial array are separated by λ/4, how many shape patterns are generated with no minor lobes?**

**a.** 2

**b.** 4

**c.** 8

**d.** 16

**ANSWER: 8**

**63) What kind of beamwidth is/are produced by Chebyshev arrays for given side lobe level (SLL)?**

**a.** Widest

**b.** Narrowest

**c.** Both a and b

**d.** None of the above

**ANSWER: Narrowest**

**64) If the length of elements of an array is greater than λ/2, which will be the operating region of an array?**

**a.** Transmission line region

**b.** Active region

**c.** Reflective region

**d.** All of the above

**ANSWER: Reflective region**

**65) Which angle of rhombic antenna represents one half of included angle of two legs of one wire?**

**a.** Apex angle

**b.** Tilt angle

**c.** Both a and b

**d.** None of the above

**ANSWER: Tilt angle**

**66) Which among the following is not a disadvantage of rhombic antenna?**

**a.** Requirement of large space

**b.** Reduced transmission efficiency

**c.** Maximum radiated power along main axis

**d.** Wastage of power in terminating resistor

**ANSWER: Maximum radiated power along main axis**

**67) Why are beverage antennas not used as transmitting antenna?**

**a.** Low radiation resistance

**b.** Low radiation efficiency

**c.** Both a and b

**d.** None of the above

**ANSWER: Both a and b**

**68) Which kind of polarization is provided by helical antennas?**

**a.** Plane

**b.** Elliptical

**c.** Circular

**d.** All of the above

**ANSWER: Circular**

**69) According to depth of penetration, what is the percentage proportion of attenuated wave w.r.t its original value?**

**a.** 17%

**b.** 27%

**c.** 37%

**d.** 57%

**ANSWER: 37%**

**70) Linear polarization can be obtained only if the wave consists of ________**

**a.** E_{x}

**b.** E_{y}

**c.** Both E_{x} & E_{y} & in phase

**d.** Both E_{x} & E_{y} & out of phase

**ANSWER: Both E _{x} & E_{y} & in phase**

**71) When an electromagnetic wave travels from transmitter to receiver, which factor/s affect/s the propagation level?**

**a.** Curvature of earth

**b.** Roughness of earth

**c.** Magnetic field of earth

**d.** All of the above

**ANSWER: All of the above**

**72) For avoiding ground losses, better is the surface conductivity, less is the __________**

**a.** Attenuation

**b.** Phase velocity

**c.** Propagation constant

**d.** Tilt angle

**ANSWER: Attenuation**

**73) On which factors of earth does the magnitude of tilt angle depend in surface wave?**

A. Permittivity

B. Conductivity

C. Resistivity

D. Reflectivity

**a.** A & B

**b.** C & D

**c.** A & C

**d.** B & D

**ANSWER: A & B**

**74) What is the direction of varying orientation of polarized surface wave at the earth surface in a wave tilt mechanism?**

**a.** Horizontal

**b.** Vertical

**c.** Diagonal

**d.** Opposite

**ANSWER: Vertical**

**75) Which layer has the atmospheric conditions exactly opposite to that of standard atmosphere?**

**a.** Depression layer

**b.** Regression layer

**c.** Inversion layer

**d.** Invasion layer

**ANSWER: Inversion layer**

**76) If the maximum electron density for F-layer in ionosphere is 4 x 10 ^{6} electrons/cm^{3}, then what will be the critical frequency of EM wave for F-layer?**

**a.** 4 MHz

**b.** 9 MHz

**c.** 18 MHz

**d.** 25 MHz

**ANSWER: 18 MHz**

**77) According to Secant law, which frequency is greater than critical frequency by a factor of secθ _{i}?**

**a.** MUF

**b.** LUF

**c.** OWF

**d.** UHF

**ANSWER: MUF**

**78) How is the effect of selective fading reduced?
**

**A. By high carrier reception
B. By low carrier reception
C. By single side band system
D. By double side band system**

**a.** A & C

**b.** B & D

**c.** A & D

**d.** B & C

**ANSWER: A & C**

**79) In lens antenna, what kind of wave energy is transformed into plane waves?**

**a.** Convergent

**b.** Divergent

**c.** Contingent

**d.** Congruent

**ANSWER: Divergent**

**80) What is the functioning role of an antenna in receiving mode?**

**a.** Radiator

**b.** Converter

**c.** Sensor

**d.** Inverter

**ANSWER: Sensor**

**81) In radio communication link, what is the shape/nature of waves generated by transmitting antenna?**

**a.** Spherical

**b.** Plane

**c.** Triangular

**d.** Square

**ANSWER: Spherical**

**82) Which among the following elucidate the generation of electromagnetic waves?**

A. Ampere’s law

B. Faraday’s law

C. Gauss’s law

D. Kirchoff’s law

**a.** A & B

**b.** B & C

**c.** A & C

**d.** B & D

**ANSWER: A & B**

**83) If an antenna draws 12 A current and radiates 4 kW, then what will be its radiation resistance?**

**a.** 22.22 ohm

**b.** 27.77 ohm

**c.** 33.33 ohm

**d.** 39.77 ohm

**ANSWER: 27.77 ohm**

**84) Under which conditions of two unit vectors, the polarization loss factor (PLF) is equal to unity?**

**a.** Perpendicular

**b.** Perfectly aligned

**c.** Angle inclination (Ψ_{p})

**d.** All of the above

**ANSWER: Perfectly aligned**

**85) Which property/ies of antenna is/are likely to be evidenced in accordance to Reciprocity theorem?**

**a.** Equality of impedances

**b.** Equality of directional patterns

**c.** Equality of effective lengths

**d.** All of the above

**ANSWER: All of the above**

**86) Self impedance of an antenna is basically __________**

**a.** Its input impedance during the removal of all other antennas

**b.** Its impedance by taking into consideration the consequences of other antennas

**c.** Both a and b

**d.** None of the above

**ANSWER: Its input impedance during the removal of all other antennas**

**87) In solution evaluation process of inhomogeneous vector potential wave equation, if points are completely removed from the source, then by which factor does the time varying field & static solution differ?**

**a.** e^{-jkr}

**b.** e^{jkr}

**c.** e^{-jk/r}

**d.** e^{(jk + r)}

**ANSWER: e ^{-jkr}**

**88) The concept of magnetic vector potential finds its major application in deriving expression of magnetic field intensity especially for ______**

**a.** Real fields

**b.** Imaginary fields

**c.** Complex fields

**d.** None of the above

**ANSWER: Complex fields**

**89) A dipole carries r.m.s. current of about 300A across the radiation resistance 2 Ω. What would be the power radiated by an antenna?**

**a.** 90 kW

**b.** 135 kW

**c.** 180 kW

**d.** 200 kW

**ANSWER: 180 kW**

**90) What is/are the major applications of an infinitesimal dipole that contribute/s to its analysis?**

**a.** Field pattern estimation due to any length of antenna

**b.** Improvement in radiation resistance by increasing dipole length

**c.** Both a and b

**d.** None of the above

**ANSWER: Both a and b**

**91) What is /are the advantages of using ferrite loops?**

A. Increase in Magnetic field intensity

B. Increase in radiation resistance

C. Decrease in Magnetic field intensity

D. Decrease in radiation resistance

**a.** A & B

**b.** C & D

**c.** A & D

**d.** B & C

**ANSWER: A & B**

**92) In an electrically large loop, an overall length of the loop is equal to ______**

**a.** λ/2

**b.** λ

**c.** λ/10

**d.** λ/50

**ANSWER: λ**

**93) How do the elements of an active region behave?**

**a.** Inductive

**b.** Capacitive

**c.** Resistive

**d.** None of the above

**ANSWER: Resistive**

**94) By how many times is an input impedance of a folded dipole at resonance greater than that of an isolated dipole with same length as one of its sides?**

**a.** 2

**b.** 3

**c.** 4

**d.** 6

**ANSWER: 4**

**95) Which mode of radiation occurs in an helical antenna due to smaller dimensions of helix as compared to a wavelength?**

**a.** Normal

**b.** Axial

**c.** Both a and b

**d.** None of the above

**ANSWER: Normal**

**96) A rectangular horn antenna operating at 4GHz has the wavelength of 0.075m and gain of about 13dBi. What will be its required capture area?**

**a.** 0.0149 m^{2}

**b.** 0.0475 m^{2}

**c.** 0.5521 m^{2}

**d.** 0.9732 m^{2}

**ANSWER: 0.0149 m ^{2}**

97 ) The relation between vector magnetic potential and current density is given by ______

a) ∇.A=J

b) ∇×A=H

c) ∇^{2} A=-μJ

d) ∇^{2} A=∇×H

Answer: ∇^{2} A=-μJ

98) The induction and radiation fields are equal at a distance of _______

a) λ/4

b) λ/6

c) λ/8

d) λ/2

Answer: λ/6

99) The ratio of radiation intensity in a given direction from antenna to the radiation intensity over all directions is called as ________

a) Directivity

b) Radiation power density

c) Gain of antenna

d) Array Facto

Answer: Directivity

100) What is the overall efficiency of a lossless antenna with reflection coefficient 0.15?

a) 0.997

b) 0.779

c) 0.669

d) 0.977

Answer: 0.977

101) The equivalent area when multiplied by the instant power density which leads to free radiation of power at antenna is called as _______

a) Loss area

b) Scattering area

c) Captured area

d) Effective area

Answer: Scattering area

102) Equivalent circuit representation of an antenna is ______

a) Series R, L, C

b) Parallel R, L, C

c) Series R, L parallel to C

d) Parallel R, C series to L

Answer: Series R, L, C

103 ) Radiation resistance of a Hertzian dipole of length λ/8 is ________

a) 12.33Ω

b) 8.54Ω

c) 10.56Ω

d) 13.22Ω

Answer: 12.33Ω

104) Relation between directivity and effective area of transmitting and receiving antenna is ________

a) D_{t} A_{t}=D_{r} A_{r}

b) D_{t} A_{r}=D_{r} A_{t}

c) A_{t} D_{t}=∈D_{r} A_{r}

d) D_{t} A_{t}=∈D_{r} A_{r}

Answer:- D_{t} A_{r}=D_{r} A_{t }

105) The axis of back lobe makes an angle of 180° with respect to the beam of an antenna.

a) True

b) False

Answer:- True

106) Radiation resistance of a half-wave dipole is ______

a) 36.56Ω

b) 18.28Ω

c) 73.12Ω

d) 40.24Ω

Answer: 73.12Ω

107) The radiation efficiency for antenna having radiation resistance 36.15Ω and loss resistance 0.85Ω is given by ________

a) 0.977

b) 0.799

c) 0.997

d) 0.779

Answer: 0.977

108)A linear antenna having length less than λ/8 is called as _______

a) Short monopole

b) Short dipole

c) Half-wave dipole

d) Quarter-wave monopole

Answer:- Short monopole

109) Find the power radiated by an antenna whose radiation resistance is 100Ω and operating with 3A of current at 2GHz frequency?

b) 1800W

c) 450W

d) 700W

Answer: 900W

110)Front-to-Back ratio is defined as ratio of power radiated in desired direction to the power radiated in back lobe.

a) True

b) False

Answer: True

111)Relation between beam solid angle Ω, horizontal half-power beam width ∅_{A}, vertical half-power beam width ∅_{E} is __________

a) Ω≈∅_{A}.∅_{E}

b) Ω≈∅_{A}+∅_{E}

c) Ω≈∅_{A}/∅_{E}

d) Ω≈∅_{A}-∅_{E}

Answer : Ω≈∅_{A}.∅_{E}

112) Which of the following field varies inversely with r^{2}?

a) Far field

b) Near field

c) Radiation field

d) Electrostatic field

Answer: Near field

113) Find the effective area of a half-wave dipole operating at frequency 100MHz and directive gain 1.8?

a) 1.28m^{2}

b) 2.18m^{2}

c) 0.128m^{2}

d) 12.8m^{2}

Answer: 1.28m^{2}

114) Which of the following option is false?

a) Omni-directional antenna is a special case of directional antenna

b) Directional antenna radiates power effectively in particular directions compared to other directions

c) Isotropic antenna radiates power in all directions

d) End-fire array antenna has its main beam normal to the axis containing antenna

Answer End-fire array antenna has its main beam normal to the axis containing antenna

115) The angular distance between two successive nulls of main lobe is called as ______

a) FNBW

b) HPBW

c) Beam width

d) FBR

Answer : FNBW

116) If beam width of the antenna increases, then directivity ________

a) Decreases

b) Increases

c) Remains unchanged

d) Depends on type of antenna

Answer: Decreases

117) The receiving antenna is designed to have ____ side-lobe-ratio and ____ SNR.

a) Low, high

b) High, high

c) Low, low

d) High, low

Answer: Low, high

118)Units of radiation intensity is _______

a) Watts/unit Solid angle

b) Watts/m^{2}

c) Watts- m^{2}

d) Watts

Answer : Watts/unit Solid angle

119) The graphical representation of the radiation properties of the antenna as a function of space coordinates is called Radiation pattern.

a) True

b) False

Answer: True

120) What is the total power radiated in Watts for the power density wr=4sinθ3r2arW/m2?

a) 4π^{2}

b) 8π^{2}/3

c) 4π^{2}/3

d) 2π^{2}/3

Answer: 4π^{2}/3

121) Which of the following pattern varies with square of magnitude of field?

a) Power Pattern

b) Electric Field Pattern

c) Current distribution

d) Array Factor

Answer: Power Pattern

122) The radiation lobe containing the direction of maximum radiation is called as _____

a) Major lobe

b) Minor lobe

c) Side lobe

d) Back lobe

Answer: Major lobe

123) Fresnel zone is also called as ____

a) Near Field

b) Far Field

c) Electrostatic Field

d) Reactive Field

**ANSWER: Near Field**

124) If FNBW is 6°, then resolution is ____

a) 12°

b) 3°

c) 2°

d) 6°

**ANSWER: 3°**

125) For a center fed short antenna, current distribution is _____ at center and ____ at ends.

a) Low, high

b) High, high

c) Low, low

d) High, low

**ANSWER: High, low**

126) Which pattern represents a plot with magnitude of field strength Vs θ at a constant φ?

a) E-plane pattern

b) H-plane pattern

c) Horizontal pattern

d) Power pattern

**ANSWER: E-plane pattern**

127) The portion of the near field immediate to the surrounding the antenna is called as _____

a) Reactive near-field

b) Radiating near-field

c) Fraunhofer zone

d) Far field

**ANSWER: Reactive near-field**

128) The region of the field that angular field distribution is independent of the distance from the antenna is called as _______

a) Reactive near-field

b) Radiating near-field

c) Fresnel zone

d) Far field

**ANSWER: Far field**

129) An ideal source in which the power is radiated equally in all directions is called as ________ radiator.

a) Isotropic

b) Omni-directional

c) Directional

d) Transducer

**ANSWER: sotropic**

130) In Isotropic radiation, which of the following vector component is absent in pointing vector?

a) arˆ

b) aθˆ

c) a∅ˆ

d) Both aθˆanda∅ˆ

**ANSWER: Both aθˆanda∅ˆ**

131) What is the amount of Electric field present at a distance of 10km for an isotropic radiator with radiating power 3kW?

a) 30mV/m

b) 60mV/m

c) 15mV/m

d) 10mV/m

**ANSWER: 30mV/m**

132) What is the radiation intensity for isotropic antenna having radiation power density 3sinθr2arW/m2?

a) 3sinθ a_{r} W/Steradian

b) 3cosθa_{r} W/Steradian

c) 6πsinθ a_{r} W/Steradian

d) 6πcosθ a_{r} W/steradian

**ANSWER: 3sinθ a _{r} W/Steradian**

133) For an isotropic source, Radiation intensity will be _____ on θ and ______ on Φ.

a) Dependent, independent

b) Independent, independent

c) Independent, dependent

d) Dependent, dependent

**ANSWER: Independent, independent**

134) Find the effective length of a receiving antenna with open circuit voltage 1V and incident electric field 200mV/m?

a) 0.2m

b) 50m

c) 5m

d) 5cm

**ANSWER: 5m**

135) For an isotropic antenna, the average power P_{av} can be expressed in terms of radiated power P_{r} as ____

a) P_{av}=P_{r}/4π

b) P_{av}=P_{r}/2πr^{2}

c) P_{av}=P_{r}/2π

d) P_{av}=P_{r}/4πr^{2}

**ANSWER: P _{av}=P_{r}/4πr^{2}**

136) Directive gain is defined as a measure of concentration of power in a particular direction.

a) True

b) False

**ANSWER: True**

137) What is the directive gain when the magnitude of radiation intensity equals to average radiation intensity?

a) 4π

b) ∞

c) 1

d) 0

**ANSWER: 1**

138) Directive gain of antenna when radiation intensity is 5W/Steradian and radiated power 5W is ____

a) 4π

b) 1/4π

c) 25

d) 1

**ANSWER: 4π**

139) The Directive gain is ______ on input power to antenna and _____ on power due to ohmic losses.

a) Independent, independent

b) Dependent, independent

c) Independent, dependent

d) Dependent, dependent

**ANSWER: Independent, independent**

140) What is the maximum directive gain of antenna with radiation efficiency 98% and maximum power gain 1?

a) 0.98

b) 1.02

c) 1.98

d) 1

**ANSWER: 1.02**

141 ) Which of the following expression is correct for radiation efficiency?

a) ηr=Rr/ Rr

b) ηr=Rr/ Rr−R

c) ηr=Rr / Rr+R

d) ηr=R1/ Rr+R

**ANSWER: Rr / Rr+R**

142) For a lossless antenna, maximum Power gain equals to the maximum directive gain.

a) True

b) False

**ANSWER: True**

143 ) The ratio of power radiated in a particular direction to the total input power of antenna is called as _____

a) Directive gain

b) Power gain

c) Directivity

d) Partial directivity

**ANSWER: Power gain**

144 ) What is the maximum power gain of antenna with radiation efficiency 98% and directive gain 1?

a) 0.98

b) 1.02

c) 1.98

d) 1

**ANSWER: 0.98**

145 ) Which of the following expression is correct for radiation efficiency?

a) ηr=Pr / Pt

b) ηr=Pr / Pr−Pt

c) ηr=Pr /Pr+Pt

d) ηr=P / Pr+Pt

**ANSWER: ηr=Pr /Pr+Pt**

146 ) Which of the following represents the relation between maximum power gain and maximum directivity gain of the antenna?

a) G_{pmax} = η_{r}G_{dmax}

b) G_{pmax} = η_{r}/G_{dmax}

c) η_{r} = √(GpmaxGdmax)

d) η_{r} = Gdmax+Gpmax / Gdmax−Gpmax

**ANSWER: G _{pmax} = η_{r}G_{dmax}**

147 ) What is the maximum power gain when the radiation resistance is 72Ω, loss resistance is 8Ω and the maximum directive gain is 1.5?

a) 1.15

b) 1.35

c) 1.25

d) 1.53

**ANSWER: 1.35**

148 ) The value of maximum power gain is always greater than or equal to the maximum directive gain.

a) True

b) False

**ANSWER: False**

149) The ratio of maximum power density in the desired direction to the average power radiated from the antenna is called as _______

a) directivity

b) directive gain

c) power gain

d) partial directivity

**ANSWER: directivity**

150) What is the Beam area for Directivity to be 1 in Steradian?

a) 4π

b) 1/2π

c) 2π

d) 1/4π

**ANSWER: 4π**

151) If directivity of antenna increases, then the coverage area _____

a) decreases

b) increases

c) increases and then decreases

d) remains unchanged

**ANSWER: decreases**

152) If half power beam width in one plane and other plane orthogonal to it are equal to π then the directivity is ____

a) π

b) 4π

c) 4/π

d) 2π

**ANSWER: 4/π**

153) Directive gain with maximum radiation intensity is called as Directivity.

a) True

b) False

**ANSWER: True**

154) How the directivity and effective aperture related to each other?

a) Inversely proportional

b) Directly proportional

c) Independent

d) Proportionality depends on input power

**ANSWER: Directly proportional**

155) What is the directivity of half-wave dipole?

a) 1.64

b) 1.5

c) 1.43

d) 1.44

**ANSWER: 1.64**

156) What is the directivity of antenna having effective aperture 1 m^{2}?

a) 4π / λ2

b) λ2 / 4π

c) 1

d) 4π

**ANSWER: 4π / λ2**

157) Effective aperture is the ability of antenna to extract energy from the electromagnetic wave.

a) True

b) False

**ANSWER: True**

158) Which of the following best describes the condition for Maximum effective aperture?

a) Load impedance must be equal to the antenna impedance

b) Load impedance must be equal complex conjugate to the antenna impedance

c) Receiver power should be minimum

d) Transmitter power should be minimum

**ANSWER: Load impedance must be equal complex conjugate to the antenna impedance**

159) What is the effective aperture of Hertzian dipole antenna operating at frequency 100 MHz?

a) 1.07m^{2}

b) 0.17m^{2}

c) 1.7m^{2}

d) 1.2m^{2}

**ANSWER: 1.07m ^{2}**

160) If physical aperture of antenna is 0.02m^{2} and aperture efficiency is 0.5, then what is the value of effective aperture?

a) 0.0004m^{2}

b) 0.001m^{2}

c) 0.01m^{2}

d) 25m^{2}

**ANSWER: 0.01m ^{2}**

161) Expression for aperture efficiency in terms of physical aperture A_{e} and effective aperture A_{em} is ____

a) Ae / Aem

b) Aem/Ae

c) Ae+Aem / Ae−Aem

d) Ae−Aem / Ae+Aem

**ANSWER: Aem/Ae**

162) What is the effective aperture of a Half-wave dipole operating at 100MHz?

a) 1.07m^{2}

b) 1.17m^{2}

c) 1.27m^{2}

d) 1.77m^{2}

**ANSWER: 1.17m ^{2}**

163) What is the relation between effective length and Effective aperture of antenna?

a) Ae=dL2η / 4Rrad

b) Ae=dL2 / 4ηRrad

c) Ae=dL2Rrad / 4η

d) Ae=dL2η2 / 4Rrad

**ANSWER: Ae=dL2η / 4Rrad**

164) The physical aperture of an isotropic radiator is _______

a) 4πη / λ2

b) 4π / λ2η

c) λ2 / 4πη

d) λ2η / 4π

**ANSWER: λ2 / 4πη**

165) What is the radiation resistance of an antenna if it radiates 1kW and current in it is I_{rms}=10A?

a) 0.1Ω

b) 1Ω

c) 10Ω

d) 100Ω

**ANSWER: 10Ω**

166) What is the radiation resistance of an antenna if input power to it is 1KW and current in it is 10A having a power loss of 200W?

a) 10Ω

b) 2Ω

c) 12Ω

d) 8Ω

**ANSWER: 8Ω**

167) What is the radiation resistance of a short dipole of length L?

a) 20π^{2} (L / λ)2

b) 80π^{2} (l/ λ )2

c) 40π^{2} (l/λ)2

d) 160π^{2} (l/λ)2

**ANSWER: 20π ^{2} (L / λ)2**

168) If the length of the dipole decreases, then the radiation resistance will________

a) increase

b) decrease

c) depends on current distribution

d) not change

**ANSWER: decrease**

169) For a half-wave dipole with length λ/12, what is the antenna efficiency if the Radiation resistance is 2Ω?

a) 0.73

b) 0.073

c) 0.37

d) 0.78

**ANSWER: 0.73**

169) Find the radiation resistance of a Hertzian dipole of length 1m and operating at a frequency 1MHz?

a) 0.08Ω

b) 8.8mΩ

c) 8.8Ω

d) 0.88Ω

**ANSWER: 8.8mΩ**

170) Radiation resistance doesn’t depend on direction of power radiated but depends on the frequency.

a) True

b) False

**ANSWER: True**

171) What is the radiation resistance of the antenna radiating at 5kW and having maximum current 2A?

a) 25kΩ

b) 2.5kΩ

c) 0.25kΩ

d) 2.5Ω

**ANSWER: 2.5kΩ**

172) Power radiated by half-wave dipole with maximum current amplitude 10A is ______

a) 3.65kΩ

b) 3.650Ω

c) 0.365kΩ

d) 36.50Ω

**ANSWER: 3.65kΩ
**

173) The radiation resistance dissipates same amount of power as it radiated by the antenna.

a) True

b) False

**ANSWER: True**

174) Relation between Quality factor, Bandwidth, and resonant frequency is _________

a) Q=BW / f0

b) Q=f0 / BW

c) Q = BW×f_{0}

d) Q=BW+f0 / BW−f0

**ANSWER: Q=f0 / BW**

175) What is the Bandwidth of the antenna operating at resonant frequency 200MHz with Quality factor 20?

a) 10Hz

b) 5MHz

c) 10MHz

d) 0.1MHz

**ANSWER: 10MHz**

176) What is the Bandwidth of the antenna operating at resonant frequency 200MHz with Quality factor 20?

a) 10Hz

b) 5MHz

c) 10MHz

d) 0.1MHz

**ANSWER: 10MHz**

177)What is the length of the half-wave dipole with bandwidth 20MHz and Quality factor 30?

a) 5m

b) 0.25m

c) 0.50m

d) 2.5m

**ANSWER: 0.25m**

178) Quality factor is defined as ________

a) 2π×energyradiatedpercycle / Totalenergystoredbyantenna

b) 4π×Totalenergystoredbyantenna / energyradiatedpercycle

c) 4π×energyradiatedpercycle / Totalenergystoredbyantenna

d) 2π×Totalenergystoredbyantenna / energyradiatedpercycle

**ANSWER: 2π×Totalenergystoredbyantenna / energyradiatedpercycle**

179) What is the quality factor of the antenna operating at 650MHz and having a bandwidth of 10MHZ?

a) 65

b) 0.65

c) 15

d) 55

**ANSWER: 65**

180) In an antenna, the lower frequency limit is determined by pattern, gain or impedance.

a) True

b) False

**ANSWER: True**

181) In the impedance v/s frequency graph of antenna, the antenna impedance at frequencies less than resonant frequency is ____

a) inductive

b) capacitive

c) resistive

d) both inductive and capacitive

**ANSWER: capacitive**

182) High the Fractional Bandwidth ___________ is the quality factor.

a) low

b) high

c) constant

d) infinity

**ANSWER: low**

183) For lower Quality factor antennas, the bandwidth is very high.

a) True

b) False

**ANSWER: True**

184) Friss transmission is applicable when same antenna is used for both transmission and reception.

a) True

b) False

**ANSWER: False
**

185) What is the distance between antennas to apply the Friss transmission equation in terms of antennas largest dimension?

a) R » 2D^{2}/λ

b) R « 2D^{2}/λ

c) R » 2λ^{2}/D

d) R « 2λ^{2}/D

**ANSWER: R » 2D ^{2}/λ**

186) Free space loss factor is given by _____

a) λ / 4πR

b) (λ / 4πR)2

c) 4πR / λ

d) (4πR / λ) 2

**ANSWER: (λ / 4πR)2**

187) Which of the following is the Friss transmission equation for the matched polarization of antennas?

a) Pr / Pt=GtGrλ2 / (4πR)2

b) Pt / Pr=GtGrλ2 / (4πR)2

c) Pr / Pt=GtGrλ2 / 4πR2

d) Pt / Pr=GtGrλ2 / 4πR2

**ANSWER: Pr / Pt=GtGrλ2 / (4πR)2 **

188) If the operating frequency increases, powers received by the receiving antenna ______

a) will decrease

b) will Increase

c) is Independent of frequency

d) is not predictable

**ANSWER: will decrease**

189) Power received by the antenna when one antenna is horizontally polarized and the other is vertically polarized is _______

a) 1

b) 0

c) PrPt=GtGrλ2 / (4πR)2

d) PrPt=GtGrλ2 / 2(4πR)2

**ANSWER: 0**

190) Find the power received by the receiving antenna if it is placed at a distance of 20m from the transmitting antenna which is radiating 50W power at a frequency 900MHz and are made-up of half-wave dipoles.

a) 23.65μW

b) 2.365μW

c) 236.5μW

d) 4.73μW

**ANSWER: 236.5μW**

191) Let’s assume a transmitting antenna having gain 10dB is placed at a distance of 100m from the receiving antenna and radiates a power of 5W. Find the gain of the receiving antenna in dB when the received power is 150μW and transmitter frequency 500MHz?

a) 1.31dB

b) 1.19dB

c) 11.19dB

d) 13.16dB

**ANSWER: 11.19dB**

192) If the distance between the transmitting and receiving antenna is decreased by a factor 2 while other factors remain same, then the new power received by the antenna _______

a) increases by factor 2

b) decreases by factor 2

c) increases by factor 4

d) decreases by factor 4

**ANSWER: increases by factor 4**

193) Assume two similar antennas for transmitting and receiving. If the operating frequency gets reduced by 3 times then the received power gets _______

a) increases by factor 3

b) decreases by factor 3

c) increases by factor 9

d) decreases by factor 9

**ANSWER: increases by factor 9**

194) Relation between brightness temperature T_{B} and physical body temperatureT_{p} is ____

a) T_{B}=(1−∣Γs∣2)Tp

b) T_{B}=Tp/(1−∣Γs∣2)

c) T_{B}=(1−∣Γs∣)Tp

d) T_{B}=(1−∣Γs∣)2Tp

**ANSWER: T _{B}=(1−∣Γs∣2)Tp**

195) If the reflection co-efficient is ½ then emissivity is ___

a) 3/4

b) 1/4

c) 1/2

d) 3/2

**ANSWER: 3/4**

196) Overall receiver noise temperature expression if T_{1}, T_{2}… are amplifier 1, 2, and so on noise Temperature and G_{1}, G_{2}, and so on are their gain respectively is_____

a) T = T1+T2 / G1+T3 / G1G2+⋯

b) T = T_{1}+T_{2} (1-G_{1})+T_{3}(1-G_{1}G_{2})+⋯

c) T = T1+T2 / (1−G1)+T3 / (1−G1G2)+⋯

d) T = T_{1}+T_{2} (G_{1})+T_{3}(G_{1}G_{2})+⋯

**ANSWER: T = T1+T2 / G1+T3 / G1G2+⋯**

197) Total noise power of the system is P=_____

a) k(T_{A}+T_{R})B

b) k(T_{A}+T_{R})/B

c) k(T_{R})B

d) kB/T_{sys}

**ANSWER: k(T _{A}+T_{R})B**

198) What is the relation between noise temperature introduced by beam T_{B} and the antenna temperature T_{A} when the solid angle obtained by the noise source is greater than antenna solid angle?

a) T_{A}= T_{B}

b) T_{A} > T_{B}

c) T_{A} < T_{B}

d) T_{A} « T_{B}

**ANSWER: T _{A}= T_{B}**

199) Which expression suits best when the solid angle obtained by the noise source is less than antenna solid angle?

a) P_{A} Ω_{A}=P_{B} Ω_{B} and ΔT_{A}=ΩB / ΩATB

b) P_{A} Ω_{B}=P_{B} Ω_{A} and ΔT_{A}=ΩB / ΩATB

c) ΔT_{A}=ΩA / ΩBTB and P_{A} Ω_{B}=P_{B} Ω_{A}

d) ΔT_{A}=ΩA / ΩBTB and P_{A} Ω_{A}=P_{B} Ω_{B}

**ANSWER: P _{A} Ω_{A}=P_{B} Ω_{B} and ΔT_{A}=ΩB / ΩATB**

200) Expression for noise figure F related to the effective noise temperature T_{e} is ____

a) F=1+Te /To

b) F=1+T0 / Te

c) F=1−Te / To

d) F=1−T0 / Te

**ANSWER: F=1+Te /To**