# ELECTRONICS IMPORTANT MCQ PDF-Antenna & Wave Propagation 1

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
d. Facsimile

3)   Wavefront is basically a locus of points acquiring similar _______
a. Phase
b. Frequency
c. Amplitude
d. Wave equation

4)   In which kind of waveform is the phase velocity defined?
a. Sinusoidal
b. Rectangular
c. Square
d. Triangular

5)   Which among the following is/are not present in free space?
a. Solid bodies
b. Ionized particles
d. All of the above

6)   Power density is basically termed as ________ power per unit area
a. Reflected
b. Refracted
d. Diffracted

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)

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

a. D-region
b. Normal E-region
d. Appleton 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)   F2 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

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

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

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

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°

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
c. Reflected
d. Far-field

18)   Which auxiliary functions assist in solving the radiation problem by evaluation of E & H using sources J & M?
a. Scalar potentials
b. Vector potentials
d. Divergence potentials

19)   Which operations are performed by vector potentials (A, F) over the radiated fields (E & H)?
b. Subtraction
c. Differentiation
d. Integration

20)   Which waveform plays a crucial role in determining the radiation pattern of the dipole/wire antennas?
a. Current
b. Voltage
c. Frequency
d. Phase

21)   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

22)   In flared transmission line, the radiation phenomenon increases due to ________ in flaring
a. Increase
b. Decrease
c. Stability
d. None of the above

23)   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

24)   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

25)   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

a. Poor
b. Good
c. Better
d. Excellent

27)   According to
the directivity of a small loop, which value of ‘θ’ contributes to
achieve the maximum value of radiation intensity (Umax)?

a.
b. 90°
c. 180°
d. 270°

28)   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

29)   What is the nature of radiation pattern of an isotropic antenna?
a. Spherical
b. Dough-nut
c. Elliptical
d. Hyperbolic

array, all the elements in the array should have similar
_______excitation along with similar amplitude excitation for maximum

a. Phase
b. Frequency
c. Current
d. Voltage

31)   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

32)   Which mode of propagation is adopted in HF antennas?
a. Ionospheric
b. Ground wave
c. Tropospheric
d. All of the above

33)   For which band/s is the space wave propagation suitable over 30 MHz?
a. VHF
b. SHF
c. UHF
d. All of the above

34)   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