Antennas and wave propagation - Electronics Engineering test questions

Antennas and wave propagation - Electronics Engineering test questions

(1) According to Siegel and Labus, antennas can be treated as

(A) Earthed transmission line
(B) Closed transmission line
(C) Opened out transmission line
(D) Shorted transmission line

(2) Triatics are

(A) Supports for antenna conductors
(B) Small height antennas directly mounted on ship, jeeps etc.
(C) The towers or masts, which are used as radiators
(D) The towers or masts, which are not used as radiators

(3) Which one of the following statement is true for log periodic antenna?

(A) Frequency dependent antenna
(B) Frequency independent antenna
(C) Directional antenna
(D) None of the above

(4) Let the directivity of a microwave antenna be 900. The maximum effective aperture will be

(A) 716.19 λ ²
(B) 71.619 λ ²
(C) 7.1619 λ ²
(D) 71619 λ ²

(5) Consider a vertical earthed antenna. This antenna will be resonant when its physical height will be

(A) λ / 4
(B) λ
(C) λ / 2
(D) 2 λ

(6) Circular polarization is formed in

(A) Helical antenna
(B) Yagi-Uda antenna
(C) Parabolic antenna
(D) Dipole antenna

(7) In loop antennas the radiation pattern formed is

(A) Semicircle
(B) Circle
(C) Cardiod
(D) None of the above

(8) Which of the following statement is true for bandwidth of an antenna?

(A) Inversely proportional to 1 / Q²
(B) Directly proportional to Q²
(C) Directly proportional to Q
(D) Inversely proportional to Q

(9) What should be the height of an antenna in order to consider it to be in free space?

(A) 2λ
(B) > 5λ
(C) < 3λ
(D) λ

(10) Radiation efficiency of an antenna is given by

(A) Directivity / Maximum power gain
(B) Maximum power gain / Directivity
(C) Radiation resistance / Antenna resistance
(D) Antenna resistance / Radiation resistance

(11) For Yagi-Uda array the term that is not applicable is

(A) Good bandwidth
(B) High gain
(C) Folded dipole
(D) Parasitic elements

(12) Consider a pyramidal horn antenna whose mouth height is 10λ. Horn is fed by a rectangular waveguide with TE?? mode. The length of an antenna will be

(A) 62.5 λ
(B) 12.5 λ
(C) 5 λ
(D) 42.5 λ

(13) The crossed dipoles in a turnstile antenna are excited with voltages

(A) In phase with each other
(B) 180° out of phase with each other
(C) 120° out of phase with each other
(D) 90° out of phase with each other

ANSWER: 90° out of phase with each other

(14) The effect of skip distance in frequency is

(A) It decreases with increase in frequency
(B) It increases with increase in frequency
(C) It increases with decrease in frequency
(D) It decreases with decrease in frequency

ANSWER: It increases with increase in frequency

(15) The electromagnetic waves get absorbed in the atmosphere. The absorption of electromagnetic waves mainly depends on

(A) Distance from the transmitter
(B) The polarization of waves
(C) The frequency in use
(D) All of the above

(16) The critical frequency of a wave is 30 MHz and departing angle is 60°. The MUF is given to be

(A) 60 MHz
(B) 15 MHz
(C) 120 MHz
(D) 30 MHz

(17) The frequency for satellite communication should be

(A) More than the critical frequency
(B) Less than the critical frequency
(C) Equal to the critical frequency
(D) None of the above

ANSWER: More than the critical frequency

(18) Which one of the following frequencies is used in troposphere?

(A) VHF
(B) UHF
(C) HF
(D) VLF

(19) The fluctuation in the received signal strength at the receiver or a random variation in the received signal is known as

(A) Absorption
(B) Cycling
(C) Fluctuation

(20) ____________ is not between F2 layer and D layer

(A) G region
(B) E layer
(C) F1 layer
(D) All of the above

(21) The abnormal variation in ionosphere is

(A) Ionospheric storm
(B) Seasonal variation
(C) Diurnal variation
(D) All of the above

(22) In the UHF range the frequencies propagate by means of

(A) Surface waves
(B) Sky waves
(C) Space waves
(D) Ground waves

(23) In high frequency propagation the layer that is least important is

(A) E layer
(B) D layer
(C) F1 layer
(D) F2 layer

(24) The fading that causes serious distortion of modulated signal is

(25) As one moves away from the transmitter, the ground waves eventually disappears because of

(A) Maximum single hop distance limitation
(B) Loss of line-of-sight condition
(C) Tilting
(D) Interference from the sky waves