PSU EXAM MCQ QUESTIONS ON MODULATION,RADAR,TELEVISION,MICROWAVE,ANTENNAS AND NAVIGATION ENGINEERING
1.The following stage in a superhetrodyne receiver provides the maximum image signal selectivity:
(a) RF amplifier (b) IF amplifier (c) AF amplifier (d) Mixer
answer: RF amplifier
2.A sinusoidal voltage amplitude modulates another sinusoidal voltage of amplitude 1 KV resulting in two sidebands each of magnitude 200 V.The modulation index mf is
(a)0.1 (b) 0.2 (c) 0.4 (d) 0.5
Answer:0.4
3.FM discriminator changes FM signal in to
(a) AM signal (b) FM signal (c) PM signal (d) Audio signal
Answer:audio signal
4.In an AM SYSTEM,antenna current(rms) before modulation is 5 A and it increases to 5.8 A after modulation.The percentage of modulation index will be
(a) 88% (b) 80% (c) 83.14% (d) 81.21%
Answer:83.14%
5.The following circuit cannot demodulate AM DSB/SC signal
(a) balanced modulator (b) BFO (c) phase discriminator (d) product detector
answer:phase discriminator
6.In a TV system, the function of equalizing pulses is
(a) To smooth out difference between the vertical sync signals
(b) to maintain horizontal synchronization
(c) to smooth out difference between the horizontal,sync signals
(d) to reduce the bandwidth of transmission
Answer:To smooth out difference between vertical sync signals
7.The modulation index of an AM DSB/FC signal is changed from 0 to 1.The total transmitted power is:
(a) un changed (b) halved (c) doubled (d) increased by 50%
Answer:increased by 50%
8.In an SSB transmitter,one is most likely to find a
(a) Class C audio amplifier
(b) tuned modulator
(c) Class B RF amplifier
(d) Class A RF output amplifier
Answer:Class A RF output amplifier
9.An FM signal with deviation & is passed through a mixer and has its frequency reduced five fold.The deviation at the input of thee mixer is
(a) 5& (b) indeterminate (c) 0.2& (d) &
Answer:&
note:& is not the correct symbol
10.An FM signal with a modulation index Mf is passed through a frequency tripler. The wave at the output of the tripler will have a modulation index of
(a) (1/3)Mf (b) Mf (c)3Mf (d) 9Mf
Answer:3Mf
11.A (75-j50) load is connected to a transmission line of characteristic impedance of Z0= 75 ohm at 11 GHz. The best method of matching consists in connecting
(a) a short circuited stub at the load
(b) an inductance at the load
(c) a capacitance at some specific distance from the load
(d) a short circuited stub at some specific distance from the load
Answer: a short circuited stub at some specific distance from the load
12. In a broadcast superhetrodyne radio receiver,the
(a) local oscillator operates below the signal frequency
(b) mixer output must be tuned to the signal frequency
(c) local oscillator frequency is normally double of the IF
(d) RF amplifier normally works at 455 KHz above the signal frequency
Answer:mixer output must be tuned to the signal frequency
13.To permit the selection of 1 out of 16 equi probable events,the number of bits required is:
(a) 2 (b) log10 16 (c) 8 (d) 4
ANSWER:4
14. The biggest disadvantage of pcm system is
(a) its inability to handle analog signals
(b) the high error rate which its quantization noise introduces
(c) its incompability with TDM
(d) the large bandwidth required for its transmission
ANSWER:THE LARGE BANDWIDTH REQUIRED FOR ITS TRANSMISSION
15.To separate channels in an FDM receiver,it is necessary to use
(a) AND gates (b) BPF (c) differentiation (d) integration
ANSWER: BPF
16. To separate channels in an TDM receiver,it is necessary to use
(a) AND gates (b) BPF (c) differentiation (d) integration
Answer: AND gates
17. Equalizing pulses in a TV system are sent during
(a) Horizontal blanking (b) vertical blanking
(c) the serrations (d) the horizontal retrace
Answer: vertical blanking
18.Vestigial side band transmissions normally used for
(a) HF point to point communications
(b) FM broadcasting
(c) TV broadcasting
(d) Stereo broadcasting
Answer: TV broadcasting
19.A SUPER hetrodyne receiver with an IF OF 450 KHz is tuned to a signal at 1200 KHz.The image signal frequency is:
(a) 750 KHz (b) 900 KHz (c) 1650 KHz (d) 2100 KHz
answer:2100 KHz
20.Pulse width modulation may be generated
(a) by differentiating pulse position modulation
(b) using monostablemultivibrator(MMV)
(C) by integrating the pulse position modulated signal
(d) using a free running muyltivibrator(AMV)
Answer: using a monostablemultivibrator
(mmv)
21.In order to reduce quantization noise in PCM system one must
(a) increase the number of standard amplitudes
(b) send pulses whose sides are more nearly vertical
(c) use an RF amplifier at the receiver end
(d) increase the number of samples per second
Answer:Increase the number of standard amplitudes
22.Time division multiplexing (TDM)
(a) can be used with PCM ONLY
(b) combines five groups in to a super group
(c) stacks 24 channels in adjacent frequency slots
(d)interleaves pulses belonging to different transmissions
Answer: interleaves pulses belonging to different transmissions
23. The video voltage applied to the picture tube of a TV receiver is fed in
(a) between grid and ground (b) to the yoke
(c) between grid and cathode (d) to the anode
ANSWER:between grid and cathode
24.the number of lines in Indian TV system is
(a) 312.5 (b) 625
(c) 50 (d) 15625
Answer:312.5
25.The dominant mode in rectangular wave guide is
(a) TM10 (b) TE10 (c) TE11 (d) TM01
ANSWER:TE10
26.Radar antennas are usually horn antennas
(a) Horn antennas (b) log periodic antennas
(c) parabolic reflectors (d) frequency independent antennas
ANSWER:PARABOLIC REFLECTORS
27.The device not used for pulse operation is
(a) BFO (b) TWT (c) Multicavity klystron (d) Magnetron
ANSWER:BFO
28.The wave guides are generally used above
(a) 100 MHz (b) 3GHz (c) 88 MHz (d) 3 MHz
ANSWER: 3 GHZ
29.The glass tube of TWT(travelling wave tube) may be coated with aquadag to
(a) Provide attenuation (b) Improve bunching
(c) Increase gain (d) Help Focussion
ANSWER:PROVIDE ATTENUATION
30. A lossless antenna has a directive gain of +6dB.If 1mW of power is fed to it,the total power is fed to it,the total radiated will be
(a) 7 mW (B) 1 mW (c) 4 mW (d) 0.25 mW
ANSWER: 4 mW
31.Microwave link repeaters are typically 50 Km apart because
(a) of atmospheric attenuation
(b) of earths curvature
(c) of limitation of transmitted power
(d) to ensure that applied dc voltage is not excessive
ANSWER: OF EARTHS CURVATURE
31. UHF and Microwave frequencies in the range 0.3 GHz TO 30 GHz can be best transmitted using
(a) Surface propagation
(b) Duct propagation
(c) ground wave propagation
(d) Sky wave propagation
ANSWER:DUCT PROPAGATION
32. A Parametric amplifier has input and output frequency of 2.25 GHz and is pumped at 4.75 GHz .
It is a
(a) Degenerate amplifier
(b) travelling amplifier
(c) Lower side band up converter
(d) upper side band up converter
ANSWER: DEGENERATIVE AMPLIFIER
33. If the length of antenna is increased,the directive gain
(a) increases (b) decreases
(c) remains same (d) becomes infinite
ANSWER: INCREASES
34.The dominant modes in rectangular and cylindrical wave guide is
(a) TE10 & TE11
(b) TE10 & TM10
(c) TE11 & TE10
(d) TE10 & TM11
ANSWER: TE10 & TE11
35. A microwave tube amplifier uses an axial magnetic field and radial electric field.This tube represents:
(a) Reflex klystron
(b) TWT
(C) Magnetron
(d) CFA
ANSWER: CFA
36. In a radar system,if the antenna diameter is increased by a factor of 4,the minimum detectable range will be increased by a factor of
(a) 2 root 3
(b) 4
(c) 3
(d) 3 root 2
ANSWER: 4
37. One of the following is very useful as a multi band HF receiving antenna. This represents
(a) Conical Horn (b) folded dipole
(c) log periodic (d) square loop
ANSWER: LOG PERIODIC
38. For a parabolic reflector antenna,the beam width is given by
(a) 70^/D
(b) 170 D/^
(c) 30^D
(D) D/(30^)
ANSWER: 70^/D
NOTE:HERE ^ MEANS LAMDA
39. A TWT is sometimes preferred to a Magnetron as a radar transmitter output tube since it is
(a) Capable of a larger duty cycle
(b) less noisy
(c) a more efficient amplifier
(d) more broad band
ANSWER: CAPABLE OF LARGER DUTY CYCLE
40. Antenna radiation efficiency can be increased by
(a) providing effective earthing
(b) increasing radiation resistance
(c) reducing radiation resistance
(d) increasing effective length
ANSWER: INCREASING RADIATION RESISTANCE
41.The device not used for pulse operation is
(a) BWO
(b) TWT
(c) Multicavity Klystron
(d) Magnetron
ANSWER:BWO
42. Top loading is sometimes used with antenna in order to increase its
(a) beam width
(b) band width
(c) input capacitance
(d) effective height
ANSWER: EFFECTIVE HEIGHT
43.The dominant mode in cylindrical wave guide is
(a) TE10
(B) TE11
(C) TM10
(D) TM11
ANSWER: TE11
(a) RF amplifier (b) IF amplifier (c) AF amplifier (d) Mixer
answer: RF amplifier
2.A sinusoidal voltage amplitude modulates another sinusoidal voltage of amplitude 1 KV resulting in two sidebands each of magnitude 200 V.The modulation index mf is
(a)0.1 (b) 0.2 (c) 0.4 (d) 0.5
Answer:0.4
3.FM discriminator changes FM signal in to
(a) AM signal (b) FM signal (c) PM signal (d) Audio signal
Answer:audio signal
4.In an AM SYSTEM,antenna current(rms) before modulation is 5 A and it increases to 5.8 A after modulation.The percentage of modulation index will be
(a) 88% (b) 80% (c) 83.14% (d) 81.21%
Answer:83.14%
5.The following circuit cannot demodulate AM DSB/SC signal
(a) balanced modulator (b) BFO (c) phase discriminator (d) product detector
answer:phase discriminator
6.In a TV system, the function of equalizing pulses is
(a) To smooth out difference between the vertical sync signals
(b) to maintain horizontal synchronization
(c) to smooth out difference between the horizontal,sync signals
(d) to reduce the bandwidth of transmission
Answer:To smooth out difference between vertical sync signals
7.The modulation index of an AM DSB/FC signal is changed from 0 to 1.The total transmitted power is:
(a) un changed (b) halved (c) doubled (d) increased by 50%
Answer:increased by 50%
8.In an SSB transmitter,one is most likely to find a
(a) Class C audio amplifier
(b) tuned modulator
(c) Class B RF amplifier
(d) Class A RF output amplifier
Answer:Class A RF output amplifier
9.An FM signal with deviation & is passed through a mixer and has its frequency reduced five fold.The deviation at the input of thee mixer is
(a) 5& (b) indeterminate (c) 0.2& (d) &
Answer:&
note:& is not the correct symbol
10.An FM signal with a modulation index Mf is passed through a frequency tripler. The wave at the output of the tripler will have a modulation index of
(a) (1/3)Mf (b) Mf (c)3Mf (d) 9Mf
Answer:3Mf
11.A (75-j50) load is connected to a transmission line of characteristic impedance of Z0= 75 ohm at 11 GHz. The best method of matching consists in connecting
(a) a short circuited stub at the load
(b) an inductance at the load
(c) a capacitance at some specific distance from the load
(d) a short circuited stub at some specific distance from the load
Answer: a short circuited stub at some specific distance from the load
12. In a broadcast superhetrodyne radio receiver,the
(a) local oscillator operates below the signal frequency
(b) mixer output must be tuned to the signal frequency
(c) local oscillator frequency is normally double of the IF
(d) RF amplifier normally works at 455 KHz above the signal frequency
Answer:mixer output must be tuned to the signal frequency
13.To permit the selection of 1 out of 16 equi probable events,the number of bits required is:
(a) 2 (b) log10 16 (c) 8 (d) 4
ANSWER:4
14. The biggest disadvantage of pcm system is
(a) its inability to handle analog signals
(b) the high error rate which its quantization noise introduces
(c) its incompability with TDM
(d) the large bandwidth required for its transmission
ANSWER:THE LARGE BANDWIDTH REQUIRED FOR ITS TRANSMISSION
15.To separate channels in an FDM receiver,it is necessary to use
(a) AND gates (b) BPF (c) differentiation (d) integration
ANSWER: BPF
16. To separate channels in an TDM receiver,it is necessary to use
(a) AND gates (b) BPF (c) differentiation (d) integration
Answer: AND gates
17. Equalizing pulses in a TV system are sent during
(a) Horizontal blanking (b) vertical blanking
(c) the serrations (d) the horizontal retrace
Answer: vertical blanking
18.Vestigial side band transmissions normally used for
(a) HF point to point communications
(b) FM broadcasting
(c) TV broadcasting
(d) Stereo broadcasting
Answer: TV broadcasting
19.A SUPER hetrodyne receiver with an IF OF 450 KHz is tuned to a signal at 1200 KHz.The image signal frequency is:
(a) 750 KHz (b) 900 KHz (c) 1650 KHz (d) 2100 KHz
answer:2100 KHz
20.Pulse width modulation may be generated
(a) by differentiating pulse position modulation
(b) using monostablemultivibrator(MMV)
(C) by integrating the pulse position modulated signal
(d) using a free running muyltivibrator(AMV)
Answer: using a monostablemultivibrator
(mmv)
21.In order to reduce quantization noise in PCM system one must
(a) increase the number of standard amplitudes
(b) send pulses whose sides are more nearly vertical
(c) use an RF amplifier at the receiver end
(d) increase the number of samples per second
Answer:Increase the number of standard amplitudes
22.Time division multiplexing (TDM)
(a) can be used with PCM ONLY
(b) combines five groups in to a super group
(c) stacks 24 channels in adjacent frequency slots
(d)interleaves pulses belonging to different transmissions
Answer: interleaves pulses belonging to different transmissions
23. The video voltage applied to the picture tube of a TV receiver is fed in
(a) between grid and ground (b) to the yoke
(c) between grid and cathode (d) to the anode
ANSWER:between grid and cathode
24.the number of lines in Indian TV system is
(a) 312.5 (b) 625
(c) 50 (d) 15625
Answer:312.5
25.The dominant mode in rectangular wave guide is
(a) TM10 (b) TE10 (c) TE11 (d) TM01
ANSWER:TE10
26.Radar antennas are usually horn antennas
(a) Horn antennas (b) log periodic antennas
(c) parabolic reflectors (d) frequency independent antennas
ANSWER:PARABOLIC REFLECTORS
27.The device not used for pulse operation is
(a) BFO (b) TWT (c) Multicavity klystron (d) Magnetron
ANSWER:BFO
28.The wave guides are generally used above
(a) 100 MHz (b) 3GHz (c) 88 MHz (d) 3 MHz
ANSWER: 3 GHZ
29.The glass tube of TWT(travelling wave tube) may be coated with aquadag to
(a) Provide attenuation (b) Improve bunching
(c) Increase gain (d) Help Focussion
ANSWER:PROVIDE ATTENUATION
30. A lossless antenna has a directive gain of +6dB.If 1mW of power is fed to it,the total power is fed to it,the total radiated will be
(a) 7 mW (B) 1 mW (c) 4 mW (d) 0.25 mW
ANSWER: 4 mW
31.Microwave link repeaters are typically 50 Km apart because
(a) of atmospheric attenuation
(b) of earths curvature
(c) of limitation of transmitted power
(d) to ensure that applied dc voltage is not excessive
ANSWER: OF EARTHS CURVATURE
31. UHF and Microwave frequencies in the range 0.3 GHz TO 30 GHz can be best transmitted using
(a) Surface propagation
(b) Duct propagation
(c) ground wave propagation
(d) Sky wave propagation
ANSWER:DUCT PROPAGATION
32. A Parametric amplifier has input and output frequency of 2.25 GHz and is pumped at 4.75 GHz .
It is a
(a) Degenerate amplifier
(b) travelling amplifier
(c) Lower side band up converter
(d) upper side band up converter
ANSWER: DEGENERATIVE AMPLIFIER
33. If the length of antenna is increased,the directive gain
(a) increases (b) decreases
(c) remains same (d) becomes infinite
ANSWER: INCREASES
34.The dominant modes in rectangular and cylindrical wave guide is
(a) TE10 & TE11
(b) TE10 & TM10
(c) TE11 & TE10
(d) TE10 & TM11
ANSWER: TE10 & TE11
35. A microwave tube amplifier uses an axial magnetic field and radial electric field.This tube represents:
(a) Reflex klystron
(b) TWT
(C) Magnetron
(d) CFA
ANSWER: CFA
36. In a radar system,if the antenna diameter is increased by a factor of 4,the minimum detectable range will be increased by a factor of
(a) 2 root 3
(b) 4
(c) 3
(d) 3 root 2
ANSWER: 4
37. One of the following is very useful as a multi band HF receiving antenna. This represents
(a) Conical Horn (b) folded dipole
(c) log periodic (d) square loop
ANSWER: LOG PERIODIC
38. For a parabolic reflector antenna,the beam width is given by
(a) 70^/D
(b) 170 D/^
(c) 30^D
(D) D/(30^)
ANSWER: 70^/D
NOTE:HERE ^ MEANS LAMDA
39. A TWT is sometimes preferred to a Magnetron as a radar transmitter output tube since it is
(a) Capable of a larger duty cycle
(b) less noisy
(c) a more efficient amplifier
(d) more broad band
ANSWER: CAPABLE OF LARGER DUTY CYCLE
40. Antenna radiation efficiency can be increased by
(a) providing effective earthing
(b) increasing radiation resistance
(c) reducing radiation resistance
(d) increasing effective length
ANSWER: INCREASING RADIATION RESISTANCE
41.The device not used for pulse operation is
(a) BWO
(b) TWT
(c) Multicavity Klystron
(d) Magnetron
ANSWER:BWO
42. Top loading is sometimes used with antenna in order to increase its
(a) beam width
(b) band width
(c) input capacitance
(d) effective height
ANSWER: EFFECTIVE HEIGHT
43.The dominant mode in cylindrical wave guide is
(a) TE10
(B) TE11
(C) TM10
(D) TM11
ANSWER: TE11
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