9294 + Mcqs in Electronics and Communication Engineering Page 163 McqOptions

8101.	If the repeller voltage in a klystron oscillator is increased the transit time of electron
A.	will be increased
B.	will be decreased
C.	will remain the same
D.	either (a) or (b)
Answer» D. either (a) or (b)

Discussion

8102.	A microstrip line has r = 9. The normalised wavelength is about
A.	10
B.	2
C.	1
D.	0.4
Answer» E.

Discussion

8103.	A square waveguide carries TE11 mode whose axial magnetic field is given by Hz = H0 , where the guide dimensions are in cms. The cut off frequency of the mode is
A.	5 GHz
B.	7.5 GHz
C.	6.5 GHz
D.	8 GHz
Answer» C. 6.5 GHz

Discussion

8104.	The rotation of direction of E field of a linearly polarized wave passing through a magnetised ferric medium is called
A.	Lorentz rotation
B.	Faraday rotation
C.	Steinmitz rotation
D.	Fleming's rotation
Answer» C. Steinmitz rotation

Discussion

8105.	If air pressure in a rectangular waveguide is increased the maximum power handling capacity
A.	is decreased
B.	is increased
C.	remains the same
D.	may increase or decrease depending on pressure
Answer» C. remains the same

Discussion

8106.	For air filled circular waveguides
A.	the attenuation due to imperfect conducting walls is negligible
B.	the attenuation due to imperfect dielectric is negligible
C.	both the attenuation i.e. due to imperfect conducting walls and due to imperfect dielectric are significant
D.	the total attenuation is almost zero
Answer» C. both the attenuation i.e. due to imperfect conducting walls and due to imperfect dielectric are significant

Discussion

8107.	In microwave circuits, a mode transducer is used to
A.	change mode of wave transmission
B.	change direction of wave transmission
C.	change polarization of wave transmission
D.	change mode, direction or polarization wave transmission
Answer» E.

Discussion

8108.	A waveguide connected to a circularly polarized antenna must be able to efficiently propagate both vertically and horizontally polarised waves.
A.	True
B.	False
Answer» B. False

Discussion

8109.	Satellite communication systems use the frequency band
A.	10 to 20 MHz
B.	50 to 70 MHz
C.	3 to 6 GHz
D.	100 to 120 GHz
Answer» D. 100 to 120 GHz

Discussion

8110.	A TR (transmitter receiver) tube has
A.	low loss for low power signals and high
B.	high loss for low power signals and low loss for high level signal
C.	low loss for both low level and high level signals
D.	high loss for both low level and high level signals
Answer» B. high loss for low power signals and low loss for high level signal

Discussion

8111.	The characteristic impedance of a cable is about
A.	300
B.	50
C.	5
D.	2
Answer» C. 5

Discussion

8112.	The reverse voltage applied to a varactor diode
A.	is less than avalanche breakdown voltage
B.	is more than avalanche breakdown voltage
C.	may be more or less than a avalanche breakdown voltage
D.	is very high as compared to avalanche breakdown voltage
Answer» B. is more than avalanche breakdown voltage

Discussion

8113.	The directivity in a receiving antenna increases the intercept area in forward directionreduces the noise picked up from other sourcesprovides a means of discriminating against undesired signals originating in directions other than in which the desired transmitter lies. Which of the above statements are correct?
A.	1 only
B.	1 and 2 only
C.	1, 2 and 3
D.	2 and 3 only
Answer» D. 2 and 3 only

Discussion

8114.	Assertion (A): PIN diode can be used as attenuator and limiter.Reason (R): PIN diode has a thin intrinsic layer.
A.	Both A and R are correct and R is correct explanation of A
B.	Both A and R are correct but R is not correct explanation of A
C.	A is correct but R is wrong
D.	A is wrong but R is correct
Answer» C. A is correct but R is wrong

Discussion

8115.	The bunching action which occurs in multicavity klystron amplifier can be represented by Applegate diagram
A.	True
B.	False
Answer» B. False

Discussion

8116.	A circular polarizer converts a linearly polarized wave into a circularly polarised wave.
A.	True
B.	False
Answer» B. False

Discussion

8117.	Consider the following statements Impedance of Gunn diode is about tens of ohms.Impedance of Impatt diode is a few ohms.Impedance of Impatt diode are of the same order.Impedance of Impatt diode is more than that of Gunn diode. Which of the above statement are correct?
A.	all
B.	1 and 2 only
C.	1, 2 and 3
D.	1, 2 and 4
Answer» C. 1, 2 and 3

Discussion

8118.	Assertion (A): Impatt diode is an avalanche diode.Reason (R): Avalanche breakdown phenomenon occurs when a p-n junction is reverse biased.
A.	Both A and R are correct and R is correct explanation of A
B.	Both A and R are correct but R is not correct explanation of A
C.	A is correct but R is wrong
D.	A is wrong but R is correct
Answer» C. A is correct but R is wrong

Discussion

8119.	In high frequency circuits impedance matching can be done by open circuited stubsshort circuited stubstransformer Which of the above correct?
A.	1, 2 and 3
B.	1 and 2 only
C.	1 and 3 only
D.	2 and 3 only
Answer» B. 1 and 2 only

Discussion

8120.	The external magnetic field in a magnetron is such that lines are
A.	parallel to the axis of cathode
B.	perpendicular to the axis of cathode
C.	inclined to the axis of cathode
D.	either (b) or (c)
Answer» B. perpendicular to the axis of cathode

Discussion

8121.	Varactor diodes use
A.	silicon
B.	GaAs
C.	either (a) or (b)
D.	neither (a) nor (b)
Answer» D. neither (a) nor (b)

Discussion

8122.	A transmission line has Z0 = 300 and ZL = (300 - j300) ohm. The transmission coefficient is
A.	1.265 - 18.43
B.	1.01 - 10
C.	1.14 66.68
D.	1.09 66.68
Answer» B. 1.01 - 10

Discussion

8123.	If D is diameter of circular waveguide the cutoff wave-length for TE11 mode is equal to
A.	1.706 D
B.	2.11 D
C.	0.82 D
D.	0.41 D
Answer» B. 2.11 D

Discussion

8124.	In a reflex klystron oscillator, repeller electrode is at
A.	low positive potential
B.	high positive potential
C.	negative potential
D.	zero potential
Answer» D. zero potential

Discussion

8125.	A (75 - J50) ohm load is connected to a coaxial of Z0 = 75 ohm at 10 GHz. The best method of matching is to connect
A.	an inductance at load
B.	a short circuited stub at load
C.	a short circuited stub at specific distance from load
D.	a capacitance at specific distance from load
Answer» D. a capacitance at specific distance from load

Discussion

8126.	A quarter wave line short circuited at load end behaves as
A.	an inductance
B.	an inductance and capacitance in series
C.	a capacitance
D.	an inductance and capacitance in parallel
Answer» E.

Discussion

8127.	A magnetron has a cylindrical cathode surrounded by an anode structure having cavities opening into interaction space by means of slots
A.	True
B.	False
Answer» B. False

Discussion

8128.	The width of a radio beam from a 1 m diameter parabolic antenna at 1 GHz is about
A.	100
B.	50
C.	5
D.	2
Answer» C. 5

Discussion

8129.	If a line having Z0 = 300 0 W is open circuited at far end, VSWR is
A.	0
B.	1
C.
D.	2
Answer» D. 2

Discussion

8130.	Assertion (A): The condition of minimum distortion in a transmission line is L = RC/G.Reason (R): Line loading means addition of inductance to satisfy the condition L = RC/G.
A.	Both A and R are correct and R is correct explanation of A
B.	Both A and R are correct but R is not correct explanation of A
C.	A is correct but R is wrong
D.	A is wrong but R is correct
Answer» C. A is correct but R is wrong

Discussion

8131.	If 'a' is the width of rectangular wave guide and ' ' is the wave length, then
A.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/11-77-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/11-77-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/11-77-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/11-77-4.png">
Answer» C. <img src="/_files/images/electronics-and-communication-engineering/microwave-communication/11-77-3.png">

Discussion

8132.	A parametric amplifier uses
A.	non linear resistance
B.	non linear reactance
C.	either (a) or (b)
D.	neither (a) nor (b)
Answer» C. either (a) or (b)

Discussion

8133.	Assertion (A): Impatt diode can be used in both amplifiers and oscillators.Reason (R): Impatt diode has a low resistance.
A.	Both A and R are correct and R is correct explanation of A
B.	Both A and R are correct but R is not correct explanation of A
C.	A is correct but R is wrong
D.	A is wrong but R is correct
Answer» C. A is correct but R is wrong

Discussion

8134.	Which one of the following can be used for amplification of microwave energy?
A.	TWT
B.	Magnetron
C.	Reflex klystron
D.	Gunn diode
Answer» B. Magnetron

Discussion

8135.	If ZTE is wave impedance for TE waves, Ed is maximum dielectric strength of insulating material, a and b are the width and height of a rectangular wave guide, the maximum power handling capability Pmax for TE10 mode is
A.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-99-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-99-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-99-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-99-4.png">
Answer» C. <img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-99-3.png">

Discussion

8136.	At frequencies of 10 MHz and higher the impedance represented by ground is primarity
A.	resistive
B.	inductive
C.	capacitive
D.	partly resistive and partly capacitive
Answer» D. partly resistive and partly capacitive

Discussion

8137.	For a rectangular waveguide having width a and height b, the cutoff wavelength for TM11 mode is equal to
A.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-88-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-88-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-88-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-88-4.png">
Answer» C. <img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-88-3.png">

Discussion

8138.	The path length between ports 1 and 2 for the two waves in a hybrid ring is
A.	1
B.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/20-246-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/20-246-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/microwave-communication/20-246-4.png">
Answer» D. <img src="/_files/images/electronics-and-communication-engineering/microwave-communication/20-246-4.png">

Discussion

8139.	A TE10 rectangular waveguide is to be designed for operation over 25-35 GHz and the band centre is 1.5 times the cutoff frequency. The dimension of broadside is
A.	15 mm
B.	10 mm
C.	9 mm
D.	7.5 mm
Answer» E.

Discussion

8140.	In a klystron amplifier the force on all electrons
A.	causes acceleration of all electrons
B.	causes retardation of all electrons
C.	causes acceleration of some electrons and retardation of others
D.	none of the above
Answer» D. none of the above

Discussion

8141.	The radiation resistance of a circular loop of one turn is 0.01 ohm. For 5 turn loop the radiation resistance is
A.	0.002
B.	0.01
C.	0.05
D.	0.25
Answer» E.

Discussion

8142.	A 75 ohm line is first short terminated and minima locations are noted. Then the short is replaced by resistive load and minima location are again noted. If minima location are not altered and VSWR is 3, the value of resistive load is
A.	25
B.	50
C.	225
D.	250
Answer» D. 250

Discussion

8143.	The inductance of a twin feeder used to connect antenna to TV receiver is about
A.	0.2 H/m
B.	0.6 H/m
C.	1.6 H/m
D.	10 H/m
Answer» D. 10 H/m

Discussion

8144.	The two terms used to describe performance of a directional coupler are
A.	coupling and directivity
B.	gain and coupling
C.	gain and directivity
D.	gain and isolation
Answer» B. gain and coupling

Discussion

8145.	The word 'LORAN' means
A.	long range navigation
B.	long range TV transmission
C.	long range cable transmission
D.	either (b) or (c)
Answer» B. long range TV transmission

Discussion

8146.	In the given figure forward voltage wave has a magnitude
A.	90 V
B.	60 V
C.	30 V
D.	10 V
Answer» D. 10 V

Discussion

8147.	The duty cycle of a radar transmitter is equal to
A.	(PRF) (pulse width)
B.	(PRF)/(pulse width)
C.	(pulse width)/(PRF)
D.	(pulse width) + (PRF)
Answer» B. (PRF)/(pulse width)

Discussion

8148.	In a klystron amplifier the bunching effect
A.	converts velocity modulation into current modulation of beam
B.	converts current modulation into velocity modulation of beam
C.	both (c) and (b)
D.	neither (a) nor (b)
Answer» B. converts current modulation into velocity modulation of beam

Discussion

8149.	The number of PM radio channels which can be accommodated in a spectrum of 300 MHz is about
A.	10
B.	100
C.	500
D.	1500
Answer» E.

Discussion

8150.	Consider the following statements Gunn diode can be used in combinational logic circuits.Gunn diode can be used in sequential logic circuits.Both Gunn diode and GaAs Mesfet can be used in logic circuits. Which of the above statements are correct?
A.	1, 2, and 3
B.	1 and 2 only
C.	2 and 3 only
D.	1 and 3 only
Answer» B. 1 and 2 only

Discussion

Explore topic-wise MCQs in Engineering.

If the repeller voltage in a klystron oscillator is increased the transit time of electron

A microstrip line has r = 9. The normalised wavelength is about

A square waveguide carries TE11 mode whose axial magnetic field is given by Hz = H0 , where the guide dimensions are in cms. The cut off frequency of the mode is

The rotation of direction of E field of a linearly polarized wave passing through a magnetised ferric medium is called

If air pressure in a rectangular waveguide is increased the maximum power handling capacity

For air filled circular waveguides

In microwave circuits, a mode transducer is used to

A waveguide connected to a circularly polarized antenna must be able to efficiently propagate both vertically and horizontally polarised waves.

Satellite communication systems use the frequency band

A TR (transmitter receiver) tube has

The characteristic impedance of a cable is about

The reverse voltage applied to a varactor diode

Assertion (A): PIN diode can be used as attenuator and limiter.Reason (R): PIN diode has a thin intrinsic layer.

The bunching action which occurs in multicavity klystron amplifier can be represented by Applegate diagram

A circular polarizer converts a linearly polarized wave into a circularly polarised wave.

Consider the following statements Impedance of Gunn diode is about tens of ohms.Impedance of Impatt diode is a few ohms.Impedance of Impatt diode are of the same order.Impedance of Impatt diode is more than that of Gunn diode. Which of the above statement are correct?

Assertion (A): Impatt diode is an avalanche diode.Reason (R): Avalanche breakdown phenomenon occurs when a p-n junction is reverse biased.

In high frequency circuits impedance matching can be done by open circuited stubsshort circuited stubstransformer Which of the above correct?

The external magnetic field in a magnetron is such that lines are

Varactor diodes use

A transmission line has Z0 = 300 and ZL = (300 - j300) ohm. The transmission coefficient is

If D is diameter of circular waveguide the cutoff wave-length for TE11 mode is equal to

In a reflex klystron oscillator, repeller electrode is at

A (75 - J50) ohm load is connected to a coaxial of Z0 = 75 ohm at 10 GHz. The best method of matching is to connect

A quarter wave line short circuited at load end behaves as

A magnetron has a cylindrical cathode surrounded by an anode structure having cavities opening into interaction space by means of slots

The width of a radio beam from a 1 m diameter parabolic antenna at 1 GHz is about

If a line having Z0 = 300 0 W is open circuited at far end, VSWR is

Assertion (A): The condition of minimum distortion in a transmission line is L = RC/G.Reason (R): Line loading means addition of inductance to satisfy the condition L = RC/G.

If 'a' is the width of rectangular wave guide and ' ' is the wave length, then

A parametric amplifier uses

Assertion (A): Impatt diode can be used in both amplifiers and oscillators.Reason (R): Impatt diode has a low resistance.

Which one of the following can be used for amplification of microwave energy?

If ZTE is wave impedance for TE waves, Ed is maximum dielectric strength of insulating material, a and b are the width and height of a rectangular wave guide, the maximum power handling capability Pmax for TE10 mode is

At frequencies of 10 MHz and higher the impedance represented by ground is primarity

For a rectangular waveguide having width a and height b, the cutoff wavelength for TM11 mode is equal to

The path length between ports 1 and 2 for the two waves in a hybrid ring is

A TE10 rectangular waveguide is to be designed for operation over 25-35 GHz and the band centre is 1.5 times the cutoff frequency. The dimension of broadside is

In a klystron amplifier the force on all electrons

The radiation resistance of a circular loop of one turn is 0.01 ohm. For 5 turn loop the radiation resistance is

A 75 ohm line is first short terminated and minima locations are noted. Then the short is replaced by resistive load and minima location are again noted. If minima location are not altered and VSWR is 3, the value of resistive load is

The inductance of a twin feeder used to connect antenna to TV receiver is about

The two terms used to describe performance of a directional coupler are

The word 'LORAN' means

In the given figure forward voltage wave has a magnitude

The duty cycle of a radar transmitter is equal to

In a klystron amplifier the bunching effect

The number of PM radio channels which can be accommodated in a spectrum of 300 MHz is about

Consider the following statements Gunn diode can be used in combinational logic circuits.Gunn diode can be used in sequential logic circuits.Both Gunn diode and GaAs Mesfet can be used in logic circuits. Which of the above statements are correct?