## Amazon Coding challenge on Time Slots

Here is the Amazon coding challenge with solution. Please do comment below if you find any issues with the solution. Ready to learn and evolve. Knowledge is Power.

Given M busy-time slots of the team members in the Kindle team, can you print all the available time slots when all of them can schedule a meeting for a duration of K minutes.
The event time will be of the form HH MM (where 0 <= HH <= 23 and 0 <= MM <= 59). K will be in the form minutes.

Input Format:

M K [M number of busy time slots , K is the duration in minutes]
This is followed by M lines with 4 numbers on each line.
Each line will be of the form StartHH StartMM EndHH EndMM  [Eg: 9am-11am time slot will be given as 9 00 11 00]
An event time slot is of the form [Start Time, End Time) which means the start time is inclusive but not the end time;
So, an event of the form 10 00  11 00 => implies that the meeting starts at 10:00 and ends at 11:00. Hence, another meeting can start at 11:00.

Sample Input:
5 120
16 00 17 00
10 30 14 30
20 45 22 15
10 00 13 15
09 00 11 00

Sample Output:
00 00 09 00
17 00 20 45

/* Enter your code here. Read input from STDIN. Print output to STDOUT */

#include
#include
using namespace std;

int main()
{
int bTimeSlots, duraInMin;
cin >> bTimeSlots >> duraInMin;

int startHH, stopHH, startMM, stopMM;
const int minPerday = 1440;
int storeBooking[minPerday] = {0};

for (int i=0;i        cin >> startHH >> startMM >> stopHH >> stopMM;

if (startHH>24 or stopHH > 24 or startMM > 59 or stopMM>59)
exit(EXIT_FAILURE);

int startMeet = startHH * 60 + startMM;
int stopMeet = stopHH * 60 + stopMM;

for (int j=startMeet;j<=stopMeet;j++){
storeBooking[j]=1;
}
}

int timeInterval = 0;
int freeTimeStart=0, freeTimeStop;

for (int k=0;k
if (storeBooking[k]==1){
if ((k/duraInMin) > 0 && storeBooking[k-1]==0){

if ((k - freeTimeStart) >= duraInMin){

cout << setfill('0') << setw(2) << freeTimeStart/60
<< " "
<< setfill('0') << setw(2) << freeTimeStart%60
<< " "
<< setfill('0') << setw(2) << k/60
<< " "
<< setfill('0') << setw(2) << k%60
<< "\n";
}

}

freeTimeStart = k;
}else if(k==minPerday -1){
if ((k - freeTimeStart) >= duraInMin){
int finalHH;
if (((k+1)/60)==24){ finalHH=0; }else{finalHH = (k+1)/60; }

cout << setfill('0') << setw(2) << freeTimeStart/60
<< " "
<< setfill('0') << setw(2) << freeTimeStart%60
<< " "
<< setfill('0') << setw(2) << finalHH
<< " "
<< setfill('0') << setw(2) << (k+1)%60
<< "\n";
}
}
}

}

## BEL PE Question Paper with Answers for Electronics - 7

BEL Placement Paper (Technical- Electronics VII)

1. The professional printed circuit board generally use the following as the raw material:
a. Paper base bakelite copper clad sheet
b. Glass epoxy copper clad sheet
c. Tin plated Nylon sheet
d. Silver plated pyrex sheet

2. Many switch contacts use silver as the material because
a. It is a good electrical conductor with low contact resistance
b. Silver does not tarnish
c. It is easily shaped as per requirement
d. It is very hard and does not wear off

3. A resistance of approximate value 85W is to be measured by using an ammeter of range 0-1 A having a resistance of 20 W and voltmeter of range 0-50V having a resistance of 5000W. Two arrangement for the measurement are shown in the figure below. Which method would you recommend?
a. Method X
b. Method Y
c. Either X or Y
d. Neither X nor Y

4. The value of capacitance across points A & B in the circuit shown below is (in microfarads)
a. 3         b. 1         c. 0.67          d. 0.33

5. It is proposed to fabricate a simple Ohm meter for measuring  resistor values. A milliammeter with an internal resistance of 50 W is available. Choosing a configuration using a 3 V battery, a large resistance and the ammeter in a loop, the unknown resistor is proposed to be measured by noting the current initially and then connecting the unknown resistor across the ammeter. If the ratio of the two current is 2, what is the value of the unknown resistor (rn W ) ?
a. 3000         b. 150         c. 100         d. 50

6. The current I flowing into the branch indicated by an arrow  in the circuit shown is equal to
a. 2 Amp         b. 0.5 Amp        c. 1 Amp         d. 0.25 Amp

7. For the circuit shown, the maximum power is delivered to the load resistance RL when the value of Rg is
a. 2 ohms        b. zero         c. 10 ohms          d. infinity

8. A signal generator is available in the laboratory, which is in good condition except for the attenuator dial which has got displaced. In order to calibrate this, a high frequency oscilloscope is available. At a particular setting of the knob an open circuit voltage of 450 mV rms is measured. If the impedance of the generator is 50 ohms, the setting of the attenuator dial is to be adjusted for
a. 6 dBm      b. 1 dBm          c. 0 dBm           d. 10 dBm

9. The relation Loge (X + Loge (1 + X) = 0 also means that
a. X2 + X + 1 = 0
b. X2 + X - 1 = 0
c. X2 + X + e = 0
d. X2 + X – e = 0

10. The Laplace transform of the function f(t) = cos wt is
a. w/(s2 + w2)
b. s2/(s2 - w2)
c. w2/(s2 + w2)
d. s/(s2 + w2)

11. If a = b = c, one value of X which satisfies the equation
=0 is given by
a. x=a         b. x=b         c. x=c         d. x=0

12. An LC oscillator is being analysed. If the LC tank circuit (with quality factor = Q) is isolated from the amplifying device, the impedance at the resonant frequency as measured looking into the amplifier will be
a. Q r [LC]1/2
b. ½ rp r [LC]1/2
c. – Q r[LC]1/2
d. Q r [LC]1/2

13. A battery eliminator is required to be constructed and an assortment of rectifiers, resistors and capacitors is available. However, the step down transformer available has no center tap. The following configurations for the rectifier are feasible. The one giving the lowest ripple will be
a. Full wave rectifier
b. Half wave rectified
c. Bridge rectifier
d. None

14. Chokes used in rectifier filter circuits are wound on a core with a small air gap. This is done in order to
a. Get as high an inductance as possible
b. Prevent saturation of the core
c. Absorb the ripple effectively

15. An integrated circuit linear regulator is used at the output of a power supply having a ripple of 1 V rms. Assuming that the IC represents a typical design generally available, the output rms ripple to be expected will be
a. 0.1 V rms      b. 0.1 mV      c. 100 mV       d. 1.0 V rms

16. The minimum PIV rating for the diode in the rectifier circuit shown should be
a. 36v       b. 18v              c. 26v               d. 52v

17. For VHF interfering waves generated by automobile ignition systems or other electrical equipment located close to the ground, specify which of the following components of the interfering signal are significant at receiving locations such as used in the reception of TV signals:
a. Horizontal polarization component
b. Vertical polarization component
c. Both horizontal and vertical polarization components
d. Neither horizontal nor vertical polarization components

18. The ratio of lower frequency limit to the MUF for radio communication at short-wave is generally
a. Smaller at night than in the day time
b. Larger at night than in the day time
c. Same at night and in the day time
d. A maximum during the evening times

19. Two UHF amateur radio antenna placed at the same height and 30 statute miles apart are to be such that each is on the radio horizon line of the other. The height of the antennas should be
a. 56.25 ft            b. 112.5ft         c. 150ft            d. 225ft

20. A transmitter with a radiated power of 1 KW produces a field strengthof 300 mv/m at a distance of 1 Km from the antenna. If the transmitter power is increased to 50 KW and the vertical directivity of the antenna is increased by a factor of 1.41, the field strength a the same distance from the antenna is approximately
a. 1.5 V/m            b. 2.115 V/m                c. 3.0 V/m      d. 6.0 V/m

21. The directive gains of non-resonant and resonant wire antennas of equal length are approximately in the ratio of
a. 4:1       b. 1.5:1            c. 1:1                d 3:1

22. A simple wire radiator produces a radiation field of intensity 100 mV/m at a distance point 25 Km away. The field produced (in mV/m) at a point 50 Km away in the same direction is
a. 25        b.50                 c. 12.5             d. 100

23. Assuming the plane of polarization of the incoming wave and the plane of the receiving antenna to be the same, the effective height of the receiving antenna is proportional to
b. Power gain of the antenna
c. Physical area of the antenna
d. Wavelength, assuming other parameters being same

24. The function performed by the following circuits is
a. General combinational logic
b. Exclusive OR logic
c. Exclusive NOR logic
d. Digital comparator logic

25. Narrow trigger pulses are required to be generated from a square wave pluse train (pulse width = T). The linear wave shaping circuit would be an RC circuit (time constant = T) with the following features:
a. High pass with T << T
b. High pass with T >> T
c. Low pass with T >> T
d. Low pass with T << T

26. The circuit given below acts as
a. An OR gate
b. An AND gate
c. An inverter
d. A NOR gate

27. In the circuit shown below. if  R = 0 and S = 1, the outputs Q and Q'  will be
a. Q low, Q'  high
b. Both low
c. Q high, Q'  low
d. Both high

28. Schmitt trigger buffers are normally used as input buffers to digital logic circuit to achieve
a. Higher isolation
b. Higher fan-in-capability
c. Higher drive capability
d. Higher noise-immunity

29. For a reverse-biased PN junction. If the applied voltage is doubled the junction capacitance decreases by a factor of 2 ½. Assuming the junction acts as a parallel plate condenser, the average spacing between the plates changes by a factor of
a. 22         b.2            c. 1/21/2            d. 21/2

30. Many frequency sources use a piezo-electric resonator in the feedback circuit essentially to achieve a
a. Miniature product
b. Low cost design
c. Stable frequency
d. Large output power

31. A pulse train has the following characteristics:
Peak amplitude = 10 V, Pulse ON time 1 sec
Pulse OFF time = 4 sec
The pulse train is passed through a high pass RC filter with a large time constant.      The amplitude of the positive peak at the output will be
a. 10 V                b. 2V        c. 4V             d. 8V

32. The results fo open circuit test on a single phase transformer are as follows:
Applied voltage =100 V, Current drawn = 0.5 Amp
Power consumed = 30 W
The magnetizing reactance of the transformer is
a. 250 ohms         b. 200 ohms           c. 400 ohms           d. 500 ohms

33. The principle of velocity modulation is NOT used in the following microwave device:
a. Traveling wave tube
b. Magnetron
c. Klystron
d. Reflex klystron

34. The ‘Pulling Figure’ of  a magnetron is due to
a. Variation in the output load
b. Variation in the input load
c. Variation in both input and output loads
d. None

35. The depletion layer in a P-N junction
a. Contains only immobile charges
b. Contains only mobile charge carriers
c. Is depleted off all charge carriers
d. Contains both mobile and immobile charge carriers

36. Consider two bars of a semiconductor of identical dimensions one of which doped P-type and the N-type, with equal number of impurity atoms, the resistance of the P-type bar is
a. Equal to that of the N-type bar
b. Greater than that of the N-type bar
c. Lesser than that of the N-type bar
d. Not related to that of the N-type bar
37. If the base width of a bipolar transistor is increased, then its current gain
a. Increases
b. Decreases first and then increases
c. Remains constant
d. Decreases
38. In a FET, the drain current beyond the pinch off point
a. Increases rapidly with increase in drain to source voltage
b. Reduces slowly with increase in drain to source voltage
c. Remains almost constant
d. Is zero
39. The key feature of CMOS inverter from the point of low power dissipation is that
a. one of the devices is cut-off in either logic state
b. it uses one each of MOS and NMOS devices
c. silicon area required is low
d. its high speed capability
40. At an ambient temperature of 25o C, the junction temperature of a transistor has reached 150oC while dissipation 100 Watts of power. The junction ambient thermal resistance of the transistor is
a. 1.25o /W
b. 0.8o /W
c. 1.5o /W
d. 2.5o /W
41. For a transmission line with air dielectric, the attenuation constant at extremely high frequencies is
a. Directly proportional to the frequency
b. Inversely proportional to the frequency
c. Directly proportional to the square root of frequency
d. Inversely proportional to the square root of frequency
42. In a transmission line with characteristic impedance 50 W a resistive load of 25W produces a VSWR of 2. The same VSWR will be produced if the resistive load is changed to
a. 75W        b. 100 W            c. 1250W             d. 2500W
43. A load resistance of 300W is tobe matched to a two wire transmission line of characteristic impedance 600 W using a quarter-wave line. The characteristic impedance of the matching line should be
a. 424W      b. 300W          c. 450W            d. 900W
44. An oscilloscope video amplifier is found to use a transistor in the common base configuration. The reason for this would be
a. It has a very good high frequency response
b. It gives a higher input impedance
c. It is a very stable configuration
d. It consumes very low current
45. RF amplifiers are generally configures as class C tuned stages. The conduction angle is kept as low as possible consistent with output power because
a. It improves distortion
b. It reduces oscillatory tendency
c. It increases RF gain
d. It improves efficiency
46. In  a directional coupler having 30 dB coupling the RF power available at the coupled output is 10mW. The power input to the directional coupler is
a. 100mW          b. 1 W           c. 10 W       d. 100 W
47. It is required to design a small instrumentation amplifier to improve the sensitivity of an available instrument. For stabilizing the gain under the operating conditions, negative voltage feedback of 10% is considered adequate. If the closed loop gain is required to be 5 (five), the open loop gain required for the amplifier will be
a. 0.5          b. 10              c. 5.5            d. 50
48. A video amplifier is required to be designed for amplifying signals from a TV camera. The back to white transition can take place within 70 nanosec from 10% to 90% of the amplitude of the picture signal. The maximum bandwidth to be chosen for the video amplifier will be
a. 70MHz           b. 7KHz         c. 7MHz         d. 5MHz
49. A microphone amplifier is available which is required to be used with a new microphone of higher sensitivity. With a supply voltage of 12V one of the class A stage is found to be clipping at 6V peak voltage. By changing the collector load to a transformer coupled design instead of resistive, clipping would occur at
a. 3V          b. same level as before          c. 12V            d. 24V
50. In order to get higher power output, two audio amplifiers working in class A are proposed to be combined. There is also an alternate way to convert both stages to class B and then combine. If this alternative is adopted, the maximum audio power can be greater than the class A case by a factor of approximately
a. 12          b. 2             c. 4             d. 6
51. Cross-over distortion in audio amplifier is generally present in
a. Class B amplifiers
b. Class A amplifiers
c. Class A amplifier with negative feedback
d. Transformer coupled class A amplifiers
52. Negative feedback is applied to audio amplifiers to obtain stable gain. As result the distortion will
a. Be unaltered
b. Increase
c. Decrease
d. Disappear
53. Many instrument preamplifiers are transistor gain stages coupled directly without capacitors. This is done in order to obtain
a. A good low frequency response
b. A good impedance match
c. A high gain
d. A low noise output
54. Class B push-pull operation gives an output signal with low distortion because
a. It operates in linear portion of V-I characteristic
b. Even harmonic components get cancelled
c. There is inherent feedback to reduce distortion
d. Distortion components are automatically filtered out
55. Cross modulation in a receiver takes place in the
a. Audio amplifier stage
b. IF amplifier stage
c. RF amplifier stage
d. Detector stage
56. Neutralizing circuits are used in tuned RF amplifiers to
a. Improve efficiency
b. Develop more RF power
c. Prevent oscillations due to internal feedback
d. Obtain good thermal stability
57. It is required to construct a simple oscillator to test transducers in the audio frequency range. It is proposed to configure a wein bridge circuit for which required resistor and capacitors are available. An amplifier is required to be produced to complete the design. The voltage gain to be specified for the amplifier is
a. +1         b. -3         c. +3             d.+10
58. Amplitude modulation is essentially a process which translates the frequency spectrum. To achieve this
a. Time varying linear systems, e.g.switching or chopping circuits only can be employed
b. Circuits using non-linear elements only can be used
c. Neither time varying linear nor non-linear circuit are required
d. Either time varying or non-linear circuits can be used
59. An envelope detector uses a parallel RC circuit to recover the message signal m(t) from an AM wave. If fm is the maximum modulating frequency and fr the cut-off frequency of the RC circuit, the relationship between fm and fris
a. fr = fm
b. fr > fm
c. fr   lies between fm and fc where fc is the carrier frequency
d. fr < fm
60. The bandwidth (in MHz) of a receiver to receive a QPSK modulated RF signal at a data rate of 1.5 MBps is
a. 2.5       b.0.75              c.3.0                d. 6.0
61. Coherent radars utilize for the transmitter oscillator a
a. Magnetron
b. Master oscillator and TWT amplifier
c. Klystron
d. Reflex klystron
62. Interlace technique is used in TV for
a. Improving horizontal resolution
b. Flicker reduction
c. Bandwidth reduction
d. Improving vertical resolution
63. Night effect is caused by
a. Horizontal polarized waves traveling parallel to the ground
b. Vertically polarized waves traveling parallel to the ground
c. Vertically polarized down coming waves
d. Horizontally polarized down coming waves
64. VOR provides bearings with respect to
a. Magnetic north
c. True north
d. Line joining the VOR and the aircraft
65. In VHF FM communication system, a high value of IF(viz. 10.7 MHz) is often used for obtaining
a. Better image rejection
b. Better IF gain
d. Better sensitivity
66. An SSB system and a fully-modulated DSB system have the same peak power. The signal-to-noise power ratio of the SSB system is greater than the DSB system by a factor of
a. 2          b. 4                  c. 16                d. 8
67. In PCM system, for random type of noise at the receiver input, the error performance exhibits a saturation effect with increasing S/N ratio. This threshold is approximately at
a. 26 dB               b. 10dB            c. 17 dB           d. 20 dB
68. In an FM system, for a given transmitter power, the maximum range at which a usable signal can be received will be
a. Greater for a narrower bandwidth
b. Greater for a larger bandwidth
c. Independent of bandwidth
d. Dependent on actual noise level
69. The IF amplification per stage in an FM receiver as compared to an AM receiver using the same amplifier devices is
a. Smaller
b. Larger
c. Same
d. Dependent on the value of the IF
70. A random experiment has 16 equally likely outcomes. The information associated with each outcome is
a. 16 bits              b. 1 bit             c. 2 bits            d. 4 bits
71. The minimum bandwidth required to receive an FM modulated signal with a modulating frequency between 0.5MHz and 5.0MHz and with a maximum deviation of 10MHz is
a. 20MHz            b. 10.5 MHz                c. 30 MHz           d. 15.5 MHz
72. The total power in the two sidebands in a 100% modulated AM wave is
a. Half the total in the modulated wave
b. One fourth the total in the modulated wave
c. One third the total in the modulated wave
d. Independent of the carrier power
73. For a two-tone modulating signal, the PEP of an AM transmitter is
a. Pavg                 b. Pavg / 2        c. 2rPavg         d. 4 r Pavg
74. The image frequency (in MHz) of a receiver with an IF of 21.4 MHz and RF input frequency of 434 MHz is
a. 455.4               b. 476.8           c. 414.6           d. 42.8
75. The noise figure of a receiver having a front end low noise amplifier of noise figure 3 dB followed by a mixer of noise figure 20 dB is
a. 4.1 dB              b. 22 dB           c. 3.2 dB          d. 2.0 dB
76. Demodulation of a single-side band signal is done using
a. Ratio detector
b. Product detector
c. Envelope detector
d. Foster Seely circuit
77. In AM transmitters, such as used for police radios, for maintaining relatively high average percentage modulation irrespective of the speaker it is necessary to use
a. AGC
b. Peak limiters
c. Volume compressors
d. AVC
78. In communication transmitters, use of saturated class C amplifiers after modulation
a. Removes incidental FM is AM systems
b. Is not desirable in FM systems
c. Is permissible in AM systems
d. Removes incidental AM in FM systems
79. Pre-emphasis is used to
a. To get better noise suppression at the low modulation frequencies
b. Maintain a constant modulation index for all modulating signals
c. Avoid signal being suppressed by large values of noise voltages
d. To improve S/N ratio at higher modulation frequencies
80. The selectivity of a Receiver is determined largely by tne characteristics of the
a. AF stage
b. Mixer stage
c. RF stage
d. IF stage
81. In a channel disturbed by white Gaussian noise, the channel capacity C in bits per second is given by C = B log 2 (1 + S / N) where B is the channel bandwidth S is the signal power and N is the noise power. If the channel bandwidth is made infinite, the channel capacity will
a. Remain constant
b. Become infinite
c. Reduce
d. Remain finite
82. The ON time in the drive voltage waveform for the horizontal deflection circuitry in a broadcast TV receiver is 16 microseconds. The duty ratio of this drive voltage is
a. 40%            b. 25%             c. 20%                  d. 75%
83. In the TV system adopted in India , the vision IF is
a. 44.4MHz         b. 38.9MHz                 c. 33.4MHz                  d. 27.9MHz
84. In a TV system, diplexer is used for
a. Using the same antenna for transmission and reception
b. Combining the visual and aural signals into the same antenna
c. Protecting the receiver from the high transmitter power
d. Transmitting two programmes from the same transmitter
85. The amplitude of the sync pulse in a composite television signal with respect to blanking level is
a. 0.3V                b. 1V               c. -0.3V           d. 4V
86. The modulator stage in a high power broadcast transmitter uses the following type of amplification
a. Class B
b. Class A
c. Class AB
d. Class C
87. The brightness control in a conventional TV receiver controls
a. Video amplitude
b. Grid voltage of the CRT
c. Frequency of the horizontal oscillator
d. Anode voltage of the CRT
88. The charge coupled device is used in television for
a. Camera
c. Transmitter
d. Networking
89. Some MTI radars distinguish between moving and stationary targets using the principle that return pulses from
a. Stationary targets contain Doppler shift
b. Stationary targets are stronger
c. Moving targets fiuctuate in phase
d. Moving targets have constant phase
90. In a pulsed radar operating at a frequency f Hz, with an interpulse period of ‘T’ seconds, the maximum unambiguous range is given by
a. cT                    b. cT/2             c. fT                 d. f T/2
91. Angular error is extracted in a modern trabking radar using
a. Cosecant square pattern of the antenna
b. Monopulse technique
c. Helical scan
d. None
92. A radar display which maps the bearing and range on a polar display is called
a. A-scope display
b. PPI display
c. B-scope display
d. C-scope display
93. For a pulsed radar operating with a 1 microsec pulse width and prf of 1 KHz, the average power is 15 W. If the prf alone is changed to 2 KHz, the average power will be
a. 7.5W               b. 15 W           c. 30W             d. 3.75W
94. Radar beacons are used for
a. Ship navigation within horizon range
c. Aircraft navigation and homing of airborne cargo
d. Transmitting distress signals
95. A parabolic antenna converts the energy from the feed located at the focus into a
a. Plane wave front without uniform phase
b. Spherical wave front
c. Curved wave front without uniform phase
d. Plane wave front of uniform phase
96. A backward wave oscillator belongs to the family of
a. Traveling wave tubes
b. Cross field tubes
c. Power grid tubes
d. None
97. The gain of a radar antenna is proportional to
a. Aperture area / Wavelength
b. Frequency / Aperture
c. Aperture area / Square of the wavelength
d. Square of the Aperture area / wavelength
98. In a rectangular waveguide of internal dimensions 12.5 mm r 25 mm, the cut off wavelength for the dominant mode will be
a. 5 cm                 b. 2.5cm           c. 1.25cm         d. 3.75cm
99. In a reflex klystron, electrons bunch around the electron entering the cavity when the RF electric field at the gap is
a. Zero and changing from accelerating to accelerating phase
b. Zero and changing from accelerating to decelerating phase
c. Maximum and in the accelerating phase
d. Maximum and the decelerating or accelerating phase
100. The Doppler frequency shift is
a. Dependent only on the radar frequency
b. Dependent on the target velocity
c. Dependent both on the relative radial velocity of the target and the radar frequency
d. Independent of the radar frequency.

Electronics-VI
1.      b
2.      d
3.      b
4.      d
5.      d
6.      c
7.      b
8.      c
9.      b
10.  d
11.  d
12.  c
13.  c
14.  b
15.  c
16.  a
17.  a
18.  b
19.  c
20.  c
21.  a
22.  a
23.  d
24.  d
25.  a
26.  b
27.  c
28.  d
29.  d
30.  c
31.  a
32.  a
33.  b
34.  a
35.  c
36.  c
37.  d
38.  c
39.  a
40.  a
41.  a
42.  b
43.  a
44.  d
45.  d
46.  d
47.  b
48.  d
49.  c
50.  a
51.  a
52.  c
53.  a
54.  b
55.  d
56.  c
57.  b
58.  d
59.  c
60.  b
61.  a
62.  c
63.  b
64.  b
65.  b
66.  b
67.  c
68.  d
69.  d
70.  b
71.  b
72.  b
73.  b
74.  b
75.  d
76.  c
77.  c
78.  b
79.  a
80.  d
81.  b
82.  b
83.  c
84.  a
85.  c
86.  a
87.  c
88.  b
89.  b
90.  c
91.  b
92.  c
93.  b
94.  a
95.  d
96.  d
97.  b
98.  a
99.  c
100. b

## BEL PE Question Papers for ECE with Answers - 6

BEL Placement Paper (Technical-Electronics 6th)

1. The gray code equivalent of binary 1100 is
a. 1011 b. 1101 c. 1010 d. 1100

2. A Multiplexer has
a. Multiple inputs and single output
b. Single input and Multiple outputs
c. Multiple inputs and Multiple outputs
d. Multiple inputs for Storage of Data

a. Adds two binary digits and produces their sum and carry
b. Adds half the sum to the carry
d. Adds two binary digits at half the speed

4. An index register in a computer is for
a. Arithmetic and logic functions
b. Storage of results
d. Counting the no of programmes

5. An example of volatile memory is
a. RAM b. ROM c. EPROM d. Magnetic tape

6. Barrier voltage in a P-N junction is caused by
a. Thermally generated electrons and holes
b. Diffusion of majority carriers across the junction
c. Migration of minority carriers across the junction
d. Flow of drift current

7. The temperature coefficient of an intrinsic semiconductor is
a. Positive b. Negative c. Zero d. Like metals

8. A silicon transistor has a leakage current 1cbo = 1 ma. If the temp. rises by 50o C the leakage current will be
a. 30 ma b. 32ma c. 50ma d. no change

9. The noise figure of an ideal amplifier in decibel is
a. 0.5 b. 0 c. 1 d. 10

10. The rise time of an amplifier is 200 nsec. Its bandwidth is
a. 70MHz b. 140MHz c. 100MHz d. 1.75Mhz

11. MOSFET operates in
a. Depletion mode only
b. Enhancement mode only
c. Depletion and enhancement mode
d. None of these of the above

12. A device which behaves like SCRs is
a. UJT b. Triac c. MOSFET d. SRD

13. A plate modulated class C RF amplifier produces 100 KW of radiated power at 100 % modulation. The modulating audio amplifier supplies approximately
a. 25KW b. 33KW c. 50KW d. 66KW

14. A 100 MHz FM carrier, modulated by a 5 KHz sine wave deviates by 50 KHz
If the frequency of the modulating sine wave is doubled, the deviation will
a. Double b. Half c. Quadruple d. Have no change

15. Noise generated by a resistor is dependent on
a. Its Value
b. Its temperature
c. Both value and temp
d. None of these

16. A 32 channel 8 bit PCM system samples at 8 KHz rate. The overall bit rate in kilobits per second will be
a. 2048 b. 2000 c. 1920 d. 64

17. Stub matching eliminates standing wave on
a. Load side of the stub
b. Source side of the stub
c. Both sides
d. On the stub

18. A half wave folded dipole has a radiation resistance of
a. 72 W b.50W c. 144W d. 288W

a. Decrease in impedance
b. Increase in bandwidth
c. Increase in effective height
d. Decease the height

20. The term critical frequency in Ionospheric propagation is
a. Lowest frequency reflected by Ionosphere
b. Highest frequency reflected by the Ionosphere at vertical incidence
c. Lowest frequency reflected by the Ionosphere at vertical incidence
d. Lowest communication frequency possible

21. The cathode ray oscilloscope can be used to measure
a. Frequency b. Time interval c. Voltage d. All the above

22. A wein bridge is used for measurement of
a. Resistance b. Capacitance c. Inductance d. Audio frequency

23. The frame rate per second used in India TV is
a. 60 b. 50 c. 25 d. 30

24. VHF signals are propagated
a. Via the ionosphere
b. Along the ground
c. Through the troposphere
d. By reflection in ionosphere

25. The impedance of a 3 element yagi antenna is around

a. 75W b. 300W c. 50W d. 100W

26. A PIN diode is microwave

a. Oscillator b. Mixer c. Detector d. Switch

27. A transmission line of VSWR 2 has a reflection coefficient

a. 0.25 b. 0.5 c. 75 d. 0

28. Microwave repeaters are typically

a. 25 b. 50 c. 75 d. 100 Kms apart

29. To overcome fading in a ship-to-ship communication system we can efficiently use

b. Directional Antenna

c. Space Diversity

d. Frequency Diversity

30. Frequency in the UHF range is propagate by waves of

a. Ground b. sky c. Space d. Surface

31. A duplexer is used to

a. Receive two signals in one antenna

b. Prevent interference between two antenna

c. Mix two signals to the same antenna

d. Allow one antenna for both transmission and reception

32. Strapping is used in a magnetron to

a. Prevent mode jumping

b. Reduce frequency drift

c. Ensure proper bunching

d. Dissipate heat

33. A rectangular waveguide behaves like a filter of

a. Band pass b. High pass c. Low pass d. Band stop

34. The signal propagation time in milliseconds for a geosynchronous satellite is

a. 540 b. 270 c. 135 d. 100

35. The silicon solar cell is a

a. Photo conductive

b. Photo emissive

c. Photo voltaic

d. Photo resistive

36. For the national TV and ratio network, INSAT-IB uses

a. 400MHz b. 2.5GHz c. 2.5 and 5GHz d. 4 and 6 GHz

37. A typical fibre-optic detector is

a. Step recovery diode

b. Light emitting diode

c. Avalanche photo diode

d. Field effect transistor

38. A modem is a device used for

a. Digitizing voice data

b. Transmission of data on lines

c. Modulating and demodulating signals sent on a line

d. Suppressing noise interference

39. The most effective anti-jamming technique is

a. Frequency hopping

c. Frequency synthesis

d. Burst transmission

40. Mono-mode is a term used in

a. Fibre-optics

c. Satellite communication

d. Magnetics

41. Monopulse technique is used in

c. Data communication

d. Fibre-optics

42. HDLC is a term for

a. Data communication protocol

b. Synchronizing pulses

d. Error checking

43. A gateway

a. Is a place where radars are connected

b. Permits dissimilar networks to communicate

c. Bifurcates the RF path of a transmitter

d. Is a feeder cable

44. Ethernet is a name of

a. Medium of computer communication

b. Network for computer communication

c. Procedures for computer communication network

d. Software for computer communication

45. If several stations in a network want to use a single channel without interfering with one another, the technique used is called

a. Carrier sense

b. Phantom-freeze

c. Packet switching

d. Multiplexing

46. In a monolithic IC, resistors are formed from

a. Ceramic materials

b. Copper

c. P-type semiconductor

d. Aluminium deposition

47. ICs made by sputtering of materials on a ceramic substrate are called

a. Monolithic b. Hybrid c. Thick film d. Thin film

48. Two coils (inductors) connected in series have a combined inductance of 15mH. When terminals of one of the coils are reversed and connected to the other, the combined inductance is measured to be 9mH. What is the value of mutual inductance

a. 1.5mH b.3mH c.6mH d.12mH

49. If a parallel LC circuit is excited at frequency less than its resonant frequency, the nature of its effective impedance is

a. Resistive b. Inductive c. Capacitive d. None of these of these

50. The wave length of 1 Giga hertz frequency signal is

a. 10cm b. 30cm c. 3cm d. 1cm

51. Which of the following microwave tubes can be considered as broad band devices

a. Magnetrons

b. Klystrons

c. Reflex klystrons

d. Traveling wave tubes[TWT]

52. Which family of the following integrated circuits has the highest speed

a. DTL b. ECL c. TTL d.CMOS

53. The most important feature of CMOS family of ICs is

a. High speed

b. Small size

c. Low power consumption

d. Low input impedance

54. What is the resolution of 8 bit A/D converter if its full scale voltage is 10v

a. 0.02v b. 0.01 c. 0.039v d. 0.078v

55. What value of resistance is to be used in LSB of 4 bit weighted ladder D/A converter if MSB has 10 kW resistor

a. 160k b. 80k c. 240k d. 100k

56. The pulse width of a radar transmitter is 0.6m sec. and the pulse repetition rate is 700 Hz. The average power measured is 420 watts. What is the peak power

a. 100KW b. 420KW c. 1MW d. None of these

57. The device used for isolating the transmitter and receiver in a radar system is called

a. Diplexer

b. Duplexer

c. Directional coupler

d. None of these

58. “Baud” is

a. Total No. of bits/sec in each character

b. Reciprocal of shortest signal element in a character

c. Duration of a character in data transmission

d. None of these

59. The advantage of Totem pole output stage in TTL ICs is

a. Low output impedance

b. Can sink more current

c. Oscillations avoided

d. None of these

60. The capacitance value of a varactor is controlled by

a. A reverse voltage applied to it

b. A series resistance

c. Varying its supply voltage

d. Current through the device

61. Electron volt is equivalent to

a. 3.8 * 10-20 erg

b. 1.602 * 10-12 erg

c. 1.602 * 10-18 erg

d. 1.602 * 10-16 erg

62. The kinetic energy of photo electrons emitted by a photo sensitive surface depends on

a. Intensity of the incident radiation

b. Wavelength of the incident radiation

c. Angle of incident of radiation

d. Surface conditions of the surface

63. Flux is expressed in radio-metric system in

a. Lumens

b. Photons

c. Watts

d. Candles

64. In a three-phase bridge rectifier circuit, the ripple frequency is

a. Same as line frequency

b. Twice the line frequency

c. Thrice the line frequency

d. Six times the line frequency

65. Energy stored in a capacitor as a function of voltage is given by

a. CV2

b. 1V2/2C

c. ½ CV2

d. 1V/2C

66. The operational amplifier used in analog computers have usually open loop flat gain approximately upto

a. 1MHz b. 100MHz c. 10MHz d. 0.1MHz

67. An oscillator of 350 MHz is fed with a pulse of rise time 2 n sec. The rise time of the displayed waveform is approximately

a. 1 n sec b. 2.2 n sec c. 2.0 n sec d. 1.7 n sec

68. A radar transmits a peak power of 100 KW with pulse width of 1 m sec and a pulse repetition rate of 100 KHz. The average output power of the radar is

a. 100KW b.10KW c. 1000KW d. 50KW

69. The incremental inductance in a coil is due to

a. Saturation

b. Superimposed DC

c. Mutual inductance

d. Change of frequency

70. Microwave tube based on velocity modulation principle is

a. Klystron

b. Magnetron

c. Light house tube

d. Traveling wave tube

71. Noise output from the receiver decreases uniformly with noise side band frequency for

a. Frequency modulation

b. Amplitude modulation

c. Pulse amplitude modulation

d. None of these

72. In amplitude modulation the maximum permissible modulation index is

a. Unity b. 100 c. infinity d. None of these

73. In frequency modulation the maximum permissible modulation index is

a. Unity b. 50 c.1000 d. no limit

74. In FM transmission and reception, the pre-emphasis and de-emphasis are used to improve the

a. Signal to noise ratio

b. Frequency response of the receiver

c. Frequency response of the transmitter

d. The sensitivity of the transmitter

75. De-emphasis network uses the combination of

a. R-L b. R-C c. R-L-C d. Transformer

76. The usage of micro sec for defining emphasis is a standard practice but this micro sec definition means

a. 3 dB point of the network means

b. mid point of the network response

c. roll off the network response

d. the stop band ripple of the network response

77. Delayed AGC is applied

a. For all singal strength

b. For singal strength exceeding a specified limit

c. For low singal strength

78. Selectivity means

a. Bandwidth

b. Gain

c. Modulation index

d. None of these

a. The quality and noise

b. Quality alone

c. Noise alone

d. Quality and intelligibility

80. Squelch means keeping the receiver

a. ON in the absence of carrier

b. OFF in the absence of carrier

c. To remove AGC

d. Increase the AGC

81. Let Z be the series impedance and Y be the shunt admittance of the transmission line, then the characteristic impedance

a. ÖZY b.ÖY/Z c. ÖZ/Y d.All the above

82. Noise figure of an amplifier is defined as

a. Input SNR output SNR

b. Input SNR / output SNR

c. Output SNR / input SNR

d. Input SNR / gain

83. A broadcast radio transmitter radiates 10 KW power when modulation is 60%. Its carrier power will be

a. 8.47KW b.8.92KW c. 8.31KW d.10.00KW

84. In AM transmission antenna current is 8 Ampere at zero modulation indexes but increased to 8.93 Ampere when modulated on single sine wave. Then the % of modulation is approximately

a. 70.1% b. 80.1% c. 65.1% d. 10.0%

85. In AM transmission antenna current is 8 Ampere at zero modulation index. At 80% modulation index the antenna current will be

a. 10.00A b. 8.72A c. 9.19A d. 9.79A

86. If two sine waves are amplitude modulated with modulation index m1 and m2, the effective modulation index is

a. Ö m12/m22

b. Ö m1 m2

c. Ö m12+m22

d. Ö m22/m12

87. If it is transmitted current and Ic is transmitter current at zero modulation index and the transmitted current at modulation index of m will

a. It = Ic Ö[1+m]

b. It = Ic Ö[1+m2]

c. It = Ic Ö[1+m/22]

d. It = IcÖ1+m2

88. If Rr is the radiation resistance and Rd is the lumped resistance, then the antenna efficiency is given as –

a. (Rr - Rd) / (Rr + Rd)

b. (Rr + Rd) / (Rr – Rd)

c. Rr / (Rr + Rd)

d. Rd / (Rr + Rd)

89. In end fire array, the current

a. Magnitude and phase in each element is the same

b. Magnitude is the same but phase is different in each element

c. Magnitude is different but no phase difference in each element

d. Magnitude and phase are different in each element

90. In a board side array, the current

a. Magnitude and phase in each element is the same

b. Magnitude is the same but phase is different

c. Magnitude is different but no phase difference in each element

d. Magnitude and phase are different in each element

91. Beam width of the 2 metre paraboloid reflector at 6 GHz is

a. 4.5o

b. 9.25o

c. 3.5o

d. 7.75o

92. The cut of wave length for TE m, n mode is in a wave guide of dimension a*b is

a. 2/Ö(m/a)2 +(n/b)2

b. 2Ö [m/a]2 + [n/b]2

c. Ö(m/a)2 + (n/b)2 /2

d. Ö [m/a]2 + [n/b]2

93. For the standard rectangular waveguide dimension of 4*2 cm the off wavelength for TM11 mode is approximately

a. 1.788cm b. 3.576cm c. 1.682cm d. 2.546cm

94. In IMPATT diode, the voltage and current are

a. In phase

b. Out off phase by 90o

c. Out off phase by 180o

d. None of these of the above

95. Which of the following statement is true

a. Tunnel diode & IMPATT diode are negative resistance devices

b. Tunnel diode is positive resistance device and the IMPATT diode is negative resistance device

c. Tunnel diode is negative resistance device and the IMPATT diode is positive resistance device

d. None of these of the above

96. In a SSB modulation system with 100% modulation index the power saving will be

a. 5/6 of carrier power

b. 2/8 of carrier power

c. 5/12 of the carrier power

d. ½ of the carrier power

97. In SSB modulation the modulation index is increased from 0.5 to 1.0, then the power will be increased by

a. 2 times b. 4 times c. 16 times d. 32 times

98. 900 rpm is equal to

99. Darlington pair is used to

a. Increase the voltage gain

b. Increase the current gain

c. Decrease voltage gain

d. Decrease current gain

100. The transfer function of the system shown is

a. G(s) / {1 + H(s)}

b. G(s) H(s) / {1 + G(s) H(s)}

c. G(s) / {1 + G(s) H(s)} d. G(s) / G(s) H(s)

1. c
2. a
3. a
4. c
5. a
6. b
7. b
8. b
9. b
10. d
11. c
12. b
13. b
14. d
15. c
16. a
17. c
18. d
19. c
20. b
21. d
22. d
23. c
24. b
25. b
26. d
27. c
28. b
29. d
30. c
31. d
32. a
33. b
34. c
35. c
36. d
37. c
38. c
39. a
40. a
41. a
42. a
43. b
44. b
45. d
46. c
47. d
48. a
49. b
50. b
51. d
52. b
3. c
54. c
55. b
6. c
57. b
58. b
59. a
60. a
61. b
62. b
63. a
64. b
65. c
66. d
67. c
68. b
69. d
70. a
71. a
72. a
73. b
74. a
75. b
76. a
77. b
78. a
79. a
80. b
81. c
82. b
83. a
84. a
85. c
86. c
87. c
88. c
89. b
90. a
91. c
92. a
93. b
94. c
95. a
96. a
97. b
98. b
99. b
100. c

## BEL PE Exam Question Paper with Answers - 4

BEL Placement Paper (Technical-Electronics-IVth)

1. The noise figure of a receiver is a measure of:
1. Excess noise generated
4. Operating frequency

1. Direct detection type
2. Super regenerative type
3. Super heterodyne type
4. None of these

3. In an amplitude modulation system, the modulation index is dependent upon:
1. Modulating frequency only
2. Carrier amplitude only
3. Modulating signal amplitude only
4. Modulating and carrier amplitudes only

4. Image rejection mixer is generally used:
1. To reject the unwanted signal
2. To improve signal amplitude
3. To improve noise figure
4. To improve conversion loss

5. The value of a resistor creating thermal noise is doubled. The noise power generated is therefore:
1. Halved
3. Doubled
4. Unchanged

6. Indicated the false statement:
1. HF mixer are generally noisier than HF amplifier
2. Impulse noise voltage is independent of bandwidth
3. Thermal noise is independent of the frequency at which it is measured
4. Industrial noise is usually of the impulse type

7. If the carrier of a 100 percent modulated AM wave is suppressed the percentage power saving will be:
1. 50 b. 70 c. 100 d. 66.6

8. A balanced modulator produces:
1. The carrier and Two side bands
2. The carrier and one side band
3. Two side bands alone
4. Carrier and a number of side bands

9. The frequency deviation in FM system is proportional to:
1. Modulating frequency
2. Carrier amplitude
3. Modulating signal amplitude
4. None of these

10. In FM, the total transmitted power is:
1. Dependent on modulating signal amplitude
2. Dependent on modulating frequency
3. Dependent on modulating index
4. Independent of the above

11. The carrier in an FM system disappears for the lowest modulation index of:
1. 0.5 b. 1.0 c. 2.4 d. 3.5

12. The difference between phase and frequency modulation:
1. Is purely theoretical because they are the same in practice
2. Is too great to make the two systems compatible
3. Lies in the poorer audio response of phase modulation
4. Lies in the different definition of the modulation index

13. The overall noise figure of two cascaded amplifiers is equal to
1. The algebraic sum of the two
2. The sum of the squares of the two
3. The square root of the product of the two
4. None of these

14. The noise power output of an amplifier is equal to:
1. KTo BFG
2. KTo FG
3. KTo F/G
4. KTo / FG

15. The effective noise temperature of an amplifier is equal to
1. (F + 1) To
2. FTo
3. (F – 1) To
4. None of these

16. The noise figure of an amplifier depends upon
1. Its bandwidth
2. Its gain
3. Its operating frequency
4. None of these

17. The velocity of electromagnetic wave in a coaxial cable is
1. Equal to the velocity in free space
2. Less than the velocity in free space
3. Greater than the velocity in free space
4. None of these

18. The standing wave ratio [SWR] in a transmission line:
1. Is proportional to the load impedance
2. Is dependent on the source impedance
3. Is a mis-match between the load and line
4. Is a measure of its power handling capability

19. The standing wave ratio (SWR) is unity in a transmission line if
1. The load impedance is equal to the characteristic impedance of the line
2. The load impedance is twice that of the characteristic impedance
3. The load impedance is half of the characteristic impedance of the line
4. None of these

20. The standing wave voltage node along a line repeats at the rate of if L is the wave length
1. L/4 b.L/2 c.L d.2L

21. A quarter wave line when short circuited at the far end behaves like
1. Pure inductor
2. Pure capacitor
3. Parallel tuned circuit
4. Series tuned circuit

22. The stub line used to match transmission line with a given load impedance is generally
1. Another open circuited line
2. Another short circuited line
3. Quarter wave transmission line
4. Half wave transmission line

23. The smith chart generally covers a distance of
1. Quarter wavelength
2. Half wavelength
3. One wavelength
4. Twice the wavelength

24. The component generally used to sample a portion of the energy transmitted in a line is
1. Isolator
2. Circulator
3. Directional coupler
4. None of these

25. The return loss in a transmission line is a measure of
1. Loss of the line
2. Standing wave ratio
3. Characteristic impedance of the line
4. None of these

26. The antenna can be considered as
1. Matching the source and free space
2. Matching the source to the line
3. Matching the line and free space
4. None of these

27. The free space impedance is approximately equal to
1. 177 W
2. 277 W
3. 377 W
4. 50 W

28. The polarization refers to
1. The physical orientation of the radiated wave
2. The directional of propagation of the wave
3. Direction perpendicular to the propagation of the wave
4. None of these

29. If u & e are the permeability and permittivity respectively the characteristic impedance of the medium is given by
1. ue b. Öu/e c. Öe/u d. Öeu

30. The power density at distance ‘r’ from an isotropic radiator with transmitted power P is:
1. P/r2
2. P/2 p r2
3. P/4 p r2
4. None of these

31. Frequencies in the UHF range is normally propagated by means of
1. Ground waves
2. Sky waves
3. Surface waves
4. Space waves

32. As electromagnetic waves travel in free space, only one of the following can happen to them
1. Absorption
2. Attenuation
3. Reflection
4. Refraction

33. High frequency waves are
1. Absorbed by the F2 layer
2. Reflected by the D layer
3. Affected by the solar cycle
4. Capable of use for long distance communications on the moon

34. Indicate which one of following terms applies to troposcatter propagation
1. SIDS
4. Atmospheric storms

35. When microwave signals follow the curvature of the earth, this in known as
2. Ducting
3. Ionospheric reflection
4. Tropospheric scattering

36. An ungrounded antenna near the ground:
1. Is unlikely to need an earth mat
2. Acts as a single antenna of twice the height
3. Must be horizontally polarized
4. Acts as an antenna array

37. One of the following consists of non-resonant antenna:
1. The folded dipole
2. The rhombic antenna
3. The end fire array

38. Balun is:
1. A circuit element to connect balance line to unbalanced antenna or line:
2. A circuit element to connect balance line to balanced line
3. A circuit element to connect unbalance line to unbalanced line
4. None of these

39. The slotted line is used to measure:
1. Standing wave ratio
3. Source impedance
4. None of these

40. In amplitude modulation Ec ( 1 + m Sin Wmt) Sin Wot, each side band amplitude will be:
1. Ecm/2
2. Ecm
3. Ec/m
4. 2Ec/m

41. FM modulation becomes equivalent to AM modulation if
1. FM index is greater than 1
2. FM index is equal to 1
3. FM index is very much less than 1
4. FM index less than or equal to 1

42. S/N improvement of FM over AM, B is the FM modulation index
1. 3B2 b.B c.2B d.B/2

43. Picture transmission in TV employs
1. Suppressed carrier modulation
2. Vestigial side band
3. Single side band
4. None of these

44. Sound transmission in TV employ
1. Amplitude modulation
2. Phase modulation
3. Frequency modulation
4. Pulse amplitude modulation

45. One of the following is an indirect way of generating FM this is the:
1. Reactance FET modulator
2. Varacter divide modulator
3. Amstrong modulator
4. Reactance bipole transistor modulator

46. The modulation index of AM wave is changed from 0 to 1. The transmitted power is
1. Un-changed
2. Halved
3. Doubled
4. Increased by 50%

47. The isotropic antenna is represented by
1. Dipole antenna
2. Rhombic antenna
3. Yagi uda antenna
4. No such antenna exists in practice

48. The gain of parabolic reflector antenna is proportional to
1. The diameter of the reflector
2. Square of the diameter of the reflector
3. Aperture area of the feed
4. None of these

49. The parabolic reflector antenna are generally used to
1. Provide high gain
2. Provide pencil beam
3. Increase bandwidth of operation
4. None of these

50. Cassegrain feed is used with a parabolic reflector to
1. Increase gain of the system
2. Increase the bandwidth of the system
3. Reduce the size of the main reflector
4. Allow the feed to be placed at a convenient point

51. A helical antenna is used for satellite tracking because of its
1. Circular polarization
2. Maneuverability
4. Good front – to – back ratio

52. The discone antenna is
1. A useful direction finding antenna
2. Used as a radar receiving antenna
3. Circularly polarized like other circular antenna
4. Useful as a VHF receiving antenna

53. Waveguides are used mainly for microwave signals because
1. They depend on straight line propagation which applies to microwaves only
2. Losses would be too heavy at lower frequencies
3. There are no generators powerful enough to excite them at lower frequencies
4. They would be too bulky at lower frequencies

54. The wavelength in a waveguide
1. Is greater than in free space
2. Depends only on the waveguide dimensions and the free-space wavelength
3. Less than the free space wavelength
4. Equal to the free space wavelength

55. The dominant mode of propagation is preferres with rectangular waveguide because(indicate false statement)
1. It leads to the smallest waveguide dimensions
2. The resulting impedance can be matched directly to coaxial lines
3. It is easier to excite than the other modes
4. Propagation of it without any spurious generation can be ensured

56. The velocity of propagation (group velocity) in a waveguide is
1. Less than the free space velocity
2. Greater than the free space velocity
3. Equal to be free space velocity
4. None of these

57. A wave can propagate in a waveguide if its cut off wavelength is
1. Greater than the free space wavelength
2. Less than the free space wavelength
3. Equal to be free space wavelength
4. None of these

58. The dominant mode in a rectangular waveguide is
1. TE11 b. TE10 c.TE20 d.TM11

59. The characteristic wave impedance of a waveguide
1. Depends on the mode of propagation
2. Does not depend on the mode of propagation
3. Is same as the free space impedance
4. None of these

60. A choke flange may be used to couple two waveguides
1. To help in the alignment of the waveguides
2. Because it is simpler than any other joint
3. To compensate the discontinuities at the joint
4. To increase the bandwidth of the system

61. The dominant mode in a circular waveguide is
1. TE01 b.TE11 c.TM01 d.TM11

62. A ferrite is
1. A non-conductor with magnetic properties
2. An inter metallic compound with particularly good conductivity
3. An insulator which heavily attenuates magnetic fields
4. A microwave semiconductor invented by farady

63. The maximum power that may be handled by a ferrite component is limited by the
1. Curie temperature
2. Saturation magnetization
3. Line width
4. Gyro magnetic resonance

64. The isolator is
1. Bidirectional
2. Unidirectional
3. Used to tap the power in a waveguide transmission line
4. Used for None of these of the above

65. Isolator is generally used:
1. To protect the high power transmitter
3. To protect the antenna
4. To avoid arcing in waveguides

66. A TR tube is used
1. To protect the high power transmitter
3. To avoid arcing in waveguides
4. For None of these of the above

67. Rieke diagrams are used to select best operating conditions for
1. TWT amplifier
2. Klystron oscillator
3. Magnetron oscillator
4. Cross field amplifiers

68. The gain bandwidth product of a microwave transistor FT, is the frequency at which the
1. Alpha of the transistor falls by 3 dB
2. Beta of the transistor falls by 3 dB
3. Beta of the transistor falls to unity
4. Power gain of the transistor falls to unity

69. The cavity magnetron uses strapping to
1. Prevent mode jumping
2. Prevent cathode-back heating
3. Ensure bunching
4. Improve the phase-focussing effect

70. The transferred – electron bulk effect occurs in
1. Germanium
2. Gallium arsenide
3. Silicon
4. Metal semiconductor junction

71. One of the following is not used as a microwave mixer or detector
1. Crystal diode
2. Schottky – barrier diode
3. Backward diode
4. PIN diode

72. SAW devices may be used as:
1. transmission media like stripline
2. filters
3. UHF amplifiers
4. Oscillators at millimeter frequencies

73. Surface acoustic waves propagate in:
1. Gallium arsenide
2. Indium phosphide
3. Stripline
4. Quartz crystal

74. A parametric amplifier has an input and output frequency of 2.25 GHz, and is pumped at 4.5 GHz is a
1. Traveling wave amplifier
2. Degenerate amplifier
3. Lower-side band up converter
4. Upper-side band up converter

75. The negative resistance in a tunnel diode
1. Is maximum at the peak point of the characteristic
2. Is available between the peak and valley points
3. Is maximum at the valley point
4. May be improved by the reverse bias

76. Microwave links repeaters are typically 50KM apart
1. Because of atmospheric attenuation
2. Because of output tube power limitations
3. Because of Earth’s curvature
4. To ensure that the applied voltage is not excessive

77. Microwave links are generally preferred to coaxial for television transmission because
1. They have less overall phase distortion
2. They are cheaper
3. Of their greater bandwidths
4. Of their relative immunity to impulse noise

78. A geostationary satellite
1. Is motionless in space(except for its spin)
2. Is not really stationary at all, but orbits the earth with a 24 hour period
3. Appears stationary over Earth’s magnetic pole
4. Is located at a height of 35800KM to ensure global coverage

79. The geostationary satellite launched by India are called
1. INTELSAT
2. INSAT
3. COMSAT
4. MARISAT

80. A parametric amplifier must be cooled
1. Because parametric amplification generates a lot of hest
2. To increase bandwidth
3. Because it cannot operate at room temperature
4. To improve the noise performance

81. If the peak transmitted power in a Radar system is increased by a factor of 16, the maximum range will be increased by a factor of
1. 2 b. 4 c.8 d. 16

82. Telephone traffic is measured
1. With echo
2. By relative congestion
3. In terms of the grade of service
4. In erlangs

83. If the antenna diameter in a radar system is increased by a factor of 4, the maximum range will be increased by a factor of:
1. Ö2 b. 2 c. 4 d. 8

84. A high PRF will (indicate the false statement)
1. Make the returned echoes easier to distinguish from noise
2. Make target tracking easier with conical scanning
3. Increase the maximum range
4. Have no effect on the range resolution

85. The bandwidth of a radar receiver is inversely proportional to the
1. Pulse width
2. Pulse repetition frequency
3. Pulse interval
4. Square root of the peak transmitted power

86. If d is the pulse width, T is pulse repetition period and P is the peak power, the duty ratio is
1. T/d b.P/T c.P/d d.d/T

87. If d is the duty ratio and P is the peak power in a pulsed transmitter, then the average power is
1. P.d b. P.2d c.P/d d. P/2d

88. If the return echo arrives after the allocated pulse interval
1. It will interfere with operation of the transmitter
3. It will not be received
4. The target will appear closer than it really is

89. If the target cross section is changing, the best system for accurate angle traking is
1. Lobe switching
2. Sequential lobing
3. Conical scanning
4. Monopulse

90. After a target has been acquired the best scanning system for tracking is
1. Nodding
2. Spiral
3. Conical
4. Helical

91. The Doppler frequency increases as the target
3. Moves perpendicular to the beam
4. Does not depend on the target velocity

92. The Doppler effect is used in (indicate the false statement)
1. Moving target plotting on the PPI
2. MTI system

93. Solution to the blind speed problem is to
1. Change the Doppler frequency
2. Vary the PRF
3. Use monopulse
4. Use MTI

94. The A-scope displays
1. Target position and range
2. Target range but not position
3. Target position but not range
4. Neither range nor position but only velocity

95. In the colour television system the sub carrier frequency in MHz is approximately
1. 3.58 b.4.5 c. 45.75 d. 5.58

96. In television 4: 3 : represents
1. The interlace ratio
2. The maximum horizontal deflection
3. Aspect ratio
4. The ratio of the two diagonals of picture tube

97. Equalizing pulses in TV are sent during the:
1. Horizontal blanking
2. Vertical blanking
3. The serrations
4. Horizontal retrace

98. The number of lines per field in Indian television system is:
1. 625 b. 312.5 c. 525 d. 262.5

99. The number of frames in Indian TV system is:
1. 50 b. 60 c. 25 d.30

100. In a TV receiver the colour killer:
1. Cuts off the chromastages during monochrome reception
2. Ensures that no colour is transmitted to monochrome receivers
4. Makes sure that the colour burst is not mistaken for sync pulses

1. a
2. c
3. b
4. c
5. b
6. b
7. d
8. c
9. c
10. d
11. c
12. d
13. d
14. a
15. c
16. d
17. b
18. c
19. a
20. b
21. c
22. b
23. b
24. c
25. b
26. c
27. c
28. c
29. b
30. c
31. d
32. b
33. c
34. b
35. b
36. d
37. b
38. a
39. a
40. a
41. c
42. a
43. b
44. c
45. c
46. d
47. d
48. b
49. b
50. d
51. a
52. d
53. d
54. a
55. b
56. a
57. c
58. b
59. a
60. b
61. c
62. a
63. a
64. b
65. a
66. b
67. c
68. a
69. d
70. b
71. d
72. b
73. d
74. b
75. b
76. c
77. a
78. b
79. b
80. d
81. d
82. a
83. c
84. c
85. a
86. d
87. a
88. d
89. d
90. c
91. a
92. a
93. b
94. b
95. a
96. c
97. b
98. b
99. a
100.a