Online Electronics and Communication Engineering Test - Communication Systems Test 2



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Instruction:

  • This is a FREE online test. DO NOT pay money to anyone to attend this test.
  • Total number of questions : 20.
  • Time alloted : 30 minutes.
  • Each question carry 1 mark, no negative marks.
  • DO NOT refresh the page.
  • All the best :-).


1.

A tweeter should be fed from the input through a

A.
low pass filter
B.
high pass filter
C.
band pass filter
D.
band stop filter

Your Answer: Option (Not Answered)

Correct Answer: Option B

Explanation:

Tweeter is high frequency loudspeaker covering the range above 5000 Hz.

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2.

In the equivalent circuit of a moving coil cone type loudspeaker, the mass of the moving system is represented by

A.
a resistance
B.
a capacitance
C.
an inductance
D.
a conductance

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

Mass has inertia and is analogous to inductance.

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3.

A directional microphone gives an output of 0.5 mV whereas an omnidirectional one gives an output of 0.5 μV in the same position for the same sound pressure. The directivity of the directional microphone is

A.
120 dB
B.
90 dB
C.
60 dB
D.
30 dB

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

Directivity =

= 60 dB.

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4.

The most commonly used transistor amplifier circuit is

A.
CB
B.
CC
C.
CE
D.
CE or CC

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

Common emitter connection has high power gain, and good current and voltage gains.

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5.

Full duplex operation

A.
requires modems at both ends of circuit
B.
requires two pairs of cables
C.
can transfer data in both directions simultaneously
D.
all of the above

Your Answer: Option (Not Answered)

Correct Answer: Option D

Explanation:

Full duplex system has all these features.

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6.

Consider the following statements as regards DPSK and DEPSK

  1. DPSK demodulator requires a device which operates at carrier frequency and provides a delay of bit time Tb
  2. In DPSK, synchronous demodulation recovers the signal b(t) and the decoding of b(t) to generate d(t) is done at base band
  3. In both DPSK and DEPSK errors always occur in pairs
Which of the above statements are correct?

A.
1 and 3
B.
1 and 2
C.
2 and 3
D.
1, 2 and 3

Your Answer: Option (Not Answered)

Correct Answer: Option B

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7.

Consider the following statements about PCM

  1. PCM is not noise resistant
  2. PCM requires complex encoding and quantizing circuitry
  3. PCM requires large bandwidth
Which of the above are correct?

A.
1 only
B.
1, 2, 3
C.
2, 3
D.
1 and 3

Your Answer: Option (Not Answered)

Correct Answer: Option C

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8.

In a TV studio the illuminance is about

A.
200 lux
B.
1000 lux
C.
10000 lux
D.
10 lux

Your Answer: Option (Not Answered)

Correct Answer: Option B

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9.

Bandwidth for practical PCM system is (where n is no. of channels, N length of PCM codes)

A.
2n N fm Hz
B.
4n fm Hz
C.
2n fm
D.
(N + 1)fm

Your Answer: Option (Not Answered)

Correct Answer: Option A

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10.

In radar PRF depends on maximum range.

A.
True
B.
False

Your Answer: Option (Not Answered)

Correct Answer: Option A

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11.

In a radio receiver with simple AGC

A.
the highest AGC voltage is produced between stations
B.
an increase in signal strength produces more AGC
C.
the audio stage gain is normally controlled by AGC
D.
the faster the time constant of AGC, more accurate the output

Your Answer: Option (Not Answered)

Correct Answer: Option B

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12.

If B is channel bandwidth, S is signal power and N is the total noise within the channel bandwidth, the channel capacity C of a white band limited gaussian channel is

A.
B.
C.
D.

Your Answer: Option (Not Answered)

Correct Answer: Option A

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13.

Industrial noise has the frequency range of

A.
1 to 100 Hz
B.
200 to 5000 Hz
C.
above 200 MHz
D.
1 to 600 MHz

Your Answer: Option (Not Answered)

Correct Answer: Option D

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14.

In phase modulation, the phase deviation is

A.
proportional to the amplitude of the signal and varies with frequency
B.
remains constant while amplitude and frequency of signal varies
C.
proportional to the amplitude of the signal and independent of the frequency
D.
none of the above

Your Answer: Option (Not Answered)

Correct Answer: Option C

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15.

BFO stands for

A.
Beat Frequency Oscillator
B.
Broad Frequency Oscillator
C.
Blocking Frequency Oscillator
D.
Ballistic Frequency Oscillator

Your Answer: Option (Not Answered)

Correct Answer: Option A

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16.

A lens has a hyperfocal distance of 7.5 m. It is focused at 7.5 m. Then

A.
all objects from 7.5 m to infinity will appear in focus
B.
all objects from 3.75 m to infinity will appear in focus
C.
all objects from 0 to 7.5 m will appear in focus
D.
all objects from 0 to 3.75 m will appear in focus

Your Answer: Option (Not Answered)

Correct Answer: Option B

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17.

The highest modulating frequency typically used in AM systems is

A.
1 kHz
B.
5 kHz
C.
20 kHz
D.
50 kHz

Your Answer: Option (Not Answered)

Correct Answer: Option B

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18.

The number of spectral component of impulse wave is

A.
1
B.
0
C.
2
D.

Your Answer: Option (Not Answered)

Correct Answer: Option D

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19.

In amplitude modulation

A.
the amplitude of carrier varies in accordance with the amplitude of the modulating signal.
B.
the modulating frequency lies in the audio range
C.
the amplitude of the carrier remains constant
D.
the amplitude of the carrier varies in accordance with the frequency of the modulating signal.

Your Answer: Option (Not Answered)

Correct Answer: Option B

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20.

If S represents the carrier synchronization at the receiver and r represents the bandwidth efficiency, then the correct statement for the coherent binary PSK is

A.
r = 0.5, S is required
B.
r = 1.0, S is required
C.
r = 0.5, S is not required
D.
r = 1.0, S is not required

Your Answer: Option (Not Answered)

Correct Answer: Option D

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