Communication Systems Test 3 - Online Electronics and Communication Engineering Test

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Total number of questions: 20.
Time allotted: 30 minutes.
Each question carries 1 mark; there are no negative marks.
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Marks : 2/20

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In CCIR-B system, the time between start of one H syn. pulse and next is

64 μs

6.4 μs

640 μs

0.64 μs

[#]

In a CD player the speed of CD is

constant at 500 rpm

constant at 200 rpm

varies from 200 to 500 rpm

none of the above

[#]

In a 100% amplitude modulated signal, the power in the upper sideband when carrier power is to be 100 W and modulation system SSBSC, is

100 W

66 W

50 W

25 W

[#]

Trinitron is a monochrome picture tube.

True

False

[#]

Two sinusoidal signals of same amplitude and frequencies 10 kHz and 10.1 kHz are added together. The combined signal is given to an ideal frequency detector. The output of the detector is

0.1 kHz sinusoidal

10.1 kHz sinusoidal

a linear function

a constant

[#]

In cellular telephone each cell is designed to handle

45 two way communications

90 two way communications

45 one way communications

180 two way communications

[#]

Which is a digital coding technique?

PCM

DPCM

All

[#]

The IF frequencies in a TV receiver

38.9 MHz for video and 33.4 MHz for audio

38.9 MHz for both video and audio

33.4 MHz for both video and audio

33.4 MHz for video and 38.9 MHz for audio

[#]

In FDM systems used for telephone, which modulation scheme is adopted?

DSB-SC

SSB-SC

[#]

10.

Noise can be reduced by increasing sampling rate

true

false

can't say

insufficient data

[#]

11.

In cell communication, cell stands for

Geographical Area

Battery

Location

No meaning

[#]

12.

If the circumference of a spherical target is between 1 to 10 wavelength in a radar system, the situation is called

resonance region

Rayleigh region

optical region

binomial region

[#]

13.

The maximum permissible distance between two samples of a 10 kHz signal

100 μ sec

50 μ sec

10 μ sec

none

[#]

14.

Square law modulators utilise

linear range of V-I characteristics of a diode

linear range of V-I characteristics of a triode

non-linear region of V-I dynamic characteristics of a diode

non-linear region of V-I dynamic characteristics of a triode

[#]

15.

If F(ω) is Fourier transform of f(t), then Fourier transform of f(t) cos² ω_ct is

F(ω) +

[F(ω + 2ω_c) + F(ω - 2ω_c)]

F(ω) +

[F(ω + 2ω_c) + F(ω - 2ω_c)]

F(ω) -

[F(ω + 2ω_c) + F(ω - 2ω_c)]

F(ω) -

[F(ω + 2ω_c) + F(ω - 2ω_c)]

[#]

16.

In AM the amplitude of carrier components ... while in FM it

remains constant, does not remain constant

does not remain constant ... remains constant

remains constant... also remains constant

does not remain constant, also does not remain constant

[#]

17.

If carrier modulated by a digital bit stream had one of the possible phases of 0°, 90°, 180°, 270°, then the modulation is called.

BPSK

QPSK

QAM

MSK

[#]

18.

The currents fed to the two dipoles of turnstile antenna are

in phase

in quadrature

in phase opposition

either (a) or (c)

[#]

19.

Consider the following statements as regards BPSK and QPSK:

In BPSK we deal individually with each bit of duration T_b
In QPSK we lump two bits to form a symbol
In both BPSK and QPSK signal changes occur at bit rate
In QPSK the symbol can have any one of four possible values

Which of the above statements are correct?

1, 2, 3, 4

1, 2, 3

1, 2, 4

2, 3, 4

[#]

20.

A pre-emphasis circuit provides extra noise immunity by

converting the phase modulation to frequency modulation

pre-amplifying the whole audio band

boosting the base frequencies

amplifying the higher audio frequencies

[#]

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Online Electronics and Communication Engineering Test - Communication Systems Test 3

Marks : 2/20

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