# Communications (Test 3)

## Gate Exam : Ec Electronics And Communication Engineering

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Q.1
Electronic communication is not possible if
A. message or information is not available in the form of electrical signals
B. if the temperature is high
C. if smell or touch is to be transmitted
D. if the humidity is high
Explaination / Solution:

As the information or message is transmitted from the source to the receiver ,it is first converted into electrical signal which is then transmiited through the communication medium.Hence in electrical communication it is must to convert raw message or information into electrical signal.Else the electronic messages will not be transmitted.

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Q.2
In Digital type signals, signals can take
A. only frequency modulated values
B. only amplitude modulated values
C. only continuous values
D. only discrete stepwise values
Explaination / Solution:
No Explaination.

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Q.3
Modulation used in radio is generally
A. AM/FM
B. TDM
C. FDM
D. PM
Explaination / Solution:

In electronics and telecommunications , modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. Most radio systems usea frequency modulation (FM) or amplitude modulation (AM) to make the carrier carry the radio broadcast.

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Q.4
Coaxial cables have a bandwidth in the range of
A. 750 MHz
B. 750 kHz
C. 750 GHz
D. 750 Hz
Explaination / Solution:
No Explaination.

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Q.5
A transmitting antenna at the top of a tower has a height 32 m and the height of the receiving antenna is 50 m. What is the maximum distance between them for satisfactory communication in LOS mode? Given radius of earth is 6.4  m.
A. 55.5 km
B. 45.5 km
C. 48.5 km
D. 58.5 km
Explaination / Solution:
No Explaination.

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Q.6
In delta modulation, the slope overload distortion can be reduced by
A. decreasing the step size
B. decreasing the granular noise
C. decreasing the sampling rate
D. increasing the step size
Explaination / Solution:
No Explaination.

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Q.7
A λ/2 dipole is kept horizontally at a height of λ0/2 above a perfectly conducting infinite ground plane. The radiation pattern in the lane of the dipole ( plane) looks approximately as
A. B. C. D. Explaination / Solution: Workspace
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Q.8
A rectangular waveguide of internal dimensions (a = 4 cm and b = 3 cm) is to be operated in TE11 mode. The minimum operating frequency is
A. 6.25 GHz
B. 6.0 GHz
C. 5.0 GHz
D. 3.75 GHz
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Q.9
A speed signal, band limited to 4 kHz and peak voltage varying between +5 V and -5 V, is sampled at the Nyquist rate. Each sample is quantized and represented by 8 bits. If the bits 0 and 1 are transmitted using bipolar pulses, the minimum bandwidth required for distortion free transmission is
A. 64 kHz
B. 32 kHz
C. 8 kHz
D. 4 kHz
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Q.10
X(t) is a stationary process with the power spectral density Sx(f)>0, for all f . The process is passed through a system shown below Let Sy (f ) be the power spectral density of Y(t). Which one of the following statements is correct
A. Sy (f ) > 0 for all f
B. Sy (f ) = 0 for |f| > 1 kHz
C. Sy (f ) = 0 for f = nf0, f0 = 2 kHz kHz, n any integer
D. Sy (f ) = 0 for f = (2n + 1) f= 1 kHz, n any integer 