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ESE EC : Communications - National Champion Test
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Question 1
A carrier signal at frequency 100 MHz is frequency modulated with modulation index 2 by a signal of 2 kHz. At what frequencies are the sidebands produced?
Question 2
Which one of the following statement is correct?
Question 3
Match List-I (Modulation) with List-II (Power input to Antenna in watts) and select the correct answer using the code given below the lists:
(assume carrier power is 1 Watt)
List-I
A) 100% AM
B) 50% AM
C) 10% AM
D) FM
List-II
1) 1.5
2) 1.125
3) 1.005
4) 1.00
(assume carrier power is 1 Watt)
List-I
A) 100% AM
B) 50% AM
C) 10% AM
D) FM
List-II
1) 1.5
2) 1.125
3) 1.005
4) 1.00
Question 4
The constellation diagram of a modern is shown in the figure given below. What does the modern use?
Question 5
Quantization process used in analog to digital conversion process is a
Question 6
Which one of the following statements is correct?
Question 7
What is the typical bandwidth of 2- wire telephone line?
Question 8
Which one of the following is the code that is very close to ‘trellis codes modulation’?
Question 9
A source generates four messages with probability 1/2, 1/4, 1/8 and 1/8. What is the entropy of the source (bits/message)?
Question 10
Assertion (A): In a step index fibre, for single mode operation, the fibre parameters should be tailored such that the V- parameter is less than 2.408.
Reason (R): Modal fields of step index fibre are represented by Bessel functions Jn(x) in the core and modified Bessel functions Kn(x) in the cladding. The first zero for J1(x) falls at x = 2.408.
Reason (R): Modal fields of step index fibre are represented by Bessel functions Jn(x) in the core and modified Bessel functions Kn(x) in the cladding. The first zero for J1(x) falls at x = 2.408.
Question 11
In optical communication, wavelength 1550 nm is used nowadays. What is/are the possible reason (s)?
1). Dispersion is very low
2). Loss is very low
3). WDM and optical amplification are feasible
Select the correct answer from the codes given below.
1). Dispersion is very low
2). Loss is very low
3). WDM and optical amplification are feasible
Select the correct answer from the codes given below.
Question 12
Which one of the following is the correct statement?
The graded index optical fibre cabel can be considered to have
The graded index optical fibre cabel can be considered to have
Question 13
Match List-I (Different Fibre Generation) with List-II (Optical Components) and select the correct answer using the code given below the lists:
List-I
A). First
B). Second
C). Third
D). Fourth
List-II
1. Graded index multimode fibre and 1310 nm LD
2). Graded index multimode fibre and 850 nm LD
3). Graded index multimode fibre and 1550 nm LD
4). Graded index multimode fibre and 1310 nm LD
List-I
A). First
B). Second
C). Third
D). Fourth
List-II
1. Graded index multimode fibre and 1310 nm LD
2). Graded index multimode fibre and 850 nm LD
3). Graded index multimode fibre and 1550 nm LD
4). Graded index multimode fibre and 1310 nm LD
Question 14
The outputs of two noise sources each producing uniformly distributed noise over the range –a of +a are added. What is the p. d. f. of the added noise?
Question 15
If the value of a resistor creating thermal noise is doubled. The noise power generated is therefore
Question 16
IF random process X(t) and Y(t) are orthogonal then.
Question 17
In measuring pulsed microwave power, the pulse duration is 1.5 μs with PRF of 1 kHz. It the CW power sensor reads 15 mW, what is the average signal power during the pulse?
Question 18
What is the reason for using frequencies of the order of a few GHz in satellite communication?
Question 19
Assertion (A): The microprocessor based products used by the general consumer must comply FCC rules.
Reason (R): FCC regulates the use of radio transmission.
Reason (R): FCC regulates the use of radio transmission.
Question 20
What does a link budget for satellite communication include?
Question 21
a balanced modulator, is used in the generation of which of the following?
Question 22
A circuit produces an output 
where 
is its input. This circuit can produce which one of the following?
where is its input. This circuit can produce which one of the following? Question 23
A bandwidth of 10 kHz is required for AM system. If the lowest frequency component in the modulated signal is 555 kHz, carrier frequency in kHz is
Question 24
The threshold effect in demodulators is
Question 25
In delta modulation, when is the slope overloading noise absent?
(h is the pulse height and sampled every Ts seconds. f(t) is the input signal, h and Ts are step-size of integration and sampling period, respectively.
(h is the pulse height and sampled every Ts seconds. f(t) is the input signal, h and Ts are step-size of integration and sampling period, respectively.
Question 26
A 12 channel TDM system where each channel signal is 4 kHz is sampled at 8 kHz. What is the bandwidth requirement?
Question 27
Four singles 
are to be multiplexed and transmitted. g1(t) and g4(t) have a bandwidth of 4 kHz, and the remaining two signals have bandwidth of 8 kHz. Each samples requires 8 bit for encoding. What is the minimum transmission bit rate of the system?
are to be multiplexed and transmitted. g1(t) and g4(t) have a bandwidth of 4 kHz, and the remaining two signals have bandwidth of 8 kHz. Each samples requires 8 bit for encoding. What is the minimum transmission bit rate of the system? Question 28
Assertion (A): TDM can be employed to transmit channels having unequal bandwidths.
Reason (R): If sampling theorem is strictly followed any analog signal can be reconstructed from its samples.
Reason (R): If sampling theorem is strictly followed any analog signal can be reconstructed from its samples.
Question 29
How much is contributed by each bit in the code word of a PCM system under uniform and symmetric quantization to the signal to noise ratio?
Question 30
Match List-I (Application of Signals) with List-II (Definition) and select the correct answer using the code given below the lists:
List-I
A). Reconstruction
B). Over sampling
C). Interpolation
D). Decimation
List-II
1). Sampling rate is chosen significantly greater than Nyquist rate
2). A mixture of continuous and discrete time signals
3). To convert the discrete time sequence back to a continuous time signal and then resample
4). Assign values between samples and signals
List-I
A). Reconstruction
B). Over sampling
C). Interpolation
D). Decimation
List-II
1). Sampling rate is chosen significantly greater than Nyquist rate
2). A mixture of continuous and discrete time signals
3). To convert the discrete time sequence back to a continuous time signal and then resample
4). Assign values between samples and signals
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Jun 10ESE & GATE EC
