Communication Systems MCQs with Answers 2027

Q81

The signal power and noise power are denoted by S and N respectively. If the signal power increases to 3S and the noise power reduces by half, the ratio of old SNR to the new SNR is given by . . . . . . . .

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Q82

Open question

In PLL, the range of input frequency for which the initially unlocked loop will lock on an input signal is known as

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Q83

Open question

In a super heterodyne receiver, which stage produces IF signal?

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Q84

Open question

The . . . . . . . . function gives a quantitative measure of the closeners or similarity between samples of a speech signal as a function of their time separation.

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Q85

Open question

The saving in power in a DSB-SC system modulated at 80% is

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Q86

Open question

If m_t is modulation index of FM. What is the value of ratio

\frac{( \frac{S}{N} ) _{WBFM}}{( \frac{S}{N} ) _{AM}}

for 100% amplitude modulation with identical total transmitted power?

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Q87

Open question

Which is not true about frequency deviation in PM

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Q88

Open question

An amplitude modulated amplifier has a radio frequency output of 50 W at 100% modulation. The internal loss in the modulator is 10 W. The unmodulated carrier power is

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Q89

Open question

What is the assigned bandwidth of each of the channels in the AM broadcast band?

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Q90

Open question

A carrier wave is phase modulated with frequency deviation of 20 kHz by a single tone frequency of 2 kHz. If the single tone frequency is increased to 2 kHz, assuming that phase deviation remains unchanged, bandwidth of the PM signal is

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Q91

Open question

Consider the following statement with regard to a PLL:
1. The 'capture range' of a PLL primarily depends upon the slope of transition band edge of the low-pass filter
2. The 'lock range' is not affected by the slope of transition band of the low-pass filter.
Which of the above statements is/are correct?

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Q92

Open question

What is the typical bandwidth of a 2-wire telephone line?

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Q93

Open question

For an FM demodulator circuit with a transfer function 0.2 V/kHz and an FM input signal with 20 kHz of peak frequency deviation, the peak output voltage is

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Q94

Open question

. . . . . . . . technique is used for blurring and for noise reduction.

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Q95

Open question

A 400 W carrier is VSB modulated to a depth of 100%. Calculate the total power if 20% of the other sideband is transmitted along with wanted sideband

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Q96

Open question

Consider a communication scheme where the binary values signal X satisfies P{X = 1} = 0.75 and P{X = -1} = 0.25. The received signal Y = X + Z, where Z is Gaussian random variable with zero mean and variance σ². The received signal Y is fed to the threshold detector. The output of the threshold detector

X^

is

X^= {+ 1, Y > τ - 1, Y \leq τ

To achieve a minimum probability of error

P {X^\neq = X},

the threshold τ should be

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Q97

Open question

Match List-I with List-II and select the correct answer using the options given below:

List-I (Communication Service)	List-II (Bandwidth)
a. AM Broadcast	1. 10 kHz
b. Telephone	2. 4 kHz
c. Wideband FM	3. 200 kHz
d. TV	4. 7 MHz

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Q98

Open question

AM broadcast systems use a SW band that extends from:

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Q99

Open question

Which one of the following statements is correct?

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Q100

Open question

An AM signal and a narrow-band FM signal with identical carriers, modulating signals and modulation indices of 0.1 are added together. The resultant signal can be closely approximated by

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