Communication Systems MCQ Questions & Answers

11

The FM techniques in telemetry is usually employed at:

A) 100 MHz and above with much larger bandwidth than AM B) 100 MHz and above with much lesser bandwidth than AM C) Less than 100 MHz with much larger bandwidth than AM D) Less than 100 MHz with much lesser bandwidth than AM

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Answer & Solution

Answer: Option A

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12

Which type of demodulator used in FM detection

A) Square law B) Envelope detector C) Synchronous detector D) Phase discrimination method

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Answer & Solution

Answer: Option D

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13

An amplitude modulated signal is (A + 0.5Acosω_mt)cosω_ct where ω_m and ω_c are respectively, modulating and carrier frequencies. The power efficiency is

A) 11.11% B) 0.25% C) 4.32% D) 50%

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Answer & Solution

Answer: Option A

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14

In radio receiver the output from local oscillator is fed to

A) RF amplifier B) Mixer C) IF amplifier D) Detector

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Answer & Solution

Answer: Option B

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15

A superheterodyne receiver has an IF of 465 kHz. If it is tuned to a station broadcasting at 500 kHz and its oscillator is operating at 965 kHz, then the 1430 kHz frequency would be the

A) Adjacent channel frequency B) Image frequency C) Gyro frequency D) Maximum usable frequency

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Answer & Solution

Answer: Option B

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16

Which of the following is a result of over modulation?

A) Weakening of signal B) Distortion C) Strengthening of a signal D) Excessive carrier power

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Answer & Solution

Answer: Option B

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17

If the covariance of two random variable X and Y is µ_XY, their correlation coefficient ρ_XY is:

A) $$\ell n{\mu _{XY}}$$ B) $$\ell n\left( {\frac{{{\mu _{XY}}}}{{{\sigma _X}{\sigma _Y}}}} \right)$$ C) $$\frac{{{\sigma _X}{\sigma _Y}}}{{{\mu _{XY}}}}$$ D) $$\frac{{{\mu _{XY}}}}{{{\sigma _X}{\sigma _Y}}}$$

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Answer & Solution

Answer: Option D

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18

When a PLL is used as an FM demodulator, the demodulated signal appears at

A) The o/p of the phase comparator B) The o/p of the low pass filter C) The VCO output D) None of these

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Answer & Solution

Answer: Option C

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19

A uniformly distributed random signal x[n] with mean m_x = 2 and variance $$\sigma _{\text{x}}^2$$ = 3, is passed through a 3-point moving-average filter having an impulse response $$\left\{ {{\text{h}}\left[ {\text{n}} \right] = \frac{1}{3},\,\frac{1}{3},\,\frac{1}{3}} \right\}.$$ What will be the mean and variance of output?

A) $${{\text{m}}_{\text{y}}} = 2,\,\sigma _{\text{y}}^2 = 1$$ B) $${{\text{m}}_{\text{y}}} = 2,\,\sigma _{\text{y}}^2 = 3$$ C) $${{\text{m}}_{\text{y}}} = 1,\,\sigma _{\text{y}}^2 = 1$$ D) $${{\text{m}}_{\text{y}}} = 3,\,\sigma _{\text{y}}^2 = 3$$

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Answer & Solution

Answer: Option A

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20

A 200-watt carrier is amplitude-modulated to a depth of 50%. What is the total power in the modulated wave?

A) 175 W B) 225 W C) 250 W D) 200 W

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Answer & Solution

Answer: Option B

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Communication Systems MCQ Questions & Answers | ECE