Communication Systems - ECE Questions and Answers

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A horizontal output stage is cutoff for retrace and 40% of trace. If time for each horizontal line is 64 μs and retrace time is 12 μs, the transistor is conducting for about

64 μs

6.4 μs

31 μs

3.1 μs

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A TV remote control works on the principle of

pulse code modulated ultra violet light

pulse code modulated infrared light

demodulation

either (a) or (b)

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As the magnitude of reverse bias is increased, the capacitance of varactor diode

increases

decreases

first increase, then decreases

first decreases then increases

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To prevent overloading in the last IF amplifier one should use

variable sensitivity

squelch

double conversion

variable selectivity

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Push pull amplifier is

class B

class A

class C

Class A or Class C

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The tape recorders used in homes have

common head and common amplifier system for recording and playback

different heads and amplifiers for recording and playback

same head but different amplifiers for recording and playback

different heads but same amplifier for recording and playback

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In a communication system, noise is most likely to affect the signal

at the receiver

at the transmitter

at the information source

in the channel

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Each frequency in the modulating wave gives rise to four side bands.

True

False

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Assertion (A): CCIR-B system has 625 scanning lines per frame and 2 : 1 interlace.

Reason (R): The aspect ratio is 4 : 3

Both A and R are correct and R is correct explanation of A

Both A and R are correct but R is not correct explanation of A

A is correct but R is wrong

A is wrong but R is correct