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ECE :: Communication Systems

Communication Systems - Section 1
Communication Systems - Section 2
Communication Systems - Section 3
Communication Systems - Section 4
Communication Systems - Section 5
Communication Systems - Section 6
Communication Systems - Section 7
Communication Systems - Section 8
Communication Systems - Section 9
Communication Systems - Section 10
Communication Systems - Section 11
Communication Systems - Section 12
Communication Systems - Section 13
Communication Systems - Section 14
Communication Systems - Section 15
Communication Systems - Section 16
Communication Systems - Section 17
Communication Systems - Section 18
Communication Systems - Section 19
Communication Systems - Section 20
Communication Systems - Section 21
Communication Systems - Section 22
Communication Systems - Section 23
Communication Systems - Section 24
Communication Systems - Section 25
Communication Systems - section-26
Communication Systems - Section-27

  1. Frequency shift keying is used mostly in

    2. A.
    telephony
    B.
    telegraphy
    C.
    radio transmission
    D.
    none of the above

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  2. Troposphere is the portion of atmosphere

    3. A.
    nearest to ground
    B.
    between 50 to 90 km above ground
    C.
    between 110 to 220 km above ground
    D.
    between 250 to 350 km above ground

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  3. Earth's curvature affects the effective height of antenna.

    4. A.
    True
    B.
    False

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  4. In PCM, the quantization noise depends on

    5. A.
    sampling rate
    B.
    signal power
    C.
    number of quantization level
    D.
    signal energy

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  5. In high power AM transmission, modulation is done at

    6. A.
    IF stage
    B.
    buffer stage
    C.
    RF stage
    D.
    oscillator stage

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  6. The noise sources shot noise, partition noise and thermal noise are associated with which component

    7. A.
    BJT
    B.
    diode
    C.
    resistor
    D.
    capacitor

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  7. Consider the following statements as regards communication receiver

    1. Variable sensitivity is used to eliminate selective fading
    2. A product demodulator can be used to receive Morse code
    3. The noise limiter cuts off receiver output during a noise pulse
    4. Double conversion is used to improve image rejection
    Which of the above statements are correct?

    8. A.
    1, 2, 3, 4
    B.
    1, 2, 3
    C.
    2, 3, 4
    D.
    1, 3, 4

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  8. In a transmission line, losses due to dielectric heating are

    9. A.
    proportional to voltage and inversely proportional to Z0
    B.
    proportional to voltage and proportional to Z0
    C.
    proportional to current and proportional to Z0
    D.
    proportional to current and inversely proportional to Z0

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  9. The power rating of radio transmitters is around

    10. A.
    100 mW
    B.
    10 W
    C.
    10 kW
    D.
    10 MW

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  10. How can the quantizing noise be reduced?

    11. A.
    By using de-emphasis circuit
    B.
    By using RF amplifier in the receiver
    C.
    By increasing the number of quantization levels
    D.
    By sending sloping pulses

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