Communication miscellaneous

Communication miscellaneous

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Communication

Communication miscellaneous
  1. Which one of the following is represented by
    V(t) = 5[cos (106 πt) – sin (103 πt) × sin (106 πt)]








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    NA

    Correct Option: D

    NA

  1. Which one of the following statement is correct? In a ratio detector:








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    The ratio detector has one major advantage over the slope detector and Foster-Seeley discriminator for FM demodulation is that it is relatively immune to amplitude variations in its input signal.
    The schematic diagram for the ratio detector is shown. As with the Foster-Seeley discriminator, a ratio detector has a single tuned circuit in the transformer secondary. Therefore, the operation of a ratio detector is similar to that of the Foster-Seeley discrimination. In fact, the diodes D1 and D2 are identical. However, with the ratio detector, one diode is reversed (D2 ) and current ld can flow around the outermost loop of the circuit. Hence alternative (D) is the correct choice.


    Correct Option: D

    The ratio detector has one major advantage over the slope detector and Foster-Seeley discriminator for FM demodulation is that it is relatively immune to amplitude variations in its input signal.
    The schematic diagram for the ratio detector is shown. As with the Foster-Seeley discriminator, a ratio detector has a single tuned circuit in the transformer secondary. Therefore, the operation of a ratio detector is similar to that of the Foster-Seeley discrimination. In fact, the diodes D1 and D2 are identical. However, with the ratio detector, one diode is reversed (D2 ) and current ld can flow around the outermost loop of the circuit. Hence alternative (D) is the correct choice.


  1. For the data in Q. 35 and if capacitor used is 100 Pf then R—








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    We know that
    Time constant τ = RC
    or

    R =
    τ
    		 =
    0.212 × 10−3
    		= 0.212 × 107 Ω
    c100 × 10 −12

    Correct Option: D

    We know that
    Time constant τ = RC
    or

    R =
    τ
    		 =
    0.212 × 10−3
    		= 0.212 × 107 Ω
    c100 × 10 −12

  1. An AM wave
    10[1 + 0·6 cos 2π 103t] cos 2π 106t
    is to be detected by a linear diode detector, the value of the time constant is—








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    The given AM wave is
    s(t) = 10[1 + 0·6 cos 2π 103t] cos 2π 106t
    Here μ = 0·6 and ωm = 2π·103
    The required condition for the detector output is to follow the envelop all the times is

    RC ≤
    1
    		 √
    1 − μ2
    ωmμ2

    or
    RC ≤
    1
    		 √
    1 − (0.6)2
    2π103(0.6)2

    or τ ≤ 0.212 ms
    or
    RC ≤
    1.33
    2π103

    Hence alternative (C) is the correct choice.

    Correct Option: C

    The given AM wave is
    s(t) = 10[1 + 0·6 cos 2π 103t] cos 2π 106t
    Here μ = 0·6 and ωm = 2π·103
    The required condition for the detector output is to follow the envelop all the times is

    RC ≤
    1
    		 √
    1 − μ2
    ωmμ2

    or
    RC ≤
    1
    		 √
    1 − (0.6)2
    2π103(0.6)2

    or τ ≤ 0.212 ms
    or
    RC ≤
    1.33
    2π103

    Hence alternative (C) is the correct choice.

  1. The filter required to obtain SSB from DSB signal is—








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    NA

    Correct Option: C

    NA