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ECE :: Radio Receivers

  1. In a radio receiver, if the intermediate frequency is too low

  2. A.
    Image-frequency rejection will improve
    B.
    Selectivity will be too sharp
    C.
    The frequency selectivity of the local oscillator will have to be lowered
    D.
    All of the above

  3. FM amplifier in a superheterodyne receiver

  4. A.
    increases selectivity
    B.
    suppresses noise
    C.
    provides improved tracking
    D.
    improves the rejection of the image frequency

  5. Padders are used in a receiver to

  6. A.
    discard the carrier
    B.
    facilitate tracking
    C.
    filter the input signal
    D.
    suppress noise

  7. In a radio receiver, the local oscillator is tuned to a frequency

  8. A.
    lower than the incoming frequency
    B.
    higher than the incoming frequency
    C.
    equal to incoming frequency
    D.
    any of the above

  9. Which of the following oscillator is generally not used at VHF?

  10. A.
    Colpitts oscillator
    B.
    Clapp oscillator
    C.
    Armstrong oscillator
    D.
    Ultra Audio oscillator

  11. An unmodulated voltage 10 V effective is applied to a dioxide detector in which load resistance is 4 x 10-5 ohms. A micrometer shows that the rectified DC current in this resistance is 30 A. The input resistance of the detector is

  12. A.
    114 kW
    B.
    336 kW
    C.
    384 kW
    D.
    455 kW

  13. The output of a diode detector contains

  14. A.
    D.C. voltage
    B.
    modulating signal
    C.
    RF ripple
    D.
    all of the above

  15. Which of the following noise does not occur in transistors?

  16. A.
    Partition noise
    B.
    Shot noise
    C.
    Flicker noise
    D.
    Resistance noise

  17. Noise generated in a resistor is also known as

  18. A.
    partition noise
    B.
    white noise
    C.
    thermal noise
    D.
    shot noise

  19. Which of the following is used to provide tracking between RF amplifier and local oscillator stages of receiver?

  20. A.
    Variable tuning inductor
    B.
    Ganged tuning inductor
    C.
    Variable capacitor
    D.
    Variable preset