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ECE :: Electromagnetic Field Thoery

  1. The transmitting antennas for lower frequencies (below 500 kHz) are generally

  2. A.
    vertical grounded wire type
    B.
    horizontal suspended wire type
    C.
    parabolic reflector type
    D.
    any of the above

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  3. In an home T.V. receiver, the leed in from the antenna is

  4. A.
    coaxial cable of 75 Ω
    B.
    ordinary twisted wire
    C.
    bar copper wire
    D.
    twin wire

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  5. A satellite that simply reflect back the signals from one region of the earth to the other region is known as

  6. A.
    orbiting satellite
    B.
    geostationary satellite
    C.
    active satellite
    D.
    passive satellite

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  7. Conductivity is measured in terms of

  8. A.
    mho/metre
    B.
    ohm/metre
    C.
    mho/metre2
    D.
    ohm/metre2

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  9. The critical frequency of 'F' layer is greater than 30 MHz.

  10. A.
    True
    B.
    False

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  11. Which of the following statement is incorrect?

  12. A.
    Z0 is an ac characteristic that is the same for any length of time
    B.
    The characteristic impedance can be measured approximately with a sensitive ohm meter
    C.
    A line terminated in its Z0 is a flat or non-resonant line
    D.
    A twin lead has higher Z0 but lower losses than coaxial cable

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  13. Which of the following will increase the antenna radiation efficiency?

  14. A.
    Use of larger section of conductor
    B.
    Providing insulation on conductor
    C.
    Top loading of antenna
    D.
    Any of the above

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  15. A waveguide operated below cut off frequency can be used as

  16. A.
    phase shifter
    B.
    an attenuator
    C.
    an isolator
    D.
    none

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  17. A time varying field is applied to a circuit with a capacitor- which of the following statements is correct?

  18. A.
    The conduction current is equal to the displacement current
    B.
    The conduction current density is J and displacement current density
    C.
    The current in the circuit consists of conduction current and displacement current
    D.
    The displacement current passes through the capacitor

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  19. Which of the following impedance inversion is obtained?

  20. A.
    Short-circuited stub
    B.
    A quarter wave line
    C.
    Balun transformer
    D.
    A half wave line

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