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  • Question

  • A reflex klystron oscillator is a


  • Options
  • A. low power device
  • B. high power device
  • C. high efficiency device
  • D. both (a) and (b)

  • Correct Answer
  • low power device 

    Explanation
    It uses a single cavity resonator for generating microwave oscillations.

    Its parts are electron gun, resonator, repeller and output coupling.

    It operates on the principle of positive feed back.

    The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity.

    This positive feedback supports oscillations. Its feature are:

    1. Frequency range - 2 to 100 GHz

    2. Power output - 10 MW to about 2 W

    3. Efficiency - 10 - 20 %

    Its applications include radar receivers, local oscillator in microwave devices, oscillator for microwave measurements in laboratories etc.

    More questions

    • 1. Performance of a PIN diode switch is represented by

    • Options
    • A. insertion loss when switch is off
    • B. insertion loss when switch is on
    • C. insertion loss when switch is on and isolation loss when switch is off
    • D. insertion loss when switch is off and isolation loss when switch is on
      • Discuss
    • 2. In a single phase full wave converter (M-2 connection) feeding on R - L load, the input voltage is v = Vm sin ?t. The expression for dc output voltage is

    • Options
    • A.
    • B.
    • C.
    • D.
      • Discuss
    • 3. The relation between thermal conductivity K (W/m/°C), heat flow density Q (watt/m2) and dT/dx (°C per metre) is

    • Options
    • A. Q = K(dT/dx)
    • B. Q = - K(dT/dx)
    • C. K = Q(dT/dx)
    • D. dT/dx = - QK
      • Discuss
    • 4. If f is the frequency of electromagnetic wave, fc is cutoff frequency, then in a rectangular waveguide

    • Options
    • A. attenuation is low when f > fc
    • B. attenuation is low when f < fc
    • C. attenuation is high when f < fc
    • D. either (b) or (c)
      • Discuss
    • 5. A parallel polarized wave is incident from air into paraffin having relative permittivity 3, the value of its Brewster angle is

    • Options
    • A. 0°
    • B. 30°
    • C. 45°
    • D. 60°
      • Discuss
    • 6. For a permanent magnetic material

    • Options
    • A. the residual induction and coercive field should be large
    • B. the residual induction and coercive field should be small
    • C. area of hysteresis loop should be small
    • D. initial relative permeability should be high
      • Discuss
    • 7. The sensitivity of a superheterodyne receiver is determined by

    • Options
    • A. the gain IF amplifier
    • B. the gain of RF amplifier
    • C. the noise figure
    • D. all of the above
      • Discuss
    • 8. In a virgin specimen of iron, the direction of spontaneous magnetisation varies from domain to domain.

    • Options
    • A. True
    • B. False
      • Discuss
    • 9. A material which is lightly repelled by a magnetic field is known as

    • Options
    • A. diamagnetic material
    • B. non-magnetic material
    • C. ferromagnetic material
    • D. paramagnetic material
      • Discuss
    • 10. In a specimen of ferromagnetic material, as the flux density is increased from zero to 2.5 T, µr will

    • Options
    • A. increase
    • B. decrease
    • C. first decrease then increase
    • D. first increase then decrease
      • Discuss

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