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Home ‣ Electronics and Communication Engineering ‣ Microwave Communication See What Others Are Saying!
  • Question

  • A magnetron requires an external magnetic field with flux lines parallel to axis of cathode


  • Options
  • A. True
  • B. False

  • Correct Answer
  • True 

    Explanation
    It is somewhat similar to TWT and can deliver microwave power over a wide frequency band.

    It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT.

    The growing RF wave travels in opposite direction to the electron beam.

    The frequency of wave can be changed by changing the voltage which controls the beam velocity.

    Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current.

    It features are:

    1. Frequency range - 1 GHz to 1000 GHz.

    2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed).

    It is used as signal source in transmitters and instruments.

    More questions

    • 1. Which of the following circuit cannot be used to demodulate SSB?

    • Options
    • A. Phase discriminator
    • B. Produce detector
    • C. Balanced modulator
    • D. Beat frequency oscillator
      • Discuss
    • 2. Negative feedback reduces noise originating at the amplifier input.

    • Options
    • A. True
    • B. False
      • Discuss
    • 3. Assertion (A): The surge current which an SCR can withstand is much higher than rms on state current.

      Reason (R): The duration of surge current is very small.


    • Options
    • A. Both A and R are correct and R is correct explanation of A
    • B. Both A and R correct but R is not correct explanation of A
    • C. A is correct but R is wrong
    • D. A is wrong but R is correct
      • Discuss
    • 4. Match the following:

      List I List II
      A. Zener diode 1. used in seven segment display
      B. Tunnel diode 2. used in voltage regulator circuits
      C. LED 3. used is solar energy utilization
      D. Photovoltaic cell 4. used in digital circuits


    • Options
    • A. A-1, B-3, C-2, D-4
    • B. A-2, B-3, C-1, D-4
    • C. A-2, B-4, C-1, D-3
    • D. A-3, B-2, C-4, D-1
      • Discuss
    • 5. For the system in the given figure the characteristic equation is

    • Options
    • A.
    • B.
    • C. K(s + 1)(s + 3) = 0
    • D. s(s + 2) = 0
      • Discuss
    • 6. The magnitudes of OC and SC input impedances of a transmission line an 100 ? and 25 ?. The characteristic impedance is

    • Options
    • A. 25 ?
    • B. 50 ?
    • C. 75 ?
    • D. 100 ?
      • Discuss
    • 7. In the given figure x6 =

    • Options
    • A. de(ax1 + bx2 + cx3)
    • B. (a + b + c) (x1 + x2 + x3) (d + e)
    • C. (ax1 + bx2 + cx3) (d + e)
    • D. a b c d e (x1 + x2 + x3)
      • Discuss
    • 8. Which of the following cannot be used to demodulate SSB?

    • Options
    • A. Complete phase-shift generator
    • B. Product detector
    • C. Diode balanced modulator
    • D. Bipolar transistor balanced modulator
      • Discuss
    • 9. The current wave shape shown in figure (1) is applied to a circuit element. The voltage across the element is shown in figure (2). The element is

    • Options
    • A. R
    • B. L
    • C. C
    • D. Semiconductor
      • Discuss
    • 10. When phase-lag compensation is used in a system, then gain cross over frequency, bandwidth and undamped frequency are respectively

    • Options
    • A. Increased, Increased, Increased
    • B. Increased, Increased, Decreased
    • C. Increased, Decreased, Decreased
    • D. Decreased, Decreased, Decreased
      • Discuss

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