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  • Question

  • Assertion (A): TWT uses a focussing mechanism to prevent the electron beam from spreading.

    Reason (R): In a TWT the electron beam has to travel a much longer distance than in klystron.


  • Options
  • A. Both A and R are correct and R is correct explanation of A
  • B. Both A and R are 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

  • Correct Answer
  • Both A and R are correct and R is correct explanation of A 

    Explanation
    In a klystron the resonant structure limits the bandwidth.

    A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave.

    The velocity of wave propagation along the helix structure is less than velocity of light.

    The beam and wave travel along the structure at the same speed.

    Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave.

    Therefore the signal gets strengthened and amplified output is delivered at the other end of tube.

    The main features of TWT are :

    1. Frequency range - 0.5 GHz to 90 GHz

    2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz

    3. Efficiency - about 5 to 20%

    4. Noise - about 5 dB for low power TWT 25 dB for high power TWT

    TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.

    More questions

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    • Options
    • A. T is kept constant and Ton is varied
    • B. Ton is kept constant T is varied
    • C. both T and Ton are varied
    • D. either T or Ton is varied
      • Discuss
    • 2. The colour code on a carbon resistor is green-blue-yellow. The tolerance is

    • Options
    • A. ± 5%
    • B. ± 10%
    • C. ± 20%
    • D. ± 30%
      • Discuss
    • 3. Wave guides are pressurised above normal atmospheric pressure for

    • Options
    • A. increasing the power handling capacity
    • B. improving conductivity of walls
    • C. preventing higher modes from propagation
    • D. varying the wave impedance
      • Discuss
    • 4. A transmission line discontinuity is defined as any interruption in the uniformity of the line.

    • Options
    • A. True
    • B. False
      • Discuss
    • 5. Which of the following is not a valid variable name in C?

    • Options
    • A. 1 a
    • B. a 1 2
    • C. a b 123
    • D. a b c 123
      • Discuss
    • 6. If an amplifier with gain of - 1000 and feedback factor ? = - 0.1 had a gain change of 20% due to temperature, the change in gain of the feedback amplifier would be

    • Options
    • A. 10%
    • B. 5%
    • C. 0.2%
    • D. 0.01%
      • Discuss
    • 7. Permeability is analogous to

    • Options
    • A. resistivity
    • B. retentivity
    • C. conductivity
    • D. coercivity
      • Discuss
    • 8. In a Gunn diode oscillator drift velocity of electron is 107 cm/s and active region length is 10 x 10-4 cm. The natural frequency of oscillation is

    • Options
    • A. 1 MHz
    • B. 10 MHz
    • C. 1 GHz
    • D. 10 GHz
      • Discuss
    • 9. A cycloconverter is a group of controlled rectifiers.

    • Options
    • A. True
    • B. False
      • Discuss
    • 10. If the valence electron is separated from a copper atom, the remaining part of atom has a net charge of

    • Options
    • A. 1
    • B. - 1
    • C. 0
    • D. + 3
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