Discussion
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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
ExplanationIn 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
- 1. The characteristic impedance of a cable is about
Options- A. 300 ?
- B. 50 ?
- C. 5 ?
- D. 2 ? Discuss
Correct Answer: 50 ?
- 2. A copper atom is neutral. Its core has a net charge of
Options- A. 0
- B. + 1
- C. - 1
- D. + 2 Discuss
Correct Answer: + 1
- 3. The characteristics of which device has peak point and valley point
Options- A. SCR
- B. PUT
- C. SCS
- D. Shockley diode Discuss
Correct Answer: PUT
- 4. Schrodinger wave equation is partial differential equation.
Options- A. True
- B. False Discuss
Correct Answer: True
- 5. The output frequency of a cycloconverter can be changed by changing the firing angle.
Options- A. True
- B. False Discuss
Correct Answer: False
- 6. Most of the memory chips in static RAM
Options- A. do not require any supply
- B. need 2 V supply
- C. need 5 V supply
- D. need 12 V supply Discuss
Correct Answer: need 5 V supply
Explanation:
Digital chips need 5 V supply.- 7. In crystalline solids, atoms are stacked in a regular manner.
Options- A. True
- B. False Discuss
Correct Answer: True
- 8. The classes of solid dielectrics are
Options- A. A, B, C, D, E, F, H
- B. A E B F H C D
- C. Y A E B F H C
- D. A E B F H C Discuss
Correct Answer: Y A E B F H C
- 9. The unit for mmf is
Options- A. A
- B. Wb
- C. T
- D. V Discuss
Correct Answer: A
- 10. In a single phase full wave regulator, the firing angles in the positive and negative half cycles are generally
Options- A. equal
- B. different
- C. equal or different
- D. different but sometimes equal Discuss
Correct Answer: equal
Explanation:
Firing angles are kept equal to get symmetrical output voltage.
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