Discussion
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- Question
In a TWT the amplitude of resultant wave travelling down the helix
Options- A. increases exponentially
- B. increases linearly
- C. decreases exponentially
- D. is almost constant
- Correct Answer
- increases exponentially
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 stud in a stud mounted SCR acts as
Options- A. anode
- B. cathode
- C. gate
- D. anode or cathode Discuss
Correct Answer: anode
- 2. As per temperature limits, the number of categories of solid dielectrics are
Options- A. 7
- B. 6
- C. 8
- D. 5 Discuss
Correct Answer: 7
- 3. In satellite communication, highly directional antennas are used to
Options- A. direct the spot beam to a particular region of space on Earth
- B. strengthen the beam to overcome the cosmic noise
- C. make corrections in change of polarisation of the beam
- D. select a particular channel in transmission and reception Discuss
Correct Answer: direct the spot beam to a particular region of space on Earth
- 4. For the transport lag G(j?) = e-j?T, the magnitude is always equal to
Options- A. 0
- B. 1
- C. 10
- D. 0.5 Discuss
Correct Answer: 1
Explanation:
Magnitude is 1.- 5. Ferroelectric materials are those which
Options- A. cannot be polarized
- B. have a permanent polarization
- C. have ae equal to zero
- D. have ?p = 0 Discuss
Correct Answer: have a permanent polarization
Explanation:
Ferroelectric materials have permanent polarization.- 6. A cable has an insulation resistance of 1010 ohms. If the length is doubled, the insulation resistance will be
Options- A. 2 x 1010 ?
- B. 0.5 x 1010 ?
- C. 1010 ?
- D. 4 x 1010 ? Discuss
Correct Answer: 0.5 x 1010 ?
Explanation:
Insulation resistance of cable is inversely proportional to length.- 7. The number of storage classes in C is
Options- A. 2
- B. 3
- C. 4
- D. 6 Discuss
Correct Answer: 4
Explanation:
C has four storage classes viz. automatic storage class, register storage class, static storage class and external storage class.- 8. A silicon controlled switch has :
Options- A. 2 leads
- B. 3 leads
- C. 4 leads
- D. 5 leads Discuss
Correct Answer: 4 leads
Explanation:
Anode, cathode, anode gate and cathode gate.- 9. Some ceramic materials become superconducting
Options- A. below liquid helium temperature
- B. between liquid helium and liquid nitrogen temperature
- C. above liquid nitrogen but below room temperature
- D. at room temperature Discuss
Correct Answer: below liquid helium temperature
- 10. In a stud mounted SCR, the stud is
Options- A. in thermal contact with heat sink
- B. insulated from heat sink
- C. in electrical and thermal contact with heat sink
- D. in either electrical or thermal contact with heat sink Discuss
Correct Answer: in electrical and thermal contact with heat sink
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