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ECE Objective Questions { Microwave Devices and Circuits }

99. The multi-cavity klystron
A. is not a good low-level amplifier because or noise
B. has a high repeller voltage to ensure a rapid transit time
C. is not suitable for pulsed operation
D. needs a long transit time through the buncher cavity to ensure current modulation

100. The TWT is sometimes preferred to the multicavity klystron amplifier, because the former
A. is more efficient
B. has a greater bandwidth
C. has a higher number of modes
D. produces a higher output power

101.  The primary purpose of the helix in a travelling-wave tube is to
A. prevent the electron beam from spreading in the long tube
B. reduce the axial velocity of the RF field
C. ensure broad band operation
D. reduce the noise figure

102. The transit time in the repeller space of a reflex klystron must be n + ?4 cycle to ensure that
A. electrons are accelerated by the gap voltage on their return
B. returning electrons given energy to the gap oscillations
C. it is equal to the period of the cavity oscillations
D. the repeller is not damaged by striking electrons

103.  Microwave ovens operate at a frequency of
A. 1.37 GHz
B. 2.45 GHz
C. 3.37 GHz
D. 22 LIHz

104.  The modes in a reflex klystron
A. result from excessive transit time across the resonator cap
B. correspond to different oscillating frequencies of the cavity
C. are caused by spurious frequency modulation
D. all give much the same frequency but different transit times

105. If a narrow slot is cut in the wall of a waveguide so that it disturbs current flow, that slot is said to be
A. A non-radiating slot
B. A radiating slot
C. None of the above
D. Both (a) and (b)

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