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Electronics Engineering Objective Questions { Transmission Lines and Waveguides }

43. For handling high powers, it is best to use
A. rectangular waveguide
B. stripline
C. coaxial cable
D. microstrip
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44. The cavity magnetron employs strapping in order to
A. prevent mode jumping
B. reduce frequency pushing and pulling
C. ensure bunching
D. permit better dissipation of heat
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45. Indicate the FALSE statement :Frequency-agile or dither-tuned magnetron
A. has a movable piston for changing its operating frequency
B. can be easily jammed
C. may be conventional or coaxial
D. is capable of sending a series of pulses each of which is at a different frequency
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46. Which statement regarding voltage tunable magnetrons (VTMs) is wrong?
A. they use high-Q cavities
B. they have an extra injection electrode to help bunching
C. their operating frequency can be varied over an octave by adjusting anode votage
D. they use cold cathodes
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47. The cut-off frequency in a waveguide means
A. longer waves will not propagate significantly
B. determine the dimensions of waveguide
C. frequency at which no transmission takes place.
D. None of above
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48. For a standard X-band waveguide of cross-sectional dimension 2.286 cm x 1.016 cm, the cut-off wavelength for a TEio mode is ___ cm.
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49.  The signal delay caused when a wave travels a distance Z metres through a hollow wave guide is where VPh' V and Vo represent phase gr velocity, group velocity and free space velocity (m/sec) respectively. given by
A. Z/Vph
D. ZN'.V
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