| 1. | In a directional coupler ? | |
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coupling (dB) equals isolation plus directivity
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isolation (dB) equals coupling plus directivity
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isolation (dB) equals (coupling) (directivity)
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directivity (dB) equals isolation plus coupling
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Report Question| 2. | A line is excited by a 100 V dc source. If reflection coefficients at both ends are 1 each then ? | |
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the oscillations will continue indefinitely
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there will be a finite number of oscillations on line
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there will be no oscillations on line
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there will be only 1 or 2 oscillations on line
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| 3. | The frequency of oscillation in a backward wave oscillator can be changed by ? | |
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changing the rate of thermionic emission
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varying the voltage which controls beam velocity
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varying the beam current
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both by varying the beam current and by light varying the voltage which controls beam velocity
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| 4. | The main disadvantage of the two hole directional coupler ? | |
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high VSWR
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narrow bandwidth
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poor directivity
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low directional coupling
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| 5. | One of the reasons why vacuum tubes eventually fail at microwave frequencies is that their ? | |
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series inductive reactances become too small
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noise figure increases
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transit time becomes too short
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shunt capacitive reactances become too large
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| 6. | Which one of the following can be used for amplification of microwave signals ? | |
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Reflex klystron
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Gunn diode
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Double cavity klystron
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Strapped magnetron
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| 7. | Low power non-solid state microwave oscillator is ? | |
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BWO
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Magnetron
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Gunn diode oscillator
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Reflex klystron
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| 8. | A microwave tube amplifier uses an axial magnetic field and radial electric field. This is ? | |
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Travelling wave magnetron
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Reflex klystron
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Coaxial magnetron
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CFA
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| 9. | Which vacuum based device is widely used as a power amplifier in satellite communication systems ? | |
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Amplitron
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TWT
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Magnetron
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Klystron
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| 10. | Why is an attenuator used in a TWT ? | |
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To increase gain
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To prevent saturation
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Two help bunching
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To prevent oscillations
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