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Microwave Communications - Mcqs (1- 5 Microwave Communications - MCQs (1- 5. Rainfall is an important factor for 300) fading of radio waves at frequencies above 1. __________ is the progressive decrease A. 10 GHz of signal strength with increasing B. 100 GHz distance. C. 1 GHz A. Radiation D. 100 MHz B. Attenuation 6. Theoretically electromagnetic radiation C. Modulation field strength varies in inverse proportion D. Propagation to the square of the distance, but when atmospheric attenuation effects and the 2. Calculate the effective earth’s radius if absorption of the terrain are taken into the surface refractivity is 301. account the attenuation can be as high as the inverse _______ power of the distance. A. 8493 km B. 8493 mmi A. Third C. 6370 km B. Fourth D. 6370 mi C. Fifth D. Sixth 3. If k-factor is greater than 1, the array beam is bent 7. What do you call an attenuation that occurs over many different wavelengths A. Away from the earth of the carrier? B. towards the ionosphere, A. Rayleigh fading C. towards the earth B. Rician fading D. towards the outer space C. Wavelength fading 4. the antenna separations (in meters) D. Slow fading required for optimum operation of a space diversity system can be calculated from: 8. Which of the reception problems below that is not due to multipath? A. S = 2λR/L A. Delayed spreading B. S = 3λR/L B. Rayleigh fading C. S = λR/RL C. Random Doppler shift D. S = λR/L D. Slow fading where R = effective earth radius (m) and L = path length (m) 9. Which causes multipath or frequency- selective fading? A. Small reflector C. At the collector end of the helix B. Nearer reflector D. At the control grid of the electron gun C. Further reflector D. Large reflector 14. Coupling into and out of a traveling- wave tube can be accompanied by a 10. In microwave transmission using digital radio, what causes most A. Waveguide match intersymbol interference? B. Cavity match A. Delayed spreading C. Direct coax-helix match B. Rayleigh fading D. All of the above C. Random Doppler shift 15. a high-power microwave pulse of the D. Slow fading order of megawatts can be generated by a 11. A shipboard equipment which measures the distance between the A. traveling-wave tube ship’s bottom and the ocean floor. B. magnetron A. Fathometer C. reflex klystron B. Echosounder D. Gunn diode C. LORAN 16. A traveling-wave tube (TWT) D. SONAR amplifies by virtue of 12. The cavity resonator A. The absorption of energy by the signal from an electron stream A. Is equivalent to an LC resonant B. The effect of an external circuit magnetic field B. In a reflect klystron has its C. The energy contained the cavity output taken from the reflector resonators plate D. The energy liberated form the C. Produces a frequency which is collector independent of the cavity size. D. Has a low Q factor for narrow 17. What is the purpose of the operation. electromagnetic field which surrounds a traveling-wave tube? 13. At what position is the input signal inserted into a traveling-wave tube? A. To accelerate the electron B. To velocity modulate the A. At the cathode end of the helix electron beam B. At the collector C. To keep the electrons from C. Density modulation at the input spreading out cavity creates velocity modulation at the output cavity D. To slow down the signal on the helix D. Phase modulation at the input cavity creates velocity modulation 18. Which of the following is used as an at the output cavity. oscillator device in the SHF band? 22. The frequency of the oscillation A. Thyratron tube generated by a magnetron, is mainly determined by B. Tunnel diode C. Klystron tube A. The flux density of the external magnet D. Both B and C B. The ratio of the dc cathode 19. Microwave frequencies are normally voltage to the magnetic flux regarded as those in the range of density C. The number of the cavity A. 1 to 500 MHz resonators B. 1000 to 10,000 GHz D. The dimension of each cavity resonator C. 1 to 100 GHz D. 10 to 1000 GHz 23. If the instantaneous RF potentials on the two sides of a magnetron cavity are 20. The highest frequency which a of opposite polarity, the operation is in conventional vacuum-tube oscillator can the generate is not limited by the A. π mode A. Electron transit time B. π/2 mode B. Distributed lead inductance C. 2π mode C. Inter-electrode capacitance D. π/4 mode D. Degree of emission from the cathode 24. The Gunn diode oscillator 21. As the electron beam moves through A. Is capable of generating a klystron’s intercavity drift space continuous microwave power of the order of kilowatt A. Frequency modulation at the B. Generates frequencies which are input cavity creates velocity below 100 MHz modulation at the output cavity C. Operates over a positive B. Velocity modulation at the input resistance characteristic cavity creates density modulation at the output cavity D. Depends on the formation of charge domain 25. What ferrite device can be used 29. Klystron oscillators are most often instead of duplexer of isolate microwave used in the frequency range of transmitter and receiver when both are connected to the same antenna? A. 300 to 3000 MHz B. 3000 to 30000 MHz A. Isolator C. 30 to 30000 MHz B. Magnetron D. 10 to 10000 MHz C. Simplex D. Circulator 30. Oscillators of a klystron tube are maintained 26. To achieve good bearing resolution when using a pulsed-radar set, an A. By bunches of electrons passing important requirement is the cavity grids B. By plate-to-cathode feedback A. A narrow, antenna-beam width in the vertical plane C. By feedback between the accelerating grid and the repeller B. A narrow, antenna-beam width in the horizontal plane D. By circulating bunches of electrons within the cavities. C. A low repetition rate 31. What allow microwave to pass in only D. A high duty cycle one direction? 27. When used in conJunction with a A. RF emitter radar set, the purpose of an echo box is B. Capacitor to provide an artificial target. C. Varactor-triac A. Which may be used to tune the D. Ferrite emitter radar synchronizer B. Which may be used to tune the 32. In an SHF pulsed radar set, a reflex radar receiver klystron can be used as a C. To the tone of the pulse A. Single mixer stage repetition B. Local oscillator D. Tune the magnetron to the correct frequency C. Transmitter oscillator D. Duplexer stage 28. In a radar-set receiver, the usual mixer stage is 33. A Class-S Emergency Position- Indicating Radio Beacon (E.P.I.R.B) A. And FET B. A tunnel diode A. Must be capable of floating or being secured to a survival C. A silicon crystal B. Must have its battery replaced D. A Rochelle salts crystal after emergency use C. May be tested during the first D. Bunching would occur earlier in five minutes of any hour time D. All of these 38. The coarse frequency adJustment of a reflex klystron is accomplished by 34. A PPI cathode-ray tube as used on a radar set A. The AFC system A. Is used to check the percentage B. AdJusting the flexible wall of the of modulation resonant cavity B. Indicates both the range and C. An adJustment in the azimuth of a target synchronizer C. Indicates only the range of a D. Varying the repeller voltage target D. Is used for receiver alignment 39. In a pulsed radar set, the STC circuit is used to 35. The resonant frequency of a cavity resonator depends upon A. Improve the target bearing resolution A. The mode of operation B. Increases receiver sensitivity for echoes from targets B. Its electrical dimensions C. Vary the pulse frequency in C. Its physical dimensions order to control the maximum D. The capacitor which tunes it target 36. The maximum usable range of the D. Reduce interference from the usual radar set (on any particular range effects of sea return setting) is determined by A. The width of the transmitted 40. In a pulsed radar set, the function of pulses the duplexer is to B. The interval between transmitted pulses A. Aid in calibrating the display unit C. The bandwidth of the receiver IF B. Prevent frequency drift in the stages klystron D. The duty cycle C. Allow the transmitter and the receiver to operate from a common antenna 37. A reflex klystron is oscillating at the frequency of its resonant cavity. If the D. All of these reflector voltage is made slightly less negative, the 41. A magnetron is operated at a duty cycle of 0.001. It has a peak power A. Oscillation will cease output of 100 kilowatts. Its average power is B. Output power would increase C. The frequency will decrease A. 10,000 watts B. 100 watts B. A reduction in horizontal resolution C. 1,000 watts C. No noticeable effect D. 1,000,000 watts D. A decrease in gain 42. The aquadag coating on the inside of PPI tube is used 46. Which of the following permits a microwave signal to travel in one A. To focus the beam of primary direction with virtually no loss, but electrons severely attenuates any signal attempting to travel in the reverse B. To shield the electron beam from direction? unidirectional magnetic C. As a second anode and to A.
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