NEETS MODULE 12 CHAPTER 1 AMPLITUDE MODULATION
Q-1. What is modulation?
Q-2. What is a transmission medium?
Q-3. What is heterodyning?
Q-4. What is demodulation?
Q-5. What waveform is the basis of all complex waveforms?
Q-6. What is the purpose of using vectors?
Q-7. What is the trigonometric ratio for the sine of an angle?
Q-8. What is the mathematical formula for computing the output voltage from a moving coil in a magnetic field?
Q-9. What is the instantaneous amplitude of a sine wave?
Q-10. What term describes how much of a cycle has been completed?
Q-11. What determines the frequency of a sine wave?
Q-12. What is the period of a cycle?
Q-13. How do you calculate the wavelength of a sine wave?
Q-14. Define the heterodyne principle.
Q-15. What is a nonlinear impedance?
Q-16. What is spectrum analysis?
Q-17. What two conditions are necessary for heterodyning to take place?
Q-18. What is amplitude modulation?
Q-19. What are the three requirements for cw transmission?
Q-20. Name two methods of oscillator keying.
Q-21. State the method used to increase the speed of keying in a cw transmitter.
Q-22. Name three advantages of cw transmission.
Q-23. Name a disadvantage of a single-stage cw transmitter.
Q-24. What is the purpose of the power-amplifier stage in a master oscillator power amplifier cw transmitter?
Q-25. What is the purpose of frequency-multiplier stages in a VHF transmitter?
Q-26. What is a microphone?
Q-27. What special electromechanical effect is the basis for carbon microphone operation?
Q-28. What is a major disadvantage of a carbon microphone?
Q-29. What property of a crystalline material is used in a crystal microphone?
Q-30. What is the difference between a dynamic microphone and a magnetic microphone?
Q-31. What are the two major sections of a typical AM transmitter?
Q-32. When 100 kilohertz and 5 kilohertz are heterodyned, what frequencies are present?
Q-33. What is the upper sideband of an AM transmission?
Q-34. Where is the intelligence in an AM transmission located?
Q-35. What determines the bandwidth of an AM transmission?
Q-36. What is percent of modulation?
Q-37. With a single modulating tone, what is the amplitude of the sideband frequencies at 100-percent modulation?
Q-38. What is the formula for percent of modulation?
Q-39. What is high-level modulation?
Q-40. For what class of operation is the final rf power amplifier of a plate-modulator circuit biased?
Q-41. The modulator is required to be what kind of a circuit stage in a plate modulator?
Q-42. How much must the fpa plate current vary to produce 100-percent modulation in a plate modulator?
Q-43. The collector-injection modulator is similar to what type of tube modulator?
Q-44. When is a control-grid modulator used?
Q-45. What type of modulator is the cathode modulator (low- or high-level)?
Q-46. What causes the change in collector current in an emitter-injection modulator?
NEETS MODULE 12 CHAPTER 2 ANGLE AND PULSE MODULATION
Q-1. What are the two types of angle modulation?
Q-2. Name the modulation system in which the frequency alternates between two discrete values inresponse to the opening and closing of a key?
Q-3. What is the primary advantage of an fsk transmission system?
Q-4. What characteristic of a carrier wave is varied in frequency modulation?
Q-5. How is the degree of modulation expressed in an fm system?
Q-6. What two values may be used to determine the bandwidth of an fm wave?
Q-7. How does the reactance-tube modulator impress intelligence onto an rf carrier?
Q-8. What characteristic of a transistor is varied in a semiconductor-reactance modulator
Q-9. What circuit section is required in the output of a multivibrator modulator to eliminate unwanted output frequencies?
Q-10. What characteristic of a varactor is used in an fm modulator?
Q-11. What type of modulation depends on the carrier-wave phase shift?
Q-12. What components may be used to build a basic phase modulator?
Q-13. Phase-shift keying is similar to what other two types of modulation?
Q-14. Overmodulating an rf carrier in amplitude modulation produces a waveform which is similar towhat modulated waveform?
Q-15. What is prt?
Q-16. What is nonpulse time?
Q-17. What is average power in a pulsed system?
Q-18. What is the primary component for a spark-gap modulator?
Q-19. What are the basic components of a thyratron modulator?
Q-20. What action is necessary to impress intelligence on the pulse train in pulse modulation?
Q-21. To ensure the accuracy of a transmission, what is the minimum number of times a modulatingwave should be sampled in pulse modulation?
Q-22. What, if any, noise susceptibility advantage exists for pulse-amplitude modulation over analog amplitude modulation?
Q-23. What characteristics of a pulse can be changed in pulse-time modulation?
Q-24. Which edges of the pulse can be modulated in pulse-duration modulation?
Q-25. What is the main disadvantage of pulse-position modulation?
Q-26. What is pulse-frequency modulation?
Q-27. Pulse-code modulation requires the use of approximations of value that are obtained by whatprocess?
Q-28. If a modulating wave is sampled 10 times per cycle with a 5-element binary code, how manybits of information are required to transmit the signal?
Q-29. What is the primary advantage of pulse-modulation systems?
NEETS MODULE 12 CHAPTER 3 DEMODULATION
Q-1. What is demodulation?
Q-2. What is a demodulator?
Q-3. What is the simplest form of cw detector?
Q-4. What are the essential components of a cw receiver system?
Q-5. What principle is used to help distinguish between two cw signals that are close in frequency?
Q-6. How does heterodyning distinguish between cw signals?
Q-7. What simple, one-transistor detector circuit uses the heterodyne principle?
Q-8. What three functions does the transistor in a regenerative detector serve?
Q-9. What are the three requirements for an AM demodulator?
Q-10. What does the simplest diode detector use to reproduce the modulating frequency?
Q-11. What is the function of the diode in a series-diode detector?
Q-12. In figure 3-5, what is the function of C2?
Q-13. How does the current-diode detector differ from the voltage-diode detector?
Q-14. Under what circuit conditions would the shunt detector be used?
Q-15. Which junction of the transistor in the common-emitter detector detects the modulation envelope?
Q-16. Which component in figure 3-7 develops the af signal at the input?
Q-17. How is the output signal developed in the common-emitter detector?
Q-18. Which junction acts as the detector in a common-base detector?
Q-19. To what circuit arrangement is a common-base detector equivalent?
Q-20. In figure 3-8, which components act as the filter network in the diode detector?
Q-21. What is the simplest form of fm detector?
Q-22. What is the function of an fm detector?
Q-23. What type of tank circuit is used in the Foster-Seeley discriminator?
Q-24. What is the purpose of CR1 and CR2 in the Foster-Seeley discriminator?
Q-25. What type of impedance does the tank circuit have above resonance?
Q-26. What is the primary advantage of a ratio detector?
Q-27. What is the purpose of C5 in figure 3-12?
Q-28. What circuit functions does the tube in a gated-beam detector serve?
Q-29. What condition must exist on both the limiter and quadrature grids for current to flow in agated-beam detector?
Q-30. Name two advantages of the gated-beam detector
Q-31. Where is the intelligence contained in a phase-modulated signal?
Q-32. Why can phase-modulated signals be detected by fm detectors?
Q-33. How is a quadrature detector changed when used for phase demodulation?
Q-34. In its simplest form, what functions must a radar detector be capable of performing?
Q-35. What characteristic of a pulse does a peak detector sample?
Q-36. What is the time constant of the resistor and capacitor in a peak detector for pam?
Q-37. How can a peak detector for pam be modified to detect pdm?
Q-38. How does a low-pass filter detect pdm?
Q-39. How is conversion used in pulse demodulation?
Q-40. What is the discharge rate for the capacitor in a pcm converter?
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