# Frenzel Self-test in Amplitude Modulation Circuits

Frenzel Self-test in Amplitude Modulation Circuits from the book COMMUNICATIONS ELECTRONICS by Louis E. Frenzel. Make sure to familiarize each and every questions.

This is the Self-test in Chapter 3: Amplitude Modulation Circuits from the book COMMUNICATIONS ELECTRONICS by Louis E. Frenzel. If you are looking for a reviewer in Communications Engineering this will definitely help. I can assure you that this will be a great help in reviewing the book in preparation for your Board Exam. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.

### Start Practice Exam Test Questions

Direction: Either Supply the missing word(s) in each statement  or Choose the letter that best answers each question.

1. In the modulator, circuit of Fig. 3-2, the carrier and modulating signals are (page 39-Frenzel)

• b. Subtracted
• c. Multiplied
• d. Divided

2. In Fig. 3-2,D1 acts as a(n) (page 39-Frenzel)

• a. Capacitor
• b. Rectifier
• c. Variable resistor

3. In Fig. 3-4, D1 acts as a(n) (page 41-Frenzel)

• a. Capacitor
• b. Rectifier
• c. Variable resistor

4. AM can be produced by passing the carrier through a circuit whose _____ or _____ can be varied in accordance with the modulating signal.

5. The name of the nonlinear response of a device that produces AM with only second-order products is _____.

6. A component that has an exponential response ideal for producing AM is the _____.

7. In Fig. 3-2, the negative peaks of the AM signal are supplied by the _____. (page 39-Frenzel)

8. In Fig. 3-5, the FET acts like a(n) _____. (page 41-Frenzel)

9. In Fig. 3-5, AM is produced by varying the _____of the op-amp circuit. (page 41-Frenzel)

10. In Fig. 3-5, a positive-going modulating signal causes the current in the FET to _____, its resistance to _____, and the gain of the circuit to _____.(page 41-Frenzel)

11. When forward-biased, a PIN diode acts like a(n) _____.

12. PIN diode modulators are used only at frequencies above about _____.

13. A PIN diode modulator is a variable

14. High current in a PIN diode means that its resistance is_____.

15. The AM signals generated by low-level modulating circuits must have their power level increased by a(n) _____ before being transmitted.

16. In a high-level AM transmitter, the output stage is usually a class _____ amplifier.

17. A high-level modulator like that in Fig. 3-8 is referred to as a _____ modulator. (page 43-Frenzel)

18. The output of a high-level modulator causes the _____ applied to the final RF amplifier to vary with the amplitude of the modulating signal.

19. The final amplifier of a high-level modulation CB transmitter has an input power of 5 W. The modulator must be able to supply a power of _____ W for 100 percent modulation.

20. The final RF power amplifier has a supply voltage of 12V. For 100 percent AM using a high-level modulator, the peak ac output of the modulation transformer must be _____ V.

21. To achieve 100 percent high-level modulation of an RF power amplifier, its _____ must also be modulated.

22. The purpose of a _____ is to recover the original modulating signal from an AM wave.

23. The most widely used amplitude demodulator is called a _____.

24. The most critical component in the circuit of Fig. 3-11 is _____.(page 46-Frenzel)

25. The charging and discharging of C1 in Fig. 3-11 produces _____ which causes _____ of the modulating signal. (page 46-Frenzel)

26. Another name for the demodulator in Fig. 3-11 is _____ detector.

27. List the two main benefits of the full-wave amplitude demodulator over the half wave circuit.

28. True or false. An amplitude demodulator is a complete radio receiver.

29. A balanced modulator eliminates which of the following from its output?

• a. Upper sideband
• b. Lower sideband
• c. Carrier
• d. Both sidebands

30. The output signal of a balanced modulator is.

• a. AM
• b. SSB
• c. FM
• d. DSB

31. Which has better carrier suppression?

• a. Lattice modulator
• b. IC balanced modulator

32. A balanced modulator using a diode bridge is called a(n) _____. (page 48-Frenzel)

33. In the balanced modulator of Fig. 3-14, the diodes are used as _____.

34. A balanced modulator has a carrier frequency of 1.9 MHz and a modulating sine wave of 2.6 kHz. The output signals are _____ and _____kHz.

35. In Fig. 3-18, transistors _____ supply a constant current. (page 51-Frenzel)

36.In Fig. 3-18, transistors Q1 to Q4 operate as_____. (page 51-Frenzel)

37. True or false. An IC analog multiplier may be used for DSB signal generation.

38. The most common way of generating an SSB signal is the _____ method.

39. A filter capable of passing the desired sideband while rejecting the other sideband must have good_____.

40. A balanced modulator has a 3-MHz carrier input and a modulating signal input of 1.5 kHz to pass the lower sideband, a filter must have a center frequency of _____ MHz.

41. The most popular filter used to select the desired sideband in an SSB generator uses _____ for selectivity.

42. Name the two ways of generating either the upper or lower sideband in a filter type SSB generator.

43. A quartz crystal acts like a highly selective _____ circuit.

44. In a filter-type SSB generator, a crystal lattice filter is used. The two crystal frequencies are 3.0 and 3.0012 MHz. The filter bandwidth is approximately _____ kHz.

45. Mechanical filters provide selectivity because they _____ at a specific frequency.

46. A ceramic filter is similar in operation to a(n) _____ filter.

47. The operating frequency range of a mechanical filter is _____ to _____ kHz.

48. In the phasing method of SSB generation, _____ is used to cancel the undesired sideband.

49. A _____ circuit is commonly used to demodulate or recover an SSB signal.

50. The circuit used to demodulate an SSB signal is typically called a(n) _____.

51. The mixing process is

• a. Linear.
• b. Nonlinear.

52. In up conversion, which signal is selected?

• a. f1 - f2
• b. f1 + f2

53. Which transistor mixer is preferred?

• a. Bipolar
• b. FET

54. Another name for the mixing process is _____.

55. The purpose of a mixer is to perform _____.

56.The output signals produced by a mixer with inputs f1 and f2 are _____, _____, _____, and _____.

57. The type of mixer most used at microwave frequencies is a(n) _____.

58. The two mixers preferred at VHF and UHF are _____.

59. Transistor mixers provide _____, while diode mixers do not.

60. A mixer producing down conversion has an input of 1390 kHz and an LO frequency of 1845 kHz. The output is _____ kHz.

61. A single-transistor circuit that combines the mixer and LO functions is known as a(n) _____.

62. The mixer circuit in the popular NE602 IC is _____.

63. In addition to a mixer and a voltage regulator, the NE602 mixer IC contains a(n) _____.

64. The output of a NE602 mixer IC is 5.5 MHz. The local oscillator is set to 26.8 MHz. The input frequency is _____.

65. True or false. Mixing is the same as AM.

66. True or false. Any balanced modulator may be used as a mixer.

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