(Last Updated On: February 9, 2020)
This is the Self-test in Chapter 2: Amplitude Modulation and Single-Sideband Modulation 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
Supply the missing word(s) in each statement.
1. Modulation causes the information signal to be _____ to a higher frequency for more efficient transmission.
2. During modulation, the information signal _____ the amplitude of a high frequency signal called the _____.
3. The circuit used to produce modulation is called a _____. Its two inputs are _____.
4. In AM, the instantaneous _____ of the carrier varies in accordance with the information signal.
5. True or false. The carrier frequency is usually lower than the modulating frequency.
6. The outline of the peaks of the carrier signal is called the _____, and it has the same shape as the _____.
7. Voltages varying over time are said to be _____ signals.
8. The trigonometric expression for the carrier is Vc = _____.
9. True or false. The carrier frequency remains constant during AM.
10. An amplitude modulator performs the mathematical operation of
11. Which of the following is the most correct?
a. Vm should be greater than Vc.
b. Vc should be greater than Vm
c. Vm should be equal to or less than Vc.
d. Vc must always equal Vm
12. Which of the following is not another name for modulation index?
a. Modulation reciprocal
b. Modulation factor
c. Degree of modulation
d. Modulation coefficient
13. The degree or depth of modulation occurring expressed as a percentage, is computed using the expression
a. 2 Vm
b. 100 / m
c. m / 100
d. 100% x m
14. The modulation index is the ratio of the _____ peak voltage of the to the _____.
15. An AM wave displayed on an oscilloscope has values of Vmax= 3.8 and Vmin= 1.5 as read from the graticule. The percentage of modulation is _____ percent.
16. The ideal percentage of modulation for maximum amplitude of Information transmission is _____ percent.
17. To achieve 85 percent modulation of a carrier of Ve = 40 volts (V), a modulating signal of Vm = _____ is needed.
18. The peak-to-peak value of an AM signal is 30 V. The peak-to-peak value of the modulating signal is 12 V. The percentage of modulation is _____ percent.
19. New signals generated by the modulation process that appear directly above and below the carrier frequency are called _____.
20. An AM radio station operating at 630 kHz is permitted to broadcast audio frequencies up to 5 kHz. The upper and lower side frequencies are
fUSB = _____ kHz
fLSB = _____ kHz
21. The total bandwidth of the signal in the above example is _____ kHz.
22. A signal whose amplitude is displayed with respect to time is called a _____ domain display. The test instrument used to present such a display is the _____.
23. A signal whose amplitude is displayed with respect to frequency is called a _____ domain display. The test instrument used to present such a display is the _____.
24. Complex modulating signals containing many frequencies produce multiple_____ thus occupying more spectrum space.
25. The AM signal that occupies the greatest bandwidth is the one modulated by a
a. 1-kHz sine wave
b. 5-kHz sine wave
c. 1-kHz square wave
d. 5-kHz square wave
26. The composite AM signal can be recreated by algebraically adding which three signals?
27. The total sideband power is what percentage of the carrier power for 100 percent modulation?
a. 25 percent
b. 50 percent
c. 100 percent
d. 150 percent
28. Information in an AM signal is conveyed in the
c. Both together.
29. The load into which the AM signal Power is dissipated is a(n) _____.
30. The total transmitted power is the sum of the _____ and _____ powers.
31. A 5-kW carrier with 60 percent modulation produces _____ kW in each sideband.
32. In an AM signal with a carrier of 18W and a modulation percentage of 75 percent, the total power in the sidebands is _____ W.
33. An AM signal with a carrier of 1 kW has 100W in each sideband. The percentage of modulation is _____ percent.
34. An AM transmitter has a carrier power of 200 W. The percentage of modulation is 60 percent. The total signal power is _____ W.
35. The total AM signal power is 2800W. The carrier power is 2000 W. The power in one sideband is _____ W. The percentage of modulation is_____.
36. The unmodulated carrier current in an antenna is 1.5 A. When the carrier is modulated by 95 percent, the total antenna current is _____ A.
37. An AM signal without a carrier is called a(n) _____ signal.
38. True or false. Two sidebands must be transmitted to retain all the information.
39. The acronym SSB means
a. Single sideband with carrier
b. Single sideband with suppressed carrier
c. Double sideband with no carrier
d. Double sideband with carrier
40. A major benefit of DSB and SSB is
a. Higher power can be put into the sideband(s).
b. Greater power consumption.
c. More carrier power.
d. Double the sideband power.
41. List four benefits of SSB over AM and DSB.
42. List two common uses of SSB.
43. A common use of DSB is
a. Two-way communication.
b. Telephone systems.
c. FM/TV stereo.
d. Satellite communications.
44. True or false. In SSB, no signal is transmitted unless the information signal is present.
45. The type of AM signal that is used in TV broadcasting is called _____ transmission.
46. An SSB signal produces a peak-to-peak voltage of 720V on voice peaks across a 75- antenna. The PEP output is _____ W.
47. An SSB transmitter has a 15O-V supply. Voice peaks produce a current of 2.3 A. The PEP input is _____ W.
48. The average output power of an SSB transmitter rated at 12W PEP is in the _____ to _____ range.
49. The process of translating a signal to a higher or lower frequency for more convenient processing is called _____.
50. The circuit used for translating the frequency of a signal is referred to as a(n) _____ or _____.
51. The input signals to a frequency translation circuit are fs = 3.7 MHz and fo = 4.155 MHz. The output signals are _____.
52. In the example given in the text, what other local oscillator frequency could be used to produce the 10.7-MHz output with a 107.1 = MHz input?
53. Unwanted mixer output signals are eliminated by a _____.
54. True or false. The local oscillator is modulated.
55. True or false. Any modulation on the input signal to be translated is retained.
56. The operation carried out by a mixer is known as _____.