Principles of Electronic Communication Systems 4th Edition Frenzel Solutions
Manual
Part B
Answers to Questions,
Problems, Critical
Thinking, and Online
ActivitiesChapter 1
Answers to Questions
1. In the ninete
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Principles of Electronic Communication Systems 4th Edition Frenzel Solutions
Manual
Part B
Answers to Questions,
Problems, Critical
Thinking, and Online
ActivitiesChapter 1
Answers to Questions
1. In the nineteenth century.
2. Transmitter, communications channel or medium,
receiver, noise. See Fig. 1-2 in the text.
3. Wire cable, free space (radio and light), fiber-optic
cable, water, the earth. The first three are the most
widely used.
4. Modulator.
5. Demodulator.
6. The combination of a transmitter and a receiver in a
single package that may share some circuits.
7. Attenuation, addition of noise.
8. Communications channel.
9. Noise.
10. Lightning, outer space (sun, stars), manufactured devices
(motors, car ignitions, fluorescent lights, etc.).
11. Baseband signals.
12. Analog and digital.
13. Simplex. Broadcasting, paging, telemetry.
14. Full-duplex. Telephones: standard, cordless, cellular.
15. Half-duplex. Two-way radio, fax machine, computer
modem.
16. Analog.
17. Digital or binary.
18. The analog signals are converted into binary signals first.
19. Information or intelligence signals.
20. Modulation.
21. Demodulation or detection.
22. One that consists of a carrier modulated by one or more
baseband signals.
23. Multiplexing.
24. Demultiplexing.
25. Radio or wireless.
26. Electric or magnetic fields.
27. 1.5 kHz: 124.2 miles, 18 MHz: 54.67 ft, 22GHz: 1.36 cm.
28. Antennas would be too long to be practical, signals
would not travel far, all signals would interfere with one
another.
29. 20 Hz to 20 kHz.
30. 300–3000 Hz.
31. Yes, but only a few, usually military or government
(navigation).
32. 535–1705 kHz.
33. Short waves.
34. VHF.
35. Two-way radio, TV, cellular telephone, radar, satellites.
36. Microwave.
37. Millimeter waves.
38. A micron is one-millionth of a meter or micrometer
(µm) or 10–6 m. It is used to express light wavelength.
39. Infrared, visible, ultraviolet.
40. Heated objects or LEDs and lasers.
41. 0.7 to 100 µm.
42. An angstrom is 10–10 m and is used to state light
wavelength.
43. 0.4 to 0.8 µm.
44. Free space and fiber-optic cable.
45. Facsimile and television.
46. Paging.
47. Telemetry.
48. Cordless telephones, cellular telephones, microwave
relay, satellites.
49. The reflection of radio waves from a distant object.
50. Sonar. Passive sonar listens to underwater sounds.
Active radar sends out an ultrasonic signal and listens
for its reflection or echo to determine range and bearing.
51. Amateur or ham radio.
52. Modem.
53. Local area networks (LANs).
54. Wireless.
55. Engineer, technologist, technician.
56. Design and analysis of circuits, equipment, and systems.
57. Bachelor’s degree (B.S.E.E.).
58. Associate’s degree (A.S.E.E., A.A.S., etc.).
59. Bachelor’s degree in technology.
60. Usually no.
61. Install, operate, maintain, troubleshoot, repair, and
service equipment.
62. Sales, technical writing, training.
63. Manufacturers create products, distributors transfer
products to resellers who market the products, service
organizations install, repair, and maintain the products,
and end users apply the products.
64. Communications standards ensure compatibility and
interoperability of equipment.
65. Communications standards define modulation and/or
multiplexing methods, frequencies of operation,
protocols, and interface methods, including mechanical
connections.
Answers to Problems
1. 7.5 MHz, 60 MHz, 3750 MHz, or 3.75 GHz.
2. ELF.
3. Radar and satellites.
Answers to Critical Thinking
1. Vary carrier amplitude, frequency, or phase.
2. TV remote control (infrared), garage door opener
(radio—VHF or UHF).
3. Stars (suns) radiate radio waves that can be received by
directional antennas that can record azimuth and
elevation to plot star positions.
4. Individual student’s choice.
5. Narrow or restrict the bandwidth of some signals and their
channel bandwidth, use more multiplexing, share
frequencies at different times or when signals do not carry
far. Use more wire or cable systems. In digital systems,
use data compression techniques. Use the optical range.
6. 982.08 ft/µs, 11.8 in/ns, 3 × 108 m/s.
7. The speed of light is 186,000 miles per second (mi/s) or
300,000,000 meters per second (m/s). The speed of
sound is only a fraction of that, or about 1129 feet per
second (ft/s) or 344 meters per second (m/s). You cannot
see light travel because its speed is so fast that it appears
instantaneous. Over long distances as in space, it takes
light-years to go from one place to another. The sun is
B-2about 93 million miles from earth. It takes light from the
sun 93,000,000 mi/186,000 mi/s = 500 seconds, or
about 8.33 minutes to reach us.
Sound speed is easily observed. Lightning at a
distance is an example. You see the lightning first, and
then hear it (the thunder clap) later.
8. Remote control of automobile door locks and alarms by
key chain transmitters, wireless speakers for stereo.
Reverse control of a cable TV box by the cable company
using digital signals, using cable TV modems for
Internet access, telemetry of signals for water, gas, or
electric utility monitoring. Radar speed measurement of
baseball pitches.
9. Student ideas and innovations.
10. Call the FCC to get advice and direction. Search the
FCC website at www.fcc.gov. Communications
consultants can be hired to help you with this. Order
copies or the relevant U.S. Government Code of Federal
Regulations (CFR) Title 47 from the U.S. Government
Printing Office.
11. Some examples are telephone, cordless telephone,
cellular telephone, CB radio, TV set with remote
control, radio, FM stereo system, garage door opener,
PC with modem to on-line service, cable TV converter
box, fax machine.
12. The “cup and string” communications system is
theoretically sound although very inefficient. If the
string is pulled taut, but not too taut, it will carry sound
waves from one cup to the other. Speaking into one cup
causes the bottom of the cup to vibrate like a diaphragm
in a microphone. This transmits the sound to the string.
The string vibrates the bottom of the receiving cup,
which acts like a speaker cone to transfer the sound to
your ear. The key to the success of this system lies in
the efficient coupling of the string to the bottom of the
cups and the tension on the string. Tension must be
present in order to pick up and transmit the sound. If the
tension is too great, it will inhibit the vibration of the
cup bottoms.
Chapter 2
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