Below are the answers key for Frenzel Self-test in Chapter 7: Communications Receivers from the book COMMUNICATIONS ELECTRONICS by Louis E. Frenzel. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.
1. selectivity
2. increase
3. narrow
4. true (resonant step-up)
5. increase(narrower bandwidth)
6. sidebands
7. 5
8. 0.53 MHz or 530 kHz (fr = 10.6 MHz, XL = 200 , Q = 20)
9. 9.95, 10.05
10. 1333.3
11. decreased
12. 2.4
13. sensitivity
14. tuned radio frequency
15. superheterodyne
16. intermediate frequency
17. local oscillator
18. IF amplifier
19. automatic gain control
20. signal or input, local oscillator
21. IF amplifier
22. c (low)
23. Image
24. 3.5
25. selectivity
26. 28
27. true
28. mixer
29. Intermediate frequency
30. 9,600
31. industrial, atmospheric, and space
32. thermal agitation, shot noise, transit-time noise
33. extraterrestrial or space
34. lightning
35. automobiles, motors, generators, fluorescent lights
36. thermal agitation
37. decibels
38. high
39. increase
40. white, Johnson
41. decrease
42. 1.36
43. shot, transit-time
44. false
45. true
46. noise figure
47. microwave
48. 48.464
49. 49. distortion
50. 50. high
51. RF amplifier, mixer
52. true
53. gain, selectivity, noise
54. MESFET or GASFET, gallium arsenide
55. IF
56. tuned circuits
57. mutual inductance
58. under, over, optimum, critical
59. limiter
60. cutoff, saturation
61. collector current
62. 100
63. automatic gain control
64. IF
65. rectifier, IF amplifier or detector
66. decrease
67. increase
68. constant-current source
69. control gate
70. automatic volume control
71. diode detector
72. reduced
73. local oscillator
74. demodulator
75. voltage-variable capacitor
76. squelch
77. audio, noise
78. tone, squelch
79. SSB, CW
80. the ceramic filter FIL1
81.As the pot arm voltage goes more positive, the reverse bias across D1 increases, thus decreasing its capacitance and the overall capacitance of D1 in series with C14; this in turn increases the local oscillator frequency.
82. volume R2 and squelch R3
83. U2, the MC1350 IF amplifier IC
84. The squelch is signal derived
85. With no BFO, the receiver cannot receive CW or SSB.
86. The gain increases.
87. pin 5 of the U3-b op amp
88.10.7 MHz injected to the ceramic filter FIL1
89. U2, the MC1350 IC, would lose supply voltage at pin 2.
90. A digital counter could be connected to monitor the local oscillator output signal at pin 6 or 7 of the NE602 mixer IC. This would read the local oscillator frequency, which is 10.7 MHz higher than the actual input signal frequency. Therefore, the counter would have to be preset to a value that is 10.7 MHz less than zero count. In this way, the IF value would effectively be subtracted from the input count to read the correct frequency. Assume that the counter is set up to count four digits, 000.0. The counter is preset to 100.0 - 10.7= 89.3, and the input signal frequency is 118 MHz. The local oscillator is tuned to 118 + 10.7 = 128.7 MHz. The counter counts 10.7 to reach 000.0 and then counts 118 more to display a final value of 118.0.
91. power supply
92. crystal filter, local oscillators
93. frequency synthesizer
94. phase-locked loop
95. frequency division ratio
96. 2.86, 10
97. mixer
98. LO for first mixer, LO for second mixer, transmitter
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