Self-Test
& Supply the missing word(s) in each statement.
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)
a. Added
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
d. Adder
3. In Fig. 3-4, D1 acts as a(n) (page 41-Frenzel)
a. Capacitor
b. Rectifier
c. Variable resistor
d. Adder
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.
True or false. Any balanced modulator may be used as a mixer.
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