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. Increasing the reverse bias on a voltage variable capacitor causes its capacitance to
- a. Increase
- b. Decrease
2. Connecting a V VC across a parallel LC circuit causes the resonant frequency to
- a. Increase
- b. Decrease
3. In the circuit of Fig. 5-3, a negative-going modulating signal causes the carrier frequency to
- a. Increase
- b. Decrease
(page 87-Frenzel)
4. A crystal is operating in its series resonant mode. A VVC is connected in series with it. The crystal frequency
- a. Increases
- b. Decreases
5. Which is capable of greater frequency deviation?
- a. LC oscillator
- b. Crystal oscillator
6. Another name for voltage-variable capacitor is _____.
7. Most VVC s have a nominal capacitance in the _____ to _____ pF range.
8. A crystal oscillator has superior _____ over an LC oscillator.
9. The acronym VCO means _____.
10. A voltage-variable crystal oscillator is referred to as a(n) _____.
11. Carrier frequency and frequency deviation may be increased by using a(n) _____ after the carrier oscillator.
12. A reactance modulator is set up to act like an inductive reactance. If the modulating signal increases in amplitude, the effective inductance decreases. This causes. The oscillator frequency to _____.
13. An IC VCO normally uses a combination of _____ and _____ to set the center operating frequency.
14. True or false. Voltage-variable capacitors should not be forward-biased.
15.True or false. For highly stable carrier generators, LC oscillators are preferred over crystal oscillators.
16. True or false. A reactance modulator is used with crystal oscillators.
17. True or false. IC VCO operates primarily at frequencies below 1 MHz.
18. Phase modulation is called _____ FM.
19. True or false. Phase modulation produces frequency variation as well as amplitude variation of the carrier.
20.In a simple RC network, the phase shift is between _____ and _____ degrees.
21. In the circuits of Fig. 5-7, phase is varied by changing the _____ or _____. (page 91-Frenzel)
22. Larger linear phase shifts are obtained with a(n) _____ circuit.
23. The control element in a phase modulator is usually a(n) _____.
24. In Fig. 5-10, the component which adjusts the deviation is _____. (page 93-Frenzel)
25.If a parallel LC circuit is at resonance, increasing C will cause the current to _____ (lead, lag) the applied voltage.
26.In Fig. 5-7(b), if C is decreased, will the phase shift increase or decrease? (page 91-Frenzel)
27. In the phase modulator of Fig. 5-8, the FET current is the phasor sum of the currents produced by _____ and _____.
28. The small phase shifts produced by indirect PM are increased by sending the PM signal to a(n) _____ circuit.
29. In the Foster-Seeley discriminator and ratio detector circuits, an input frequency variation produces a(n) _____ that causes an output voltage variation.
30. In the pulse-averaging discriminator, a low pass filter averages the fixed-width, fixed amplitude pulses from a(n) _____.
31. Should the input frequency increase or decrease for the average voltage output of the low-pass filter in a pulse-averaging discriminator to increase?
32. Quadrature refers to a _____° phase difference.
33. In Fig. 5-13, does input B lag or lead input A? (page 96-Frenzel)
34. The phase detector in a quadrature detector is usually a(n) _____.
35. The quadrature detector input circuit produces a varying _____ as the input frequency changes.
36. The varying-width pulses produced by the quadrature detector are converted into the original modulating signal by a(n) _____.
37. The circuit in a differential peak detector IC that temporarily stores the peak value of an input sine wave is called a(n) _____.
38. In the differential peak detector, the components _____ convert frequency variations into the amplitude variations that ultimately become the output.
39. The three main elements of a PLL are _____.
40. The _____ circuit In a PLL recognizes _____ or _____ changes between the input and VCO signals.
41. The part _____ of a PLL is a simple frequency modulator.
42. It is the _____ signal in the PLL that varies the VCO frequency.
43. The range of frequencies over which a PLL will cause the input and VCO signals to remain synchronized is known as the _____ range.
44. If the PLL input is zero, the VCO will operate at its _____ frequency.
45. The range of frequencies over which a PLL will latch onto or recognize an input signal is called the _____ range.
46. Since a PLL will only respond to signals over a narrow frequency range, it acts like a(n) _____.
47. In a PLL frequency demodulator, the error signal is the _____.
48. In a PLL demodulating an FM signal, the VCO output is an exact reproduction of the _____.
49. True or false. The Foster-Seeley discriminator is sensitive to input amplitude as well as frequency variations.
50. True or false. The ratio detector requires a limiter.
51. True or false. The lock range of a PLL is narrower than the capture range.
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