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| 1 | |
A semiconductor device operated in reverse-bias mode whose capacitance can change in response to a modulating signal is the |
| | A) | zener diode |
| | B) | tunnel diode |
| | C) | varactor diode |
| | D) | unijunction transistor |
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| 2 | |
 <![CDATA[<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0070667551/462276/06_12.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (5.0K)</a>]]>
In the circuit shown above, if the modulating signal amplitude at the output of amplifier A becomes more positive the |
| | A) | varactor becomes forward biased |
| | B) | varactor’s capacitance increases |
| | C) | circuit produces more phase shift |
| | D) | circuit produces less deviation |
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| 3 | |
Most phase modulators are capable of producing an amount of phase shift essentially limited to |
| | A) | ± 5° |
| | B) | ± 10° |
| | C) | ± 15° |
| | D) | ± 20° |
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| 4 | |
Circuits used to recover the original modulating signal from an FM transmission are called |
| | A) | modulators |
| | B) | synthesizers |
| | C) | discriminators |
| | D) | deflectors |
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| 5 | |
Which of the following is probably the most widely used FM demodulator? |
| | A) | quadrature detector |
| | B) | slope detector |
| | C) | pulse-averaging discriminator |
| | D) | PLL detector |
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| 6 | |
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When the frequency-modulated signal is applied through C1 in the circuit illustrated above, the |
| | A) | tuned circuit appears as an inductance |
| | B) | tuned circuit appears as a low value of pure resistance |
| | C) | tuned circuit appears as a high value of pure resistance |
| | D) | output across the tuned circuit at the carrier frequency is very close to 45° |
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| 7 | |
Which of the following is not a basic element of a phase-locked loop circuit? |
| | A) | phase detector |
| | B) | parallel tuned circuit |
| | C) | voltage-controlled oscillator |
| | D) | low-pass filter |
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| 8 | |
Circuits that make use of techniques for varying the frequency of the carrier oscillator in accordance with the modulating signal are referred to as |
| | A) | direct FM |
| | B) | indirect FM |
| | C) | phase modulation |
| | D) | demodulation |
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| 9 | |
Which of the following oscillators can provide a highly accurate carrier frequency and have frequency stability over a wide temperature range? |
| | A) | Colpitts |
| | B) | crystal |
| | C) | Hartley |
| | D) | Armstrong |
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| 10 | |
Oscillators whose frequencies are controlled by an external input voltage are generally referred to as |
| | A) | phase-locked loops |
| | B) | crystal oscillators |
| | C) | voltage-controlled oscillators |
| | D) | Colpitts |
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