Online Questions and Answers Topic Outline
- MCQs in Amplitude Modulation
- MCQs in Phase Modulation
- MCQs in Sound Pressure Level
- MCQs in Frequency Modulation
- MCQs in Pulse Modulation
MCQs in Modulation Series
Following is the list of multiple choice questions in this brand new series:
Continue Practice Exam Test Questions Part X of the Series
451. The process of impressing a low frequency information signals onto a high-frequency carrier signal is called _____.
- a. demodulation
- b. oscillation
- c. modulation
- d. amplification
452. A silicon varactor diode exhibits a capacitance of 200pF at zero bias. If it is in parallel with a 60-pF capacitor and a 200-uH inductor, calculate the range of resonant frequency as the diode varies through a reverse bias of 3 to 15V.
- a. 679 kHz to 2.13 MHz
- b. 966 kHz to 1.15 MHz
- c. 355 kHz to 3.12 MHz
- d. 143 kHz to 4.53 MHz
453. A process where the received signal is transformed into its original form.
- a. demodulation
- b. damping
- c. amplification
- d. oscillation
454. It is the process of changing the amplitude of a relative high frequency carrier signal in proportion with the instantaneous value of the modulating signal.
- a. frequency modulation
- b. digital modulation
- c. phase modulation
- d. analog modulation
455. Most of the power in an AM signal is in the
- a. carrier
- b. upper sideband
- c. lower sideband
- d. modulating signal
456. Amplitude modulation is the same as
- a. linear mixing
- b. analog multiplexing
- c. signal summation
- d. multiplexing
457. The shape of the amplitude-modulated wave is called ______.
- a. sidebands
- b. modulating signal
- c. envelope
- d. carrier signal
458. In a diode modulator, the negative half of the AM wave is supplied by
- a. tuned circuit
- b. transformer
- c. capacitor
- d. inductor
459. It is a term used to describe the amount of amplitude change present in an AM waveform.
- a. coefficient of modulation
- b. modulation index
- c. depth of modulation
- d. any of these
460. When the modulation index in an AM wave is greater than one it will cause _______.
- a. buck-shot
- b. splatter
- c. overmodulation
- d. any of these
461. The ideal value of modulation index in AM.
- a. 1
- b. 0
- c. 100
- d. infinity
462. When the amplitude of the information in an AM modulator is equal to zero, what is the value of the modulation index?
- a. 1
- b. 0
- c. 100
- d. infinity
463. Amplitude modulation can be produced by
- a. having the carrier vary a resistance
- b. having the modulating signal vary a capacitance
- c. varying the carrier frequency
- d. varying the gain of the amplifier
464. When the modulation index is equal to zero, the total transmitted power is equal to ________.
- a. one of the sidebands
- b. carrier
- c. double sidebands
- d. an AM wave
465. When the modulation takes place prior to the output element of the final stage of the transmitter, prior to the collector of the output transistor in a transistorized transmitter, this is called ______.
- a. high-level modulation
- b. low-level modulation
- c. zero-modulation
- d. constant modulation
466. A circuit that monitors the received signal level and sends a signal back to the RF and IF amplifiers to adjust their gain automatically.
- a. automatic phase control
- b. automatic gain control
- c. automatic frequency control
- d. automatic volume control
467. When the modulation takes place in the final element of the final stage where the carrier signal is at its maximum amplitude, it is called _____.
- a. constant modulation
- b. zero-modulation
- c. low-level modulation
- d. high-level modulation
468. If a superheterodyne receiver is tuned to a desired signal at 1000kHz and its conversion (local) oscillator is operating at 1300kHz, what would be the frequency of an incoming signal that would possibly cause image reception?
- a. 1600 kHz
- b. 2300 kHz
- c. 1250 kHz
- d. 3420 kHz
469. When modulation requires a much higher amplitude modulating signal to achieve a reasonable percent modulation, this is called
- a. high-level modulation
- b. low-level modulation
- c. zero-modulation
- d. constant modulation
470. Amplitude modulators that vary the carrier amplitude with the modulating signal by passing it through an attenuator work on principle of
- a. rectification
- b. resonance
- c. variable resistance
- d. absorption
471. A circuit which function is to raise the amplitude of the source signal to a usable level while producing minimum nonlinear distortion adding as little thermal noise as possible.
- a. power amplifier
- b. non-linear amplifier
- c. buffer amplifier
- d. preamplifier
472. A circuit that has a low-gain, high-input impedance linear amplifier which is used to isolate the oscillator from the high-power amplifiers.
- a. power amplifier
- b. bandpass filter
- c. signal driver
- d. buffer amplifier
473. With high-level transmitters, which of the following is not a primary function of the modulator circuit?
- a. it provides the capacity necessary for modulation to occur
- b. it serves as a final amplifier
- c. it serves as a frequency up-converter
- d. it serves as a mixer
474. It is a form of amplitude distortion introduced when positive and negative alternations in the AM modulated signal are not equal.
- a. phase shift
- b. carrier shift
- c. amplitude variations
- d. frequency shift
475. A carrier is simultaneously modulated by two sine waves with modulation indices of 0.3 and 0.4, the total modulation index
- a. is 1
- b. cannot be calculated unless the phase relations are known
- c. is 0.5
- d. is 0.7
476. The component used to produce AM AT very high frequencies is a
- a. varactor
- b. thermistor
- c. cavity resonator
- d. PIN diode
477. It is also known as upward modulation
- a. carrier shift
- b. amplitude variations
- c. frequency shift
- d. phase shift
478. Also known as downward modulation
- a. carrier shift
- b. amplitude variations
- c. frequency shift
- d. phase shift
479. It is a form of amplitude modulation where signals from two separate information sources modulate the same carrier frequency at the same time without interfering with each other.
- a. QPSK
- b. QUAM
- c. PSK
- d. FSK
480. A receiver has a dynamic range of 81 dB. It has 0.55nW sensitivity. Determine the maximum allowable input signal.
- a. 59 mW
- b. 69 mW
- c. 79 mW
- d. 88 mW
481. The information sources modulate the same carrier after it has been separated into two carrier signals are at 90 degrees out of phase with each other.
- a. QPSK
- b. QUAM
- c. PSK
- d. FSK
482. Demodulating quadrature AM signal requires a carrier recovery circuit to reproduce the original carrier frequency and phase and two balanced modulators to actually demodulate the signals. This is called ________.
- a. asynchronous detection
- b. quadrature demodulation
- c. synchronous detection
- d. quadrature detection
483. Quadrature amplitude modulation is also known as ________.
- a. phase division multiplexing
- b. phase division modulation
- c. phase amplitude multiplexing
- d. phase angle modulation
484. Amplitude modulation generated at a very low voltage or power amplitude is known as
- a. high-level modulation
- b. low-level modulation
- c. collector modulation
- d. minimum modulation
485. It is the first stage of the receiver and is therefore often called the receiver front end.
- a. mixer
- b. RF section
- c. local oscillator
- d. IF stage
486. In an SSB transmitter, one is most likely to find a
- a. class C audio amplifier
- b. tuned modulator
- c. class B RF amplifier
- d. class A RF output amplifier
487. The section of the receiver than down-converts the received RF frequencies to intermediate frequencies.
- a. RF section
- b. local oscillator
- c. power amplifier
- d. mixer
488. The circuit that demodulates the AM wave and converts it to the original information signal.
- a. power amplifier
- b. local oscillator
- c. detector
- d. IF section
489. A collector modulator has a supply voltage of 48 V. The peak-to-peak amplitude of the modulating signal for 100 percent modulation is
- a. 24 V
- b. 48 V
- c. 96 V
- d. 120 V
490. What signals might feed into an FM broadcast station audio control console?
- a. microphones
- b. turntables
- c. remote lines
- d. any of these
491. The noise reduction ratio achieved by reducing the bandwidth is called
- a. dynamic range
- b. noise figure
- c. bandwidth efficiency
- d. bandwidth improvement
492. It is the minimum RF signal level that can be detected at the input to the receiver and still produce a usable demodulated information signal.
- a. selectivity
- b. sensitivity
- c. Q-factor
- d. bandwidth
493. For ideal AM, which of the following is true
- a. m = 0
- b. m = 1
- c. m < 1
- d. m > 1
494. Why are limiters used in FM receivers?
- a. provide better noise performance
- b. clip noise peaks
- c. prevent overdrive of discriminators
- d. any of these
495. Why are limiters used in FM transmitters?
- a. clip noise peaks
- b. prevent overdrive of discriminators
- c. prevent overdeviation
- d. any of these
496. It is defined as the difference in decibels between the minimum input level necessary to discern the signal and the input level that will overdrive the receiver and produce distortion.
- a. dynamic range
- b. noise figure
- c. bandwidth efficiency
- d. bandwidth improvement
497. It is the input power range over which the receiver is useful.
- a. dynamic range
- b. noise figure
- c. bandwidth efficiency
- d. bandwidth improvement
498. It is defined as the output power when the RF amplifier response is 1-dB less than the ideal linear gain response.
- a. 1-dB compression point
- b. 1-dB threshold point
- c. 1-dB shoot-off point
- d. 1-dB pinch-off point
499. It is the measure of the ability of a communications system to produce, at the output of the receiver, an exact replica of the original source information.
- a. sensitivity
- b. threshold
- c. selectivity
- d. fidelity
500. A SSB signal generated around a 200-kHz carrier. Before filtering, the upper and lower sidebands are separated by 200 Hz. Calculate the filter Q required to obtain 40-dB suppression.
- a. 1500
- b. 1900
- c. 2500
- d. 2000
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