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 XV of the Series
701. Frequency modulators are also known as _________.
- a. phase deviators
- b. frequency deviators
- c. phase modulators
- d. amplitude deviators
702. A 70 kHz carrier has a frequency deviation of 4 kHz with a 1000 Hz signal. What is the bandwidth of the FM signal?
- a. 4 kHz
- b. 7kHz
- c. 10 kHz
- d. 28 kHz
703. The controlled oscillator synthesizer is sometimes preferred to the direct one because
- a. it is simpler piece of equipment
- b. its frequency stability is better
- c. it does not require crystal oscillators
- d. it is relatively free of spurious frequencies
704. A system with a differentiator followed by an FM modulator is called
- a. PM modulator
- b. FM modulator
- c. PM demodulator
- d. FM demodulator
705. The image frequency of a superheterodyne receiver
- a. is created within the receiver itself
- b. is due to insufficient adjacent channel rejection
- c. is not rejected by the IF tuned circuits
- d. is independent of the frequency to which the receiver is tuned
706. A system with FM demodulator followed by an integrator
- a. PM modulator
- b. PM demodulator
- c. FM modulator
- d. FM demodulator
707. A system with an integrator followed by a PM modulator
- a. PM modulator
- b. FM modulator
- c. PM demodulator
- d. FM demodulator
708. An FM transmitter has a maximum deviation of 12 kHz and a maximum modulating frequency of 12 kHz. The bandwidth by Carson's rule is
- a. 24 kHz
- b. 33.6 kHz
- c. 38.8 kHz
- d. 48 kHz
709. A system with PM demodulator followed by a differentiator
- a. PM modulator
- b. FM modulator
- c. PM demodulator
- d. FM demodulator
710. A receiver has poor IF selectivity. It will therefore also have poor
- a. blocking
- b. double-spotting
- c. diversity reception
- d. sensitivity
711. Three point tracking is achieved with
- a. variable selectivity
- b. the padder capacitor
- c. double spotting
- d. double conversion
712. He mathematically proved that for a given modulating signal frequency a frequency-modulated wave cannot be accommodated in a narrower bandwidth than an amplitude modulated wave.
- a. R.C. Alpine
- b. E.H. Armstrong
- c. J.R. Carson
- d. J.J. Thomson
713. The maximum allowed deviation of the FM sound signal in TV is 25 kHz. If the actual deviation is 18 kHz, the percent modulation is
- a. 43 percent
- b. 72 percent
- c. 96 percent
- d. 139 percent
714. The local oscillator of a broadcast receiver is tuned to a frequency higher than the incoming frequency
- a. to help the image frequency rejection
- b. to permit easier tracking
- c. because otherwise an intermediate frequency could not be produced
- d. to allow adequate frequency coverage without switching
715. Which of the following is not a major benefit of FM over AM?
- a. greater efficiency
- b. noise immunity
- c. capture effect
- d. lower complexity and cost
716. Low-index FM systems are also known as __________.
- a. wideband FM
- b. narrowband FM
- c. commercial FM
- d. medium FM
717. For high-index signal, a method of determining the bandwidth is called ________ approach
- a. quasi-stationary
- b. quasi-movement
- c. quasi-deviation
- d. any of these
718. When a receiver has a good blocking performance, this means that
- a. it does not suffer from double-spotting
- b. its image frequency rejection is poor
- c. it is unaffected by AGC derived from a nearby transmission
- d. its detector suffers from burnout
719. He established a general rule to estimate the bandwidth for all angle-modulated system regardless of the modulation index.
- a. R.C. Alpine
- b. E.H. Armstrong
- c. J.R. Carson
- d. J.J. Thomson
720. An AM receiver uses a diode detector for demodulation. This enables it satisfactorily to receive
- a. single-sideband, suppressed carrier
- b. single-sideband, reduced carrier
- c. independent sideband
- d. single-sideband, full carrier
721. The primary disadvantage of FM is its
- a. higher cost and complexity
- b. excessive use of spectrum space
- c. noise susceptibility
- d. lower efficiency
722. A rule that approximates the bandwidth necessary to transmit an angle-modulated wave as twice the sum of the peak frequency deviation and the highest modulating frequency.
- a. Carson's rule
- b. Shannon's rule
- c. Hartley's law
- d. Hartley-Shannon law
723. It is the worst case modulation index and is equal to the maximum peak frequency deviation divided by the maximum modulating signal frequency
- a. peak phase deviation
- b. frequency deviation
- c. deviation ratio
- d. signal to noise ratio
724. The receiver circuit that rids FM noise is the
- a. modulator
- b. demodulator
- c. limiter
- d. low-pass filter
725. The phenomenon of a strong FM signal dominating a weaker signal on a common frequency is referred to as the
- a. capture effect
- b. blot out
- c. quieting factor
- d. domination syndrome
726. The highest side frequencies form one channel are allowed to spill over into adjacent channels producing an interference known as _________.
- a. co-channel interference
- b. adjacent channel interference
- c. splatter
- d. overmodulation
727. A pre-emphasis is usually a ________.
- a. high-pass filter
- b. band-stop filter
- c. low-pass filter
- d. bandpass filter
728. Frequency modulation transmitters are more efficient because their power is increased by what type of amplifier?
- a. class A
- b. class B
- c. class C
- d. all of the above
729. Noise interferes mainly with modulating signals that are
- a. sinusoidal
- b. non-sinusoidal
- c. low frequencies
- d. high frequencies
730. A de-emphasis is usually a _________.
- a. high pass filter
- b. band-stop filter
- c. low-pass filter
- d. bandpass filter
731. A pre-emphasis is a __________.
- a. integrator
- b. differentiator
- c. either integrator or differentiator
- d. neither integrator or differentiator
732. A de-emphasis is a _____________.
- a. integrator
- b. differentiator
- c. either integrator or differentiator
- d. neither integrator or differentiator
733. Pre-emphasis circuit boost what modulating frequencies before modulation?
- a. high frequencies
- b. mid-range frequencies
- c. low frequencies
- d. all of the above
734. The primary disadvantage of direct PM
- a. relatively unstable LC oscillators must be used to produce carrier frequency which prohibits using crystal oscillators
- b. relatively high frequency deviations and modulation indices are easily obtained due to the fact that the oscillators are inherently unstable.
- c. crystal oscillators are inherently stable and therefore more difficult for them to achieve high phase deviations and modulation indices
- d. carrier oscillator is isolated form the actual modulator circuit and therefore can be stable source.
735. It is an angle modulation in which the frequency of the carrier is deviated by the modulating signal
- a. direct PM
- b. PM
- c. indirect FM
- d. any of these
736. One of the following is a method of performing frequency up conversion
- a. heterodyning
- b. amplification
- c. modulation
- d. none of these
737. A pre-emphasis circuit is a
- a. low-pass filter
- b. high-pass filter
- c. phase shifter
- d. bandpass filter
738. Pre emphasis is compensated for the receiver by a
- a. phase inverter
- b. bandpass filter
- c. high-pass filter
- d. low-pass filter
739. A circuit that compares the frequency of the non-crystal carrier oscillator to a crystal reference oscillator and then produces a correction voltage proportional to the difference between the two frequencies
- a. AFC
- b. squelch circuit
- c. AGC
- d. heterodyning circuit
740. A frequency selective device whose output voltage is proportional to the difference between the input frequency and its resonant frequency
- a. modulator
- b. squelch circuit
- c. frequency discriminator
- d. FM transmitters
741. Allows FM receiver to differentiate between two signals received with the same frequency but different amplitudes
- a. flywheel effect
- b. amplitude limiting
- c. noise immunity
- d. capture effect
742. If an FM transmitter employs one doubler, one tripler, and one quadrupler, what is the carrier frequency swing when the oscillator frequency swing is 2 kHz?
- a. 24 kHz
- b. 48 kHz
- c. 14 kHz
- d. 12 kHz
743. The cut-off frequency of pre-emphasis and de-emphasis circuits is
- a. 1 kHz
- b. 2.122 kHz
- c. 5 kHz
- d. 75 kHz
744. Which of the following is not a disadvantage of angle modulation?
- a. wide bandwidth
- b. complex
- c. high cost
- d. less noise
745. In FM receivers, which of the following rejects the image frequency?
- a. preselector
- b. detector
- c. IF amplifier
- d. mixer
746. In FM receivers, which of the following provides most gain and selectivity of the receiver?
- a. detector
- b. RF amplifier
- c. local oscillator
- d. IF amplifier
747. Another name for Voltage Variable Capacitor is
- a. PIN diode
- b. varactor diode
- c. snap diode
- d. hot carrier diode
748. The depletion region in a junction diode forms what part of a capacitor?
- a. plates
- b. leads
- c. package
- d. dielectric
749. Which of the following removes the information from the modulated wave in FM receivers?
- a. amplifiers
- b. mixer
- c. speakers
- d. discriminator
750. The final IF amplifier in FM receivers is sometimes called ___________.
- a. tuned amplifier
- b. limiter
- c. passband filter
- d. any of these
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