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 XVII of the Series
801. What is the maximum deviation for monoaural TV sound
- a. 25 kHz
- b. 75 kHz
- c. 50 kHz
- d. 125 kHz
802. What is the maximum deviation for stereo TV sound?
- a. 25 kHz
- b. 75 kHz
- c. 50 kHz
- d. 125 kHz
803. In FM stereo broadcasting, the L + R signal
- a. double-sideband modulates a subcarrier
- b. modulates the FM carrier
- c. frequency modulates a subcarrier
- d. is not transmitted
804. In FM stereo broadcasting, the L - R signal
- a. double-sideband modulates a subcarrier
- b. modulates the FM carrier
- c. frequency modulates a subcarrier
- d. none of these
805. The SCA signal if used in FM broadcasting is transmitted via
- a. a 19 kHz subcarrier
- b. a 38 kHz subcarrier
- c. a 67 kHz subcarrier
- d. the main FM carrier
806. Which of the following is considered as an indirect method of generating FM?
- a. reactance modulator
- b. balanced modulator
- c. varactor diode modulation
- d. armstrong system
807. In an FM system, if the modulation index is doubled by halving the modulating frequency, what will be the effect on the maximum deviation?
- a. remains the same
- b. doubles
- c. decrease by 1/2
- d. increase by 1/4
808. Determine from the following the common use of DSB in broadcast and telecommunication.
- a. satellite communications
- b. FM/TV stereo
- c. two-way communications
- d. telephone systems
809. Phase modulation emission type
- a. F3F
- b. G3E
- c. F3E
- d. F3C
810. The range of frequencies over which a PLL will cause the input of the VCO signals to remain synchronized is known as the _________ range.
- a. capture
- b. lock
- c. acquisition
- d. any of these
811. If the PLL input is zero, the VCO will operate at its ____________ frequency.
- a. free-running
- b. natural
- c. operating
- d. any of these
812. Since a PLL will only respond to signals over a narrow frequency range, it acts likes a ________.
- a. low-pass filter
- b. high-pass filter
- c. bandpass filter
- d. bandstop filter
813. In a PLL demodulating an FM signal, the VCO output is an exact reproduction of the ___________.
- a. modulating signal
- b. carrier signal
- c. carrier amplitude
- d. VCO output
814. In a PLL demodulating an FM signal, the VCO output is an exact reproduction of the ________.
- a. FM input
- b. VCO input
- c. modulating signal
- d. error signal
815. After the IF stages have been aligned, the next state to align in FM receiver is
- a. local oscillator
- b. limiter stage
- c. RF amplifier
- d. mixer stage
816. The modulation system used for telegraphy is
- a. frequency-shift keying
- b. two-tone modulation
- c. purse-code modulation
- d. single-tone modulation
817. What is emission F3F?
- a. Facsimile
- b. RTTY
- c. modulated CW
- d. television
818. What is a frequency discriminator?
- a. a circuit for filtering two closely adjacent signals
- b. a circuit for detecting FM signals
- c. an FM generator
- d. an automatic band switching circuit
819. Type of radio communication transmission utilizing frequency modulation technique
- a. television video
- b. broadcasting in 535-1606 kHz
- c. single sideband HF transmission
- d. television audio
820. Why was FM first developed?
- a. to compete with AM
- b. to overcome noise
- c. to increase listeners
- d. to supplement AM
821. To what feature of the modulating tone is FM deviation proportional?
- a. amplitude
- b. frequency
- c. phase
- d. phase shift
822. Which of the following is not a basic filed of FM?
- a. broadcast
- b. TV video
- c. mobile communications
- d. amateur radio
823. Under what condition would a 1 kHz AF signal produce a single pair of FM sidebands?
- a. wideband
- b. broadcast FM
- c. TV audio FM
- d. narrowband FM
824. What deviation is considered 100% for FM broadcast stations?
- a. 75 kHz
- b. 220 kHz
- c. 270 kHz
- d. 75 kHz or 220 kHz
825. In FM broadcasting, what is the highest required modulating frequency?
- a. 75 kHz
- b. 50 kHz
- c. 25 kHz
- d. 15 kHz
826. In FM broadcasting, what is the lowest required modulating frequency?
- a. 50 Hz
- b. 30 Hz
- c. 10 Hz
- d. 5 Hz
827. What is the disadvantage of slope detection of FM>
- a. no discrimination against noise
- b. less AF distortion
- c. less AF out
- d. no filtering of carrier
828. What is the unction of the dc that comes out of the dc amplifier in a PLL-type FM detector?
- a. carrier signal
- b. filter signal
- c. error signal
- d. phase signal
829. What is the function of the dc that comes out of the dc amplifier in a PLL-type FM detector?
- a. oscillators
- b. AF signal
- c. RF signal
- d. carrier signal
830. Why should discriminators be tuned for a straight characteristic S-curve?
- a. less AF distortion
- b. greater AF out
- c. less RF out
- d. less RF distortion
831. What band for high-Q coils be more desirable for stagger-tuned-type discriminator transformer?
- a. wide
- b. intermediate
- c. interfacing
- d. narrow
832. In a Foster-Seeley circuit, the AF output voltage is ________.
- a. varying DC
- b. varying AC
- c. steady DC
- d. steady AC
833. In a stagger-tuned discriminator, the AF output voltage is _________.
- a. varying DC
- b. varying AC
- c. steady DC
- d. steady AC
834. In a ratio detector, the AF output voltage is
- a. steady AC
- b. varying AC
- c. steady DC
- d. varying DC
835. In a gated-beam detector, the AF output voltage is _________.
- a. steady DC
- b. varying AC
- c. varying DC
- d. steady AC
836. Which of the following discriminator circuits require limiters ahead of them?
- a. quadrature detector
- b. foster-seeley discriminator
- c. slope detector
- d. stagger-tuned
837. Which of the following discriminator circuits provide an automatic gain control voltage?
- a. ratio detector
- b. balanced slope detector
- c. quadrature detector
- d. stagger-tuned detector
838. Which of the following discriminator circuits has its diodes in series?
- a. ratio
- b. quadrature detector
- c. round-travis detector
- d. slope detector
839. To what frequency must the gated-beam quadrature circuit be tuned in a TV receiver?
- a. 10.7 MHz
- b. 455 kHz
- c. 70 MHz
- d. 4.5 MHz
840. To what frequency must the gated-beam quadrature circuit be tuned in an FM broadcast receiver?
- a. 4.3 MHz
- b. 10.7 MHz
- c. 11 MHz
- d. 4.8 MHz
841. What is the advantage of PM?
- a. can use crystal oscillator
- b. uses more multistage
- c. less selective fading
- d. simplicity
842. With what FM detectors would AGC be an advantage?
- a. foster-seeley detector
- b. ratio detector
- c. quadrature detector
- d. phase-locked loop
843. What is the reason for using pre-emphasis?
- a. increase amplitude
- b. reduce carrier shift
- c. amplify RF signal
- d. reduce noise reception
844. What are the two types of stages in an FM receiver that differ from those in an AM receiver?
- a. limiting IF and detectors
- b. oscillators and IF amplifiers
- c. mixers and RF amplifiers
- d. local oscillators and mixers
845. What special circuits are used in a squelch system that can follow changing noise levels?
- a. noise amplifiers
- b. rectifier
- c. dc amplifier
- d. any of these
846. Why might FM be better than AM for mobile ________.
- a. better coverage
- b. not affected by solar cycles
- c. reduce flutter
- d. not absorbed by ionosphere
847. What is the order of circuit alignment in an FM receiver?
- a. discriminator, limiters, IF, mixer and RF
- b. RF, limiters, IF, mixer and discriminator
- c. limiters, mixer, RF, discriminator and IF
- d. RF, mixer, RF, IF, limiters and discriminator
848. What is the another name for the reactance-tube modulator?
- a. Crosby
- b. Foster-Seeley
- c. Round Travis
- d. Messier
849. What effect would be produced if a small inductance were used in place of the 50 pF capacitance in the reactance-tube modulator?
- a. the circuit becomes resistive
- b. reactance modulator looks like an inductive circuit
- c. reactance modulator looks like Xc
- d. any of these
850. The following are significant circuits in the AFC system except:
- a. crystal
- b. mixer
- c. IF
- d. filter
851. Besides the reactance-tube modulator, what is another method of producing direct FM?
- a. armstrong modulator
- b. voltage variable capacitor
- c. impedance modulator
- d. slug indicator
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