MCQs in Communications Engineering Part 1

(Last Updated On: September 10, 2019)

MCQs in Communications Engineering

This is the Uncategorized Multiples Choice Questions Part 1 of the Series in Communications Engineering. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including past Board Questions in Communications Engineering field (Electronics Systems and Technologies). In the actual board, you have to answer 100 items in Electronic Systems and Technologies within 5 hours. You have to get at least 70% to pass the subject. Electronic Systems and Technologies is 30% of the total 100% Board Rating along with Mathematics (20%), General Engineering and Applied Sciences (20%) and Electronics Engineering (30%).

Practice Exam Test Questions

Following is the list of multiple choice questions in this brand new series:

Miscellaneous Communications Engineering MCQs
PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II
PART 3: MCQs from Number 101 – 150                 Answer key: PART III
PART 4: MCQs from Number 151 – 200                 Answer key: PART IV
PART 5: MCQs from Number 201 – 250                 Answer key: PART V
PART 6: MCQs from Number 251 – 300                 Answer key: PART VI
PART 7: MCQs from Number 301 – 350                 Answer key: PART VII
PART 8: MCQs from Number 351 – 400                 Answer key: PART VIII
PART 9: MCQs from Number 401 – 450                 Answer key: PART IX
PART 10: MCQs from Number 451 – 500                 Answer key: PART X

Start Part I of the Series

Choose the letter of the best answer in each questions.

1. “Pink” noise has:

  • A. Equal power per Hertz
  • B. Equal power per octave
  • C. Constant power
  • D. None of the above

2. The Miller Effect can be avoided by:

  • A. Using a common-emitter amplifier
  • B. Using a common-base amplifier
  • C. Increasing the Q of the tuned circuit
  • D. It cannot be avoided

3. Indicate the true statement. Most receivers conforms to the

  • A. Amplitude-modulated group
  • B. Frequency-modulated group
  • C. Superheterodyne group
  • D. Tuned radio frequency receiver group

4. Indicate the false statement. The need for modulation can best be exemplified by the following.

  • A. Antenna lengths will be approximately λ/4 long
  • B. An antenna in the standard broadcast AM band is 16,000 ft
  • C. All sound is concentrated from 20 Hz to 20kHz
  • D. A message is composed of unpredictable variations in both amplitude and frequency

5. Space noise generally covers a wide frequency spectrum, but the strongest interference occurs

  • A. Between 8 MHz and 1.43 GHz
  • B. Below 20 MHz
  • C. Between 20 to 120 MHz
  • D. Above 1.5 GHz

6. Infrared frequencies range from ___ to ___:

  • A. 0.3 THz – 300 THz
  • B. 0.3 PHz – 3 PHz
  • C. 0.03 THz – 3000 THz
  • D. 0.03 PHz – 3000 PHz

7. At frequencies above ____, atmospheric noise is relatively insignificant

  • A. 30 Hz
  • B. 30 kHz
  • C. 30 MHz
  • D. 30 GHz

8. The ideal noise factor is

  • A. 0
  • B. 1
  • C. Infinity
  • D. A negative value

9. Determine the modulation index of a standard FM broadcast having a hypothetical maximum carrier frequency deviation of +/-12 kHz and a maximum modulating frequency of 4 kHz.

  • A. 9
  • B. 6
  • C. 3
  • D. 4

10. One way to derive FM from PM is:

  • A. Integrate the modulating signal before applying to the PM oscillator
  • B. Integrate the signal out of the PM oscillator
  • C. Differentiate the modulating signal before applying to the PM oscillator
  • D. Differentiate the signal out of the PM oscillator

11. A pre-emphasis of 75 ms refers to:

  • A. The time it takes for the circuit to work
  • B. The “dead time” before de-emphasis occurs
  • C. The time delay between the L and R channels
  • D. The time-constant of the filter circuits used

12. Practical transmitters are usually designed to drive a load impedance of:

  • A. 50 ohms resistive
  • B. 75 ohms resistive
  • C. 300 ohms resistive
  • D. 600 ohms resistive

13. What is the frequency of an electromagnetic wave whose maximum peaks are separated by a distance of 8 in?

  • A. 1.4778 GHz
  • B. 37.5 MHz
  • C. 14.778 GHz
  • D. 3.75 MHz

14. Determine the equivalent noise temperature of a receiver with a noise figure of 4 dB at 300 K environment temperature.

  • A. 900 K
  • B. 453.6 K
  • C. 635.4 K
  • D. 90 K

15. These are active filters made of op-amps, capacitors, and transistor switches.

  • A. Bandpass filters
  • B. Smoothing filter
  • C. Commutating filters
  • D. Audio filter

16. This is used to keep the receiver audio tuned off until an RF signal appears at the receiver input.

  • A. Limiter
  • B. Squelch
  • C. Bleeder
  • D. Filter

17. It is the process of converting a frequency or band of frequencies to another location in the total frequency spectrum.

  • A. Modulation
  • B. Frequency conversion
  • C. Frequency modulation
  • D. Heterodyning

18. The current of an AM transmitter is 12 A when unmodulated but increases to 13 A when modulated. Calculate %m.

  • A. 59%
  • B. 95%
  • C. 46%
  • D. 64%

19. An RG-11/U foam coaxial cable has a maximum voltage standing wave of 52 V and a minimum voltage of 17 V. Find the value of a resistive load in the given situation.

  • A. 37.54 ohms
  • B. 24.59 ohms
  • C. 59.42 ohms
  • D. 73.45 ohms

20. A polar diagram or graph representing field strengths or power densities at various angular positions relative to an antenna.

  • A. Footprint
  • B. Absolute radiation pattern
  • C. Radiation pattern
  • D. Relative radiation pattern

21. Common mode rejection ratios for common balanced transmission lines.

  • A. 10 dB to 30 dB
  • B. 100 dB to 300 dB
  • C. 40 dB to 70 dB
  • D. 4 dB to 7 dB

22. Indicate the false statement. The SWR on a transmission line is infinity; the line is terminated in

  • A. A short circuit
  • B. A complex impedance
  • C. An open circuit
  • D. A pure reactance

23. Indicate the true statement below. The directional coupler is

  • A. A device used to connect a transmitter to a directional antenna
  • B. A coupling device for matching impedance
  • C. A device used to measure transmission line power
  • D. An SWR measuring instrument

24. The two basic specifications for a receiver are:

  • A. The sensitivity and the selectivity
  • B. The number of converters and the number of Ifs
  • C. The spurious response and the tracking
  • D. The signal and the noise

25. When comparing values for shape factor:

  • A. A value of 1.414 dB is ideal
  • B. A value of 0.707 is ideal
  • C. A value of 1.0 is ideal
  • D. There is no ideal value

26. Compared to a 300-ohm line, the loss of a 50-ohm cable carrying the same power:

  • A. Would be less
  • B. Would be more
  • C. Would be the same
  • D. Cannot be compared

27. The typical antenna in an AM radio is a:

  • A. Dipole
  • B. Folded dipole
  • C. Ferrite “loop-stick”
  • D. None of the above

28. The radiated beam from a parabolic “dish” transmitting antenna is:

  • A. Collimated
  • B. Phased
  • C. Dispersed
  • D. None of the above

29. A balanced format transmission line used at low frequencies. Applications include 4-wire telephony and microphone circuits.

  • A. Twisted pair
  • B. Twin lead
  • C. Coaxial cable
  • D. Star quad

30. Twisted pair was invented by:

  • A. Alexander Graham Bell
  • B. Oliver Heaviside
  • C. Joseph John “J. J.” Thomson
  • D. None of the above

31. A type of cable used in electronics to carry alternating current, designed to reduce the skin effect and proximity effect losses in conductors used at frequencies up to about 1 MHz.

  • A. Feeder cable
  • B. Twisted pairs
  • C. Litz wire
  • D. Solid wire

32. CAT-3 cable must have at least _____ turns per inch.

  • A. One
  • B. Two
  • C. Three
  • D. Four

33. The characteristic impedance of LMR-900 is

  • A. 75 ohms
  • B. 73 ohms
  • C. 53 ohms
  • D. 50 ohms

34. It is a coaxial cable constructed using round copper, silver or gold tubing or a combination of such metals as a shield. It used in broadcasting as well as many other forms of radio communication.

  • A. Leaky cable
  • B. Hard line
  • C. Triaxial cable
  • D. Biaxial cable

35. Determine the power saving in percent when the carrier is suppressed in an AM signal modulated to 80%.

  • A. 75.8%
  • B. 80%
  • C. 66.7%
  • D. 100%

36. To couple a coaxial line to a parallel-wire line, it is best to use a

  • A. Slotted line
  • B. Balun
  • C. Directional coupler
  • D. Quarter-wave transformer

37. A phase-locked loop has a VCO with a free-running frequency of 12 MHz. As the frequency of the reference input is gradually raised from zero, the loop locks at 10 MHz and comes out again at 16 MHz. Find the lock range.

  • A. 16 kHz
  • B. 15 kHz
  • C. 4 kHz
  • D. 8MHz

38. A folded dipole has a typical impedance equal to:

  • A. 73
  • B. 75
  • C. 50
  • D. 300

39. A shorted quarter-wave line at the operating frequency acts like a(n)

  • A. Series resonant circuit
  • B. Parallel resonant circuit
  • C. Capacitor
  • D. Inductor

40. Calculate the thickness of a crystal in inches if its natural frequency is 75 MHz

  • A. 873 x 10^-9 in
  • B. 175 x 10^-9 in
  • C. 436 x 10^-9 in
  • D. 345 x 10^-9 in

41. Level or Category of UTP cable which was developed for IEEE 802.5 token ring local area networks operating at a transmission rates of 4 Mbps:

  • A. Level 1 or Cat 1
  • B. Cat 3
  • C. Level 2 or Cat 2
  • D. Cat 4

42. A quarter wave vertical antenna with drooping radials typically has an impedance equal to:

  • A. 73
  • B. 75
  • C. 50
  • D. 300

43. A transducer that transmits or receives electromagnetic waves.

  • A. Transmitting antenna
  • B. Receiving antenna
  • C. Parabolic dish
  • D. Aerial

44. The axis through the main lobe is called the ___:

  • A. Secondary axis
  • B. Boresight axis
  • C. Minor axis
  • D. Line of nodes

45. A positive voltage pulse sent down a transmission line terminated with its characteristic impedance:

  • A. Would reflect as a positive pulse
  • B. Would reflect as a negative pulse
  • C. Would reflect as a positive pulse followed by a negative pulse
  • D. Would not reflect at all

46. The “attenuation of free space” is due to:

  • A. Losses in the characteristic impedance of free space
  • B. Losses due to absorption in the upper atmosphere
  • C. The decrease in energy per square meter due to expansion of the wavefront
  • D. The decrease in energy per square meter due to absorption of the wavefront

47. The first complete system of wireless communications was provided by:

  • A. Samuel Morse
  • B. Guglielmo Marconi
  • C. James Maxwell
  • D. Heinrich Hertz

48. 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

49. Which of the following is the simplest form of tuned-circuit frequency discriminator?

  • A. Foster-Seeley discriminator
  • B. Ratio detector
  • C. Slope detector
  • D. PLL detector

50. For a low-power transistor modulator with a modulation coefficient of 0.4, a quiescent voltage gain of 80, and input carrier amplitude of 0.002V, what is maximum and minimum voltage gains?

  • A. 112 and 48
  • B. 110 and 46
  • C. 100 and 40
  • D. 115 and 51

Complete List of MCQs in Communications Engineering per topic

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