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Blake: MCQ in Introduction to Communication Systems

Blake: MCQ in Introduction to Communication Systems

This is the Multiple Choice Questions in Chapter 1: Introduction to Communication Systems from the book Electronic Communication Systems by Roy BlakeBlake: MCQ in Introduction to Communication Systems. If you are looking for a reviewer in Communications Engineering this will definitely help. I can assure you that this will be a great help in reviewing the book in preparation for your Board Exam. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.

See also: MCQ in Electronic Communication Systems by George Kennedy

Start Practice Exam Test Questions

Choose the letter of the best answer in each questions.

MULTIPLE CHOICE

1. The theory of radio waves was originated by:

a. Marconi

b. Bell

c. Maxwell

d. Hertz

View Answer:

Answer: Option C

Solution:

2. The person who sent the first radio signal across the Atlantic ocean was:

a. Marconi

b. Bell

c. Maxwell

d. Hertz

View Answer:

Answer: Option A

Solution:

3. The transmission of radio waves was first done by:

a. Marconi

b. Bell

c. Maxwell

d. Hertz

View Answer:

Answer: Option D

Solution:

4. A complete communication system must include:

a. a transmitter and receiver

b. a transmitter, a receiver, and a channel

c. a transmitter, a receiver, and a spectrum analyzer

d. a multiplexer, a demultiplexer, and a channel

View Answer:

Answer: Option B

Solution:

5. Radians per second is equal to:

a. 2π x f

b. f x 2π

c. the phase angle

d. none of the above

View Answer:

Answer: Option A

Solution:

6. The bandwidth required for a modulated carrier depends on:

a. the carrier frequency

b. the signal-to-noise ratio

c. the signal-plus-noise to noise ratio

d. the baseband frequency range

View Answer:

Answer: Option D

Solution:

7. When two or more signals share a common channel, it is called:

a. sub-channeling

b. signal switching

c. SINAD

d. multiplexing

View Answer:

Answer: Option D

Solution:

8. TDM stands for:

a. Time-Division Multiplexing

b. Two-level Digital Modulation

c. Time Domain Measurement

d. none of the above

View Answer:

Answer: Option A

Solution:

9. FDM stands for:

a. Fast Digital Modulation

b. Frequency Domain Measurement

c. Frequency-Division Multiplexing

d. none of the above

View Answer:

Answer: Option C

Solution:

10. The wavelength of a radio signal is:

a. equal to f ÷ c

b. equal to c ÷ λ

c. the distance a wave travels in one period

d. how far the signal can travel without distortion

View Answer:

Answer: Option C

Solution:

11. Distortion is caused by:

a. creation of harmonics of baseband frequencies

b. baseband frequencies “mixing” with each other

c. shift in phase relationships between baseband frequencies

d. all of the above

View Answer:

Answer: Option D

Solution:

12. The collection of sinusoidal frequencies present in a modulated carrier is called its:

a. frequency-domain representation

b. Fourier series

c. spectrum

d. all of the above

View Answer:

Answer: Option D

Solution:

13. The baseband bandwidth for a voice-grade (telephone) signal is:

a. approximately 3 kHz

b. 20 Hz to 15,000 Hz

c. at least 5 kHz

d. none of the above

View Answer:

Answer: Option A

Solution:

14. Noise in a communication system originates in:

a. the sender

b. the receiver

c. the channel

d. all of the above

View Answer:

Answer: Option D

Solution:

15. “Man-made” noise can come from:

a. equipment that sparks

b. temperature

c. static

d. all of the above

View Answer:

Answer: Option A

Solution:

16. Thermal noise is generated in:

a. transistors and diodes

b. resistors

c. copper wire

d. all of the above

View Answer:

Answer: Option D

Solution:

17. Shot noise is generated in:

a. transistors and diodes

b. resistors

c. copper wire

d. none of the above

View Answer:

Answer: Option A

Solution:

18. The power density of “flicker” noise is:

a. the same at all frequencies

b. greater at high frequencies

c. greater at low frequencies

d. the same as “white” noise

View Answer:

Answer: Option C

Solution:

19. So called “1/f” noise is also called:

a. random noise

b. pink noise

c. white noise

d. partition noise

View Answer:

Answer: Option B

Solution:

20. “Pink” noise has:

a. equal power per Hertz

b. equal power per octave

c. constant power

d. none of the above

View Answer:

Answer: Option B

Solution:

21. When two noise voltages, V1 and V2, are combined, the total voltage VT is:

a. VT = sqrt(V1 x V1 + V2 x V2)

b. VT = (V1 + V2)/2

c. VT = sqrt(V1 x V2)

d. VT = V1 + V2

View Answer:

Answer: Option A

Solution:

22. Signal-to-Noise ratio is calculated as:

a. signal voltage divided by noise voltage

b. signal power divided by noise power

c. first add the signal power to the noise power, then divide by noise power

d. none of the above

View Answer:

Answer: Option B

Solution:

23. SINAD is calculated as:

a. signal voltage divided by noise voltage

b. signal power divided by noise power

c. first add the signal power to the noise power, then divide by noise power

d. none of the above

View Answer:

Answer: Option D

Solution:

24. Noise Figure is a measure of:

a. how much noise is in a communications system

b. how much noise is in the channel

c. how much noise an amplifier adds to a signal

d. signal-to-noise ratio in dB

View Answer:

Answer: Option C

Solution:

25. The part, or parts, of a sinusoidal carrier that can be modulated are:

a. its amplitude

b. its amplitude and frequency

c. its amplitude, frequency, and direction

d. its amplitude, frequency, and phase angle

View Answer:

Answer: Option D

Solution:

COMPLETION

1. The telephone was invented in the year ____________________.

View Answer:

Answer: 1863

Solution:

2. Radio signals first were sent across the Atlantic in the year ____________________.

View Answer:

Answer: 1901

Solution:

3. The frequency band used to modulate the carrier is called the ____________________ band.

View Answer:

Answer: base

Solution:

4. The job of the carrier is to get the information through the ____________________.

View Answer:

Answer: channel

Solution:

5. The bandwidth of an unmodulated carrier is ____________________.

View Answer:

Answer: zero

Solution:

6. The ‘B’ in Hartley’s Law stands for ____________________.

View Answer:

Answer: bandwidth

Solution:

7. The more information per second you send, the ____________________ the bandwidth required.

View Answer:

Answer: greater / larger / wider

Solution:

8. In ____________________, you split the bandwidth of a channel into sub-channels to carry multiple signals.

View Answer:

Answer: FDM

Solution:

9. In ____________________, multiple signal streams take turns using the channel.

View Answer:

Answer: TDM

Solution:

10. VHF stands for the ____________________ frequency band.

View Answer:

Answer: very high

Solution:

11. The VHF band starts at ____________________ MHz.

View Answer:

Answer: 30

Solution:

12. The UHF band starts at ____________________ MHz.

View Answer:

Answer: 300

Solution:

13. A radio signal’s ____________________ is the distance it travels in one cycle of the carrier.

View Answer:

Answer: wavelength

Solution:

14. In free space, radio signals travel at approximately ____________________ meters per second.

View Answer:

Answer: 300 million

Solution:

15. The equipment used to show signals in the frequency domain is the _________________________.

View Answer:

Answer: spectrum analyzer

Solution:

16. Mathematically, a spectrum is represented by a ____________________ series.

View Answer:

Answer: Fourier

Solution:

17. Disabling a receiver during a burst of atmospheric noise is called ____________________.

View Answer:

Answer: noise blanking / blanking

Solution:

18. For satellite communications, ____________________ noise can be a serious problem.

View Answer:

Answer: solar

Solution:

19. Thermal noise is caused by the random motions of ____________________ in a conductor.

View Answer:

Answer: electrons

Solution:

SHORT ANSWER

1. Name the five elements in a block diagram of a communications system.

View Answer:

Answer: Source, Transmitter, Channel, Receiver, Destination

Solution:

2. Name five types of internal noise.

View Answer:

Answer: Thermal, Shot, Partition, 1/f, transit-time

Solution:

3. Why is thermal noise called “white noise”?

View Answer:

Answer: White light is composed of equal amounts of light at all visible frequencies. Likewise, thermal noise has equal power density over a wide range of frequencies.

Solution:

4. What is “pink noise”?

View Answer:

Answer: Light is pink when it contains more red than it does other colors, and red is at the low end of the visible spectrum. Likewise, pink noise has higher power density at lower frequencies.

Solution:

5. Suppose there is 30 µV from one noise source that is combined with 40 µV from another noise source. Calculate the total noise voltage.

View Answer:

Answer: 50 µV

Solution:

6. If you have 100 mV of signal and 10 mV of noise, both across the same 100-ohm load, what is the signal-to-noise ratio in dB?

View Answer:

Answer: 20 dB

Solution:

7. The input to an amplifier has a signal-to-noise ratio of 100 dB and an output signal-to-noise ratio of 80 dB. Find NF, both in dB and as a ratio.

View Answer:

Answer: 20 dB, NF = 100

Solution:

8. A microwave receiver has a noise temperature of 145 K. Find its noise figure.

View Answer:

Answer: 1.5

Solution:

9. Two cascaded amplifiers each have a noise figure of 5 and a gain of 10. Find the total NF for the pair.

View Answer:

Answer: 5.4

Solution:

10. Explain why you could use a diode as a noise source with a spectrum close to that of pure thermal noise. How would you control the amount of noise generated?

View Answer:

Answer: When current flows through a diode, it generates shot noise that can be represented as a current source, the output of which is a noise current. The equation for the noise current is very similar to the equation for thermal noise voltage. Since the power in the shot noise is proportional to the diode current, controlling the diode current controls the noise power.

Solution:

Complete List of MCQ in Electronic Communication Systems by Blake

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