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Blake: MCQ in Angle Modulation

Blake: MCQ in Angle Modulation

This is the Multiple Choice Questions in Chapter 4: Angle Modulation from the book Electronic Communication Systems by Roy BlakeBlake: MCQ in Angle Modulation. 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 FM modulation index:

a. increases with both deviation and modulation frequency

b. increases with deviation and decreases with modulation frequency

c. decreases with deviation and increases with modulation frequency

d. is equal to twice the deviation

View Answer:

Answer: Option B

Solution:

2. 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

View Answer:

Answer: Option A

Solution:

3. The bandwidth of an FM signal is considered to be limited because:

a. there can only be a finite number of sidebands

b. it is equal to the frequency deviation

c. it is band-limited at the receiver

d. the power in the outer sidebands is negligible

View Answer:

Answer: Option D

Solution:

4. Mathematically, the calculation of FM bandwidth requires the use of:

a. ordinary trigonometry and algebra

b. Bessel functions

c. Taylor series

d. fractals

View Answer:

Answer: Option B

Solution:

5. FM bandwidth can be approximated by:

a. Armstrong’s Rule

b. Bessel’s Rule

c. Carson’s Rule

d. none of the above

View Answer:

Answer: Option C

Solution:

6. NBFM stands for:

a. National Broadcast FM

b. Non-Broadcast FM

c. Near Band FM

d. Narrowband FM

View Answer:

Answer: Option D

Solution:

7. When FM reception deteriorates abruptly due to noise, it is called:

a. the capture effect

b. the threshold effect

c. the noise effect

d. the limit effect

View Answer:

Answer: Option B

Solution:

8. An FM receiver switching suddenly between two stations on nearby frequencies is called:

a. the capture effect

b. the threshold effect

c. the “two-station” effect

d. none of the above

View Answer:

Answer: Option A

Solution:

9. Pre-emphasis is used to:

a. increase the signal to noise ratio for higher audio frequencies

b. increase the signal to noise ratio for lower audio frequencies

c. increase the signal to noise ratio for all audio frequencies

d. allow stereo audio to be carried by FM stations

View Answer:

Answer: Option A

Solution:

10. A pre-emphasis of 75 µs 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

View Answer:

Answer: Option D

Solution:

11. FM stereo:

a. uses DSBSC AM modulation

b. is implemented using an SCA signal

c. has a higher S/N than mono FM

d. is not compatible with mono FM

View Answer:

Answer: Option A

Solution:

12. An SCA signal:

a. can use amplitude modulation

b. can use FM modulation

c. is monaural

d. all of the above

View Answer:

Answer: Option D

Solution:

13. The modulation index of an FM signal can be determined readily:

a. using measurements at points where J0 equals one

b. using measurements at points where J0 equals zero

c. using measurements at points where the deviation equals zero

d. only by using Bessel functions

View Answer:

Answer: Option B

Solution:

COMPLETION

1. FM and PM are two forms of ____________________ modulation.

View Answer:

Answer: angle

Solution:

2. PM is extensively used in ____________________ communication.

View Answer:

Answer: data

Solution:

3. Compared to AM, the signal-to-noise ratio of FM is usually ____________________.

View Answer:

Answer: better

Solution:

4. Compared to AM, the bandwidth of FM is usually ____________________.

View Answer:

Answer: wider / greater

Solution:

5. FM transmitters can use Class ____________________ amplifiers since amplitude linearity is not important.

View Answer:

Answer: C

Solution:

6. Both the power and amplitude of an FM signal ____________________ as modulation is applied.

View Answer:

Answer: stay constant

Solution:

7. In FM, the frequency deviation is proportional to the instantaneous ____________________ of the modulating signal.

View Answer:

Answer: amplitude

Solution:

8. The frequency deviation of an FM signal occurs at a rate equal to the ____________________ of the modulating signal.

View Answer:

Answer: frequency

Solution:

9. Mathematically, the number of sidebands in an FM signal is ____________________.

View Answer:

Answer: infinite

Solution:

10. As FM sidebands get farther from the center frequency, their power ____________________.

View Answer:

Answer: decreases

Solution:

11. Mathematically, the value of an FM modulation index can be as high as ____________________.

View Answer:

Answer: any number

Solution:

12. In FM, as the modulating frequency decreases, the modulation index ____________________.

View Answer:

Answer: increases

Solution:

13. In FM, as the frequency deviation decreases, the modulation index ____________________.

View Answer:

Answer: decreases

Solution:

14. As the FM modulation index increases, the number of significant sidebands ____________________.

View Answer:

Answer: increases

Solution:

15. For certain values of mf, such as 2.4, the amplitude of the carrier frequency ____________________.

View Answer:

Answer: disappears / goes to zero

Solution:

16. The bandwidth of an FM signal can be approximated using ____________________ rule.

View Answer:

Answer: Carson’s

Solution:

17. FM bandwidth can be calculated precisely using ____________________ functions.

View Answer:

Answer: Bessel

Solution:

18. The ____________________ effect is characteristic of FM reception in a noisy environment.

View Answer:

Answer: threshold

Solution:

19. The ____________________ effect is seen when an FM receiver is exposed to two FM signals that are close to each other in frequency.

View Answer:

Answer: capture

Solution:

20. Rest frequency is another name for an FM ____________________ frequency.

View Answer:

Answer: carrier

Solution:

SHORT ANSWER

1. If a 2-volt instantaneous value of modulating signal amplitude causes a 10-kHz deviation in carrier frequency, what is the deviation sensitivity of the modulator?

View Answer:

Answer: 5 kHz / volt

Solution:

2. If a 2-kHz audio tone causes a frequency deviation of 4 kHz, what is the modulation index?

View Answer:

Answer: 2

Solution:

3. What will be the deviation caused by a 3-kHz tone if the modulation index is 3?

View Answer:

Answer: 9 kHz

Solution:

4. If the deviation sensitivity of an FM modulator is 2 kHz /V, what will be the modulation index caused by a 1-volt, 1-kHz audio signal?

View Answer:

Answer: 2

Solution:

5. At a modulation index of 2, how much power is in the carrier of a 1000-watt FM transmitter?

View Answer:

Answer: 48.4 watts

Solution:

6. At a modulation index of 2, how much power is in the first pair of sidebands of a 1000-watt FM transmitter?

View Answer:

Answer: 673 watts

Solution:

7. At a modulation index of 2, how much power is in the fifth pair of sidebands of a 1000-watt FM transmitter?

View Answer:

Answer: 200 mW (0.2 watt)

Solution:

8. Using Carson’s rule, what is the approximate bandwidth of an FM signal with a modulation index of 2 being modulated by a 5-kHz signal?

View Answer:

Answer: 30 kHz

Solution:

9. Using the Bessel chart of Figure 4.1, what is the bandwidth of an FM signal with a modulation index of 2 being modulated by a 5-kHz signal if we ignore sidebands containing less than 1% of the total power?

View Answer:

Answer: 30 kHz

Solution:

10. How would you use the fact that J0 is zero for certain known values of mf (2.4, 5.5, etc) to measure the frequency deviation of an FM modulator?

View Answer:

Answer: Use an audio frequency generator to modulate the FM carrier. Using a spectrum analyzer, adjust the audio frequency until the carrier amplitude vanishes. Record the audio frequency. Then do the calculation: δ = fm x mf where mf will have one of the known values. For example, if fm is measured to be 2 kHz when mf is 5.5, then δ is 11 kHz.

Solution:

Complete List of MCQ in Electronic Communication Systems by Blake

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