Blake: MCQ in Amplitude Modulation

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(Last Updated On: January 3, 2020)

Blake: MCQ in Amplitude Modulation

This is the Multiple Choice Questions in Chapter 3: Amplitude Modulation from the book Electronic Communication Systems by Roy BlakeBlake: MCQ in Amplitude 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. AM stands for:

a. Audio Modulation

b. Amplitude Modulation

c. Angle Modulation

d. Antenna Modulation

View Answer:

Answer: Option B

Solution:

2. The “envelope” of an AM signal is due to:

a. the baseband signal

b. the carrier signal

c. the amplitude signal

d. none of the above

View Answer:

Answer: Option A

Solution:

3. If the audio Va sin(ωat) modulates the carrier Vc sin(ωct), then the modulation index, m, is:

a. m = ωa / ωc

b. m = Va / Vc

c. m = (Va / Vc)2

d. m = Va / ωa

View Answer:

Answer: Option B

Solution:

4. The equation for full-carrier AM is:

a. v(t) = (Ec + Em) x sin(ωct)

b. v(t) = (Ec + Em) x sin(ωmt) + sin(ωct)

c. v(t) = (Ec x Em) x sin(ωmt) x sin(ωct)

d. v(t) = (Ec + Em sin(ωmt)) x sin(ωct)

View Answer:

Answer: Option D

Solution:

5. Overmodulation causes:

a. distortion

b. splatter

c. both a and b

d. none of the above

View Answer:

Answer: Option C

Solution:

6. The peak voltage of an AM signal goes from Emax to Emin. The modulation index, m, is:

a. m = Emin / Emax

b. m = Emax / Emin

c. m = (Emax – Emin) / (Emax + Emin)

d. m = (Emax + Emin) / (Emax – Emin)

View Answer:

Answer: Option C

Solution:

7. If Va sin(ωat) amplitude modulates the carrier Vc sin(ωct), it will produce the frequencies:

a. ωc + ωa and ωc – ωa

b. (ωc + ωa)/2 and (ωc – ωa)/2

c. ωc + ωa and 2ωc + 2ωa

d. none of the above

View Answer:

Answer: Option A

Solution:

8. At 100% modulation, the total sideband power is:

a. equal to the carrier power

b. twice the carrier power

c. half the carrier power

d. 1.414 x carrier power

View Answer:

Answer: Option C

Solution:

9. If a 5-kHz signal modulates a 1-MHz carrier, the bandwidth of the AM signal will be:

a. 5 kHz

b. 10 kHz

c. 1.005 MHz

d. none of the above

View Answer:

Answer: Option B

Solution:

10. If an AM radio station increases its modulation index, you would expect:

a. the audio to get louder at the receiver

b. the received RF signal to increase

c. the signal-to-noise ratio to increase

d. all of the above

View Answer:

Answer: Option D

Solution:

11. The modulation index can be derived from:

a. the time-domain signal

b. the frequency-domain signal

c. both a and b

d. none of the above

View Answer:

Answer: Option C

Solution:

12. The main problem in using quadrature AM would be:

a. requires too much bandwidth

b. requires too much power

c. incompatibility with ordinary AM radios

d. all of the above

View Answer:

Answer: Option C

Solution:

13. As compared to plain AM, SSB AM:

a. is more efficient

b. requires a more complex demodulator circuit

c. requires less bandwidth

d. all of the above

View Answer:

Answer: Option D

Solution:

14. The SC in SSB SC stands for:

a. single-carrier

b. suppressed-carrier

c. sideband-carrier

d. none of the above

View Answer:

Answer: Option B

Solution:

15. PEP stands for:

a. Peak Envelope Power

b. Peak Efficiency Power

c. Peak Envelope Product

d. none of the above

View Answer:

Answer: Option A

Solution:

16. If an SSB transmitter radiates 1000 watts at peak modulation, what will it radiate with no modulation?

a. 1000 watts

b. 500 watts

c. 250 watts

d. 0 watts

View Answer:

Answer: Option D

Solution:

17. Music on AM radio stations is “low-fidelity” because:

a. AM is susceptible to noise

b. commercial AM stations use low power

c. commercial AM stations have a narrow bandwidth

d. all of the above

View Answer:

Answer: Option C

Solution:

18. The type of information that can be sent using AM is:

a. audio

b. video

c. digital data

d. all of the above

View Answer:

Answer: Option D

Solution:

19. Two tones modulate an AM carrier. One tone causes a modulation index of m1 and the other tone causes a modulation index of m2. The total modulation index is:

a. m1 + m2

b. (m1 + m2) / 2

c. sqrt(m1 x m2 + m2 x m1)

d. sqrt(m1 x m1 + m2 x m2)

View Answer:

Answer: Option D

Solution:

20. To demodulate a USB SSB signal, the receiver must:

a. be set to USB mode

b. reinsert the carrier

c. both a and b

d. none of the above

View Answer:

Answer: Option C

Solution:

COMPLETION

1. An advantage of AM is that the receiver can be very ____________________.

View Answer:

Answer: simple

Solution:

2. A disadvantage of AM is its ____________________ use of power.

View Answer:

Answer: inefficient

Solution:

3. The ____________________ of an AM signal resembles the shape of the baseband signal.

View Answer:

Answer: envelope

Solution:

4. In AM, modulating with a single audio tone produces ____________________ sidebands.

View Answer:

Answer: two

Solution:

5. Compared to the USB, the information in the LSB is ____________________.

View Answer:

Answer: the same

Solution:

6. Compared to the USB, the power in the LSB is ____________________.

View Answer:

Answer: the same

Solution:

7. In AM, total sideband power is always ____________________ than the carrier power.

View Answer:

Answer: less

Solution:

8. In AM, as the modulation index increases, the carrier power _________________________.

View Answer:

Answer: remains constant

Solution:

9. The power in an AM signal is maximum when the modulation index is ____________________.

View Answer:

Answer: one

Solution:

10. In AM, a voice-band signal of 300 Hz to 3000 Hz will require a bandwidth of ____________________.

View Answer:

Answer: 6000 Hz

Solution:

11. With a 1-MHz carrier, if the LSB extends down to 990 kHz, then the USB will extend up to ____________________.

View Answer:

Answer: 1010 Hz

Solution:

12. If an AM transmitter puts out 100 watts with no modulation, it will put out ____________________ watts with 100% modulation.

View Answer:

Answer: 150

Solution:

SHORT ANSWER

1. An AM transmitter generates 100 watts with 0% modulation. How much power will it generate with 20% modulation?

View Answer:

Answer: 102 watts

Solution:

2. If the carrier power is 1000 watts, what is the power in the USB at 70.7% modulation?

View Answer:

Answer: 125 watts

Solution:

3. A carrier is modulated by three audio tones. If the modulation indexes for the tones are 0.3, 0.4, and 0.5, then what is the total modulation index?

View Answer:

Answer: 0.707

Solution:

4. You look at an AM signal with an oscilloscope and see that the maximum Vpp is 100 volts and the minimum Vpp is 25 volts. What is the modulation index?

View Answer:

Answer: 0.6

Solution:

5. A SSB transmitter is connected to a 50-ohm antenna. If the peak output voltage of the transmitter is 20 volts, what is the PEP?

View Answer:

Answer: 4 watts

Solution:

Complete List of MCQ in Electronic Communication Systems by Blake

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