Question 1

The reason modulation is used in electronic communication is:

Accepted Answer

A)  Efficient transmission and reception of radio waves are not possible unless extremely large antennas are used. 
B)  Since all intelligence signals occur at approximately the same frequency, there would be catastrophic interference problems if these frequencies were used. 
C)  Audio frequency radio waves do not propagate long distances very reliably 
D)  All of the above 
A)  Efficient transmission and reception of radio waves are not possible unless extremely large antennas are used. 
B)  Since all intelligence signals occur at approximately the same frequency, there would be catastrophic interference problems if these frequencies were used. 
C)  Audio frequency radio waves do not propagate long distances very reliably 
D)  All of the above D

Question 2

High-level modulation is used:

Accepted Answer

A)  in high-power applications such as standard radio broadcasting. 
B)  when the intelligence signal is added to the carrier at the last possible point before the transmitting antenna. 
C)  when the transmitter must be made as power efficient as possible. 
D)  all of the above. 
A)  in high-power applications such as standard radio broadcasting. 
B)  when the intelligence signal is added to the carrier at the last possible point before the transmitting antenna. 
C)  when the transmitter must be made as power efficient as possible. 
D)  all of the above. D

Question 3

A 250W carrier is to be modulated at an 85% modulation level. What is the total transmitted power?

Accepted Answer

A)  356.3 watts 
B)  340.3 watts 
C)  183.7 watts 
D)  430.6 watts 
A)  356.3 watts 
B)  340.3 watts 
C)  183.7 watts 
D)  430.6 watts B

Question 4

Which of the following is not created by nonlinear mixing?

Accepted Answer

A)  dc (0 Hz) 
B)  The sum and difference of the two original frequencies 
C)  The original two frequencies 
D)  Harmonics of the sum and difference frequencies 
A)  dc (0 Hz) 
B)  The sum and difference of the two original frequencies 
C)  The original two frequencies 
D)  Harmonics of the sum and difference frequencies

Question 5

The process of neutralization is:

Accepted Answer

A)  a technique for filtering out all of the undesired frequencies produced by mixing action in a nonlinear amplifier except for the carrier, sum, and difference frequencies. 
B)  placing a negative feedback capacitor in an RF amplifier to reduce the tendency for self-oscillation. 
C)  the process of adjusting the percent modulation to its desired level in a modulator stage. 
D)  the process of adjusting the tank circuit so that the transmitter produces the proper output frequency. 
A)  a technique for filtering out all of the undesired frequencies produced by mixing action in a nonlinear amplifier except for the carrier, sum, and difference frequencies. 
B)  placing a negative feedback capacitor in an RF amplifier to reduce the tendency for self-oscillation. 
C)  the process of adjusting the percent modulation to its desired level in a modulator stage. 
D)  the process of adjusting the tank circuit so that the transmitter produces the proper output frequency.

Question 6

If the % modulation of an AM transmitter is 60% and the unmodulated antenna current is 10 A, what is the modulated current?

Accepted Answer

A)  11 A 
B)  5 A 
C)  14 A 
D)  13 A 
A)  11 A 
B)  5 A 
C)  14 A 
D)  13 A

Question 7

Which of the following is considered a nonlinear device?

Accepted Answer

A)  Resistor 
B)  Transistor 
C)  Potentiometer 
D)  Capacitor 
A)  Resistor 
B)  Transistor 
C)  Potentiometer 
D)  Capacitor

Question 8

The equation defining the AM envelope is

Accepted Answer

A)  e = Ec sin wc*t 
B)  e = Ei sin it + sin wc*t 
C)  e = Ec sin wc*t e = Ei sin wi*t 
D)  e =(Ec +Ei sin wi*t) sin wc*t 
E)  none of the above 
A)  e = Ec sin wc*t 
B)  e = Ei sin it + sin wc*t 
C)  e = Ec sin wc*t e = Ei sin wi*t 
D)  e =(Ec +Ei sin wi*t) sin wc*t 
E)  none of the above

Question 9

Which of the following is NOT produced when two sine waves are combined through a nonlinear device?

Accepted Answer

A)  Harmonics of the two original frequencies 
B)  Components of each of the two original frequencies 
C)  Components at the sum and difference frequencies 
D)  an ac level 
A)  Harmonics of the two original frequencies 
B)  Components of each of the two original frequencies 
C)  Components at the sum and difference frequencies 
D)  an ac level

Question 10

A 2.5 MHz carrier is modulated by a music signal that has frequency components ranging from 100 Hz to 5 kHz. What is the range of frequencies generated for the upper sideband?

Accepted Answer

A)  2.5 MHz to 2.505 MHz 
B)  2.5001 MHz to 2.505 MHz 
C)  2.495 MHz to 2.499 MHz 
D)  2.495 MHz to 2.505 MHz 
A)  2.5 MHz to 2.505 MHz 
B)  2.5001 MHz to 2.505 MHz 
C)  2.495 MHz to 2.499 MHz 
D)  2.495 MHz to 2.505 MHz

Question 11

The total output power of an AM transmitter that is being operated at 50% modulation is measured to be 1800 watts. What is the carrier power?

Accepted Answer

A)  1440 watts 
B)  2025 watts 
C)  1600 watts 
D)  900 watts 
A)  1440 watts 
B)  2025 watts 
C)  1600 watts 
D)  900 watts

Question 12

The O.T.A. is:

Accepted Answer

A)  a linear integrated circuit that creates AM with an absolute minimum of design considerations. 
B)  an operational transconductance amplifier. 
C)  a special type of op amp used to create an AM signal. 
D)  all of the above. 
A)  a linear integrated circuit that creates AM with an absolute minimum of design considerations. 
B)  an operational transconductance amplifier. 
C)  a special type of op amp used to create an AM signal. 
D)  all of the above.

Question 13

A 2 kHz sinewave is mixed with a 1.5 MHz carrier sinewave through a nonlinear device. Which frequency is not present in the output signal?

Accepted Answer

A)  3 MHz 
B)  1.498 MHz 
C)  3.004 MHz 
D)  1.502 MHz 
A)  3 MHz 
B)  1.498 MHz 
C)  3.004 MHz 
D)  1.502 MHz

Question 14

The result of the trigonometric identity (sin x)( sin y) is

Accepted Answer

A)  0.5 cos(x-y) - 0.5 cos(x+y) 
B)  cos(x-y) - cos(x+y) 
C)  -0.5 cos(x-y) + 0.5cos(x+y) 
D)  -0.5 cos(x-y) + cos(x+y) 
E)  none of the above 
A)  0.5 cos(x-y) - 0.5 cos(x+y) 
B)  cos(x-y) - cos(x+y) 
C)  -0.5 cos(x-y) + 0.5cos(x+y) 
D)  -0.5 cos(x-y) + cos(x+y) 
E)  none of the above

Question 15

If the carrier transmits 12 kW, what is the modulated power from Problem 4?

Accepted Answer

A)  16 kW 
B)  14 kW 
C)  12 kW 
D)  10 kW 
A)  16 kW 
B)  14 kW 
C)  12 kW 
D)  10 kW

Question 16

An AM broadcast station operates at its maximum allowed output power of 80W at a percent modulation of 60%. What is the upper sideband power?

Accepted Answer

A)  18.47 watts 
B)  12.2 watts 
C)  6.1 watts 
D)  9.23 watts 
A)  18.47 watts 
B)  12.2 watts 
C)  6.1 watts 
D)  9.23 watts

Question 17

The last stage of intelligence amplification before mixing with the carrier occurs in:

Accepted Answer

A)  the RF linear amplifier. 
B)  the modulated amplifier 
C)  the buffer. 
D)  the modulator. 
A)  the RF linear amplifier. 
B)  the modulated amplifier 
C)  the buffer. 
D)  the modulator.

Question 18

Overmodulation:

Accepted Answer

A)  is undesirable because it produces sideband splatter. 
B)  results when the modulation index exceeds unity. 
C)  causes the AM signal to become distorted so that the receiver cannot produce a clean replica of the original intelligence signal. 
D)  all of the above. 
A)  is undesirable because it produces sideband splatter. 
B)  results when the modulation index exceeds unity. 
C)  causes the AM signal to become distorted so that the receiver cannot produce a clean replica of the original intelligence signal. 
D)  all of the above.

Question 19

The antenna current of an AM transmitter is 5A when it is not modulated. It increases to 6A when it is modulated. Its modulation index expressed as a percentage is:

Accepted Answer

A)  83.3% 
B)  93.8% 
C)  63.2% 
D)  69.4% 
A)  83.3% 
B)  93.8% 
C)  63.2% 
D)  69.4%

Question 20

Which of the following modulation techniques is the most economical?

Accepted Answer

A)  Low-level 
B)  High-level 
C)  Ultra low-level 
D)  Medium-level 
A)  Low-level 
B)  High-level 
C)  Ultra low-level 
D)  Medium-level

The reason modulation is used in electronic communication is:

High-level modulation is used:

A 250W carrier is to be modulated at an 85% modulation level. What is the total transmitted power?

Which of the following is not created by nonlinear mixing?

The process of neutralization is:

If the % modulation of an AM transmitter is 60% and the unmodulated antenna current is 10 A, what is the modulated current?

Which of the following is considered a nonlinear device?

The equation defining the AM envelope is

Which of the following is NOT produced when two sine waves are combined through a nonlinear device?

A 2.5 MHz carrier is modulated by a music signal that has frequency components ranging from 100 Hz to 5 kHz. What is the range of frequencies generated for the upper sideband?

The total output power of an AM transmitter that is being operated at 50% modulation is measured to be 1800 watts. What is the carrier power?

The O.T.A. is:

A 2 kHz sinewave is mixed with a 1.5 MHz carrier sinewave through a nonlinear device. Which frequency is not present in the output signal?

The result of the trigonometric identity (sin x)( sin y) is

If the carrier transmits 12 kW, what is the modulated power from Problem 4?

An AM broadcast station operates at its maximum allowed output power of 80W at a percent modulation of 60%. What is the upper sideband power?

The last stage of intelligence amplification before mixing with the carrier occurs in:

Overmodulation:

The antenna current of an AM transmitter is 5A when it is not modulated. It increases to 6A when it is modulated. Its modulation index expressed as a percentage is:

Which of the following modulation techniques is the most economical?

Introductory Topics

Amplitude Modulation: Reception

Single-Sideband Communications

Frequency Modulation: Transmission

Frequency Modulation: Reception

Communications Techniques

Digital Communications: Coding Techniques

Wired Digital Communications

Wireless Digital Communications

Network Communications

Transmission Lines

Wave Propagation

Antennas

Waveguides and Radar

Microwaves and Lasers

Television

Fiber Optics

Filters

Exam 2: Amplitude Modulation: Transmission

The reason modulation is used in electronic communication is:

High-level modulation is used:

A 250W carrier is to be modulated at an 85% modulation level. What is the total transmitted power?

Which of the following is not created by nonlinear mixing?

The process of neutralization is:

If the % modulation of an AM transmitter is 60% and the unmodulated antenna current is 10 A, what is the modulated current?

Which of the following is considered a nonlinear device?

The equation defining the AM envelope is

Which of the following is NOT produced when two sine waves are combined through a nonlinear device?

A 2.5 MHz carrier is modulated by a music signal that has frequency components ranging from 100 Hz to 5 kHz. What is the range of frequencies generated for the upper sideband?

The total output power of an AM transmitter that is being operated at 50% modulation is measured to be 1800 watts. What is the carrier power?

The O.T.A. is:

A 2 kHz sinewave is mixed with a 1.5 MHz carrier sinewave through a nonlinear device. Which frequency is not present in the output signal?

The result of the trigonometric identity (sin x)( sin y) is

If the carrier transmits 12 kW, what is the modulated power from Problem 4?

An AM broadcast station operates at its maximum allowed output power of 80W at a percent modulation of 60%. What is the upper sideband power?

The last stage of intelligence amplification before mixing with the carrier occurs in:

Overmodulation:

The antenna current of an AM transmitter is 5A when it is not modulated. It increases to 6A when it is modulated. Its modulation index expressed as a percentage is:

Which of the following modulation techniques is the most economical?

Introductory Topics

Amplitude Modulation: Reception

Single-Sideband Communications

Frequency Modulation: Transmission

Frequency Modulation: Reception

Communications Techniques

Digital Communications: Coding Techniques

Wired Digital Communications

Wireless Digital Communications

Network Communications

Transmission Lines

Wave Propagation

Antennas

Waveguides and Radar

Microwaves and Lasers

Television

Fiber Optics

Filters