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Blake: MCQ in Transmitters

Blake: MCQ in Transmitters

This is the Multiple Choice Questions in Chapter 5: Transmitters from the book Electronic Communication Systems by Roy BlakeBlake: MCQ in Transmitters. 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 ability to change operating frequency rapidly without a lot of retuning is called:

a. agility

b. expansion

c. VFO

d. spread-spectrum

View Answer:

Answer: Option A

Solution:

2. The difference between the DC power into a transmitter and the RF power coming out:

a. is a measure of efficiency

b. heats the transmitter

c. may require water cooling

d. all of the above

View Answer:

Answer: Option D

Solution:

3. Baseband compression produces:

a. a smaller range of frequencies from low to high

b. a smaller range of amplitude from soft to loud

c. a smaller number of signals

d. none of the above

View Answer:

Answer: Option B

Solution:

4. ALC stands for:

a. Amplitude Level Control

b. Automatic Level Control

c. Accurate Level Control

d. none of the above

View Answer:

Answer: Option B

Solution:

5. In an AM transmitter, ALC is used to:

a. keep the modulation close to 100%

b. keep the modulation below 100%

c. maximize transmitted power

d. all of the above

View Answer:

Answer: Option D

Solution:

6. With high-level AM:

a. all RF amplifiers can be nonlinear

b. minimum modulation power is required

c. minimum RF power is required

d. all of the above

View Answer:

Answer: Option A

Solution:

7. With high-level AM:

a. the RF amplifiers are typically Class A

b. the RF amplifiers are typically Class B

c. the RF amplifiers are typically Class C

d. the RF amplifiers are typically Class AB

View Answer:

Answer: Option C

Solution:

8. With low-level AM:

a. the RF amplifiers must be Class A

b. the RF amplifiers must be Class B

c. the RF amplifiers must be linear

d. the RF amplifiers must be low-power

View Answer:

Answer: Option C

Solution:

9. Power amplifiers must be linear for any signal that:

a. is complex

b. has variable amplitude

c. has variable frequency

d. all of the above

View Answer:

Answer: Option B

Solution:

10. In high-level AM, “high-level” refers to:

a. the power level of the carrier

b. the power level of the modulation

c. the power level of the final RF amplifier

d. none of the above

View Answer:

Answer: Option D

Solution:

11. In high-level AM, the power in the sidebands comes from:

a. the modulating amplifier

b. the RF amplifier

c. the driver stage

d. the carrier

View Answer:

Answer: Option A

Solution:

12. In an AM transmitter with 100% modulation, the voltage of the final RF stage will be:

a. approximately half the DC supply voltage

b. approximately twice the DC supply voltage

c. approximately four times the DC supply voltage

d. none of the above

View Answer:

Answer: Option C

Solution:

13. 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

View Answer:

Answer: Option A

Solution:

14. Which of the following can be used for impedance matching?

a. pi network

b. T network

c. both a and b

d. a bridge circuit

View Answer:

Answer: Option C

Solution:

15. When a transmitter is connected to a resistor instead of an antenna, the resistor is called:

a. a heavy load

b. a dummy load

c. a temporary load

d. a test load

View Answer:

Answer: Option B

Solution:

16. When a transmitter is connected to a resistor instead of an antenna, the resistor must be:

a. wire-wound

b. noninductive

c. 1% tolerance or better

d. all of the above

View Answer:

Answer: Option B

Solution:

17. A Class D amplifier is:

a. very efficient

b. essentially pulse-width modulation

c. essentially pulse-duration modulation

d. all of the above

View Answer:

Answer: Option D

Solution:

18. To generate a SSB signal:

a. start with full-carrier AM

b. start with DSBSC

c. start with a quadrature signal

d. all of the above

View Answer:

Answer: Option B

Solution:

19. The carrier is suppressed in:

a. a balanced modulator

b. a mixer

c. a frequency multiplier

d. none of the above

View Answer:

Answer: Option A

Solution:

20. To remove one AM sideband and leave the other you could use:

a. a mechanical filter

b. a crystal filter

c. both a and b

d. none of the above

View Answer:

Answer: Option C

Solution:

21. A direct FM modulator:

a. varies the frequency of the carrier oscillator

b. integrates the modulating signal

c. both a and b

d. none of the above

View Answer:

Answer: Option A

Solution:

22. An indirect FM modulator:

a. requires a varactor in the carrier oscillator

b. varies the phase of the carrier oscillator

c. both a and b

d. none of the above

View Answer:

Answer: Option B

Solution:

23. AFC stands for:

a. Amplitude to Frequency Conversion

b. Automatic Frequency Centering

c. Automatic Frequency Control

d. Audio Frequency Control

View Answer:

Answer: Option C

Solution:

24. Frequency multipliers are:

a. essentially balanced modulators

b. essentially Class C amplifiers

c. essentially mixers

d. none of the above

View Answer:

Answer: Option B

Solution:

25. With mixing:

a. the carrier frequency can be raised

b. the carrier frequency can be lowered

c. the carrier frequency can be changed to any required value

d. the deviation is altered

View Answer:

Answer: Option C

Solution:

COMPLETION

1. The accuracy and stability of a transmitter frequency is fixed by the ____________________ oscillator.

View Answer:

Answer: carrier

Solution:

2. In the USA, the ____________________ sets requirements for accuracy and stability of a transmitter’s frequency.

View Answer:

Answer: FCC

Solution:

3. In Canada, _________________________ sets requirements for accuracy and stability of a transmitter’s frequency.

View Answer:

Answer: Industry Canada

Solution:

4. Frequency ____________________ is the ability of a transmitter to change frequency without a lot of retuning.

View Answer:

Answer: agility

Solution:

5. Power output of SSB transmitters is rated by ____________________.

View Answer:

Answer: PEP

Solution:

6. Reducing the dynamic range of a modulating signal is called ____________________.

View Answer:

Answer: compression

Solution:

7. The opposite of compression is called ____________________.

View Answer:

Answer: expansion

Solution:

8. ALC is a form of ____________________.

View Answer:

Answer: compression

Solution:

9. High-level modulation allows the RF amplifiers to operate more ____________________.

View Answer:

Answer: efficiently

Solution:

10. Low-level modulation requires the RF amplifiers to be ____________________.

View Answer:

Answer: linear

Solution:

11. To isolate the oscillator from load changes, a ____________________ stage is used.

View Answer:

Answer: buffer

Solution:

12. The peak collector voltage in a Class C RF amplifier is ____________________ than the DC supply voltage.

View Answer:

Answer: higher

Solution:

13. Most practical transmitters are designed to operate into a ____________________-ohm load.

View Answer:

Answer: 50

Solution:

14. Transmitters built with transistor RF amplifiers often use a ____________________ network for impedance matching.

View Answer:

Answer: T

Solution:

15. Matching networks also act as filters to help reduce ____________________ levels.

View Answer:

Answer: harmonic

Solution:

16. Severe impedance ____________________ can destroy a transmitter’s output stage.

View Answer:

Answer: mismatch

Solution:

17. Transceivers combine a transmitter and a ____________________ into one “box”.

View Answer:

Answer: receiver

Solution:

18. To allow a high modulation percentage, it is common to modulate the ____________________ as well as the power amplifier in transistor modulators.

View Answer:

Answer: driver

Solution:

19. Pulse-width modulation is the same as pulse-____________________ modulation.

View Answer:

Answer: duration

Solution:

20. Switching amplifiers are sometimes called Class ____________________ amplifiers.

View Answer:

Answer: D

Solution:

21. Because the sideband filter in a SSB transmitter is fixed, ____________________ is used to operate at more than one frequency.

View Answer:

Answer: mixing

Solution:

22. To generate a SSB signal, it is common to start with a ____________________ signal.

View Answer:

Answer: DSBSC

Solution:

23. Indirect FM is derived from ____________________ modulation.

View Answer:

Answer: phase

Solution:

24. Using a varactor to generate FM is an example of a ____________________ modulator.

View Answer:

Answer: reactance

Solution:

25. The modern way to make a stable VFO is to make it part of a ____________________ loop.

View Answer:

Answer: phase-locked

Solution:

SHORT ANSWER

1. If a 50-MHz oscillator is accurate to within 0.001%, what is the range of possible frequencies?

View Answer:

Answer: 50 MHz – 500 hertz

Solution:

2. What is the efficiency of a 100-watt mobile transmitter if it draws 11 amps from a 12-volt car battery?

View Answer:

Answer: 75.8%

Solution:

3. The power amplifier of an AM transmitter draws 100 watts from the power supply with no modulation. Assuming high-level modulation, how much power does the modulation amplifier deliver for 100% modulation?

View Answer:

Answer: 50 watts

Solution:

4. If the final RF amplifier of an AM transmitter is powered by 100 volts DC, what is the maximum collector voltage at 100% modulation?

View Answer:

Answer: 400 volts

Solution:

5. Suppose the output of a balanced modulator has a center frequency of 10 MHz. The audio modulation frequency range is 1 kHz to 10 kHz. To pass the USB, what should be the center frequency of an ideal crystal filter?

View Answer:

Answer: 10.005 MHz

Solution:

6. Suppose you have generated a USB SSB signal with a nominal carrier frequency of 10 MHz. What is the minimum frequency the SSB signal can be mixed with so that the output signal has a nominal carrier frequency of 50 MHz?

View Answer:

Answer: 40 MHz

Solution:

7. Suppose you have an FM modulator that puts out 1 MHz carrier with a 100-hertz deviation. If frequency multiplication is used to increase the deviation to 400 hertz, what will be the new carrier frequency?

View Answer:

Answer: 4 MHz

Solution:

8. Suppose you had an FM signal with a carrier of 10 MHz and a deviation of 10 kHz. Explain how you could use it to get an FM signal at 100 MHz with a deviation of 20 kHz.

View Answer:

Answer: First, put the signal through a frequency doubler to get a 20-MHz carrier with a 20-kHz deviation. Then mix that signal with an 80-MHz carrier to generate a 100-MHz carrier with 20-kHz deviation.

Solution:

Complete List of MCQ in Electronic Communication Systems by Blake

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