(Last Updated On: March 27, 2020) This is the Multiple Choice Questions in Chapter 6: Receivers from the book Electronic Communication Systems by Roy Blake . 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.

#### Start Practice Exam Test Questions

Choose the letter of the best answer in each questions.

MULTIPLE CHOICE

1. The two basic specifications for a receiver are:

a. the sensitivity and the selectivity

b. the number of converters and the number of IFs

c. the spurious response and the tracking

d. the signal and the noise

Solution:

2. The superheterodyne receiver was invented by:

a. Foster

b. Seeley

c. Armstrong

d. Hertz

Solution:

a. two types of adjusting tools

Solution:

4. “Skin effect” refers to:

a. the way radio signals travel across a flat surface

b. the tissue-burning effect of a strong RF signal

c. the increase of wire resistance with frequency

d. none of the above

Solution:

5. The “front end” of a receiver can include:

a. the tuner

b. the RF amplifier

c. the mixer

d. all of the above

Solution:

6. “IF” stands for:

a. intermediate frequency

b. intermodulation frequency

c. indeterminate frequency

d. image frequency

Solution:

7. AGC stands for:

a. Audio Gain Control

b. Automatic Gain Control

c. Active Gain Control

d. Active Gain Conversion

Solution:

8. The frequency of the local oscillator:

a. is above the RF frequency

b. is below the RF frequency

c. can be either above of below the RF frequency

d. is fixed, typically at 455 kHz.

Solution:

9. The local oscillator and mixer are combined in one device because:

a. it gives a greater reduction of spurious responses

b. it increases sensitivity

c. it increases selectivity

d. it is cheaper

Solution:

10. Basically, sensitivity measures:

a. the weakest signal that can be usefully received

b. the highest-frequency signal that can be usefully received

c. the dynamic range of the audio amplifier

d. none of the above

Solution:

11. Basically, selectivity measures:

a. the range of frequencies that the receiver can select

b. with two signals close in frequency, the ability to receive one and reject the other

c. how well adjacent frequencies are separated by the demodulator

d. how well the adjacent frequencies are separated in the mixer

Solution:

12. When comparing values for shape factor:

a. a value of 1.414 dB is ideal

b. a value of 0.707 is ideal

c. a value of 1.0 is ideal

d. there is no ideal value

Solution:

13. When comparing values for shape factor:

a. a value of 2 is better than a value of 4

b. a value of 4 is better than a value of 2

c. both values are basically equivalent

d. none of the above

Solution:

14. Distortion in a receiver can occur in:

a. the mixer

b. the detector

c. the IF amplifiers

d. all of the above

Solution:

15. Phase distortion is important in:

a. voice communications systems

d. all of the above

Solution:

16. The response of a receiver to weak signals is usually limited by:

a. the AGC

b. noise generated in the receiver

c. the dynamic range of the receiver

d. the type of detector circuit being used

Solution:

17. Image frequencies occur when two signals:

a. are transmitted on the same frequency

b. enter the mixer, with one being a reflected signal equal to the IF frequency

c. enter the mixer, one below and one above the local oscillator by a difference equal to the IF

d. enter the mixer, and the difference between the two signals is equal to twice the IF

Solution:

18. An image must be rejected:

a. prior to mixing

b. prior to IF amplification

c. prior to detection

d. images cannot be rejected

Solution:

19. Image frequency problems would be reduced by:

a. having an IF amplifier with the proper shape factor

b. having a wideband RF amplifier after the mixer

c. having a narrowband RF amplifier before the mixer

d. none of the above

Solution:

20. A common AM detector is the:

a. PLL

b. envelope detector

c. ratio detector

d. all of the above

Solution:

21. An FM detector is the:

a. PLL

b. ratio detector

d. all of the above

Solution:

22. Germanium diodes are used in AM detectors because:

a. they are faster than silicon diodes

b. they are cheaper than silicon diodes

c. they minimize distortion from nonlinearity

d. all of the above

Solution:

23. A common SSB detector is:

a. a PLL

b. a diode

c. a BFO

d. a product detector

Solution:

24. BFO stands for:

a. Beat Frequency Oscillator

b. Barrier Frequency Oscillator

c. Bipolar Frequency Oscillator

d. Bistable Frequency Oscillator

Solution:

25. To demodulate both SSB and DSBSC, you need to:

a. use a Foster-Seeley discriminator

b. reinject the carrier

c. use double conversion

d. use one diode for SSB and two diodes for DSBSC

Solution:

26. Which would be best for DSBSC:

a. carrier detection

b. coherent detection

c. envelope detection

d. ratio detection

Solution:

27. An FM detector that is not sensitive to amplitude variations is:

a. Foster-Seeley detector

c. a PLL detector

d. all of the above

Solution:

28. The function of a limiter is:

a. to remove amplitude variations

b. to limit spurious responses

c. to limit dynamic range

d. to limit noise response

Solution:

29. Suppressing the audio when no signal is present is called:

a. AGC

b. squelch

c. AFC

d. limiting

Solution:

30. LNA stands for:

a. Limited-Noise Amplifier

b. Low-Noise Amplifier

c. Low-Noise Audio

d. Logarithmic Noise Amplification

Solution:

31. AFC stands for:

a. Audio Frequency Compensator

b. Autodyne Frequency Compensation

c. Automatic Frequency Control

d. Autonomous Frequency Control

Solution:

32. The function of AFC is:

a. maintain a constant IF frequency

b. match the local oscillator to the received signal

c. lock the discriminator to the IF frequency

d. none of the above

Solution:

33. SAW stands for:

a. Symmetrical Audio Wave

b. Surface Acoustic Wave

c. Silicon-Activated Wafer

d. Software-Activated Wave

Solution:

34. The important property of a SAW is:

a. it stabilizes the audio in a receiver

b. it allows software radios to be built

c. it is a stable bandpass filter

d. none of the above

Solution:

35. The main function of the AGC is to:

a. keep the gain of the receiver constant

b. keep the gain of the IF amplifiers constant

c. keep the input to the detector at a constant amplitude

d. all of the above

Solution:

36. DSP stands for:

a. Dynamic Signal Properties

b. Direct Signal Phase

c. Distorted Signal Packet

d. Digital Signal Processor

Solution:

a. Sinusoidal Amplitude Distortion

b. Signal and Noise Amplitude Distortion

c. Signal-plus-Noise-to-Noise Ratio

d. Signal-plus-Noise and Distortion-to-Noise and Distortion Ratio

Solution:

38. TRF stands for:

Solution:

COMPLETION

1. Almost all modern receivers use the _________________________ principle.

Solution:

2. The first radio receiver of any kind was built in the year ____________________.

Solution:

3. When two tuned circuits ____________________ each other, it means that when the frequency of one is adjusted, the other changes with it.

Solution:

4. The ____________________ effect causes the resistance of wire to increase with frequency.

Solution:

5. The superhet was invented in the year ____________________.

Solution:

6. In a receiver, the ____________________ refers to the input filter and RF stage.

Solution:

7. In a superhet, the output of the ____________________ goes to the IF amplifiers.

Solution:

8. In a superhet, the ____________________ frequency is the difference between the local oscillator frequency and the received signal frequency.

Solution:

9. The ____________________ circuit adjusts the gain of the IF amplifiers in response to signal strength.

Solution:

10. An ____________________ converter uses the same transistor for both the local oscillator and the mixer.

Solution:

11. In low-side injection, the local oscillator is ____________________ than the received signal frequency.

Solution:

12. ____________________ is the ability of a receiver to separate two signals that are close to each other in frequency.

Solution:

13. ____________________ is the ability of a receiver to receive and successfully demodulate a very weak signal.

Solution:

14. A receiver with two different IF frequencies is called a double-____________________ receiver.

Solution:

15. A multiple-conversion receiver will have better rejection of ____________________ frequencies.

Solution:

16. A demodulator is also called a ____________________.

Solution:

17. An ____________________ detector uses a diode to half-wave rectify an AM signal.

Solution:

18. A ____________________ detector is used for SSB signals.

Solution:

19. A BFO produces a locally generated ____________________.

Solution:

20. A DSBSC signal requires a ____________________ detection circuit.

Solution:

21. FM detectors have a characteristic ____________________-shaped curve.

Solution:

22. While still commonly found, the Foster-Seeley and ratio detectors are ____________________.

Solution:

23. Unlike the PLL detector, the quadrature detector is sensitive to changes in ____________________ of the input signal.

Solution:

24. A dual-____________________ MOSFET is useful for AGC.

Solution:

25. Diode mixers are too ____________________ to be practical in most applications.

Solution:

26. The IF amplifiers in an AM receiver must be Class ____________________.

Solution:

27. A double-tuned IF transformer is usually ____________________ coupled for the response to have a flat top and steep sides.

Solution:

28. Multiple IF stages can be ____________________-tuned to increase the bandwidth.

Solution:

29. Compared to tuned circuits, ceramic and crystal IF filters do not require ____________________.

Solution:

30. Up-conversion is when the output of the mixer is a ____________________ frequency than the incoming signal.

Solution:

31. In a block converter, the frequency of the first local oscillator is ____________________.

Solution:

32. Typically, AGC reduces the gain of the ____________________ amplifiers.

Solution:

33. An ____________________-meter is designed to indicate signal strength in many communications receivers.

Solution:

34. The effectiveness of FM ____________________ is measured by a receiver’s quieting sensitivity.

Solution:

35. A ____________________ refers to any kind of FM or PM detector.

Solution:

1. Suppose the bandwidth of a tuned circuit is 10 kHz at 1 MHz. Approximately what bandwidth would you expect it to have at 4 MHz?

Solution:

2. Using high-side injection for a 1-MHz IF, what is the frequency of the local oscillator when the receiver is tuned to 5 MHz?

Solution:

ANS:

3. An IF filter has a –60 dB bandwidth of 25 kHz and a –6 dB bandwidth of 20 kHz. What is the shape factor value?

Solution:

4. Suppose a receiver uses a 5-MHz IF frequency. Assuming high-side injection, what would be the image frequency if the receiver was tuned to 50 MHz?

Solution:

5. Suppose a SSB receiver requires an injected frequency of 1.5 MHz. What would be the acceptable frequency range of the BFO if the maximum acceptable baseband shift is 100 hertz?

Answer: 1.5 MHz ± 100 hertz

Solution:

6. The transformer of a double-tuned IF amplifier has a Q of 25 for both primary and secondary. What value of kc do you need to achieve optimal coupling?

Solution:

7. What value of transformer coupling would a double-tuned 10-MHz IF amplifier with optimal coupling need to get a bandwidth of 100 kHz?

Solution:

### Complete List of MCQ in Electronic Communication Systems by Blake

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