Question 1

An FM signal has an intelligence frequency of 5 kHz and a maximum deviation of 30 kHz. Its index of modulation is:

Accepted Answer

A)   6
B)   35
C)   60
D)   150E) A) and B)
F) A) and C)

Question 2

The first working FM system was developed by:

Accepted Answer

A)   Armstrong.
B)   Marconi.
C)   Hartley.
D)   Sarnoff.E) A) and C)
F) C) and D)

Question 3

Determine the worst case output signal-to-noise ratio for a broadcast FM receiver with a maximum deviation of 75 kHz and a maximum intelligence frequency of 15 kHz if the input signal-to-noise ratio is 3:1.

Accepted Answer

A)   3:1
B)   10:1
C)   5:1
D)   14.7:1E) None of the above
F) B) and D)

Question 4

Determine the worst case output signal-to-noise ratio for a broadcast FM receiver with a maximum deviation of 75 kHz and a maximum intelligence frequency of 15 kHz if the input signal-to-noise ratio is 2:1.

Accepted Answer

A)   5:1
B)   14.7:1
C)   10:1
D)   3:1E) C) and D)
F) All of the above

Question 5

In a stereo FM broadcast transmitter, when the 38 kHz pilot carrier is mixed with the L-R signal, what is produced?

Accepted Answer

A)   an L-R double sideband suppressed carrier signal
B)   an FM signal containing L+R and L-R sidebands
C)   a 19 kHz pilot carrier
D)   a 38 kHz AM signalE) A) and D)
F) All of the above

Question 6

Which of the following is indirect FM generation?

Accepted Answer

A)   Crosby modulator
B)   varactor diode
C)   Armstrong modulator
D)   reactance modulatorE) A) and C)
F) B) and D)

Question 7

Which of the following is not an example of a direct FM modulator?

Accepted Answer

A)   reactance modulator
B)   566 VCO modulator
C)   varactor diode modulator
D)   Armstrong modulatorE) A) and D)
F) A) and C)

Question 8

The standard time constant used for pre-emphasis in a non-Dolby system is:

Accepted Answer

A)   75 us
B)   50 us
C)   25 us
D)   175 usE) B) and C)
F) C) and D)

Question 9

The modulation index is:

Accepted Answer

A)   top envelope divided by center frequency
B)   VCO voltage divided by center frequency
C)   deviation divided by intelligence frequency
D)   all of the aboveE) All of the above
F) A) and D)

Question 10

The modulation index that occurs when the deviation and intelligence frequencies are maximum is called:

Accepted Answer

A)   the maximum modulation index
B)   the maximum bandwidth
C)   the deviation ratio
D)   the maximum side frequency componentE) None of the above
F) All of the above

Question 11

The amount of frequency deviation is proportional to the amplitude of the intelligence signal in:

Accepted Answer

A)   a PM signal
B)   an FM signal
C)   both FM and PM signals
D)   neither FM nor PM signalsE) A) and D)
F) A) and C)

Question 12

A stage that produces a specific dc output voltage level based on the exact frequency of the input signal is known as:

Accepted Answer

A)   an indirect FM modulator
B)   a frequency multiplier
C)   a direct FM modulator
D)   a discriminatorE) B) and C)
F) None of the above

Question 13

The most important advantage of FM over AM is:

Accepted Answer

A)   its conservation of energy
B)   its frequency stability
C)   its limited bandwidth
D)   its superior noise characteristicsE) None of the above
F) All of the above

Question 14

FM systems utilizing a direct FM modulator with an automatic frequency control (AFC)  are known as:

Accepted Answer

A)   PLL systems
B)   Crosby systems
C)   Armstrong systems
D)   Hartley systemsE) B) and C)
F) A) and D)

Question 15

Carson's rule is:

Accepted Answer

A)   a quick approximation method to find the index of modulation of a PM signal
B)   a quick approximation method to find the bandwidth of a PM signal.
C)   a quick approximation method to find the bandwidth of an FM signal
D)   a quick approximation method to find the index of modulation of an FM signalE) B) and D)
F) B) and C)

Question 16

The main purpose of pre-emphasis and de-emphasis networks in FM communication systems is to:

Accepted Answer

A)   allow for a reduction in bandwidth of the FM communication channel
B)   provide a near constant noise reduction capability between low and high frequency intelligence signals
C)   filter out noise produced by the FM transmitter's modulator stage
D)   allow for stereo broadcasts to be received by a monaural receiverE) A) and C)
F) C) and D)

Question 17

Narrowband FM stations:

Accepted Answer

A)   are found in police, aircraft, taxicabs, weather service, and industrial applications
B)   use intelligence frequencies ranging from 100 Hz to 3 kHz
C)   use a maximum deviation of 10 kHz
D)   all of the aboveE) A) and B)
F) A) and C)

Question 18

A phase modulator can be made to create FM indirectly by:

Accepted Answer

A)   ensuring that the audio signal has an amplitude that varies inversely proportional to its frequency.
B)   integrating the intelligence signal prior to phase modulation
C)   feeding the intelligence signal through a frequency correcting network
D)   all of the aboveE) All of the above
F) None of the above

Question 19

Standard FM broadcast stations use a maximum intelligence frequency of:

Accepted Answer

A)   5 kHz
B)   150 kHz
C)   15 kHz
D)   75 kHzE) A) and B)
F) C) and D)

Question 20

In an FM modulator, the amplitude of the intelligence signal determines the:

Accepted Answer

A)   rate of the carrier frequency deviation
B)   amount of carrier frequency deviation
C)   power level of the FM signal
D)   phase angle of the carrier frequency componentE) B) and C)
F) A) and C)

Exam 5: Frequency Modulation: Transmission

Determine the worst case output signal-to-noise ratio for a broadcast FM receiver with a maximum deviation of 75 kHz and a maximum intelligence frequency of 15 kHz if the input signal-to-noise ratio is 2:1.

Correct AnswerverifiedShow Answer

Carson's rule is:

Correct AnswerverifiedShow Answer

The main purpose of pre-emphasis and de-emphasis networks in FM communication systems is to:

Correct AnswerverifiedShow Answer

An FM signal has an intelligence frequency of 5 kHz and a maximum deviation of 30 kHz. Its index of modulation is:

Correct AnswerverifiedShow Answer

A phase modulator can be made to create FM indirectly by:

Correct AnswerverifiedShow Answer

A stage that produces a specific dc output voltage level based on the exact frequency of the input signal is known as:

Correct AnswerverifiedShow Answer

FM systems utilizing a direct FM modulator with an automatic frequency control (AFC) are known as:

Correct AnswerverifiedShow Answer

In an FM modulator, the amplitude of the intelligence signal determines the:

Correct AnswerverifiedShow Answer

In a stereo FM broadcast transmitter, when the 38 kHz pilot carrier is mixed with the L-R signal, what is produced?

Correct AnswerverifiedShow Answer

Standard FM broadcast stations use a maximum intelligence frequency of:

Correct AnswerverifiedShow Answer

The most important advantage of FM over AM is:

Correct AnswerverifiedShow Answer

Narrowband FM stations:

Correct AnswerverifiedShow Answer

Determine the worst case output signal-to-noise ratio for a broadcast FM receiver with a maximum deviation of 75 kHz and a maximum intelligence frequency of 15 kHz if the input signal-to-noise ratio is 3:1.

Correct AnswerverifiedShow Answer

The amount of frequency deviation is proportional to the amplitude of the intelligence signal in:

Correct AnswerverifiedShow Answer

The standard time constant used for pre-emphasis in a non-Dolby system is:

Correct AnswerverifiedShow Answer

Which of the following is indirect FM generation?

Correct AnswerverifiedShow Answer

Which of the following is not an example of a direct FM modulator?

Correct AnswerverifiedShow Answer

The modulation index that occurs when the deviation and intelligence frequencies are maximum is called:

Correct AnswerverifiedShow Answer

The first working FM system was developed by:

Correct AnswerverifiedShow Answer

The modulation index is:

Correct AnswerverifiedShow Answer

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