Question 1

The disadvantage of indirect FM modulators is

Accepted Answer

A)   they can only work at low intelligence frequencies
B)   they have insufficient frequency deviation
C)   they only work with large signal amplitudes
D)   they have very limited frequency stabilityE) A) and D)
F) All of the above

Question 2

An FM stereo broadcast is an example of

Accepted Answer

A)   frequency-division multiplexing
B)   amplitude-division multiplexing
C)   time-division multiplexing
D)   phase-division multiplexingE) None of the above
F) B) and C)

Question 3

FM systems that utilize an indirect FM modulator consisting of a phase modulator stage are known as:

Accepted Answer

A)   Crosby systems
B)   Hartley systems
C)   Armstrong systems
D)   PLL systemsE) All of the above
F) C) and D)

Question 4

The worst case signal-to-noise ratio at the output of an FM detector occurs when:

Accepted Answer

A)   the desired signal is 90 degrees out of phase with the intelligence signal.
B)   the desired signal is 90 degrees out of phase with the resultant signal of adding the signal to the noise.
C)   the noise signal is 90 degrees out of phase with the resultant signal of adding the signal to the noise.
D)   the desired signal is 90 degrees out of phase with the noise signal.E) C) and D)
F) None of the above C

Question 5

An indirect FM wideband transmitter can have its output signal be at the proper carrier frequency and at the same time have the required deviation by:

Accepted Answer

A)   using a balanced modulator and a 90 degree phase shifter
B)   using a reactance modulator
C)   using combinations of mixers and multiplier stages
D)   using a frequency correcting networkE) All of the above
F) A) and D)

Question 6

The deviation ratio for broadcast FM radio is

Accepted Answer

A)   5
B)   1.67
C)   6.71
D)   2.5
E)   .5F) A) and B)
G) A) and C)

Question 7

Multiplex transmission is:

Accepted Answer

A)   using two transmitters to transmit two separate channels of information
B)   the technique of separating the L and R signals into L+R and L-R in a stereo FM transmitter.
C)   the simultaneous transmission of two or more signals on one carrier
D)   using two carriers to transmit two separate channels of informationE) B) and D)
F) B) and C)

Question 8

The advantage of indirect FM modulation over direct FM modulation is:

Accepted Answer

A)   in their ability to work at higher intelligence frequencies
B)   in their increased frequency deviation
C)   in their ability to work with small signal amplitudes
D)   in their improved frequency stabilityE) None of the above
F) B) and C)

Question 9

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 10 kHz if the input signal-to-noise ratio is 2:1

Accepted Answer

A)   30:1
B)   15:1
C)   2:1
D)   10:1E) None of the above
F) B) and C)

Question 10

A de-emphasis network has:

Accepted Answer

A)   an upper cutoff frequency of 2.120 kHz.
B)   a high-frequency roll-off rate of -20 db per decade.
C)   a time constant of 75 microseconds.
D)   all of the aboveE) A) and D)
F) A) and C)

Question 11

In FM stereo broadcasts, why are the left and right audio signals first converted to L+R and L-R signals before being frequency modulated?

Accepted Answer

A)   This permits higher intelligence frequencies to be used
B)   This permits compatibility between monaural and stereo systems
C)   This is necessary to be able to be multiplexed properly
D)   This produces higher signal-to-noise ratiosE) A) and B)
F) B) and C)

Question 12

Why can low-level modulated FM signals be amplified by class C power amplifier stages without distorting unlike AM or SSB signals?

Accepted Answer

A)   These FM signals have only one upper and lower sideband frequency components.
B)   These FM signals do not vary in amplitude.
C)   The FM signals do not have a carrier frequency component.
D)   These FM signals have larger bandwidths than do AM or SSB signals.E) A) and B)
F) C) and D)

Question 13

Phase modulation is an indirect form of:

Accepted Answer

A)   frequency modulation
B)   angle modulation
C)   amplitude modulation
D)   pulse modulationE) None of the above
F) All of the above A

Question 14

Why are stereo FM broadcasts more prone to noise than are monophonic FM broadcasts?

Accepted Answer

A)   Stereo has two separate channels that can become covered by noise rather than the single channel of the monophonic broadcast.
B)   The L-R signal is weaker than the L+R signal.
C)   The L-R signal is at higher modulating frequencies than the L+R signal.
D)   all of the aboveE) All of the above
F) A) and B) D

Question 15

The deviation return for NTSC broadcast television is

Accepted Answer

A)   .5
B)   2.5
C)   6.71
D)   1.67
E)   5F) B) and D)
G) All of the above

Question 16

Standard FM broadcast stations use a maximum frequency deviation of:

Accepted Answer

A)   75 kHz
B)   5 kHz
C)   200 kHz
D)   150 kHzE) None of the above
F) B) and C)

Question 17

The main disadvantage of direct FM modulators is:

Accepted Answer

A)   they can only work at low radio frequencies
B)   they have very limited frequency stability
C)   they have insufficient frequency deviation
D)   they work reliably only with low-level intelligence signalsE) C) and D)
F) All of the above

Question 18

In an FM modulator, the intelligence frequency determines the:

Accepted Answer

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

Question 19

The two types of angle modulation are:

Accepted Answer

A)   amplitude and frequency modulation
B)   phase and amplitude modulation
C)   phase and frequency modulation
D)   pulse and frequency modulationE) B) and D)
F) A) and B)

Question 20

Which best describes how a varactor diode modulator creates FM?

Accepted Answer

A)   The intelligence signal causes the diode to create phase shift which indirectly creates FM
B)   The intelligence signal alters the capacitance of the diode to shift the resonant frequency of a tank circuit.
C)   The intelligence signal creates mixing action in the nonlinear varactor diode to create an FM signal.
D)   The intelligence signal alters the amount of forward bias of the varactor diode to create an FM signal.E) A) and B)
F) A) and C)

Exam 5: Frequency Modulation: Transmission

The disadvantage of indirect FM modulators is

Correct AnswerverifiedShow Answer

An FM stereo broadcast is an example of

Correct AnswerverifiedShow Answer

FM systems that utilize an indirect FM modulator consisting of a phase modulator stage are known as:

Correct AnswerverifiedShow Answer

The worst case signal-to-noise ratio at the output of an FM detector occurs when:

Correct AnswerverifiedC

An indirect FM wideband transmitter can have its output signal be at the proper carrier frequency and at the same time have the required deviation by:

Correct AnswerverifiedShow Answer

The deviation ratio for broadcast FM radio is

Correct AnswerverifiedShow Answer

Multiplex transmission is:

Correct AnswerverifiedShow Answer

The advantage of indirect FM modulation over direct FM modulation is:

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 10 kHz if the input signal-to-noise ratio is 2:1

Correct AnswerverifiedShow Answer

A de-emphasis network has:

Correct AnswerverifiedShow Answer

In FM stereo broadcasts, why are the left and right audio signals first converted to L+R and L-R signals before being frequency modulated?

Correct AnswerverifiedShow Answer

Why can low-level modulated FM signals be amplified by class C power amplifier stages without distorting unlike AM or SSB signals?

Correct AnswerverifiedShow Answer

Phase modulation is an indirect form of:

Correct AnswerverifiedA

Why are stereo FM broadcasts more prone to noise than are monophonic FM broadcasts?

Correct AnswerverifiedD

The deviation return for NTSC broadcast television is

Correct AnswerverifiedShow Answer

Standard FM broadcast stations use a maximum frequency deviation of:

Correct AnswerverifiedShow Answer

The main disadvantage of direct FM modulators is:

Correct AnswerverifiedShow Answer

In an FM modulator, the intelligence frequency determines the:

Correct AnswerverifiedShow Answer

The two types of angle modulation are:

Correct AnswerverifiedShow Answer

Which best describes how a varactor diode modulator creates FM?

Correct AnswerverifiedShow Answer

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C

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A

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D

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