Modulation

Key Topic 57:  Frequency Modulation

3-57H1 The deviation ratio is the:

A. Audio modulating frequency to the center carrier frequency.

B. Maximum carrier frequency deviation to the highest audio modulating frequency.

C. Carrier center frequency to the audio modulating frequency.

D. Highest audio modulating frequency to the average audio modulating frequency.

Modulation

Key Topic 57: Frequency Modulation

3-57H2 What is the deviation ratio for an FM phone signal having a maximum frequency deviation of plus or minus 5 kHz and accepting a maximum modulation rate of 3 kHz?

A. 60

B. 0.16

C. 0.6

D. 1.66

Modulation

Key Topic 57: Frequency Modulation

3-57H3 What is the deviation ratio of an FM-phone signal having a maximum frequency swing of plus or minus 7.5 kHz and accepting a maximum modulation rate of 3.5 kHz?

A. 2.14

B. 0.214

C. 0.47

D. 47

Modulation

Key Topic 57: Frequency Modulation

3-57H4 How can an FM-phone signal be produced in a transmitter?

A. By modulating the supply voltage to a class-B amplifier.

B. By modulating the supply voltage to a class-C amplifier.

C. By using a balanced modulator.

D. By feeding the audio directly to the oscillator.

Modulation

Key Topic 57: Frequency Modulation

3-57H5 What is meant by the term modulation index?

A. The ratio between the deviation of a frequency modulated signal and the modulating frequency.

B. The processor index.

C. The FM signal-to-noise ratio.

D. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency.

Modulation

Key Topic 57: Frequency Modulation

3-57H6 In an FM-phone signal, what is the term for the maximum deviation from the carrier frequency divided by the maximum audio modulating frequency?

A. Deviation index.

B. Modulation index.

C. Deviation ratio.

D. Modulation ratio.

Modulation

Key Topic 58:  SSB Modulation

3-58H1 In Figure 3H17, the block labeled 4 would indicate that this schematic is most likely a/an:

[image]

A. Audio amplifier.

B. Shipboard RADAR.

C. SSB radio transmitter.

D. Wireless LAN (local area network) computer.

Modulation

Key Topic 58: SSB Modulation

3-58H2 In Figure 3H17, which block diagram symbol (labeled 1 through 4) represents where audio intelligence is inserted?

A. 1

B. 2

C. 3

D. 4

Modulation

Key Topic 58: SSB Modulation

3-58H3 What kind of input signal could be used to test the amplitude linearity of a single-sideband phone transmitter while viewing the output on an oscilloscope?

A. Whistling in the microphone.

B. An audio frequency sine wave.

C. A two-tone audio-frequency sine wave.

D. An audio frequency square wave.

Modulation

Key Topic 58: SSB Modulation

3-58H4 What does a two-tone test illustrate on an oscilloscope?

A. Linearity of a SSB transmitter.

B. Frequency of the carrier phase shift.

C. Percentage of frequency modulation.

D. Sideband suppression.

Modulation

Key Topic 58: SSB Modulation

3-58H5 How can a double-sideband phone signal be produced?

A. By using a reactance modulator.

B. By varying the voltage to the varactor in an oscillator circuit.

C. By using a phase detector, oscillator, and filter in a feedback loop.

D. By modulating the supply voltage to a class C amplifier.

Modulation

Key Topic 58: SSB Modulation

3-58H6 What type of signals are used to conduct an SSB two-tone test?

A. Two audio signals of the same frequency, but shifted 90 degrees in phase.

B. Two non-harmonically related audio signals that are within the modulation band pass of the transmitter.

C. Two different audio frequency square wave signals of equal amplitude.

D. Any two audio frequencies as long as they are harmonically related.

Modulation

Key Topic 59:  Pulse Modulation

3-59H1 What is an important factor in pulse-code modulation using time-division multiplex?

A. Synchronization of transmit and receive clock pulse rates.

B. Frequency separation.

C. Overmodulation and undermodulation.

D. Slight variations in power supply voltage.

Modulation

Key Topic 59: Pulse Modulation

3-59H2 In a pulse-width modulation system, what parameter does the modulating signal vary?

A. Pulse frequency.

B. Pulse duration.

C. Pulse amplitude.

D. Pulse intensity.

Modulation

Key Topic 59: Pulse Modulation

3-59H3 What is the name of the type of modulation in which the modulating signal varies the duration of the transmitted pulse?

A. Amplitude modulation.

B. Frequency modulation.

C. Pulse-height modulation.

D. Pulse-width modulation.

Modulation

Key Topic 59: Pulse Modulation

3-59H4 Which of the following best describes a pulse modulation system?

A. The peak transmitter power is normally much greater than the average power.

B. Pulse modulation is sometimes used in SSB voice transmitters.

C. The average power is normally only slightly below the peak power.

D. The peak power is normally twice as high as the average power.

Modulation

Key Topic 59: Pulse Modulation

3-59H5 In a pulse-position modulation system, what parameter does the modulating signal vary?

A. The number of pulses per second.

B. The time at which each pulse occurs.

C. Both the frequency and amplitude of the pulses.

D. The duration of the pulses.

Modulation

Key Topic 59: Pulse Modulation

3-59H6 What is one way that voice is transmitted in a pulse-width modulation system?

A. A standard pulse is varied in amplitude by an amount depending on the voice waveform at that instant.

B. The position of a standard pulse is varied by an amount depending on the voice waveform at that instant.

C. A standard pulse is varied in duration by an amount depending on the voice waveform at that instant.

D. The number of standard pulses per second varies depending on the voice waveform at that instant.