# 3D1X3 Vol 1 CDC Ed 2

100 Questions | Total Attempts: 182  Settings  3d1x3 Vol 1 CDC Ed 2

• 1.
(001) What is one reason for modulation that involves modulatiing low frequency signals for transmission over long distances?
• A.

Spectrum Conservation

• B.

Channel allocation

• C.

• D.

Companding

• 2.
(001) What are the three general categories used to produce modulation in radio frequency (RF) transmission today?
• A.

Binary amplitude shift keying, frequency shift keying, and phase shift keying.

• B.

Pulse amplitude, pulse width, and pulse position.

• C.

Amplitude, frequency, and phase.

• D.

Analog, digital and shift keying.

• 3.
(002) When the modulating signal and carrier signal are combined within a modulator, the output signal contains
• A.

Modulating signal, upper sideband, and lower sideband.

• B.

Carrier, upper sideband, and lower sideband.

• C.

Upper sideband and modulating signal.

• D.

Carrier and modulating signal.

• 4.
(002) If a carrier frequency of 1 MHz and a modulating tone of 10 kHz goes to the modulator, the output signal include
• A.

1.01 MHz, 1 MHz, and 0.99 MHz.

• B.

1.1 MHz, 1 MHz, and 0.9 MHz.

• C.

1.11 MHz, 1 MHz, 0.99 MHz.

• D.

1.111 MHz, 1 MHz, 0.999 MHz.

• 5.
(002) The bandwidth of an amplitude modulated signal is
• A.

Two times the modulating signal.

• B.

The same as the modulating signal.

• C.

Determined by the modulation index.

• D.

Defined in terms of maximum amount of modulation.

• 6.
(002) Use the formula on page 1–3. If an oscilloscope displays a modulation envelope having an Emax of 200 volts and an Emin of 20 volts, what is the modulation percentage?
• A.

81.8

• B.

85.5

• C.

88

• D.

122

• 7.
(002) Which statement concerning bandwidth is true?
• A.

Overmodulating increases bandwidth because the distortion produces harmonics.

• B.

Undermodulating increases bandwidth because the distortion produces harmonics.

• C.

Overmodulating increases bandwidth because the output’s increased amplitude.

• D.

Undermodulating increases bandwidth because the output’s decreased amplitude.

• 8.
(003) The output of the oscillator in a frequency modulation (FM) modulator increases in frequency with each
• A.

Positive half cycle of the carrier.

• B.

Negative half cycle of the carrier.

• C.

Positive half cycle of the modulating signal.

• D.

Negative half cycle of the modulating signal.

• 9.
(003) In frequency modulation, a significant sideband contains at least what percentage of the total transmitted power?
• A.

1

• B.

3

• C.

10

• D.

0.1

• 10.
(003) What is the formula to find the modulating index?
• A.

Deviation divided by frequency of modulation.

• B.

Deviation times frequency of modulation.

• C.

Sideband divide by carrier frequency.

• D.

Sideband times carrier frequency.

• 11.
(003) A 5 kHz modulating signal has enough peak voltage to cause a deviation of 15 kHz. What is the modulation index?
• A.

5

• B.

0.5

• C.

0.3

• D.

3

• 12.
(003) What is it called when a narrow frequency band between adjacent stations prevent frequency modulated sidebands from overlapping?
• A.

Space

• B.

Guard Band

• C.

Buffer zone

• D.

Prevention field

• 13.
(004) In phase modulation, what part of the carrier signal is varied?
• A.

Frequency

• B.

Amplitude

• C.

Height

• D.

Phase

• 14.
(004) In phase modulation, the carrier’s
• A.

Phase is shifted at the rate of the modulating signal.

• B.

Phase shifted with the phase of the modulating signal.

• C.

Amplitude is shifted at the rate of the modulating signal.

• D.

Amplitude is shifted with the phase of the modulating signal.

• 15.
(005) What is the first step in the pulse code modulation process?
• A.

Discrete amplitudes are assigned to the sampling pulses.

• B.

A binary code number is assigned to the sample.

• C.

The quantizer limits the amplitude of the pulses.

• D.

The analog signal is band limited.

• 16.
(005) What part of the pulse code modulation process converts a continuous time signal into a discrete time signal?
• A.

Sampling

• B.

Rectifying

• C.

Oscillating

• D.

Band Limiting

• 17.
(006) In asynchronous transmissions, what bit is used by the receiving device to verify that the transmission was received correctly?
• A.

Control

• B.

Parity

• C.

Start

• D.

Stop

• 18.
(006) If an error should occur, what transmission is lost in an synchronous transmission?
• A.

One Character

• B.

Block of data

• C.

A parity bit

• D.

A stop bit

• 19.
(007) When using vertical redundancy check, what significance does the amount of ones have in a data bit pattern?
• A.

Determines parity.

• B.

Determines transmission rate.

• C.

Determines whether transmission is in ASCII format.

• D.

Determines whether transmission is synchronous or asynchronous.

• 20.
(007) What error detection method is used for checking a data block greater than 512 and is about 99percent effective in most applications?
• A.

Checksum.

• B.

Cyclic redundancy check

• C.

Vertical redundancy check.

• D.

Longitudinal redundancy check.

• 21.
(007) When using forward error control as a method of error correction, where does error correction take place?
• A.

Receiving end.

• B.

In the oscillator.

• C.

Transmitting end.

• D.

In the primary buffers.

• 22.
(008) Light sources that are applicable to fiber optic waveguide are light-emitting diodes and
• A.

Photo transistors.

• B.

Hybrid photodiodes.

• C.

Semiconductor laser diodes.

• D.

Integrated photodiode/preamplifiers.

• 23.
(008) What type of light is emitted from a laser?
• A.

Incoherent.

• B.

Coherent.

• C.

Ordinary.

• D.

Invisible.

• 24.
(009) What are the two main types of photodetectors?
• A.

Positive intrinsic negative and avalanche photodiode.

• B.

Light-emitting diode and avalanche photodiode.

• C.

Light emitting diode and semiconductor laser.

• D.

Tunnel and zener diodes.

• 25.
(009) What photo detector converts one photon to one electron?
• A.

Light emitting diode.

• B.

Avalanche photodiode.

• C.

Positive intrinsic negative diode.

• D.

Integrated photodiode/preamplifier.

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