# 3D153 CDC, Volume 1. General Subjects

100 Questions | Total Attempts: 123  Settings  3D153-01-1009, Edit Code 01 This quiz is to help new Airmen study for their CDCs and for Senior Airmen to study for Staff. This quiz is made up by all the UREs from the first 3D153 CDC volume. Edited and updated as of December 16, 2012 If you have find an error on a question you can email me at [email protected] Com and I will fix it!

• 1.
001 - What reason for modulation involves modulating low frequency signals for transmission over long distances?
• A.

Spectrum conservation

• B.

Channel allocation

• C.

• D.

Companding

• 2.
001 - What are the three genereal 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/an
• A.

Modulating signal, upper sideband (USB), lower sideband (LSB)

• B.

Carrier, USB, and LSB

• C.

USB 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 includes
• 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, .0999 MHz

• 5.
002 - If the modulating audio signal is 10 kHz wide, what is the bandwidth of the transmitted amplitude modulated signal?
• A.

5 kHz

• B.

10 kHz

• C.

15 kHz

• D.

20 kHz

• 6.
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

• 7.
002 - The amount of effect or change that the intelligence has on the carrier in an amplitude modulated signal is expressed as the
• A.

Percent of modulation

• B.

Modulation index

• C.

Bandwidth

• D.

Deviation

• 8.
002 - Which statement concerning bandwidth is true?
• A.

Overmodulating increases bandwidth due to the production of harmonics.

• B.

Undermodulating increases bandwidth due to the production of harmonics.

• C.

Overmodulating increases bandwidth due to the output's increased amplitude.

• D.

Undermodulating increases bandwidth due to the output's decreased amplitude.

• 9.
002 - Reducing modulation to less than 100% gives
• A.

More total power

• B.

A reduction in carrier power

• C.

No reduction in carrier power

• D.

A reduction in carrier and sideband power

• 10.
003 - In frequency modulation (FM), the amount of oscillator frequency change is
• A.

Inversely proportional to the amplitude of the modulating signal

• B.

Directly proportional to the amplitude of the modulating signal

• C.

Inversely proportional to the phase of the modultaing signal

• D.

Directly proportional to the phase of the modulating signal

• 11.
003 - In FM, what is considered a significant sideband?
• A.

Sibebands (SB) containing at least 1% of the total transmitted power

• B.

SB containing at least 3% of the total transmitted power

• C.

SB containing at least 10 percent of the total transmitted power

• D.

SB containing at least 0.1% of the total transmitted power

• 12.
003 - What is the formula to find the modulating index?
• A.

Deviation divided by frequency of modulation.

• B.

Deviation time frequency of modulation.

• C.

Sideband divided by carrier frequency.

• D.

Sideband times carrier frequency.

• 13.
004 - In Phase Modulation (PM), 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.

• 14.
• A.

Easier detection.

• B.

Smaller bit error rate.

• C.

Better signal-to-noise ratio.

• D.

Higher data rates within a given bandwidth.

• 15.
005 - What is the first step in pulse code modulation (PCM) 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 (PCM) process converts a continuous time signal into a discrete time signal?
• A.

Sampling.

• B.

Rectifying.

• C.

Oscillating.

• D.

Band Limiting.

• 17.
005 - A type of pulse modulation (PM) that causes the amplitude of the pulse train to vary according to the amplitude of the input signal is called
• A.

Pulse width modulation (PWM)

• B.

Pulse position modulation (PPM)

• C.

Pulse duration modulation (PDM)

• D.

Pulse amplitude modulation (PAM)

• 18.
006 - If an error should occur, what data transmission is lost in a synchronous transmission?
• A.

One character.

• B.

Block of data.

• C.

A parity bit.

• D.

Synchronization (SYNC) bit.

• 19.
007 - When using vertical redundancy check (VRC), 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 American Standard code for Information Interchange (ASCII) format

• D.

Determines whether transmission is synchronous or asynchronous

• 20.
007 - What two error detection methods, when used together, are 98 percent effective in detecting errors?
• A.

Checksum and cyclic redundancy check

• B.

Longitudinal redundancy check and checksum

• C.

Cyclic redundancy check and vertical redundancy check

• D.

Vertical redundancy check and longitudinal redundancy check

• 21.
007 - What error detection method adds stacked characters, divides it by 255, and disregards the answer except for the remainder?
• A.

Checksum

• B.

Block check character

• C.

Cyclic redundancy check

• D.

Vertical redundancy check

• 22.
007 - What error-correction technique sends a retransmittal request by the receiver to the sender if it finds an error in a received frame?
• A.

Error-correcting code (ECC)

• B.

Forward error control (FEC)

• C.

Redundant data transfer (RDT)

• D.

Automatic retransmit on request (ARQ)

• 23.
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.

• 24.
008 - What does an optical source do?
• A.

Terminates fiber optics cable

• B.

Converts electrical energy into optical energy

• C.

Extends the distance and to preserve signal integrity

• D.

Accepts optical signals and converts them into electrical signals

• 25.
008 - Light sources that are applicable to fiber optic waveguide are light-emitting diodes (LED) and
• A.

Photo transistors.

• B.

Hybrid photodiodes.

• C.

Emiconductor laser diodes (LD).

• D.

Integrated photodiode preamplifiers.

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