# Rf 3D1X3 CDC Vol 1 Unit 1-4

64 Questions | Attempts: 78  Settings  Unit 1-4 URE

• 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 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, frequency, and phase

• 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 signals contains a/an
• A.

Modulating signal, upper sideband, 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) 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 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 percent 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 modulating signal

• D.

Directly proportional to the phase of the modulating signal

• 11.
(003) In frequency modulation (FM), what is considered a significant sideband?
• A.

Sidebands containing at least 1 percent of the total transmitted power

• B.

Sidebands containing at least 3 percent of the total transmitted power

• C.

Sidebands containing at least 10 percent of the total transmitted power

• D.

Sidebands containing at least 0.1 percent 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 times frequency of modulation

• C.

Sideband divide 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 the 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 changes 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

• C.

Pulse duration modulation

• D.

Pulse amplitude modulation

• 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

• B.

Forward error control

• C.

Redundant data transfer

• D.

Automatic retransmit on request

• 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 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.

Semiconductor laser diodes

• D.

Integrated photodiode/preamplifiers

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