# Rf 3D1X3 CDC Vol 1 Unit 1-4

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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

Explanation
Modulating low frequency signals for transmission over long distances allows for ease of radiation. This means that the modulated signal can be efficiently transmitted and radiated without significant loss or distortion. By modulating the low frequency signals, the signal can be effectively transmitted over long distances without experiencing significant degradation or interference. This is important for ensuring clear and reliable communication over long distances.

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• 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

C. Amplitude, frequency, and phase
Explanation
The correct answer is amplitude, frequency, and phase. These three general categories are used to produce modulation in radio frequency transmission today. Amplitude modulation (AM) involves varying the amplitude of the carrier signal to transmit information. Frequency modulation (FM) involves varying the frequency of the carrier signal. Phase modulation (PM) involves varying the phase of the carrier signal. These modulation techniques are widely used in radio frequency transmission to encode and transmit information efficiently and reliably.

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• 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

B. Carrier, upper sideband, and lower sideband
Explanation
When the modulating signal and carrier signal are combined within a modulator, the output signals contain a carrier signal, an upper sideband, and a lower sideband. This is because the modulating signal is used to modulate the carrier signal, resulting in the creation of sidebands above and below the carrier frequency. These sidebands carry the information from the modulating signal. Therefore, the output signals consist of the original carrier signal along with the upper and lower sidebands.

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• 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

A. 1.01 MHz, 1 MHz, and 0.99 MHz
Explanation
When a carrier frequency of 1 MHz and a modulating tone of 10 kHz are fed into the modulator, the output signal will include frequencies that are the sum and difference of the carrier frequency and the modulating tone. In this case, the output signal will consist of the carrier frequency (1 MHz), the sum of the carrier frequency and the modulating tone (1.01 MHz), and the difference between the carrier frequency and the modulating tone (0.99 MHz).

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• 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

D. 20 kHz
Explanation
The bandwidth of an amplitude modulated signal is determined by the sum of the highest frequency component of the modulating signal and the carrier frequency. In this case, the modulating audio signal is 10 kHz wide, so the highest frequency component is 10 kHz. If we assume a carrier frequency of 10 kHz, the bandwidth would be the sum of the highest frequency component and the carrier frequency, which is 20 kHz. Therefore, the correct answer is 20 kHz.

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• 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

A. Two times the modulating signal
Explanation
The bandwidth of an amplitude modulated signal is two times the modulating signal. This means that the range of frequencies required to accurately transmit the modulating signal is twice the range of frequencies present in the modulating signal itself. This is because in amplitude modulation, the modulating signal is used to vary the amplitude of the carrier signal, resulting in the creation of sidebands around the carrier frequency. These sidebands contain the information from the modulating signal and require additional frequency space, leading to a bandwidth that is twice the modulating signal.

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• 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

A. Percent of modulation
Explanation
The correct answer is percent of modulation. In amplitude modulation, the amount of effect or change that intelligence has on the carrier signal is expressed as the percent of modulation. This refers to the percentage of change in the amplitude of the carrier signal caused by the modulation process. The percent of modulation is a measure of the strength or intensity of the modulating signal in relation to the carrier signal. It determines the depth of modulation and affects the overall quality and fidelity of the modulated signal.

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• 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

A. Overmodulating increases bandwidth due to the production of harmonics
Explanation
Overmodulating increases bandwidth due to the production of harmonics. When a signal is overmodulated, it means that the amplitude of the signal is exceeding the maximum limit. This causes distortion in the signal, resulting in the production of harmonics. These harmonics contain additional frequency components that increase the overall bandwidth of the signal. Therefore, overmodulation leads to an increase in bandwidth due to the presence of harmonics.

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• 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

C. No reduction in carrier power
Explanation
Reducing modulation to less than 100 percent means that the amplitude of the modulating signal is reduced, resulting in a decrease in the depth of modulation. This reduction in modulation does not affect the carrier power, as the carrier signal remains unchanged in amplitude. Therefore, there is no reduction in carrier power when modulation is reduced to less than 100 percent.

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• 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

B. Directly proportional to the amplitude of the modulating signal
Explanation
In frequency modulation (FM), the amount of oscillator frequency change is directly proportional to the amplitude of the modulating signal. This means that as the amplitude of the modulating signal increases, the frequency of the oscillator also increases, and vice versa. This relationship allows for the encoding of information in the frequency variations of the FM signal.

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• 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

A. Sidebands containing at least 1 percent of the total transmitted power
Explanation
In frequency modulation (FM), a significant sideband is considered to be one that contains at least 1 percent of the total transmitted power. This means that the sideband carries a substantial amount of the signal information and contributes significantly to the overall transmission. Sidebands containing less than 1 percent of the total transmitted power may not be strong enough to effectively convey the desired information.

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• 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

A. Deviation divided by frequency of modulation
Explanation
The formula to find the modulating index is the deviation divided by the frequency of modulation. The modulating index represents the ratio of the maximum deviation of the carrier frequency to the frequency of the modulating signal. By dividing the deviation by the frequency of modulation, we can calculate the modulating index, which is a crucial parameter in frequency modulation (FM) systems.

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• 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

A. Phase is shifted at the rate of the modulating signal
Explanation
In phase modulation (PM), the phase of the carrier signal is shifted at the rate of the modulating signal. This means that the instantaneous phase of the carrier wave is varied in accordance with the modulating signal. The amplitude of the carrier signal remains constant, but its phase changes based on the modulating signal. This allows for the encoding of information in the phase of the carrier signal, making PM a form of angle modulation.

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• 14.

• A.

Easier detection

• B.

Smaller bit error rate

• C.

Better signal-to-noise ratio

• D.

Higher data rates within a given bandwidth

D. Higher data rates within a given bandwidth
Explanation
Adding more phase shifts allows for higher data rates within a given bandwidth. This is because each phase shift represents a different symbol or bit, and by increasing the number of phase shifts, more symbols can be transmitted per unit of time. This allows for a higher data transmission rate, meaning more information can be sent in the same amount of bandwidth.

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• 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

D. The analog signal is band-limited
Explanation
In pulse code modulation (PCM), the first step is to band-limit the analog signal. This means that the analog signal is filtered to remove any frequencies that are outside the desired range. This is done to ensure that the signal can be accurately represented using discrete samples. By band-limiting the signal, it prevents any frequencies that are higher than the Nyquist frequency from being included in the sampling process, which could cause aliasing and distortion in the digital representation of the signal.

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• 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

A. Sampling
Explanation
The part of the pulse code modulation (PCM) process that converts a continuous time signal into a discrete time signal is sampling. Sampling involves taking regular intervals of the continuous signal and converting them into discrete values. This allows the signal to be represented digitally and processed by a computer or other digital devices. Sampling is a fundamental step in PCM and is necessary to accurately capture and reproduce the original analog signal.

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• 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

D. Pulse amplitude modulation
Explanation
Pulse Amplitude Modulation (PAM) is a type of pulse modulation where the amplitude of the pulse train is varied according to the amplitude of the input signal. In PAM, the amplitude of the pulses represents the information being transmitted. By varying the amplitude of the pulses, the signal can be modulated to carry different levels of information. Hence, pulse amplitude modulation is the correct answer in this case.

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• 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

B. Block of data
Explanation
In synchronous transmission, data is sent in blocks rather than individual characters. Each block of data is transmitted together with synchronization bits to ensure accurate and efficient data transfer. If an error occurs during transmission, it is likely that the entire block of data is lost, rather than just one character or a specific bit. Therefore, the correct answer is "block of data".

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• 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

A. Determines parity
Explanation
The amount of ones in a data bit pattern determines parity. Parity is a form of error checking where an extra bit, either 0 or 1, is added to a group of bits to make the total number of ones even or odd. This allows the receiver to detect if any errors occurred during transmission. By counting the number of ones in the data bit pattern, the receiver can determine whether the transmission is error-free or if there was a bit error.

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• 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

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

A. Checksum
Explanation
Checksum is an error detection method that involves adding up all the characters in a message, dividing the sum by 255, and considering only the remainder. This remainder is then appended to the message and sent along with it. At the receiving end, the same process is performed, and if the remainder obtained matches the one received, it indicates that no errors were introduced during transmission. The checksum method is simple and efficient for detecting errors in data transmission.

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• 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

D. Automatic retransmit on request
Explanation
Automatic retransmit on request is the error-correction technique that sends a retransmittal request by the receiver to the sender if it finds an error in a received frame. This technique allows the receiver to request the sender to resend the frame in case of errors, ensuring that the data is correctly received. It helps in improving the reliability and accuracy of the data transfer process by providing a mechanism for error detection and recovery.

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• 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

A. Receiving end
Explanation
Error correction takes place at the receiving end when using forward error control as a method of error correction. This means that the errors in the transmitted data are detected and corrected at the destination or receiver of the data.

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• 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

B. Converts electrical energy into optical energy
Explanation
An optical source is a device that converts electrical energy into optical energy. This means that it takes electrical signals and converts them into light signals, which can then be transmitted through fiber optic cables. This conversion is necessary for the transmission of data over long distances and helps to preserve the integrity of the signal.

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• 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

C. Semiconductor laser diodes
Explanation
Semiconductor laser diodes are applicable to fiber optic waveguides because they provide a concentrated and coherent beam of light that can efficiently transmit through the fiber optic cable. LED light sources are also applicable, but they have a wider beam and are less efficient for long-distance transmission. Photo transistors and hybrid photodiodes are not used as light sources, but rather as detectors to receive the light signal at the end of the fiber optic cable. Integrated photodiode/preamplifiers are also used as detectors, but not as light sources.

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• 26.

### (008) What type of ligh is emitted from a laser?

• A.

Incoherent

• B.

Coherent

• C.

Ordinary

• D.

Invisible

B. Coherent
Explanation
A laser emits coherent light. Coherent light refers to light waves that have a fixed phase relationship with each other, meaning they are in sync and have the same frequency and wavelength. This allows the light to travel in a narrow, focused beam with minimal spreading or divergence. In contrast, incoherent light consists of waves with random phase relationships, which results in light that is not focused and spreads out in various directions. Therefore, the correct answer is coherent.

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• 27.

### (008) Laser diode power coupling is measured in which range

• A.

Megawatt

• B.

Mircowatt

• C.

Milliwatt

• D.

Kilowatt

C. Milliwatt
Explanation
Laser diode power coupling is measured in milliwatts. Milliwatt is the unit of power that is equal to one thousandth of a watt. Laser diodes are typically low-power devices, and their power output is usually in the milliwatt range. This measurement is important in determining the efficiency and performance of laser diodes in various applications such as telecommunications, laser pointers, and optical data storage.

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• 28.

### (009) A device that accepts optical signals from an optical fiber and converts them into electrical signals is called an optical

• A.

Regenerator

• B.

Transmitter

• C.

Amplifier

• D.

Explanation
A device that accepts optical signals from an optical fiber and converts them into electrical signals is called a receiver. Receivers are an essential component in optical communication systems as they are responsible for converting the optical signals back into electrical signals that can be processed and interpreted by electronic devices. This conversion allows for the transmission of data over long distances using optical fibers.

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• 29.

### (009) Small current that flows from a photodiode even with no light is called

• A.

Dark current

• B.

Dispersion

• C.

Distortion

• D.

Ionization

A. Dark current
Explanation
Dark current refers to the small current that flows through a photodiode even in the absence of light. This current is caused by the thermal generation of electron-hole pairs within the photodiode's semiconductor material. As temperature increases, more electron-hole pairs are generated, leading to an increase in dark current. Dark current can affect the accuracy and sensitivity of photodiodes, especially in low-light conditions, and measures are taken to minimize its impact in various applications.

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• 30.

### (009) The responsivity of a photo detector is dependent on the

• A.

Emitter rise time

• B.

Wavelength of light

• C.

Signal-to-noise ratio (SNR)

• D.

Emitter modulation speed

B. Wavelength of light
Explanation
The responsivity of a photo detector is dependent on the wavelength of light. Responsivity refers to the ability of a device to convert incident light into an electrical signal. Different photo detectors are designed to be sensitive to specific wavelengths of light. The responsivity is highest at the wavelength that the detector is designed for, and decreases as the wavelength deviates from this value. Therefore, the wavelength of light plays a crucial role in determining the responsivity of a photo detector.

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• 31.

### (009) What are the two main types of photodetectors?

• A.

Positive intrinsic negative and avalanche photodiode

• B.

Light-emitting diode (LED) and avalanche photodiode

• C.

LED and semiconductor laser

• D.

Tunnel and zener diodes

A. Positive intrinsic negative and avalanche photodiode
Explanation
The correct answer is positive intrinsic negative and avalanche photodiode. Photodetectors are devices that convert light into electrical signals. The positive intrinsic negative (PIN) photodiode is a type of photodetector that operates based on the principle of the internal photoelectric effect. It consists of three layers: P-type, intrinsic, and N-type. The avalanche photodiode (APD) is another type of photodetector that operates based on the avalanche effect. It has a higher sensitivity and gain compared to the PIN photodiode. Therefore, both PIN and APD are the two main types of photodetectors.

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• 32.

### (009) What photo detector converts one photon to one electron?

• A.

Light emitting diode (LED)

• B.

Avalanche photodiode

• C.

Positive intrinsic negative (PIN) diode

• D.

Integrated photodiode/preamplifier (IDP)

C. Positive intrinsic negative (PIN) diode
Explanation
The correct answer is positive intrinsic negative (PIN) diode. A PIN diode is a type of photo detector that converts one photon to one electron. It is designed with an intrinsic layer between the p-type and n-type layers, which allows for efficient photon absorption and electron-hole pair generation. This makes it suitable for applications that require high sensitivity and low noise, such as optical communication systems and photovoltaic devices.

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• 33.

### (010) What is used to extend the distance of a fiber optic communication systems link?

• A.

• B.

Transmitter

• C.

Repeater

• D.

Patch cords

C. Repeater
Explanation
A repeater is used to extend the distance of a fiber optic communication system's link. A repeater receives the optical signal, converts it to an electrical signal, amplifies it, and retransmits it as an optical signal. This process allows the signal to travel over longer distances without losing its strength or quality. By placing repeaters at intervals along the fiber optic link, the signal can be effectively transmitted over long distances, making it an essential component for extending the reach of fiber optic communication systems.

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• 34.

### (010) Which repeater amplifiers optical signal without converting to and from the electrical domain?

• A.

Repeaters

• B.

Regenerators

• C.

Optical amplifiers

• D.

C. Optical amplifiers
Explanation
Optical amplifiers are devices that amplify optical signals without converting them to and from the electrical domain. Unlike repeaters and regenerators, which regenerate and amplify electrical signals, optical amplifiers directly amplify the optical signal itself. Receivers, on the other hand, are used to detect and convert optical signals back into electrical signals. Therefore, optical amplifiers are the correct answer as they specifically amplify optical signals without any electrical conversion.

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• 35.

### (011) Short sections of signle fiber cables that has a connector at each end is called a

• A.

Pigtail

• B.

Patch cord

• C.

Jumper

• D.

Breakout cables

B. Patch cord
Explanation
A short section of single fiber cables that has a connector at each end is called a patch cord. It is used to connect devices or components in a network or communication system. Patch cords are typically used for temporary or semi-permanent connections and are often color-coded for easy identification. They are commonly used in data centers, telecommunications, and computer networking environments.

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• 36.

### (011) Which fiber-optic connector uses quick-release, keyed bayonet that are preferred in situations where severe vibrations are not expected?

• A.

Biconic

• B.

Field connector (FC)

• C.

Straight tip (ST)

• D.

Sub-miniature, type A (SMA)

C. Straight tip (ST)
Explanation
The straight tip (ST) fiber-optic connector uses a quick-release, keyed bayonet design that is preferred in situations where severe vibrations are not expected. This type of connector provides a secure and reliable connection, but it is not as resistant to vibrations as other connectors like the biconic or field connector (FC). The ST connector is commonly used in telecommunications and data networks where stability and ease of installation are important factors.

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• 37.

### (011) Which fiber optic connector uses a push-pull engagement for mating?

• A.

Biconic

• B.

Field (FC)

• C.

Subscriber (SC)

• D.

Sub-miniature, type A (SMA)

C. Subscriber (SC)
Explanation
The subscriber (SC) fiber optic connector uses a push-pull engagement for mating. This means that the connector can easily be inserted and removed by simply pushing and pulling it. This type of connector is commonly used in telecommunications and data networking applications because of its ease of use and reliability.

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• 38.

### (012) What initial nuclear radiation elements generate electromagnetic pulses?

• A.

Gamma rays and neutrons

• B.

Thermally generated x-rays

• C.

• D.

Neutrons and thermally generated x-rays

A. Gamma rays and neutrons
Explanation
Gamma rays and neutrons are capable of generating electromagnetic pulses. Gamma rays are high-energy photons that can cause ionization and excitation of atoms, leading to the production of electromagnetic pulses. Neutrons, on the other hand, can induce electromagnetic pulses through the process of neutron-induced electromagnetic radiation (NIER). When neutrons interact with materials, they can generate secondary radiation, including electromagnetic pulses. Therefore, gamma rays and neutrons are the initial nuclear radiation elements that can generate electromagnetic pulses.

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• 39.

### (012) High-altitude electromagnetic pulse is what type of frequency phenomenon, and involves which frequency range?

• A.

Secondary; 1 hertz to 1 gigahertz

• B.

Wideband; 1 hertz to 1 gigahertz

• C.

Secondary; 10 hertz to 10 gigahertz

• D.

Wideband; 10 hertz to 10 gigahertz

B. Wideband; 1 hertz to 1 gigahertz
Explanation
High-altitude electromagnetic pulse (HEMP) is a wideband phenomenon that involves frequencies ranging from 1 hertz to 1 gigahertz. This means that HEMP encompasses a broad range of frequencies, from very low to very high, making it a wideband phenomenon. The correct answer choice accurately describes the frequency range associated with HEMP.

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• 40.

### (012) A system-generated electromagnetic pulse is a problem for satellites and reentry vehicles that are

• A.

Susceptible to the wideband frequency phenomenon

• B.

Directly exposed to nuclear radiations from a high-altitude burst

• C.

Affected by the azimuthal magnetic fields and time-varying air conductivity

• D.

Influenced by the signal fading or waveform distortion caused by the structured plasma field

B. Directly exposed to nuclear radiations from a high-altitude burst
Explanation
Satellites and reentry vehicles that are directly exposed to nuclear radiations from a high-altitude burst are susceptible to a system-generated electromagnetic pulse. This is because the nuclear radiation from the burst can generate an electromagnetic pulse that can disrupt or damage the electronic components of the satellites and reentry vehicles.

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• 41.

### (012) Which distinct region of the source region electromagnetic pulse is produced by the interactions between the weapon products and the earth's atmosphere?

• A.

Secondary

• B.

• C.

Plasma

• D.

Source

D. Source
Explanation
The correct answer is "source." In this context, the source region refers to the area where the weapon products interact with the Earth's atmosphere to generate the electromagnetic pulse. This region is distinct from the secondary region, which is the area where the pulse propagates and causes damage, and the radiated region, where the pulse is emitted into space. The plasma region is also not the correct answer as it does not specifically refer to the interaction between the weapon products and the atmosphere.

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• 42.

### (012) What electromagnetic pulse region is the principal threat to electronic systems by cable?

• A.

Local

• B.

Source

• C.

• D.

Long-line

Explanation
Radiated electromagnetic pulse (EMP) is the principal threat to electronic systems by cable. When an EMP occurs, it releases a burst of electromagnetic radiation that can induce currents and voltages in nearby cables, leading to damage or disruption of electronic systems. This can happen even if the cables are shielded or insulated. Therefore, the radiated EMP poses a significant danger to electronic systems connected by cables.

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• 43.

### (012) How does scintillation effects communications?

• A.

Large attenuation of the transmitted signal casusing the received signal-to-noise ratio (SNR) to fall below unity

• B.

Transmitted signal fading caused by multiple path propagation through the structured plasma field

• C.

Layers of charged electrons that are trapped and prevent transmissions through the layer

• D.

Absorption of the transmitted signal through the contaminated area

A. Large attenuation of the transmitted signal casusing the received signal-to-noise ratio (SNR) to fall below unity
Explanation
Scintillation effects communications by causing a large attenuation of the transmitted signal, which results in the received signal-to-noise ratio (SNR) falling below unity. This means that the strength of the received signal is significantly weakened, making it difficult to distinguish the signal from background noise. This can lead to poor quality and unreliable communication, especially in situations where a strong and clear signal is crucial.

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• 44.

### (012) Atmospheric disturbances from initial nuclear radiation on higher frequencies affect communications by which types of effects?

• A.

Blackout

• B.

Absorption

• C.

Scintillation

• D.

Attenuation

C. Scintillation
Explanation
Scintillation refers to the rapid fluctuations in the amplitude and phase of radio waves caused by atmospheric disturbances. These disturbances, which are a result of initial nuclear radiation, can cause the radio waves to scatter and change direction, leading to fluctuations in signal strength. This can disrupt communications by causing signal fading and interference, making it difficult for the receiver to accurately decode the transmitted information.

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• 45.

### (013) Which one of the following statements are true concerning shielding?

• A.

Cables should be of unshielded construction

• B.

Only ventilation ports are shielded along the walls

• C.

Sensitive equipment will be located within the shielded barrier

• D.

All power lines supplying shielded areas does not require filters

C. Sensitive equipment will be located within the shielded barrier
Explanation
Sensitive equipment needs to be located within a shielded barrier to protect it from electromagnetic interference. Shielding helps to block or reduce the electromagnetic radiation that can interfere with the proper functioning of sensitive equipment. By placing the equipment within a shielded barrier, it is protected from external electromagnetic interference, ensuring its performance and reliability.

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• 46.

### (013) What is the purpose of bonding?

• A.

To isolate facility from any external electrical electromagnetic propagation

• B.

To reduce interference coupling around circuits and around interconnecting lines

• C.

To ensure a mechanically strong, low impedance interconnection between metal objects

• D.

To eliminate harmful differences of potential between the various telephone cables entering facility

C. To ensure a mechanically strong, low impedance interconnection between metal objects
Explanation
The purpose of bonding is to ensure a mechanically strong, low impedance interconnection between metal objects. This helps to create a reliable and efficient electrical pathway, reducing resistance and preventing the buildup of harmful differences in potential. By establishing a solid bond between metal objects, interference coupling is also minimized, leading to better overall performance and reduced electromagnetic propagation.

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• 47.

### (013) Which types of filters are always used in combination with surge arresters?

• A.

Linear

• B.

Alternating current (AC) line

• C.

Direct current (DC)DC line

• D.

Power line

A. Linear
Explanation
Linear filters are always used in combination with surge arresters because surge arresters are designed to protect electrical systems from voltage spikes or surges. These surges can occur in both AC and DC power lines. Linear filters help to reduce electromagnetic interference (EMI) and noise in the power supply, which can be caused by switching devices or other electrical equipment. By using linear filters in combination with surge arresters, the electrical system is better protected from both voltage surges and EMI, ensuring the smooth and efficient operation of the system.

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• 48.

### (014) If the interference can be eliminated by disconnecting the receiving antenna, the source of the disturbance is most likely

• A.

Line noise

• B.

• C.

• D.

Explanation
If disconnecting the receiving antenna eliminates the interference, it suggests that the source of the disturbance is external to the radio. This means that the interference is likely being caused by something outside of the radio, such as nearby electrical devices or other radio signals.

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• 49.

### (014) What is an example of intentionally induced electromagnetic interference (EMI)?

• A.

Jamming

• B.

Spurious responses

• C.

Intermodulation

• D.

Power line noise

A. Jamming
Explanation
An example of intentionally induced electromagnetic interference (EMI) is jamming. Jamming refers to the deliberate disruption or interference of electronic communications, such as radio signals or wireless networks, by transmitting a strong interfering signal. This interference can disrupt or block the intended communication, causing interference and rendering the system ineffective.

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• 50.

### (014) What type of electromagnetic interference (EMI) occurs when a receiver responds to off-frequency signals?

• A.

Rusty bolt

• B.

Co-channel

• C.

Brute force

• D.

Spurious responses

D. Spurious responses
Explanation
Spurious responses refer to a type of electromagnetic interference (EMI) that occurs when a receiver responds to off-frequency signals. This means that the receiver picks up and responds to signals that are not within its intended frequency range. These off-frequency signals can cause disruptions or distortions in the receiver's performance, leading to interference with the desired signals. Therefore, spurious responses can negatively impact the overall functionality and reliability of the receiver.

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• Current Version
• Oct 18, 2023
Quiz Edited by
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• Nov 23, 2011
Quiz Created by
Brocj357

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