CDC 3D153 Rf Journeyman Volume 1, Unit 1

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  • 1/28 Questions

    (001) What is one reason for modulation that involves modulating low frequency signals for transmission over long distances?

    • Spectrum conservation
    • Channel allocation
    • Ease of radiation
    • Companding
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About This Quiz

This quiz, titled 'CDC 3D153 RF Journeyman Volume 1, Unit 1', assesses knowledge on RF transmission modulation techniques. It covers reasons for modulation, categories of modulation, signal combinations, and calculation of modulation percentage. Essential for learners in communications engineering.

CDC 3D153 Rf Journeyman Volume 1, Unit 1 - Quiz

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  • 2. 

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

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

    • Pulse amplitude, pulse width, and pulse position

    • Amplitude, frequency, and phase

    • Analog, digital, and shift keying

    Correct Answer
    A. Amplitude, frequency, and phase
    Explanation
    The three general categories used to produce modulation in radio frequency (RF) transmission today are amplitude, frequency, and phase. Modulation is the process of varying one or more properties of a carrier signal in order to transmit information. In amplitude modulation (AM), the amplitude of the carrier signal is varied to encode the information. In frequency modulation (FM), the frequency of the carrier signal is varied. In phase modulation (PM), the phase of the carrier signal is varied. These three types of modulation are commonly used in RF transmission to carry information efficiently.

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  • 3. 

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

    • Modulating signal, upper sideband, and lower sideband

    • Carrier, upper sideband, and lower sideband

    • Upper sideband and modulating signal

    • Carrier and modulating signal

    Correct Answer
    A. Carrier, upper sideband, and lower sideband
    Explanation
    When the modulating signal and carrier signal are combined within a modulator, the output signal contains the carrier signal, as well as the upper sideband and lower sideband. This is because the modulating signal affects the carrier signal by shifting its frequency, resulting in the creation of sidebands. The upper sideband has frequencies higher than the carrier frequency, while the lower sideband has frequencies lower than the carrier frequency. Therefore, the correct answer is carrier, upper sideband, and lower sideband.

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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

    • 1.01 MHz, 1 MHz, and 0.99 MHz

    • 1.1 MHz, 1 MHz, and 0.9 MHz

    • 1.11 MHz, 1 MHz, 0.99 MHz

    • 1.111 MHz, 1 MHz, 0.000 MHz

    Correct Answer
    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 combined in a modulator, the output signal will include the carrier frequency (1 MHz) and the sidebands resulting from modulation. In this case, the sidebands will be at frequencies of 1.01 MHz (1 MHz + 10 kHz) and 0.99 MHz (1 MHz - 10 kHz). Therefore, the correct answer is 1.01 MHz, 1 MHz, and 0.99 MHz.

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  • 5. 

    (002) The bandwidth of an amplitude modulated signal is

    • Two times the modulating signal

    • The same as the modulating signal

    • Determined by the modulation index

    • Defined in terms of maximum amount of modulation

    Correct Answer
    A. Two times the modulating signal
    Explanation
    The correct answer is "two times the modulating signal." In amplitude modulation, the bandwidth refers to the range of frequencies required to accurately transmit the modulating signal. Since the modulating signal is multiplied by both its positive and negative copies, the bandwidth is two times the modulating signal.

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  • 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?

    • 81.8

    • 85.5

    • 88

    • 122

    Correct Answer
    A. 81.8
    Explanation
    The modulation percentage can be calculated using the formula: (EMax - EMin) / (EMax + EMin) * 100. In this case, the EMax is 200 volts and the EMin is 20 volts. Plugging these values into the formula, we get (200 - 20) / (200 + 20) * 100 = 180 / 220 * 100 = 81.8. Therefore, the modulation percentage is 81.8.

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  • 7. 

    (002) Which statement concerning bandwidth is true?

    • Overmodulating increases bandwidth because the distortion produces harmonics

    • Undermodulating increases bandwidth because the distortion produces harmonics

    • Overmodulating increases bandwidth because the output's increased amplitude

    • Undermodulating increases bandwidth because the output's decreased amplitude

    Correct Answer
    A. Overmodulating increases bandwidth because the distortion produces harmonics
    Explanation
    Overmodulating refers to the process of increasing the amplitude of a signal beyond its normal range. This causes distortion in the signal, which in turn produces harmonics. Harmonics are additional frequencies that are multiples of the original signal frequency. As a result, the bandwidth of the signal increases because it now contains these additional frequencies. Therefore, the statement "Overmodulating increases bandwidth because the distortion produces harmonics" is true.

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  • 8. 

    (003) The output of the oscillator in a frequency modulation (FM) modulator increase in frequency with each

    • Positive half cycle of the carrier

    • Negative half cycle of the carrier

    • Positive half cycle of the modulating signal

    • Negative half cycle of the modulating signal

    Correct Answer
    A. Positive half cycle of the carrier
    Explanation
    In frequency modulation (FM), the output of the oscillator increases in frequency with each positive half cycle of the carrier. This means that as the carrier wave goes through its positive half cycle, the frequency of the oscillator increases. This change in frequency is what carries the information in FM modulation.

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  • 9. 

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

    • 1

    • 3

    • 10

    • 0.1

    Correct Answer
    A. 1
    Explanation
    In frequency modulation, a significant sideband contains at least 1% of the total transmitted power. This means that when a signal is modulated in frequency, at least 1% of the power is distributed in the sidebands that are created around the carrier frequency. These sidebands contain the information being transmitted and are important for the receiver to demodulate the signal accurately.

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  • 10. 

    (003) What is the formula to find the modulating index?

    • Deviation divided by frequency of modulation

    • Deviation times frequency of modulation

    • Sideband divide by carrier frequency

    • Sideband times carrier frequency

    Correct Answer
    A. Deviation divided by frequency of modulation
    Explanation
    The modulating index is the ratio of the frequency deviation (the difference between the carrier frequency and the highest frequency in the modulating signal) to the frequency of modulation (the frequency of the modulating signal). Therefore, the formula to find the modulating index is deviation divided by frequency of modulation.

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  • 11. 

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

    • 5

    • 0.5

    • 0.3

    • 3

    Correct Answer
    A. 3
    Explanation
    The modulation index is a measure of the extent of frequency deviation in a modulated signal. In this question, the modulating signal has a frequency of 5 kHz and it causes a deviation of 15 kHz. The modulation index can be calculated by dividing the peak frequency deviation by the modulating signal frequency. Therefore, the modulation index in this case would be 15 kHz / 5 kHz = 3.

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  • 12. 

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

    • Space

    • Guard band

    • Buffer zone

    • Prevention field

    Correct Answer
    A. Guard band
    Explanation
    A guard band is a narrow frequency band that is used to prevent frequency modulated sidebands from overlapping between adjacent stations. It acts as a buffer zone, ensuring that there is enough space between the frequencies of different stations to avoid interference and maintain clear communication. This helps to prevent signal distortion and maintain the integrity of the transmitted information.

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  • 13. 

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

    • Frequency

    • Amplitude

    • Height

    • Phase

    Correct Answer
    A. Phase
    Explanation
    In phase modulation, the part of the carrier signal that is varied is the phase. This means that the timing of the carrier signal is altered, resulting in a change in the position of the signal on the waveform. The amplitude and frequency of the carrier signal remain constant, but the phase is adjusted to encode the information being transmitted.

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  • 14. 

    (004) In phase modulation, the carrier's

    • Phase is shifted at the rate of the modulating signal

    • Phase shifted with the phase of the modulating signal

    • Amplitude is shifted at the rate of the modulating signal

    • Amplitude is shifted with the phase of the modulating signal

    Correct Answer
    A. Phase is shifted at the rate of the modulating signal
    Explanation
    In phase modulation, the phase of the carrier signal is shifted at the rate of the modulating signal. This means that the instantaneous phase of the carrier signal is varied in accordance with the changing amplitude of the modulating signal. As the modulating signal changes, the phase of the carrier signal also changes, resulting in a phase-shifted carrier signal. This phase shift is what carries the information of the modulating signal.

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  • 15. 

    (005) What is the first step in the pulse code modulation process?

    • Discrete amplitudes are assigned to the sampling pulses.

    • A binary code number is assigned to the sample

    • The quantizer limits the amplitude of the pulses

    • The analog signal is band limited.

    Correct Answer
    A. The analog signal is band limited.
    Explanation
    In pulse code modulation (PCM), the first step is to band limit the analog signal. Band limiting involves restricting the frequency range of the analog signal to prevent aliasing and ensure accurate representation in the digital domain. This is done by applying a low-pass filter to remove any high-frequency components that are beyond the Nyquist limit. By band limiting the analog signal, it becomes suitable for the subsequent steps of sampling, quantization, and encoding into binary code numbers.

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  • 16. 

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

    • Sampling

    • Rectifying

    • Oscillating

    • Band limiting

    Correct Answer
    A. Sampling
    Explanation
    Sampling is the part of the pulse code modulation process that converts a continuous time signal into a discrete time signal. In this process, the continuous signal is sampled at regular intervals to obtain a series of discrete samples. These samples represent the amplitude of the original signal at specific time points. By converting the continuous signal into discrete samples, it becomes easier to process, transmit, and store the signal digitally.

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  • 17. 

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

    • Control

    • Parity

    • Start

    • Stop

    Correct Answer
    A. Parity
    Explanation
    Parity bit is used in asynchronous transmissions to verify the accuracy of the received data. It is an extra bit added to the data being transmitted that helps in error detection. The receiving device checks the parity bit to determine if any errors occurred during transmission. If the parity bit does not match the expected value, it indicates that an error has occurred. Therefore, the correct answer is Parity.

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  • 18. 

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

    • One character

    • Block of data

    • A parity bit

    • A stop bit

    Correct Answer
    A. Block of data
    Explanation
    In synchronous transmission, data is transmitted in blocks. Each block of data consists of multiple characters. If an error occurs during transmission, it means that the entire block of data is lost, not just one character. Therefore, the correct answer is "Block of data".

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  • 19. 

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

    • Determines parity

    • Determines transmission rate

    • Determines whether transmission is in ASCII format

    • Determines whether transmission is synchronous or asynchronous

    Correct Answer
    A. Determines parity
    Explanation
    The amount of ones in a data bit pattern determines the parity. Parity is a form of error checking in which an extra bit is added to the data to ensure that the number of ones in the pattern is either even (even parity) or odd (odd parity). This allows the receiver to detect if any errors occurred during transmission by comparing the received parity bit with the calculated parity. If the number of ones in the received pattern does not match the expected parity, an error is detected. Therefore, the amount of ones in the data bit pattern is significant in determining the parity.

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  • 20. 

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

    • Checksum

    • Cyclic redundancy check

    • Vertical redundancy check

    • Longitudinal redundancy check

    Correct Answer
    A. Cyclic redundancy check
    Explanation
    Cyclic redundancy check (CRC) is an error detection method used for checking a data block greater than 512 and is about 99 percent effective in most applications. CRC involves dividing the data block by a predetermined divisor and appending the remainder as a checksum to the original data. Upon receiving the data, the recipient performs the same division and compares the remainder with the received checksum. If they match, it is highly likely that the data has been transmitted correctly. CRC is widely used in various communication protocols to ensure data integrity.

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  • 21. 

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

    • Receiving end

    • In the oscillator

    • Transmitting end

    • In the primary buffers

    Correct Answer
    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 by the receiving device before the data is processed or displayed. The receiving end analyzes the received data and uses error correction techniques to correct any errors that may have occurred during transmission.

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  • 22. 

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

    • Photo transistors

    • Hybrid photodiodes

    • Semiconductor laser diodes

    • Integrated photodiode/preamplifiers

    Correct Answer
    A. Semiconductor laser diodes
    Explanation
    Semiconductor laser diodes are applicable to fiber optic waveguides because they can emit light that is coherent and focused, allowing for efficient transmission through the fiber optic cables. Unlike light-emitting diodes (LEDs), which emit incoherent light, semiconductor laser diodes produce a single wavelength of light that can be easily coupled into the fiber optic waveguide. This makes them ideal for long-distance communication and high-speed data transmission applications. Photo transistors, hybrid photodiodes, and integrated photodiode/preamplifiers are not typically used as light sources in fiber optic waveguides.

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  • 23. 

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

    • Incoherent

    • Coherent

    • Ordinary

    • Invisible

    Correct Answer
    A. Coherent
    Explanation
    A laser emits coherent light. Coherent light is characterized by its waves having a constant phase relationship with each other, meaning that the peaks and troughs of the waves align perfectly. This results in a concentrated, focused beam of light that is highly directional and has a single wavelength. Unlike ordinary light sources, such as a light bulb, which emit incoherent light with random phase relationships, lasers produce a highly organized and synchronized light beam.

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  • 24. 

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

    • Positive intrinsic negative and avalanche photodiode

    • Light-emitting diode and avalanche photodiode

    • Light emitting diode and semiconductor laser

    • Tunnel and zener diodes

    Correct Answer
    A. Positive intrinsic negative and avalanche photodiode
    Explanation
    The correct answer is positive intrinsic negative and avalanche photodiode. Photodetectors are devices that convert light energy into electrical signals. Positive intrinsic negative (PIN) photodiodes are widely used in optical communication systems due to their high sensitivity and low noise characteristics. Avalanche photodiodes (APDs) are also commonly used in applications that require high gain and high-speed detection. These two types of photodetectors are essential in various fields such as telecommunications, imaging, and sensing.

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  • 25. 

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

    • Light emitting diode

    • Avalanche photodiode

    • Positive intrinsic negative diode

    • Integrated photodiode/preamplifier

    Correct Answer
    A. Positive intrinsic negative diode
    Explanation
    A positive intrinsic negative (PIN) diode is a type of photo detector that converts one photon to one electron. It is designed to have a high sensitivity to light and is commonly used in applications such as optical communication systems and photovoltaic devices. The other options mentioned in the question, such as light emitting diode, avalanche photodiode, and integrated photodiode/preamplifier, do not specifically convert one photon to one electron.

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  • 26. 

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

    • Receiver

    • Repeater

    • Regenerators

    • Optical amplifiers

    Correct Answer
    A. Optical amplifiers
    Explanation
    Optical amplifiers are devices that enhance the strength of an optical signal without converting it to an electrical signal. They use a process called stimulated emission to amplify the signal directly in the optical domain. This allows for long-distance transmission of optical signals without the need for frequent conversion to and from electrical signals. Unlike repeaters, which regenerate and reshape the electrical signal, optical amplifiers solely focus on amplifying the optical signal, making them more efficient and cost-effective for optical communication systems.

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  • 27. 

    (011) A short section of single fiber cable that has a connector at each end is called a

    • Pigtail

    • Jumper

    • Patch cord

    • Breakout cables

    Correct Answer
    A. Patch cord
    Explanation
    A short section of single fiber cable that has a connector at each end is called a patch cord. A patch cord is used to connect devices or components together in a network or telecommunications system. It provides a temporary or permanent connection and allows for easy installation, maintenance, and reconfiguration of the network.

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  • 28. 

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

    • Biconic

    • Field (FC)

    • Straight tip (ST)

    • Sub-miniature, type A (SMA)

    Correct Answer
    A. Straight tip (ST)
    Explanation
    The Straight tip (ST) fiber-optic connector uses quick-release, keyed bayonet couplings that are preferred in situations where severe vibrations are not expected. This type of connector provides a secure and reliable connection, but it may not be suitable for environments with high levels of vibrations that could potentially loosen the connection. Therefore, in situations where severe vibrations are not expected, the ST connector is a suitable choice.

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  • Current Version
  • Mar 08, 2024
    Quiz Edited by
    ProProfs Editorial Team
  • Jan 12, 2017
    Quiz Created by
    David

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