Z3D153 - 2016 Edit Code 3, Volume 1 Part 3
RF Transmissions Journeyman CDCs. Split up 20 questions at a time.
Questions and Answers
- 1.
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.
Correct Answer
C. 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 represent 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 modulation techniques are widely used in RF transmission to encode and transmit data.Rate this question:
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- 2.
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.
Correct Answer
B. 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 along with the upper sideband and lower sideband. The upper sideband is the frequency range above the carrier frequency, while the lower sideband is the frequency range below the carrier frequency. This is a result of the modulation process where the modulating signal alters the amplitude, frequency, or phase of the carrier signal, creating these additional frequency components in the output signal.Rate this question:
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- 3.
What factor determines the spacing of the sidebands in an amplitude modulated signal?
- A.
Amplitude of the modulating signal.
- B.
Frequency of the modulating signal.
- C.
Amplitude of the carrier signal.
- D.
Frequency of the carrier signal.
Correct Answer
B. Frequency of the modulating signal.Explanation
The spacing of the sidebands in an amplitude modulated signal is determined by the frequency of the modulating signal. In amplitude modulation, the modulating signal is superimposed onto the carrier signal, resulting in the creation of sidebands. These sidebands are located above and below the carrier frequency, and their spacing is directly proportional to the frequency of the modulating signal. Therefore, the higher the frequency of the modulating signal, the wider the spacing between the sidebands.Rate this question:
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- 4.
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.
Correct Answer
A. Percent of modulation.Explanation
The amount of effect or change that the intelligence has on the carrier in an amplitude modulated signal is expressed as the percent of modulation. This refers to the percentage of variation in the amplitude of the carrier signal caused by the modulation. It indicates the strength or intensity of the modulating signal and how much it influences the carrier signal. The higher the percent of modulation, the greater the impact of the modulating signal on the carrier signal.Rate this question:
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- 5.
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.
Correct Answer
C. No reduction in carrier power.Explanation
When modulation is reduced to less than 100 percent, it means that the amplitude of the carrier signal is not fully varied. In this case, the carrier power remains constant and does not decrease. The reduction in modulation only affects the sideband power, which is the power carried by the frequency components surrounding the carrier signal. Therefore, the correct answer is that there is no reduction in carrier power.Rate this question:
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- 6.
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.
Correct Answer
C. Positive half cycle of the modulating signal.Explanation
In frequency modulation (FM), the output of the oscillator increases in frequency with each positive half cycle of the modulating signal. This means that as the amplitude of the modulating signal increases during the positive half cycle, the frequency of the oscillator also increases. This results in a change in the frequency of the carrier signal, which is the basis of FM modulation.Rate this question:
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- 7.
A 5 kilohertz (kHz) modulating signal has enough peak voltage to cause a deviation of 15kHz. What is the modulation index?
- A.
5.
- B.
3.
- C.
0.5.
- D.
0.3.
Correct Answer
B. 3.Explanation
The modulation index is a measure of the extent of modulation in a signal. It is calculated by dividing the peak frequency deviation by the modulating signal frequency. In this case, the modulating signal frequency is 5 kHz and the peak frequency deviation is 15 kHz. Therefore, the modulation index is 15 kHz / 5 kHz = 3. This means that the modulating signal is causing a frequency deviation that is three times its own frequency.Rate this question:
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- 8.
What is the narrow frequency band between adjacent stations used to prevent frequency modulated sidebands from overlapping?
- A.
Space.
- B.
Guard band.
- C.
Buffer zone.
- D.
Prevention field.
Correct Answer
B. Guard band.Explanation
A guard band is a narrow frequency band that is used to prevent frequency modulated sidebands from overlapping. It acts as a buffer zone between adjacent stations, ensuring that there is no interference or signal overlap. By allocating a specific frequency range as a guard band, it helps maintain the integrity and clarity of the signals transmitted by different stations.Rate this question:
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- 9.
What is the advantage of adding more phase shifts?
- A.
Easier detection.
- B.
Smaller bit error rate.
- C.
Better signal-to-noise ratio.
- D.
Higher data rates within a given bandwidth.
Correct Answer
D. Higher data rates within a given bandwidth.Explanation
By adding more phase shifts, it allows for a larger number of distinct symbols to be transmitted within a given bandwidth. This means that more information can be transmitted per unit of time, resulting in higher data rates. This advantage is especially important in scenarios where there is limited bandwidth available, as it allows for more efficient use of the available resources.Rate this question:
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- 10.
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.
Correct Answer
D. The analog signal is band limited.Explanation
The first step in the pulse code modulation process is to band limit the analog signal. This means that the signal is filtered to remove any frequencies outside of a certain range. This is done to ensure that the signal can be accurately represented using discrete amplitudes and binary code numbers. By band limiting the signal, it becomes easier to assign discrete amplitudes to the sampling pulses and to assign binary code numbers to the samples. This is because the band limited signal has a reduced range of frequencies, making it simpler to represent digitally.Rate this question:
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- 11.
Quantization in the pulse code modulation process is
- A.
Converting a continuous time signal into a discrete time signal.
- B.
Ensuring the input to the sampler never exceeds maximum frequency.
- C.
Placing an infinite number of amplitude values to a finite number of values.
- D.
Limiting the highest and lowest frequency encoded before it goes to the sampler.
Correct Answer
C. Placing an infinite number of amplitude values to a finite number of values.Explanation
Quantization in the pulse code modulation process involves placing an infinite number of amplitude values to a finite number of values. This means that the continuous time signal is approximated by assigning discrete amplitude values to represent different levels of the signal. This allows for the efficient encoding and transmission of the signal while still maintaining a reasonable level of accuracy.Rate this question:
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- 12.
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.
Correct Answer
B. Parity.Explanation
Parity is used by the receiving device in asynchronous transmissions to verify that the transmission was received correctly. Parity is a simple error-checking technique that involves adding an extra bit to each transmitted byte. The value of this extra bit is determined based on the number of 1s in the byte. When the receiving device receives the byte, it counts the number of 1s and compares it to the value of the parity bit. If they match, it indicates that the transmission was received correctly.Rate this question:
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- 13.
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.
Correct Answer
B. Block of data.Explanation
In synchronous transmission, data is transmitted in blocks. Each block of data includes multiple characters, which are composed of several bits. If an error occurs during transmission, it is possible for an entire block of data to be lost. Therefore, the correct answer is "Block of data."Rate this question:
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- 14.
The significance the amount of ones have in a data bit pattern when using vertical redundancy check (VRC) is that it determines
- A.
Parity.
- B.
Transmission rate.
- C.
Whether transmission is synchronous or asynchronous.
- D.
Whether transmission is in American Standard Code for Information Interchange (ASCII) format.
Correct Answer
A. Parity.Explanation
The significance of the amount of ones in a data bit pattern when using vertical redundancy check (VRC) is that it determines the parity. Parity refers to the number of ones in a data bit pattern. VRC is a simple method of error detection in which an additional bit, called the parity bit, is added to the data. The parity bit is set to 1 or 0 in a way that ensures the total number of ones (including the parity bit) is always even or odd. By checking the parity bit, errors in transmission can be detected.Rate this question:
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- 15.
What two error detection methods, when used together, are 98 percent effective in detecting errors?
- A.
Longitudinal redundancy check (LRC) and checksum.
- B.
Checksum and cyclic redundancy check (CRC).
- C.
Vertical redundancy check (VRC) and CRC.
- D.
VRC and LRC.
Correct Answer
D. VRC and LRC.Explanation
The VRC (Vertical Redundancy Check) and LRC (Longitudinal Redundancy Check) methods, when used together, are 98 percent effective in detecting errors. The VRC is a simple parity check that adds an extra bit to each character to ensure the total number of 1s is either even or odd. The LRC is a more complex method that generates a parity bit for each character and then adds all the parity bits together. By combining these two methods, a high level of error detection can be achieved.Rate this question:
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- 16.
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.
Correct Answer
A. Receiving end.Explanation
When using forward error control as a method of error correction, error correction takes place at the receiving end. This means that the receiver is responsible for detecting and correcting errors that may have occurred during the transmission of data. By implementing forward error control at the receiving end, any errors that are detected can be corrected before the data is processed or displayed, ensuring the accuracy and integrity of the received information.Rate this question:
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- 17.
In telecommunications cable, the “tip” or “primary” wire color group order is
- A.
White, blue, green, yellow, and violet.
- B.
Blue, orange, green, brown, and slate.
- C.
White, red, black, yellow, and violet.
- D.
Blue, green, yellow, red, and orange.
Correct Answer
C. White, red, black, yellow, and violet.Explanation
The correct answer is white, red, black, yellow, and violet. This is the correct order for the "tip" or "primary" wire color group in telecommunications cable. The colors blue, green, red, and orange are not part of the correct order.Rate this question:
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- 18.
Two types of network cables are
- A.
Straight through and crossover.
- B.
Straight through and flip/flop.
- C.
High and low baud.
- D.
“n” and “g”.
Correct Answer
A. Straight through and crossover.Explanation
The correct answer is straight through and crossover. Straight through cables are used to connect different types of devices, such as a computer to a switch or a router to a modem. The wires in these cables are connected in the same order on both ends. On the other hand, crossover cables are used to connect similar devices, such as a computer to another computer or a switch to another switch. In crossover cables, the wires are crossed over, so that the transmit and receive signals can be properly exchanged between the devices.Rate this question:
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- 19.
An optical transmitter is comprised of
- A.
Positive intrinsic negative and avalanche photodiodes.
- B.
Repeaters, regenerators, and optical amplifiers.
- C.
A driver, optical source, and fiber optic pigtail.
- D.
A light detector and output circuits.
Correct Answer
C. A driver, optical source, and fiber optic pigtail.Explanation
The correct answer is a driver, optical source, and fiber optic pigtail. An optical transmitter is a device that converts electrical signals into optical signals for transmission over fiber optic cables. The driver is responsible for converting the electrical signal into a format suitable for the optical source, which generates the optical signal. The fiber optic pigtail is used to connect the optical source to the fiber optic cable, allowing the optical signal to be transmitted.Rate this question:
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- 20.
What is the bandwidth of multimode step-index optical fiber cable?
- A.
10 MHz – 100 MHz/km.
- B.
100 MHz – 200 MHz/km.
- C.
200 MHz – 1000 MHz/km.
- D.
Up to 50 GHz/km.
Correct Answer
A. 10 MHz – 100 MHz/km.Explanation
Multimode step-index optical fiber cable has a bandwidth of 10 MHz – 100 MHz/km. This means that it is capable of transmitting data at frequencies ranging from 10 MHz to 100 MHz per kilometer of cable. The bandwidth determines the amount of data that can be transmitted over the cable, with higher bandwidths allowing for faster data transmission.Rate this question:
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Mar 21, 2023Quiz Edited by
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Nov 30, 2017Quiz Created by
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