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NCTI MT1 MT2 AND NCTI MT2 MT
EXAMS REAL EXAMS QUESTIONS
AND ANSWERS | LATEST VERSIONS
(2024) | VERIFIED ANSWERS |
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Across 6 MHz, what is the maximum in- channel frequency response (ICFR) defined in the Data Over Cable Service Interface Specification (DOCSIS)? ------CORRECT ANSWER--------------3.0 dB peak-to-valley (P/N). When sweeping the upstream return path in a hybrid fiber coax (HFC) network, where are the upstream levels and sweep responses measured? - -----CORRECT ANSWER--------------The Headend. Even though the downstream sweep test pulses are intended to fit in the narrow frequency band between channels, what parameter can cause interference if set too high? ------CORRECT ANSWER--------------Sweep test pulse amplitude. What does a normalized reference trace from a fiber-node test point eliminate from the sweep process? ------CORRECT ANSWER-------------- Slope response variations of the Headend and optical transport. How must a directional test point be installed in an amplifier to enable insertion of upstream sweep pulses and view the downstream sweep? ------ CORRECT ANSWER--------------In a path common to the downstream and upstream.
What could cause low-frequency roll-off of the downstream spectrum discovered when sweeping an amplifier? ------CORRECT ANSWER---------- ----A loose seizure screw in the downstream path. When standing waves are displayed in the sweep response, what does the frequency separation between response peaks indicate? ------CORRECT ANSWER--------------The approximate distance from the test point to the fault. What do normalized reference traces taken at a fiber-node test point establish? ------CORRECT ANSWER--------------Baseline sweep responses that are used to balance and sweep all the amplifiers serviced by that fiber- node. Why is the main downstream output/upstream input port of a distribution amplifier typically the first to be swept in the downstream direction? ------ CORRECT ANSWER--------------To select equalizers and set the output amplitude levels. If the power out of a transformer must equal the power in, assuming zero efficiency loss, what happens to the output current when the transformed output voltage is 10% lower? ------CORRECT ANSWER--------------The current increases 10%. What is the voltage on the secondary of a transformer if the number of secondary windings is 25% of the primary windings? ------CORRECT ANSWER--------------25% of the voltage on the transformer's primary.
In a basic step-up switcher circuit design, what is the relationship of the square- wave duty cycle to the output voltage? ------CORRECT ANSWER-- ------------The larger the duty cycle, the higher the voltage. What characteristic of a ferroresonant power supply provides voltage regulation as the source voltage changes? ------CORRECT ANSWER-------- ------With the flux in the core saturated, then the secondary voltage remains constant as the primary voltage changes. What enables set-top boxes (STB) and Data Over Cable Service Interface Specification (DOCSIS) modems to operate as completely separate systems that operate independent of each other? ------CORRECT ANSWER--------------STB and DOCSIS modems are assigned different upstream channels with dedicated receivers in the headend. What did the 1.1 version of the Data Over Cable Service Interface Specification (DOCSIS) introduce, incorporating solutions for transporting real-time data applications (such as voice traffic) over the cable operator's managed IP network, and doing so with quality comparable to that of the telephone company? ------CORRECT ANSWER--------------PacketCable. According to SCTE- and NCTA- recommended trunk system map symbols, fiber-optic cable is represented by ------CORRECT ANSWER-------------- Double arrows within a small circle on a solid line. The forward path signal in a traditional tree-and-branch architecture ------ CORRECT ANSWER--------------originates at the headend and is transmitted downstream through coaxial trunk cable and trunk amplifier.
In a HFC network, ------CORRECT ANSWER--------------Processing equipment in the headend converts the forward RF signal to a light signal. During aerial plant construction, ------CORRECT ANSWER--------------The strand is tensioned so its sag profile matches that of the overhead utility power lines. With underground plant construction, ------CORRECT ANSWER-------------- The fiber-optic and coaxial cables are often places underground with other utility lines to jointly share construction costs. Standby power supplies ------CORRECT ANSWER--------------continue providing an output voltage even during a utility power outage by using a back up power source. Centralized power configurations ------CORRECT ANSWER-------------- provide the advantage of increased reliability through sharing of expensive backup generators and sophisticated monitoring equipment among different power realms. When transmitting broadband signals ------CORRECT ANSWER-------------- In a two way hybrid fiber/coax (HFC) network, two or more individual optical fibers are required for each optical node location.
If a large signal leak is found in the aerial plant, what is a good first step in locating the leak? ------CORRECT ANSWER--------------Drive around until an absolute peak is found. Which of the following best describes demand maintenance procedures with regard to signal leakage? ------CORRECT ANSWER--------------The demand maintenance procedures can improve the CLI measurement results by identifying and correcting the largest leaks first. When troubleshooting signal leakage in the drop system, what is indicated if all signs of signal leakage disappear when the ground block is disconnected and terminated on the side connected to the customer premises? ------CORRECT ANSWER--------------The backward route from the ground block to the tap can be eliminated as a source of The backward route from the ground block to the tap can be eliminated as source of leakage. Which typical over-the-air signal sources can cause a false alarm with a signal leakage detector? ------CORRECT ANSWER--------------Typical sources include aircraft communication signals and ham, mobile, and government radio broadcasts. When adjusting or selecting the elements of a dipole antenna for measuring signal leakage, what is the approximate length of each element relative to the wavelength of the signal being measured? ------CORRECT ANSWER--------------One-quarter wavelength.
Which of the following problem(s) are caused by egress? ------CORRECT ANSWER--------------Interference with aeronautieal navigation and communication, amateur radio public service, and cellular communications. What cumulative leakage index (CLI) meets Federal Communications Commission (FCC) requirements? ------CORRECT ANSWER-------------- 64 or less What is the maximum allowable signal detectable in the airspace during a flyover? ------CORRECT ANSWER--------------10 uv/m. CLI calculations do not include leakage below: ------CORRECT ANSWER--- -----------50 uv/m. Which of the following is a repair order specification when measuring leakage levels? ------CORRECT ANSWER--------------The location of the leak. What is the FCC specification regarding repair of leakage of the 20 uv/m level?. ------CORRECT ANSWER--------------There is no FCC specified time. A dipole antenna is used for FCC tests because: ------CORRECT ANSWER--------------Its performance is well characterized.
What system is a byproduct of the "funneling effect"? ------CORRECT ANSWER--------------A many-to-one system. House amplifiers with a passive return path are used for what type of situation? ------CORRECT ANSWER--------------For situations when long service drops are used and the forward path needs to be amplified but return path amplification is unnecessary. Why does the output level from customer premises equipment (CPE) vary? ------CORRECT ANSWER--------------To compensate for variable amounts of attenuation in the return path of each device. When calculating return path attenuation in the drop system, what is the attenuation loss through the hot-leg of an unbalanced three-way splitter at sub- split frequencies? ------CORRECT ANSWER--------------3.5 dB. What purpose do diplex filters fulfill when installed at the input and output of a two- way amplifier module? ------CORRECT ANSWER--------------To route the forward and return signals over different circuit paths to the appropriate section so that they can be amplified separately. How does the signal attenuation through coaxial cable in the sub-band frequency spectrum compare to the attenuation at forward path frequencies? ------CORRECT ANSWER--------------At sub-band frequencies, the signal attenuation is significantly less than in the forward path. What recourse do broadband cable operators have if citizens band (CB) and ham radio signals ingress into their network? ------CORRECT
ANSWER--------------None, as long as the radio transmissions are at or below legal power levels, it is the cable operator's obligation to prevent these signals from entering their network. How is impulse noise characterized when viewed on a spectrum analyzer? ------CORRECT ANSWER--------------Impulse noise will appear as random spikes of energy across the entire return path frequency spectrum (5 to 42 MHz). How can the amount of thermal noise added to a network be minimized? --- ---CORRECT ANSWER--------------By ensuring that the RF input is at or above the specified minimum input level to all amplifiers.. What location in the network is common path distortion (CPD) most severe? ------CORRECT ANSWER--------------At the output of a forward amplifier because the forward levels are highest and the return levels are lowest. What distinguishes a micro-reflection from other types of signal reflections? ------CORRECT ANSWER--------------In micro-reflections, the echoed signals arrive back at the source with a time delay relative to the incident or transmitted signal, ranging from nanoseconds (ns) to few microseconds (us). What are the symptoms of hum on an upstream digital modulation channel? ------CORRECT ANSWER--------------Bit errors occur, similar to impulse noise and ingress on the upstream path.
What should be done when the location of electrical interference in the power network is identified? ------CORRECT ANSWER--------------Notify the power company with the exact location so the cause of the interference can be repaired. What can be used with a signal level meter (SLM) to check the drop system for RF continuity at sub-band frequencies? ------CORRECT ANSWER-------- ------A signal generator What information can be gathered by a return path monitoring system that captures the quadrature amplitude modulation (QAM) return channel from a DOCSIS modem? ------CORRECT ANSWER--------------The group delay, in-band ripple/tilt, and micro-reflections on the QAM channel. What feature of DOCSIS proactive network maintenance (PNM) can save the technician hours of troubleshooting? ------CORRECT ANSWER----------- ---PNM peforms correlation of data from all the modems in an area to pinpoint where the likely problem in the network can be found. When should a preamplifier be used to measure impairments with a spectrum analyzer? ------CORRECT ANSWER--------------If the noise floor drops less than 10 dB when the input signal is removed from the spectrum analyzer. What does the spectrum analyzer Zero Span function do? ------CORRECT ANSWER--------------The Zero Span function stops the analyzer's sweep and parks its tuner to a specific frequency, displaying amplitude vs. time
How is laser clipping in the return path characterized on a spectrum analyzer? ------CORRECT ANSWER--------------By an elevated noise floor above 42 MHz after the optical signal has been converted back to RF typically in the headend. If a return path impairment appears to be caused by impulse noise, why is it a good idea to begin troubleshooting at distribution taps of 17 dB or lower? ------CORRECT ANSWER--------------Low value taps have less isolation between ports and offer less attenuation to ingress and impulse noise coming from an individual drop system. What amplitude level should the output of return amplifiers be adjusted? ---- --CORRECT ANSWER--------------So that the amplifier gain is equal to the path attenuation that follows the amplifier. What should be checked if a large percentage of set-top boxes (STB) transmit above 55 dBmV, the upper end of the STB transmission level range? ------CORRECT ANSWER--------------The value of the attenuator pad at the input of the STB demodulator. What type of measurement removes any errors attributable to bandwidth and provides an "apples-to-apples" comparison between carriers of differing bandwidths? ------CORRECT ANSWER--------------The constant power per hertz (power/H2) measurement. Why are RF return channel carriers unusable for aligning return path equipment? ------CORRECT ANSWER--------------RF return channel carriers are of short duration and from multiple sources.
Equalizers come in 2 dB increments and attenuator pads in dB increments? ------CORRECT ANSWER--------------A O dB equalizer, and 3 dB attenuator pad. ( 3.2-2.5=.7) Which type of digital modulation contains four symbols with 2 bits in each symbol? ------CORRECT ANSWER--------------Quadrature phase shift keying (QPSK), decimal values can eight bits How many of data represent? ------CORRECT ANSWER-------------- 256 What is a characteristic of orthogonal frequency division multiplexing (OFDM) channel subcarriers? ------CORRECT ANSWER--------------They can be modulated at the maximum order of modulation for a given bandwidth that is suitable for the condition of the network. What media access control (MAC) protocols are specified for digital set-top boxes (STB)? ------CORRECT ANSWER--------------ALOHA and time division multiple access (TDMA). Which advanced Physical Layer (PHY) technology developed and added to DOCSIS 2.0 includes byte interleaving? ------CORRECT ANSWER----------- ---Advanced time division multiple access (A TDMA). Chipsets with ingress cancellation algorithms are most effective for removing impairments in what portion of the RF return frequency spectrum? ------CORRECT ANSWER--------------Within the upstream channel bandwidth
The code words and spreading algorithm of synchronous code division multiple access (S-CDMA) enable simultaneous transmission of up to how many modems on the same RF return channel? ------CORRECT ANSWER- ------------- 128 What happens to the data throughput when transitioning from quadrature phase shift keying (QPSK) to 16-QAM (quadrature amplitude modulation) in a channel of the same bandwidth? ------CORRECT ANSWER-------------- The data throughput doubles. What access schemes were introduced with advanced Physical (PHY) Layer technologies in DOCSIS 2.0? ------CORRECT ANSWER-------------- Advanced time division multiple access (A-TDMA) and synchronous code division multiple access (S CDMA). In a DOCSIS 3.1 orthogonal frequency division multiple access (OFDMA) upstream channel, the average power of the subcarriers are normalized to what bandwidth? ------CORRECT ANSWER--------------1.6 MHz. Which optical band is used for optical amplifiers due to the attenuation loss and availability of economical optical amplifiers? ------CORRECT ANSWER--------------The C band. What is one limitation of Fabry-Perot (FP) lasers that is eliminated in distributed feedback (DFB) lasers? ------CORRECT ANSWER-------------- Side modes
What evolved after the introduction of switched digital video (SDV) illustrated some limitations of legacy hybrid fiber coax (HFC) networks? -----
- CORRECT ANSWER--------------Distributed access architecture (DAA) What is it necessary in the optical return path to get the most performance from the DOCSIS 3.1 specification? ------CORRECT ANSWER-------------- Some combination of higher transmit power, more sensitive receivers, and lower path loss. The proper calibration of test equipment is necessary to ensure accurate measurements. Calibration must be performed using test equipment and signals whose accuracy is validated and traceable to what agency? ------ CORRECT ANSWER--------------The National Institute of Standards and Technology (NIST). Specific test equipment is necessary to complete proof-of-performance (POP) tests in the headend. Which piece of test equipment is used for headend POP measurements? ------CORRECT ANSWER--------------A waveform monitor. Which calibration is acceptable for FCC proof-of-performance (POP) testing? ------CORRECT ANSWER--------------By the manufacturer or approved service center. Why is the use of spreadsheets to detail proof-of-performance test procedures recommended? ------CORRECT ANSWER--------------Because of the calculations required.
What must occur in a video signal in order to observe the composite triple beat (CBT) on a spectrum analyzer? ------CORRECT ANSWER-------------- The signal must be turned off The number of field test points for proof- of-performance tests depends on: ------CORRECT ANSWER--------------The number of customers, To minimize the burden on small cable operators, FCC proof-of- performance (POP) testing is required in systems having a minimum of how many customers? ------CORRECT ANSWER--------------1, Where should at least one proof-of- performance test point be located? -----
- CORRECT ANSWER--------------At the end of the longest cascade, What guidelines does the FCC specify for how the proof-of-performance (POP) tests are performed? ------CORRECT ANSWER--------------Proof of good engineering practices and that test procedures are documented When performing proof-of-performance (POP) testing, why should a bandpass filter be used during the video signal to coherent beats test? ------ CORRECT ANSWER--------------To eliminate interference generated by the spectrum analyzer itself.
