Progression: Maintenance Tech I - II Conventional Exam with 100% Correct Answers 2023

In the tree-and-branch architecture, how is the downstream signal from the trunk fed to the distribution branches? - Correct answer-Within each trunk amplifier, a portion of the downstream is fed to a bridger amplifier to boost the signal before being split and routed to the distribution branches. What is a common solution when congestion from modem activity and traffic becomes unacceptable in a hybrid fiber/coax (HFC) network? - Correct answer-Node splitting, the subdividing of serving areas into two or more smaller serving areas. What technologies are defined in DOCSIS 4.0 to help sustain the hybrid fiber/coax (HFC) network infrastructure for several more years? - Correct answer-Full Duplex DOCSIS (FDX) and Extended Spectrum DOCSIS (ESD). How can a less-experienced technician identify what non-standard symbols on the network design maps represent? - Correct answer-The legend at the bottom of the network design map that defines the map symbols, cable types, and amplifier data. What is the RF distribution tap value indicated on the tap face plate by a sticker or number stamped into the housing? - Correct answer-The signal loss between the tap downstream input port and the tap ports. How can a distribution amplifier be identified in the network or on a network design map? - Correct answer-The distribution amplifier has multiple downstream outputs. What is spliced into the hardline coaxial cable to combine the AC power with the transported RF signal in a hybrid fiber/coax (HFC) network? - Correct answer-A power inserter. What test instrument sends out a test signal and displays any reflections caused by impedance mismatches in the cable that are characteristic of cable faults? - Correct answer-Time domain reflectometer (TDR) What should you be looking for when analyzing the network design maps to troubleshoot a problem? - Correct answer-The device common to those customers affected before traveling to make signal status checks. What is required for checking the physical network integrity when maintaining the coaxial cable network? - Correct answer-Being observant and performing some minor tasks while engaged in regularly scheduled activities. Which of the following problem(s) are caused by egress from a hybrid fiber/coax (HFC) network? - Correct answer-Interference with aeronautical navigation and communication, amateur radio, public service, and cellular communications. What leakage level must be entered in the leakage log? - Correct answer-Leaks 20 microvolts per meter (μV/m) or higher measured 10 feet from the cable. Which is a benefit of an aggressive signal leakage policy? - Correct answer-Decreased ingress-related service calls. What is done for leak measuring 1.25 microvolts per meter (μV/m) from about 160 feet away from the coaxial cable network? - Correct answer-The leak level is likely 20 μV/m or higher when measured 10 feet from the cable and must be fixed and recorded in the leakage log. If the leakage detector indicates there is a leak and displays a reading of 14 microvolts per meter (uV/m) measured at 80 feet from a possible leak source, what is the approximate calculated level of the leak from 10 feet? - Correct answer-112 uV/m. When using the triangulation technique to find the source of a leak, why is a dipole antenna used? - Correct answer-The dipole antenna is directional and picks up the strongest signal that is at a right angle, or perpendicular to the antenna elements. When trying to find the source of a very strong leakage signal, what should be done? - Correct answer-Reduce the sensitivity of the leakage detector or even remove the antenna and allow the connector alone to pick up the leakage signal. When troubleshooting signal leakage in the drop system, what does it mean 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-Something in the customer premises is the leakage source. According to the Federal Communications Commission (FCC) leakage regulations, what distance must an antenna be from the network for leakage level measurements? - Correct answer-The antenna must be 3 meters (10 feet) from the network elements and 3 meters (10 feet) above the ground. When calculating the network cumulative leakage index (CLI), what is done with leaks that are equal to or greater than 50 microvolts per meter (µVm) measured 10 feet from the network? - Correct answer-The leakage values are squared and then added together, then multiplied times a factor based on how much of the network was tested in 90 days. In modern sweep systems, what type of nonintrusive and noninterfering test signal is inserted into the downstream? - Correct answer-Narrow-band continuous wave (CW) test carriers, called pulses, at frequencies between channels. 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/V). 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 and 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. What advantage is realized by increasing the voltage in a broadband cable network from 60 volts alternating current (VAC) to 90 volts? - Correct answer-Operating with 50% more voltage reduces the voltage drop and current drawn in the network for more efficient power utilization. How does surge protection at the input and output of a ferroresonant power supply defend against voltage surges? - Correct answer-By passing voltage surges (within the surge device rating) to ground without damage. Which part of a ferroresonant transformer regulates the load on the secondary winding? - Correct answer-The magnetic shunt. In a standby network power supply, what comes online to convert the battery voltage to alternating current (AC), which then goes to the ferroresonant transformer? - Correct answer-The battery-powered inverter. In a power inserter with three filtering networks, what is the purpose of the high-pass filter? - Correct answer-To prevent the 60 hertz (Hz) alternating current (AC) from passing between the two radio frequency (RF)/AC ports. What inserts alternating current (AC) into the network with a direct connection to an amplifier rather than using a power inserter? - Correct answer-The amplifier AC circuitry. What is the advantage for supplying alternating current (AC) to multiple amplifiers from one network power supply? - Correct answer-Allows the designer to place amplifiers without concern about access to electrical utility power. Where is a clamp-on ammeter attached to measure the output current from a network power supply? - Correct answer-Clamped around the conductor attached to the lug that tightens down on the coaxial cable connector pin. What is a priority in any standby power supply maintenance program? - Correct answerBattery care. What is the voltage into the second amplifier in cascade, if each amplifier draws 1.5 amps of current, the loop resistance of each section of cable is 1.38 ohms, and the alternating current (AC) source is a 90 volts AC (VAC) network power supply? - Correct answer-83.77 VAC. 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. Why is 38 MHz typically the highest frequency in the sub-band frequency that is used for upstream modem transmissions? - Correct answer-The upper edge of the sub-band frequency spectrum is prone to group delay caused by the diplex filters. What enables the set-top box (STB) upstream carrier to be located below 20 MHz and still be reliably received? - Correct answer-The narrow bandwidth and quadrature phase shift keying (QPSK) modulation. 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 a few microseconds (µs). 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. Why is it imperative to keep all ingress and impulse noise, even that outside the frequency range of the RF return carriers, to a minimum? - Correct answer-Regardless of the frequency, if the impulse noise or ingress is high enough, it can cause laser clipping. When looking at a cable modem's PreEqualization Tap response, what do you know if the ninth bar is less than 10 dB below the eighth bar? - Correct answer-That there are high micro-reflections and that the cause is near the modem, likely in the drop system. What practice can uncover potential return path problems in the drop system that can be mitigated before entering the network? - Correct answer-Prescreening the drop system for ingress or egress. Why is installing high-pass filters (HPF) at the tap on drops without two-way services considered a short-term solution to ingress and impulse noise migrating into the hybrid fiber/coax (HFC) network? - Correct answer-The HPF will have to be removed when cable modems and digital set-top boxes (STB) are activated at the addresses that have an HPF installed. Main Menu2of12 What should be done before diagnosing a return path problem in the drop system? - Correct answer-Confirm that the hybrid fiber/coax (HFC) network is working properly. What spectrum analyzer function is particularly useful as it captures and holds ingress, impulse noise, and other impairments on its display so that they can be viewed and analyzed? - Correct answer-The Max Hold function. 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 performs 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/Hz) 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. Why are 6 MHz and 41 MHz good choices for test carriers when injecting test carriers into a return path spectrum of 5 MHz to 42 MHz? - Correct answer-These frequencies are at the edges of the return frequency spectrum and are available. Where should the injected sweep pulses be placed to avoid interference with active return carriers when sweeping the return path? - Correct answer-Between active return