System Technician Conventional
What does "micro" in micro-reflections denote?
A close-in reflection whose time delay relative to the incident signal ranges from less than a symbol period to perhaps several symbol periods.
In addition to device and network parameters from DOCSIS modems, what information is needed to isolate the source of a problem in the network?
Analysis of the data along with network topology and device location.
Which must be done to create an oscillator if the circuit transistor is in the common emitter configuration?
Another 180-degree phase shift is necessary for positive feedback.
Why are micro-reflections some of the more difficult issues to diagnose?
Because they require physical inspection of the connectors and cable to find.
What spectrum analyzer function can be left on for extended periods of time to capture transient signals and ingress, including intermittent signals that can be difficult to identity?
Max Hold.
What spectrum analyzer function can be used to capture consistent, low-amplitude level signals that interfere with the short-duration return path channels?
Min Hold.
When directly burying coaxial cable,
Avoid reverse bending of the coaxial cable when unreeling the coaxial cable.
What may be required to remove a very large rock from the ground during trenching?
Backhoe
Chapter 12
Chapter 12
Chapter 7
Chapter 7
When standing waves are displayed in the sweep response, what does the frequency separation between response peaks indicate?
The approximate distance from the test point to the fault.
What risk is there in coupling the output of an oscillator to another circuit stage?
The oscillator frequency could be changed (or pulled by) the next circuit stage.
What could cause low-frequency roll-off of the downstream spectrum discovered when sweeping an amplifier?
A loose seizure screw in the downstream path.
When there is reflection indicated by an adaptive equalize, how do test instruments calculate the unknown distance to a reflection?
By dividing the time delay between the reflection and the incident signal by the cable velocity of propagation (VoP) per 100 feet.
Which resonant circuit mode of a crystal should be used in applications in which frequency accuracy is most important?
Series resonant.
A chain trencher
Should be inspected for any loose bolts, broken chain teeth, or any types of fluid leaks before beginning its operation.
What is the benefit of spectrum analyzers capable of automated measurements specifically for broadband cable networks?
Technicians with only basic instructions can obtain accurate measurements.
What is the primary difference between the Hartley and Colpitts oscillator circuits?
The Colpitts oscillator uses capacitive feedback, and the Hartley uses inductive feedback.
Which type of vibratory plow is an attachment to a tractor or trencher and requires a ground person to manually guide the conduit into the feed chute as the plow cuts through the ground?
The modular vibratory plow.
What is the proper method for removing the coaxial cable from its reel for a direct burial operation?
With the reel on an appropriate stand, pull the cable from the bottom of the reel.
What is the expected DC voltage on most hybrid fiber coax (HFC) network equipment?
+24 VDC, ± 0.5 V.
When setting proactive network maintenance (PNM) severity metrics for main tap ratio (MTR), how much level change is typically worthy of attention?
3 dB.
Across 6 MHz, what is the maximum in-channel frequency response (ICFR) defined in the Data Over Cable Service Interface Specification (DOCSIS)?
3.0 dB peak-to-valley (P/V).
How much contraction will 1,200 feet of conduit have if the temperature changes from 94 degrees F to 54 degrees F when the rate of contraction is 1 1/2 inches per 100 feet per 20 degrees F change?
36 inches.
What is sent with digital TV (DTV) transmissions that enables the receiver to synchronize with the sending device to decode and place the data in the correct sequence?
A 27 MHz program clock reference (PCR)
What is installed in the input stage of a distribution amplifier for a flat frequency response into the input amplifier when the input signal has negative tilt?
A cable equalizer with positive slope.
If only one modem indicated a group delay issue in the return path, what would you suspect to be the culprit in the customer's drop system?
A high-pass filter, data-only filter, or a step attenuator.
When preparing to plow conduit, how long should the starter trench be?
A length that allows the plow blade to be lowered to the burial depth without violating the minimum bend radius of the attached conduit.
When using a surface dry boring machine, what is the preferred forward speed of the machine?
A speed that allows the boring bit to work freely without being forced.
When included in an oscillator circuit, what component enables the oscillator frequency to be controlled by voltage, hence, the voltage controlled oscillator (VCO)?
A varactor (or varicap) diode.
In a swept-tuned spectrum analyzer, which element gives the instrument its "swept-tuned" characteristic?
An internal sweep generator.
In a broadband cable network, where would a block convertor be most likely used?
At the node
What do normalized reference traces taken at a fiber-node test point establish?
Baseline sweep responses that are used to balance and sweep all the amplifiers serviced by that fiber-node.
How is the AC voltage separated from the RF signal in a distribution amplifier?
By a capacitor that passes RF but blocks the low frequency 60 hertz (Hz) AC voltage which finds a low resistance path through the RF choke that blocks RF.
What must all fluid assisted boring machine operators and crew members do in case of an inadvertent utility cut or other unforeseen accident?
Call all the utility companies to let them know about the digging activity in the area.
What value of interstage equalizer should be installed if the associated amplifier tombstone field is blank and the amplifier output slope is 7 dB?
Factory
When digging the trench,
First confirm that all utilities have located their lines.
When backfilling the trench,
Gravel, a soil stabilizer, or a slurry mixture should be used when proper compaction is difficult to obtain with the present trench material.
What mechanisms do pit dry boring machines utilize to bore through soil and underneath obstacles?
Hydraulic power, a rod pusher, steel rods, and a piercing tool.
How must a directional test point be installed in an amplifier to enable insertion of upstream sweep pulses and view the downstream sweep?
In a path common to the downstream and upstream.
In which areas is the use of a vibratory plow much more economical than trenching?
In undeveloped areas where a large tractor can be maneuvered.
What does the time-gated switch function on a spectrum analyzer enable?
In-service measurements of noise, beats, and ingress without disrupting service.
The boom on a chain trencher
Is usually spring-loaded to create tension on the chain.
What is the purpose of a portable conduit fishing system?
It ensures that the specified maximum pulling tension for that cable is not exceeded.
How should coaxial cable be plowed using a plow machine without a cable reel carrier?
Lay the coaxial cable along the bury route and have a helper guide the coaxial cable into the feed chute of the forward-moving plow.
In modern sweep systems, what type of nonintrusive and noninterfering test signal is inserted into the downstream?
Narrow-band continuous wave (CW) test carriers, called pulses, at frequencies between channels.
In which portion of a filter's frequency passband is group delay most likely to be encountered?
Near the filter's lower and upper frequency band edge.
What term describes the frequency spectrum into an amplifier having higher amplitude at low frequencies than the high frequencies?
Negative tilt.
Which of the following describes reactive maintenance?
Network activity initiated by metrics that show degraded service performance.
What do the electrical grid mats that are bonded to a fluid-assisted boring system provide?
Operator protection, in case of contact with electrical lines, the boring equipment and machine operators are at the same electrical potential.
When backfilling a boring pit or trench, what should be done to protect the buried conduit or cable in conduit (CIC)?
Remove accessible rocks and backfill all but the top 12 inches of the pit or trench with sand.
What does a normalized reference trace from a fiber-node test point eliminate from the sweep process?
Slope and response variations of the headend and optical transport.
The detail of a displayed signal can be viewed and modified by adjusting the frequency range that the spectrum analyzer is sweeping via which setting?
Span.
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?
Sweep test pulse amplitude.
The amplitude, or vertical deflection on the spectrum analyzer display is adjusted by what instrument settings?
The RF input attenuator and intermediate frequency (IF) gain.
What is significant about how a crystal is cut with respect to the orientation of the quartz crystal lattice structure?
The cut dictates pretty much all crystal characteristics, including frequency drift with temperature.
When configuring the upstream return in a distribution amplifier with multiple upstream ports, the amplitude levels for which port should be adjusted first?
The distribution amplifier upstream port with the most attenuation in its upstream path.
When sweeping the upstream return path in a hybrid fiber coax (HFC) network, where are the upstream levels and sweep responses measured?
The headend.
When configuring the input stage of a distribution amplifier, what element values can vary from those in the amplifier tombstone, depending on the input amplitude measurements?
The input equalizer and attenuator pad values.
Why is the term "gain control" applied to amplifier gain and controls inaccurate?
The only way to vary the output of any amplifier is to adjust the amplitude level of the signal going into the amplifier.
A micro-reflection signature consists of what pair of characterizing elements?
The relative level of the reflected signal compared to the main signal, and the delay of the reflected signal.
What do the cable modem termination system (CMTS) calculated adaptive equalizer coefficients received from the modems describe?
The residual linear channel distortion remaining after any pre-equalization.
In combination with the sweep time, which spectrum analyzer setting determines how well signals will be defined and displayed on the spectrum analyzer's screen?
The resolution bandwidth (RBW) setting.
Which spectrum analyzer setting adjusts the amount of time the analyzer circuitry takes to sample the input signal or channel and then trace the amplitude and signature on the analyzer's display?
The sweep setting.
What are some of the factors in determining the total length of preassembled cable in a conduit for a trench site?
Thermal expansion/contraction allowance.
When using a fluid-assisted boring machine, why is the drilling fluid added when pulling the drill string back through the hole?
To help the rotating back-reamer expand the drilled pilot hole diameter and reduce the drag on the conduit that is being pulled into place.
Describe an application for a distribution amplifier in a hybrid fiber/coax (HFC) network?
To maintain downstream amplitude levels to the addresses farthest from the fiber-node.
In a distribution amplifier, why is the frequency response at the input of the second output stage sloped
To reduce intermodulation distortion levels caused by amplifying high amplitude input levels.
How is the spectrum analyzer video bandwidth (VBW) filter used?
To reduce the noise displayed by the spectrum analyzer to view low amplitude signals more clearly without changing measurement results.
Why is the main downstream output/upstream input port of a distribution amplifier typically the first to be swept in the downstream direction?
To select equalizers and set the output amplitude levels.
What is a characteristic of the monostable multivibrator?
When given a suitable input signal, it generates a single pulse of fixed length.
When is a temperature-controlled crystal oscillator (TCXO) likely to be used?
When techniques to compensate for crystal drift are inadequate for the application.
