PROGRESSION: MAINTENANCE TECH 2025/2026
QUESTIONS WITH SOLUTIONS GRADED A+
✔✔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? -
✔✔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? - ✔✔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? - ✔✔PacketCable.
✔✔Why is 38 MHz typically the highest frequency in the sub-band frequency that is
used for upstream modem transmissions? - ✔✔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? - ✔✔The narrow bandwidth and quadrature phase shift
keying (QPSK) modulation.
✔✔What system is a byproduct of the "funneling effect"? - ✔✔A many-to-one system.
✔✔House amplifiers with a passive return path are used for what type of situation? -
✔✔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? - ✔✔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? -
✔✔3.5 dB.
✔✔What purpose do diplex filters fulfill when installed at the input and output of a two-
way amplifier module? - ✔✔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? - ✔✔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? - ✔✔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? -
✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔The HPF will have to be removed when cable modems
QUESTIONS WITH SOLUTIONS GRADED A+
✔✔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? -
✔✔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? - ✔✔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? - ✔✔PacketCable.
✔✔Why is 38 MHz typically the highest frequency in the sub-band frequency that is
used for upstream modem transmissions? - ✔✔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? - ✔✔The narrow bandwidth and quadrature phase shift
keying (QPSK) modulation.
✔✔What system is a byproduct of the "funneling effect"? - ✔✔A many-to-one system.
✔✔House amplifiers with a passive return path are used for what type of situation? -
✔✔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? - ✔✔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? -
✔✔3.5 dB.
✔✔What purpose do diplex filters fulfill when installed at the input and output of a two-
way amplifier module? - ✔✔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? - ✔✔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? - ✔✔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? -
✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔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? - ✔✔The HPF will have to be removed when cable modems
