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SCTE Broadband SCTE Broadband
Distribution Specialist Distribution Specialist Distribution Specialist Distribution Specialist
Certification PrepCertification Prep
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Presentaion GoalsPresentaion Goals
•• Answer the question "why certify?"Answer the question "why certify?"
•• Getting Started in SCTE CertificationGetting Started in SCTE Certification•• Getting Started in SCTE CertificationGetting Started in SCTE Certification
– Prepare
– Getting Certified
– Staying Certified
•• Overview BDS SCTE Certification Overview BDS SCTE Certification
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HFC Network SegmentsHFC Network Segments
Hub
Hub
Master Headend
TelecomCenterTelecomCenter DistributionDistributionTransportTransport PremisesPremises
Hub
Hub
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Broadband Premises Broadband Premises Specialist (BPS) Specialist (BPS) ((REVISEDREVISED) )
•• Technology, Systems, Technology, Systems,
RequirementsRequirements
•• Premises DevicesPremises Devices
•• InstallationInstallation
•• Troubleshooting and Troubleshooting and •• Troubleshooting and Troubleshooting and
MaintenanceMaintenance
•• StandardsStandards
•• SafetySafety
The revised BPS Certifications include 3 Lines of Business:The revised BPS Certifications include 3 Lines of Business:Video Video –– Voice Voice –– DataData
Broadband Premises Installer (BPI) and Technician (BPT)Broadband Premises Installer (BPI) and Technician (BPT)Broadband Premises Expert (BPE)Broadband Premises Expert (BPE)
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Broadband Distribution Broadband Distribution Specialist (BDS)Specialist (BDS)
•• System ArchitecturesSystem Architectures
•• Distribution ComponentsDistribution Components
•• Signal TypesSignal Types•• Signal TypesSignal Types
•• Troubleshooting and Troubleshooting and
MaintenanceMaintenance
•• ConstructionConstruction
•• SafetySafety
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Broadband Transport Broadband Transport Specialist (BTS)Specialist (BTS)
•• Fiber Optic TheoryFiber Optic Theory
•• Optical Optical Transport Transport
SystemsSystems
Hub
SystemsSystems
•• Link PerformanceLink Performance
•• Troubleshooting and Troubleshooting and
MaintenanceMaintenance
•• Alternative Transport Alternative Transport
SystemsSystems
Hub
Hub
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Broadband Broadband TelecomCenterTelecomCenterSpecialist (BTCS)Specialist (BTCS)
•• Baseband SignalsBaseband Signals
•• Signal ReceptionSignal Reception
•• Channel EquipmentChannel Equipment•• Channel EquipmentChannel Equipment
•• Tests and Tests and
MeasurementsMeasurements
•• FacilitiesFacilitiesEndorsements:Endorsements:
VideoVideo VoiceVoice DataData
Master Headend
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SCTE CertificationsSCTE Certifications
Master Headend
Hub
Hub
Hub
Master Headend
TelecomCenter DistributionTransport Premises
Broadband Broadband Telecomm Telecomm Center Center SpecialistSpecialist
Broadband Broadband Transport Transport SpecialistSpecialist
Broadband Broadband Distribution Distribution SpecialistSpecialist
Broadband Broadband Premises Premises Specialist (x3)Specialist (x3)
BCT/E Certification (will be retired)BCT/E Certification (will be retired)
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Why Certify?Why Certify?
Certification Benefits Both…Certification Benefits Both…•• IndividualsIndividuals
•• Our industryOur industry
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Why Certify?Why Certify?
What What certification does certification does for for an individualan individual
•• Professional certification demonstrates Professional certification demonstrates solid knowledgesolid knowledge
•• Demonstrates Demonstrates drive, selfdrive, self--discipline, discipline, •• Demonstrates Demonstrates drive, selfdrive, self--discipline, discipline, professionalismprofessionalism
•• Career advancementCareer advancement
•• Consistency Consistency -- transportabletransportable
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Why Certify?Why Certify?
What What certification does certification does for our for our industryindustry
•• SCTE certifications raise the bar on SCTE certifications raise the bar on technical knowledgetechnical knowledge
•• Certification provides a competitive Certification provides a competitive •• Certification provides a competitive Certification provides a competitive advantageadvantage
•• Certification inspires the confidence of Certification inspires the confidence of your customersyour customers
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Getting StartedGetting Started
•• Preparing to CertifyPreparing to Certify
•• Getting CertifiedGetting Certified
•• Staying CertifiedStaying Certified•• Staying CertifiedStaying Certified
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Preparing to CertifyPreparing to Certify
•• Study Guides Study Guides –– Exam TopicsExam Topics
•• Books, Manuals, andBooks, Manuals, andPersonalized Prep GuidesPersonalized Prep Guides
•• Jones/NCTI CoursesJones/NCTI Courses•• Jones/NCTI CoursesJones/NCTI Courses
•• Corporate UniversitiesCorporate Universities
•• SCTE BookstoreSCTE Bookstore
•• Study GroupsStudy Groups
•• Individual MentorsIndividual Mentors
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Getting CertifiedGetting Certified
•• OnlineOnline
•• 50 question multiple50 question multiple--choice examschoice exams•• (DVEP currently 100 questions)(DVEP currently 100 questions)
•• Immediate feedbackImmediate feedback•• Immediate feedbackImmediate feedback
•• Fee per examFee per exam
•• Example Exam Page (next slide)Example Exam Page (next slide)
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Staying CertifiedStaying Certified
•• Certification Valid for Three YearsCertification Valid for Three Years
•• To Maintain Certification Status:To Maintain Certification Status:
– Retake exam
– Earn Recertifications Units (RUs)– Earn Recertifications Units (RUs)
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BDS SectionsBDS Sections
Distribution ComponentsDistribution Components
Maintenance & TroubleshootingMaintenance & Troubleshooting
Safety & ConstructionSafety & ConstructionSafety & ConstructionSafety & Construction
Signal TypesSignal Types
System ArchitecturesSystem Architectures
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Understanding FrequenciesUnderstanding Frequencies
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The Radio Frequency (RF) The Radio Frequency (RF)
Spectrum Spectrum •• Each electromagnetic wave has an associated Each electromagnetic wave has an associated
wavelength and frequency which are inversely wavelength and frequency which are inversely related by a simple mathematical formula:related by a simple mathematical formula:Frequency (f) x Wavelength (λ) = Speed of Light Frequency (f) x Wavelength (λ) = Speed of Light (c)(c)
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(c)(c)
•• The speed of light is a fixed numberThe speed of light is a fixed number----299,792,458 meters/second or 186,282.4 299,792,458 meters/second or 186,282.4 miles/second in a vacuum.miles/second in a vacuum.
•• Electromagnetic waves with high frequencies Electromagnetic waves with high frequencies have short wavelengths and waves with low have short wavelengths and waves with low frequencies have long wavelengths. frequencies have long wavelengths.
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HertzHertz
•• RF signals are typically depicted as RF signals are typically depicted as
sinusoidal (sine) waves that vary in amplitude sinusoidal (sine) waves that vary in amplitude
over time.over time.
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•• A frequency of one cycle per second is called A frequency of one cycle per second is called
a hertz.a hertz.
•• One hertz simply means "one per second" One hertz simply means "one per second"
(1/s). (1/s).
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HertzHertz•• Some of the common frequency nomenclatures Some of the common frequency nomenclatures
that we use in the cable industry are:that we use in the cable industry are:
•• Kilohertz (KHz)Kilohertz (KHz) = 1,000 cycles/second = 1,000 cycles/second
(One thousand Hertz)(One thousand Hertz)
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(One thousand Hertz)(One thousand Hertz)
•• Megahertz (MHz)Megahertz (MHz) = 1,000,000 cycles/second = 1,000,000 cycles/second
(One million Hertz)(One million Hertz)
•• Gigahertz (GHz)Gigahertz (GHz) = 1,000,000,000 = 1,000,000,000
cycles/second (One billion Hertz)cycles/second (One billion Hertz)
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HertzHertz
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Frequency Use Authorization Frequency Use Authorization
The Federal Communications Commission The Federal Communications Commission
(FCC) is a government agency responsible for (FCC) is a government agency responsible for
regulating and assigning frequencies regulating and assigning frequencies
throughout the United States.throughout the United States.
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throughout the United States.throughout the United States.
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Frequency Bands Frequency Bands
•• Federal Communication Commission (FCC) Federal Communication Commission (FCC)
assigns and regulates frequenciesassigns and regulates frequencies
•• Frequency ranges assigned to radio, television, Frequency ranges assigned to radio, television,
wire, satellite and cablewire, satellite and cable
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wire, satellite and cablewire, satellite and cable
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CATV NetworksCATV Networks
•• CATV signals travel in a closed environment CATV signals travel in a closed environment
over coaxial cable.over coaxial cable.
•• Compromises in the integrity of the coax plant Compromises in the integrity of the coax plant
could allow RF energy to leak out, or egress could allow RF energy to leak out, or egress
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could allow RF energy to leak out, or egress could allow RF energy to leak out, or egress
from the cable. from the cable.
•• Egress is a Latin term which means to exit.Egress is a Latin term which means to exit.
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CATV Networks CATV Networks (cont.)(cont.)
•• Signals leaking out of the system can interfere Signals leaking out of the system can interfere
with licensed users of the airways like air traffic with licensed users of the airways like air traffic
control and public service.control and public service.
•• Cable operators normally operate the forward Cable operators normally operate the forward
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•• Cable operators normally operate the forward Cable operators normally operate the forward
portion of the cable plant within the 50 MHz to 1 portion of the cable plant within the 50 MHz to 1
GHz portion of the spectrum.GHz portion of the spectrum.
•• The portion of the spectrum occupied by the The portion of the spectrum occupied by the
reverse path is between 5reverse path is between 5--42 MHz.42 MHz.
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Typical CATV NetworkTypical CATV Network
Layout DownstreamLayout Downstream
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Return Path Frequencies Return Path Frequencies
Versus OverVersus Over--thethe--Air UseAir Use
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Analog Signal Analog Signal National TV Standards Committee (NTSC)
establishes television signal structure, which
permits standardized television receivers to be
manufactured.
NTSC requires each channel to be 6 MHz,
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NTSC requires each channel to be 6 MHz,
divided into separate segments for
Video
Audio
Color
Horizontal sweep information located at specific
points
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Digital SignalDigital Signal
Digital refers to a method of encoding
information using a binary system made up
of zeroes and ones.
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Technology has made it possible to
compress many digital channels into a 6
MHz space.
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Anatomy of a 6 MHz Analog Anatomy of a 6 MHz Analog
ChannelChannelVisual CarrierVisual Carrier
ColorColor SubcarrierSubcarrier
Aural CarrierAural Carrier
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Lower Lower
ChannelChannel
BoundaryBoundary
Upper Upper
ChannelChannel
BoundaryBoundary
6 MHz6 MHz
4.5 MHz4.5 MHz
3.58 MHz3.58 MHz1.25 MHz1.25 MHz
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Actual Snapshot of an Analog Actual Snapshot of an Analog
ChannelChannel
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Network Design and MapsNetwork Design and Maps
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Network Design Principles Network Design Principles
•• In HFC systems, the design focus was on In HFC systems, the design focus was on
cascading amplifiers.cascading amplifiers.
•• New design strategy is called New design strategy is called power domain power domain
nodenode (PDN)(PDN) architecture, node size is architecture, node size is
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nodenode (PDN)(PDN) architecture, node size is architecture, node size is
determined by power supply capacity not determined by power supply capacity not
amplifier cascade.amplifier cascade.
•• There is usually one power supply for each There is usually one power supply for each
node.node.
•• The power supply is usually loaded to 80% The power supply is usually loaded to 80%
capacity.capacity.
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Determining Node SizeDetermining Node Size
•• When designers use When designers use PDN PDN deign criteria the deign criteria the
primary design consideration for node size is primary design consideration for node size is
power supply capacity.power supply capacity.
•• However, designers also consider additional However, designers also consider additional
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•• However, designers also consider additional However, designers also consider additional
information to determine node size, such as:information to determine node size, such as:
•• Power supply capacity/ reliabilityPower supply capacity/ reliability
•• Amplifier cascade limitationsAmplifier cascade limitations
•• Homes passedHomes passed
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The Network Design ProcessThe Network Design Process
The following process describes the steps The following process describes the steps followed by the network design group to followed by the network design group to design (or redesign) a broadband network: design (or redesign) a broadband network:
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– Step 1. Perform a “walkout.”
– Step 2. Design the base and routing.
– Step 3. Lay out the nodes.
– Step 4. Lay out the RF design.
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The Network Design ProcessThe Network Design Process
– Step 5. Perform an internal quality check. of
initial design.
– Step 6. Print network design maps.
– Step 7. Construction group performs a
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– Step 7. Construction group performs a
“walkout.”
– Step 8. Construction group builds the network.
– Step 9. “As built” changes made in the network
design system.
– Step 10. Final network design maps are released
to operations.
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System Map ReadingSystem Map Reading•• Key Terms & Reference MaterialsKey Terms & Reference Materials
•• Tombstone Tombstone –– A chart used to display A chart used to display various information about a node, amplifier, various information about a node, amplifier, or a line extender.or a line extender.
37
or a line extender.or a line extender.
•• Power amplifying devices (PADs) and Power amplifying devices (PADs) and equalizers equalizers –– PADs and equalizers (EQs) are PADs and equalizers (EQs) are plugplug--in components used within amplifiers to in components used within amplifiers to control certain aspects of signals. control certain aspects of signals. PADs and PADs and EQs will be discussed in further detail in EQs will be discussed in further detail in other chapters of the HFC technician other chapters of the HFC technician program.program.
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HFC Network ModelsHFC Network Models
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CATV NetworkCATV Network
•• HeadendHeadend –– The primary facility of any cable The primary facility of any cable
network.network.
•• NodeNode –– A device that converts the light onto the A device that converts the light onto the
fiber optic network.fiber optic network.
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fiber optic network.fiber optic network.
•• AmplifierAmplifier –– Boost the RF signal level along the Boost the RF signal level along the
main coaxial cables.main coaxial cables.
•• TapTap –– Located on the feeder line to provide Located on the feeder line to provide
connection to customers drop.connection to customers drop.
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CATV Network CATV Network (cont.)(cont.)
•• Drop cableDrop cable –– Transport RF CATV signals from Transport RF CATV signals from
the tap to the inthe tap to the in--house wiring.house wiring.
•• Customer premises equipment (CPE)Customer premises equipment (CPE) ––
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•• Customer premises equipment (CPE)Customer premises equipment (CPE) ––
Consumers electronics used to provide video, Consumers electronics used to provide video,
audio, telephony, and highaudio, telephony, and high--speed Internet speed Internet
services for the customer.services for the customer.
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HFC Network ModelHFC Network Model
•• Optical transportOptical transport
– Headend to hub
– Point-to-point
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– Point-to-point
•• Optical distributionOptical distribution
– Headend or hub to node
– Point-to-multipoint
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HFC Network Model HFC Network Model (cont.)(cont.)
•• Coaxial distributionCoaxial distribution
– Service area
– Express plant
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– Express plant
– Feeder plant
•• Subscriber dropSubscriber drop
– Tap to customer premises
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Characteristics of the HFC Characteristics of the HFC
NetworkNetwork
•• Carry RF signals (5 MHz up to 1 GHz)Carry RF signals (5 MHz up to 1 GHz)
•• Carry A/C powerCarry A/C power
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•• Impedance of 75 ohms to prevent Impedance of 75 ohms to prevent
ingress/egressingress/egress
•• Unity gain Unity gain
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HFC Network Segments
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HFC Network Segments HFC Network Segments (cont.)(cont.)
Segment 1 Segment 1 -- Optical TransportOptical Transport
Headend-to-hub optical link
Carry signals 30 to 40 miles without
degradation
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degradation
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HFC Network Segments (cont.)
Segment 2 Segment 2 –– Optical DistributionOptical Distribution
Hub-to-node link
Range from 2 to 4 miles
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Almost exclusively analog amplitude
modulation (AM) laser
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Fiber-to-feeder (FTF)
Fiber-to-the-serving area (FSA)
Optical service area (OSA)
Coaxial Distribution Model
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Optical service area (OSA)
Fiber to the home (FTH)
The coaxial plant consists of two segment
• Express
• Feeder
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Coaxial Distribution Model
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Segment 3 Segment 3 –– Express Coaxial PlantExpress Coaxial Plant
Typical short cascade of amplifiers (1 to 3)
HFC Network Segments
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Typical covers less than 2000 feet
Key to the future upgradeability of the HFC
network
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Segment 4 Segment 4 –– Feeder Coaxial PlantFeeder Coaxial Plant
Line extender amplifier L/E commonly a high
output level amplifier delivers the signals to
HFC Network Segments
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output level amplifier delivers the signals to
the passive portion of the network and
eventually to the customer premises.
Passive feeder segment is the last link to the
customer premises
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Segment 5 Segment 5 –– Subscriber DropSubscriber Drop
The portion from the tap to the customer
premises
HFC Network Segments
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premises
The portion from the side of the customer
premises to the subscriber terminal
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Other ArchitecturesOther Architectures
Fiber DeepFiber Deep
No RF Amplifiers after the node
Fiber is within a few hundred feet of the
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Fiber is within a few hundred feet of the
customer
Return path is digitized at the node
Ability to implement targeted FTTH to
specific customers on a node by node basis
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Standard HFC NetworkStandard HFC Network
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2 power supplies
27 RF amplifiers
1 optical node
595 homes passed 79 HPM
7.49 miles UG
595 Homes per node
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Fiber Deep NetworkFiber Deep Network
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1.1 miles per node
7 optical nodes
595 homes passed 79 HPM
7.49 miles UG
85 homes per node average
1 power supply
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FTTH still converts fiber to coax
FTTH takes the fiber to the house demark or
NIU
Fiber To The Home – FTTH
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Customer will own the drop wire
Could be cases where our competitor takes
the drop.
Our policy to make sure rectify the issue
without putting the customer in the middle!
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Typical NIU used for FTTHTypical NIU used for FTTH
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Signal TypesSignal Types
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What is Modulation?What is Modulation?
•• Modulation is the process by which Modulation is the process by which
intelligence signals are added to an RF intelligence signals are added to an RF
carriercarrier
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Amplitude Modulation (AM)Amplitude Modulation (AM)
•• The amplitude of the carrier wave is varied The amplitude of the carrier wave is varied
in direct proportion to that of a modulating in direct proportion to that of a modulating
signalsignal
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signalsignal
•• Video carriers use amplitude modulationVideo carriers use amplitude modulation
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Frequency Modulation (FM)Frequency Modulation (FM)
•• The frequency of the carrier varies with the The frequency of the carrier varies with the
content signal levelcontent signal level
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•• Frequency modulation is more robust Frequency modulation is more robust
against interference against interference
•• This is why FM was chosen for “FM Radio”This is why FM was chosen for “FM Radio”
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Phase Modulation (PM)Phase Modulation (PM)
•• The phase of the carrier wave is varied in The phase of the carrier wave is varied in
accordance with an input signal accordance with an input signal
•• Phase modulation is also a special case of Phase modulation is also a special case of
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•• Phase modulation is also a special case of Phase modulation is also a special case of
quadrature amplitude modulation (QAM)quadrature amplitude modulation (QAM)
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PhasePhase--Shift Keying (PSK)Shift Keying (PSK)
PSK refers to the phase modulation by a PSK refers to the phase modulation by a
simple signal with a discrete number of states, simple signal with a discrete number of states,
such as in Morse code or radio teletype such as in Morse code or radio teletype
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such as in Morse code or radio teletype such as in Morse code or radio teletype
applicationsapplications
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AnalogAnalog
•• Analog signals utilize amplitude, phase, Analog signals utilize amplitude, phase,
and frequencyand frequency
•• Video carrierVideo carrier----amplitudeamplitude modulatedmodulated
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•• Audio carrierAudio carrier----frequencyfrequency modulatedmodulated
•• Color burst carrierColor burst carrier----phasephase modulatedmodulated
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Digital SignalsDigital Signals
•• Digital signals are transmitted using binary Digital signals are transmitted using binary
code that has two data levels, on or off.code that has two data levels, on or off.
•• Using binary code, Using binary code, you can you can compress the compress the
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•• Using binary code, Using binary code, you can you can compress the compress the
signal within the bandwidth of a single signal within the bandwidth of a single
analog channel to a 12:1 compression analog channel to a 12:1 compression
ratio. ratio.
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SamplingSampling
The process of determining the amplitude of The process of determining the amplitude of
an RF signal at fixed points in time.an RF signal at fixed points in time.
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QuantizingQuantizing
The process of recording each sample as a The process of recording each sample as a
number corresponding to the amplitude of the number corresponding to the amplitude of the
signal at the time of sampling.signal at the time of sampling.
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signal at the time of sampling.signal at the time of sampling.
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EncodingEncoding
The process of converting the quantizing The process of converting the quantizing
samples into binary data or bits that can be samples into binary data or bits that can be
stored or transmitted.stored or transmitted.
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stored or transmitted.stored or transmitted.
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Digital CompressionDigital Compression
•• IntraframeIntraframe (I(I--frame): This frame contains all of frame): This frame contains all of
the information needed to complete a frame of the information needed to complete a frame of
videovideo
•• PredictivePredictive (P(P--frame): Contains the difference frame): Contains the difference
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•• PredictivePredictive (P(P--frame): Contains the difference frame): Contains the difference
between the actual image and the predicted between the actual image and the predicted
imageimage
•• BiBi--directional Predictive directional Predictive (B(B--frame): Uses frame): Uses
motionmotion--compensation prediction from past andcompensation prediction from past and
future reference picturesfuture reference pictures
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QPSKQPSK
Quadrature Phase Shift Quadrature Phase Shift
KeyingKeying•• Also known as 4Also known as 4--QAM, uses two carriers QAM, uses two carriers
with identical frequency, phase shifted 90 with identical frequency, phase shifted 90
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with identical frequency, phase shifted 90 with identical frequency, phase shifted 90
degrees apart, and two possible amplitude degrees apart, and two possible amplitude
levelslevels
•• Being phased out in favor of 16Being phased out in favor of 16--QAM QAM
modem signalsmodem signals
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QAMQAM
Quadrature Amplitude Quadrature Amplitude
ModulationModulation•• Uses phase shifting like QPSK, but also Uses phase shifting like QPSK, but also
modulates the amplitude of the signal as modulates the amplitude of the signal as
wellwell
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wellwell
•• Common types include 64Common types include 64--QAM and 256QAM and 256--
QAM and is typically used for HSD QAM and is typically used for HSD
downstream trafficdownstream traffic
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Distribution NetworkDistribution Network
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System Performance: System Performance:
Concepts and IssuesConcepts and Issues Perfect system
• The perfect broadband system would yield uniform
signal quality and thus service quality at all
72
signal quality and thus service quality at all
frequencies.
Perfect system
• But the real world does not work that way. Every
component affects the system “flatness” differently.
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Cable IssuesCable Issues
Simplest component in the system
Loss increases as signal frequency increases.
Non-Linear cable loss
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Non-Linear cable loss
• Natural (and unavoidable) characteristic of coax
Equalizers are needed to compensate for this
effect.
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Hardware IssuesHardware Issues
Every component’s return loss and flatness
characteristic affect a system’s peak to valley
response, often referred to as a “signature
contribution.”
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contribution.”
• Return Loss
• Flatness
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Network IntegrityNetwork Integrity•• ConnectorsConnectors
•• HousingsHousings
•• Cable spansCable spans
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•• Corrosions and looseningCorrosions and loosening
These issues can cause the following problemsThese issues can cause the following problems
– Loss of ground integrity
– Loss of signal
– Suckout
•Seizure
assembly loss
•Resonant peaks
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Network Integrity Network Integrity (cont.)(cont.)
Suckout
• An extreme loss of energy over a narrow
frequency range.
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Seizure assembly loss
• Ends to attenuate lower frequencies more than
higher frequencies
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Network Integrity Network Integrity (cont.)(cont.)
Resonate peak
• May form as a result of constructive reflected
energy
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The preceding effects are extreme examples
of what may result from inadequate work
practices or from aging equipment. They can
compromise system integrity and allow
leakage (ingress/egress).
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Coaxial Cable Coaxial Cable (cont.)(cont.)
Coaxial cable - types
• Armored Sheath
• Flooded / Underground
• Messenger
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• Messenger
Coaxial cable – selection
• During the design phase several other factors
such as distance and cable loss characteristics
must be evaluated in order to determine proper
cable size.
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Skin EffectSkin Effect
Higher frequencies travel closer to the outer diameter or the “skin” of the center conductor.
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center conductor.
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Bending Radius of the CableBending Radius of the Cable
Bending radius is specific to the size and
manufacturer of the coaxial cable.
The radii can be obtained in your cable
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The radii can be obtained in your cable
hand book
Always use an approved bending board
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Powers of 10 Powers of 10
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Positive & Negative Powers Positive & Negative Powers
of 10 of 10
•• Examples of positive powers of 10Examples of positive powers of 10
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•• Examples of negative powers of 10Examples of negative powers of 10
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Characteristics of Scientific Characteristics of Scientific
NotationNotation•• Numbers written in scientific notation have these Numbers written in scientific notation have these
characteristics: characteristics:
•• The base number is always written with only one The base number is always written with only one
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•• The base number is always written with only one The base number is always written with only one
digit to the left of the decimal place (1 through digit to the left of the decimal place (1 through
9). 9).
•• The base number is multiplied by 10 raised to a The base number is multiplied by 10 raised to a
particular power. particular power.
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Characteristics of Scientific Characteristics of Scientific
Notation Notation
•• Converting from scientific to standard Converting from scientific to standard notation notation
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•• Converting from standard to scientific Converting from standard to scientific notationnotation
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Prefixes for Large Prefixes for Large
and Small Numbers and Small Numbers
•• Kilo K frequency, stated as Kilo K frequency, stated as kilohertzkilohertz (KHz)(KHz)
•• Mega M frequency, stated as Mega M frequency, stated as megahertzmegahertz (MHz)(MHz)
85
•• Mega M frequency, stated as Mega M frequency, stated as megahertzmegahertz (MHz)(MHz)
•• Giga G frequency, stated as Giga G frequency, stated as gigahertzgigahertz (GHz)(GHz)
•• Tera T frequency, stated as Tera T frequency, stated as terahertz terahertz (THz)(THz)
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Prefixes for Large Prefixes for Large
and Small Numbers and Small Numbers (cont.)(cont.)
•• Milli voltage, stated as Milli voltage, stated as millivolts millivolts (mV)(mV)
•• Micro voltage, stated as Micro voltage, stated as microvoltsmicrovolts ((µµV)V)
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•• Nano voltage, stated as Nano voltage, stated as nanovoltsnanovolts (nV) (nV)
•• Pico capacitance, stated as Pico capacitance, stated as picofarads picofarads (pf)(pf)
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Ratios Ratios
•• Examples of ratios Examples of ratios
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•• Finding the unknown termFinding the unknown term
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Decibels Decibels
•• The Bel The Bel
•• The decibel The decibel
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•• Definition of the decibel Definition of the decibel
•• Power ratioPower ratio
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Basic Electronic PrinciplesBasic Electronic Principles
•• ConductorsConductors
•• VoltageVoltage
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•• VoltageVoltage
•• ResistanceResistance
•• Ohm’s Law Ohm’s Law
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Basic Electronic Principles Basic Electronic Principles (cont.)(cont.)
•• I (current)I (current) equals E (voltage) divided equals E (voltage) divided
by R (resistanceby R (resistance))
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•• R (resistance)R (resistance) equals E (voltage) equals E (voltage)
divided by I (current)divided by I (current)
•• E E (voltage(voltage) equals I (current) equals I (current) )
multipliedmultiplied by R (resistance)by R (resistance)
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Review of Basic CircuitsReview of Basic Circuits
Series CircuitsSeries Circuits
R1+ R2 = Rt
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Review of Basic CircuitsReview of Basic Circuits (cont.)(cont.)
Parallel CircuitsParallel Circuits
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Review of Basic Circuits Review of Basic Circuits (cont.)(cont.)
Series/Parallel CircuitsSeries/Parallel Circuits
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Review of Basic Circuits Review of Basic Circuits (cont.)(cont.)
Voltage DropsVoltage Drops
Calculate the voltage drops and current draw across the Calculate the voltage drops and current draw across the
circuitcircuit
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Review of Basic Circuits Review of Basic Circuits (cont.)(cont.)
•• Decibel Millivolts (dBmV) Decibel Millivolts (dBmV)
•• Measuring SignalsMeasuring Signals
•• One dBmV indicates an absolute signal power One dBmV indicates an absolute signal power level on a logarithmic scale with 0 dBmV level on a logarithmic scale with 0 dBmV
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level on a logarithmic scale with 0 dBmV level on a logarithmic scale with 0 dBmV representing 1 mV across a 75Ω impedance.representing 1 mV across a 75Ω impedance.
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Essential Power ConceptsEssential Power Concepts
•• Any Any doublingdoubling of power is represented of power is represented by a by a +3 dB gain+3 dB gain..
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by a by a +3 dB gain+3 dB gain..
•• Any Any halvinghalving of power is represented of power is represented by a by a --3 dB loss3 dB loss..
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Essential Voltage Concepts Essential Voltage Concepts (cont.)(cont.)
•• Any Any doublingdoubling of voltage is represented of voltage is represented by a by a +6 dB gain+6 dB gain..
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by a by a +6 dB gain+6 dB gain..
•• Any Any halvinghalving of voltage is represented of voltage is represented by a by a --6 dB loss6 dB loss
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Distribution Cable Loss Distribution Cable Loss
•• Every type of cable affects signal loss Every type of cable affects signal loss differently. differently.
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differently. differently.
•• Ratios are used to determine the amount Ratios are used to determine the amount of loss for a specific amount of cable. of loss for a specific amount of cable.
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Signal Level Calculations Signal Level Calculations
The method of calculating signal levels in The method of calculating signal levels in the distribution can be done at any point in the distribution can be done at any point in the system. Once the cable loss is the system. Once the cable loss is
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the system. Once the cable loss is the system. Once the cable loss is calculated, use addition and subtraction to calculated, use addition and subtraction to find the level at any point in the system. find the level at any point in the system.
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Amplifiers in Conventional Amplifiers in Conventional
Cable ArchitectureCable Architecture Active devices
• Nodes
• Amplifiers
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• Amplifiers
Trunk amplifier
Bridging amplifier
Line extender (LEs)
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Physical Description of Physical Description of
a Broadband Amplifiera Broadband Amplifier Push/pull
Feed forward
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Power doubling
Note:Note: Another Important component found in every amplifier is the DC Another Important component found in every amplifier is the DC Power Pack.Power Pack.
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Older-style Amplifier Components Newer-style Amplifier Components
Housing Housing
Baseplate (also called a motherboard) A single module
Plug-in modules
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The Amplifier HousingThe Amplifier Housing
Lid
Input and output connections
Fins/heat sink
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Fins/heat sink
Gasket
Mesh/RFI gasket
Bolts
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Tightening the Amplifier LidTightening the Amplifier Lid
Sequence and torque for each amplifier is
listed in the manufacturer’s specifications
Old-Style interior amplifier components
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Old-Style interior amplifier components
Newer-style interior amplifier component
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How an Amplifier WorksHow an Amplifier Works
Note:
Return bandwidth varies by system. Your
system may operate at 5-45 MHz, 5-40 MHz,
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system may operate at 5-45 MHz, 5-40 MHz,
5-42 MHz, or 5-30MHz. Check with your
supervisor for the correct specifications for
you system.
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Automatic Gain ControlAutomatic Gain Control
AGC – Automatic gain control
TLC - Thermal level control
ALS – Automatic level and slope control
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ALS – Automatic level and slope control
Note: Thermal controls are also key components in the
nodes to compensate for air temperature changes inside
the housing.
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Key Components of an Key Components of an
AmplifierAmplifier Hybrids (gain stages)
Diplex filter
RF/AC diplex filter
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RF/AC diplex filter
Input test point
Output test point
Input and interstage PADs
Input and interstage equalizers
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Key Components of an Key Components of an
AmplifierAmplifier
Input and interstage equalizers
Power pack
AGC/ASC/ALS
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AGC/ASC/ALS
Thermal Control
Shunts/fuses/power blocks
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Coaxial Cable Coaxial Cable
and Broadband Amplifiersand Broadband Amplifiers Characteristics of coaxial cable
• Attenuation
• Tilt
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Definition of attenuation and tilt
• Tilt = Slope
Conventions for citing levels in the network
• Single RF Level = High channel (e.g. 116 in 750 MHz
system
• High and low channel (e.g. 46/35) 46 is the high
channel (ch.116) and 35 is the low channel (ch.2) 109
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Coaxial Cable Coaxial Cable
and Broadband Amplifiers and Broadband Amplifiers (cont)(cont)
Unity gain
Amplifier spacing
Using PADs to achieve unity gain
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Using PADs to achieve unity gain
• Attenuator PADs
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CAUTION: Removing the forward PAD will halt forward
service until the PAD is replaced. The is true for the
reverse PAD as well. Follow your system’s guidelines
for adjusting levels.
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Using Equalizers Using Equalizers
to Achieve Unity Gainto Achieve Unity GainCAUTION: Removing equalizers in an active amplifier will
halt forward service until the EQ is replaced. Follow your
system’s guidelines for adjusting EQ levels.
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system’s guidelines for adjusting EQ levels.
Equalizers
Equalizers labeled differently
There are two ways of labeling equalizers:
• By the amount of tilt offset the EQ actually provides
• dB cable length at the high channel for which the EQ
compensates111
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Using Equalizers Using Equalizers
to Achieve Unity Gainto Achieve Unity Gain Cable attenuation and frequency
Cable loss ratio
•
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• The relationship between the cable’s attenuation
of a higher frequency to the attenuation of a
lower frequency.
Equalizer attenuation curve
Equalizer function
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Using Equalizers Using Equalizers
to Achieve Unity Gainto Achieve Unity Gain PAD and equalizer practice
Summary – Balancing an amplifier with manual gain and slope controls
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gain and slope controls
• For exact procedures and setting, refer to amplifier manufacturer’s specifications.
Summary – Balancing an amplifier with automatic gain and slope controls
• Some amplifiers are balanced by using fixed value plug-ins for gain and equalization rather than by using variable controls. 113
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System Sweep ProcessSystem Sweep Process
Definition
Equipment
Procedures
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Procedures
Installing the sweep transmitter
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System Sweep Process System Sweep Process (cont.)(cont.)
Reverse fiber receivers
Sweeping a fiber node
Sweep and balance
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• Balancing the node
• Taking references
• Raw sweep (forward path)
• Referencing (forward path)
• Balance and sweep forward path
• Sweep the return 115
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System Sweep Process System Sweep Process (cont.)(cont.)
Analyzing a sweep trace
Suckout
Roll-off – low end of the passband
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Roll-off – low end of the passband
Roll-off – high end
Standing waves
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AmplifiersAmplifiers
Frequency response
AC power direction
Amplifier power direction
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Amplifier power direction
Setting up and amplifier for proper power
direction
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Amplifiers Amplifiers (cont.)(cont.)
Fusing an amplifier output
Blocking power
Checking an active device’s “vital signs”
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Checking an active device’s “vital signs”
• Check for signal leakage
• Check the physical characteristics
• Measure AC and DC voltage
• Measure RF signal
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Line Extender SetupLine Extender Setup
All service interruptions must be All service interruptions must be within maintenance window.within maintenance window.
•• Verify LE AC is set for pass or blocked based Verify LE AC is set for pass or blocked based
on design. Look for bucking AC and the setup on design. Look for bucking AC and the setup
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on design. Look for bucking AC and the setup on design. Look for bucking AC and the setup
of surrounding amplifiers before making any of surrounding amplifiers before making any
changes.changes.
•• Measure AC and DC and verify that the levels Measure AC and DC and verify that the levels
fall within specification.fall within specification.
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Line Extender Setup Line Extender Setup (cont.)(cont.)
•• Place station in manual mode. (ALC or AGC Place station in manual mode. (ALC or AGC
turned off)turned off)
•• Verify “minimum full gain” of the station. Verify “minimum full gain” of the station.
Remember the total possible gain will be Remember the total possible gain will be
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Remember the total possible gain will be Remember the total possible gain will be
larger than operating gain. The reserved gain larger than operating gain. The reserved gain
is used by the ALC or AGC to give back during is used by the ALC or AGC to give back during
higher temperatures.higher temperatures.
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Line Extender Line Extender (cont.)(cont.)
•• Set EQ value in accordance with design, Set EQ value in accordance with design,
manufacture specification, and first hybrid chip. manufacture specification, and first hybrid chip.
Calculated value should be within Calculated value should be within ±± 0.5 dB of 0.5 dB of
actual value. Remember that in some LE actual value. Remember that in some LE
designs, the input EQ contributes to part of the designs, the input EQ contributes to part of the
121
designs, the input EQ contributes to part of the designs, the input EQ contributes to part of the
total output tilt.total output tilt.
•• Set input PAD value so that it combines with the Set input PAD value so that it combines with the
total input loss at the highest frequency and total input loss at the highest frequency and
equals the operating gain of the station. Total equals the operating gain of the station. Total
input loss + PAD = operating gaininput loss + PAD = operating gain
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Line Extender Line Extender (cont.)(cont.)
•• Adjust the ALC/AGC (if so equipped) according Adjust the ALC/AGC (if so equipped) according
to the LE specification. Keep the outside to the LE specification. Keep the outside
temperature in mind.temperature in mind.
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Passive DevicesPassive Devices
•• RF Line Splitter: Divides input power into two or RF Line Splitter: Divides input power into two or
more outputs.more outputs.
•• Directional Couplers: Divides input power into Directional Couplers: Divides input power into
unequal or unbalanced outputs.unequal or unbalanced outputs.
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unequal or unbalanced outputs.unequal or unbalanced outputs.
•• Power Inserter: Used to combine or separate Power Inserter: Used to combine or separate
line power supply (AC) and RF signals.line power supply (AC) and RF signals.
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Passive DevicesPassive Devices
•• MultiMulti--Taps: A directional coupler with one or Taps: A directional coupler with one or
more splitter on the high loss side to serve more splitter on the high loss side to serve
individual customers.individual customers.
•• In Line Equalizer: Use just like an equalizer in an In Line Equalizer: Use just like an equalizer in an
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•• In Line Equalizer: Use just like an equalizer in an In Line Equalizer: Use just like an equalizer in an
amplifier. This is a passive devise used to amplifier. This is a passive devise used to
attenuate a certain section of the bandwidth attenuate a certain section of the bandwidth
usually the lower frequencies. usually the lower frequencies.
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Physical CharacteristicsPhysical Characteristics•• Housing and face plateHousing and face plate
•• Weatherproof gasket and RF Weatherproof gasket and RF
Integrity gasket (RFI)Integrity gasket (RFI)
•• Notice isolation and insertion Notice isolation and insertion
lossloss
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Bypass BarBypass Bar
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Socket for Return ConditionerSocket for Return Conditioner
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RF Integrity Gasket and RF Integrity Gasket and
Rubber Weather GasketRubber Weather Gasket
128
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Seizure Screw CorrosionSeizure Screw Corrosion
129
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Voltage Measurement from Voltage Measurement from
TapTap
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Current Measurement from Current Measurement from
TapTap
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Physical CharacteristicsPhysical Characteristics
of Power Insertersof Power Inserters
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Types of Taps Types of Taps
Feed-Through and Terminating Taps
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Application Criteria Application Criteria
Selecting theSelecting the Number of Tap PortsNumber of Tap Ports
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Selecting Tap Value Selecting Tap Value
Calculating Tap Signal Levels Calculating Tap Signal Levels
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Return PathReturn Path
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Frequency AllocationFrequency Allocation
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Services using the ReturnServices using the Return
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• Telephone • High-speed Data (HSD) • IPPV (Impulse Pay-per-View) • Status monitoring• VOD (Video on Demand) • IPG (Interactive Program Guide)
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Upstream Allocations
5 MHz 12 MHz
13 MHz
20 MHz 42 MHz
50 MHz
26.975 MHz
29.75 MHz
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8 to 12 MHz
13 to 20 MHz
20 to 42 MHz
Motorola Upstream Traffic
12 to 13 MHzStatus Monitoring
SA Upstream Traffic
CMTS Traffic
CB & HAM Radio Spectrum
50 MHz
Should not exceed 40 MHz due to Diplex Filtering
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OffOff--air Signals Using air Signals Using
Return Path FrequenciesReturn Path Frequencies
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Ham RadioHam Radio
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CB RadioCB Radio
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Impulse/Electrical NoiseImpulse/Electrical Noise
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Ingress/Noise Over TimeIngress/Noise Over Time
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Return Path Signal FormatsReturn Path Signal Formats
Telephone Signal on the Return PathTelephone Signal on the Return Path
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HSD (DOCSIS) SignalHSD (DOCSIS) Signal
on Return Path on Return Path (cont.)(cont.)
•• DOCSIS 1.1 included upgrades to launch VoIP DOCSIS 1.1 included upgrades to launch VoIP
telephonytelephony
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•• DoCSISDoCSIS 3.0 will allow us to offer similar data 3.0 will allow us to offer similar data
rates to rates to Verizon’s Verizon’s FiOSFiOS or other FTTH operatorsor other FTTH operators
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CM
DOCSIS OverviewDOCSIS OverviewNew Services
Opportunities DOCSIS CableHome
• HVAC control• Fire sense & control• Security• Air quality monitoring• Child monitoring• Energy management,
etc.
PacketCable
MPEG Services
CM
CMCMTS
CM
CM
Operator Operator Core
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CM
CM
Aggregation Network Access NetworkCore Network
Operator administered
• Remote file sharing
• Shared calendar• Unified messaging• Managed services
CPEHeadendBackend
IP Services
CM
CM
CM
CM
CMTS
CMTS
CM
Operator Aggregation
network
Operator Core Backbone
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Review of Return Path SetupReview of Return Path Setup
Unlike the forward path, where amplifiers are Unlike the forward path, where amplifiers are
set up to compensate for loss that has set up to compensate for loss that has
occurred between it and the previous amplifier occurred between it and the previous amplifier
upstream, on the return path the opposite is upstream, on the return path the opposite is
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upstream, on the return path the opposite is upstream, on the return path the opposite is
true. A return amplifier is set up to compensate true. A return amplifier is set up to compensate
for the loss between it and the next amplifier. for the loss between it and the next amplifier.
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Review of Return Path Setup Review of Return Path Setup (cont.)(cont.)
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Unity Gain on the HFC Unity Gain on the HFC
NetworkNetwork
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Unity Gain Reference PointsUnity Gain Reference Points
Using the reverse telemetry level recorded Using the reverse telemetry level recorded
during the reverse sweep reference at the node, during the reverse sweep reference at the node,
a technician can balance the reverse amplifiers a technician can balance the reverse amplifiers
for unity gain by PADing at the reverse output of for unity gain by PADing at the reverse output of
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for unity gain by PADing at the reverse output of for unity gain by PADing at the reverse output of
the amplifier to match the telemetry level the amplifier to match the telemetry level
recorded at the node.recorded at the node.
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Unity Gain Reference Points Unity Gain Reference Points (cont.)(cont.)
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Raw Sweep (Reverse Path)Raw Sweep (Reverse Path)
The most efficient way of aligning the coaxial The most efficient way of aligning the coaxial
portion reverse plant is through the use of a portion reverse plant is through the use of a
sweep. During this process you can align the sweep. During this process you can align the
reverse amplifier levels and also test the reverse amplifier levels and also test the
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reverse amplifier levels and also test the reverse amplifier levels and also test the
frequency response of the coaxial plant.frequency response of the coaxial plant.
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Raw Sweep (Reverse Path) Raw Sweep (Reverse Path) (cont.)(cont.)
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Referencing Reverse PathReferencing Reverse Path
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Reverse Sweep “Rule of Thumb”Reverse Sweep “Rule of Thumb”
•• PAD for telemetry or reference PAD for telemetry or reference –– matching matching
telemetry/reference level will ensure proper telemetry/reference level will ensure proper
return alignment.return alignment.
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•• EQ for flatness EQ for flatness –– use the return equalizer to use the return equalizer to
flatten response. This has a similar affect as a flatten response. This has a similar affect as a
forward EQ has.forward EQ has.
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Exercise Exercise –– Modem Output Modem Output
LevelLevel
The output level of the modem or other reverse
transmitting devices is determined by four main
factors
• Drop system and splitter flat loss
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• Drop system and splitter flat loss
• Tap loss
• Feeder system cable losses and passive
device insertion loss
• Minimum reverse input to the first active
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Exercise Exercise –– Modem Output Modem Output
Level Level (cont.)(cont.)
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Dynamic RangeDynamic Range
•• Reverse transmitting devices typically have a Reverse transmitting devices typically have a
maximum output level of 55 to 60 maximum output level of 55 to 60 dBmVdBmV. It is . It is
desirable for these devices to transmit in the desirable for these devices to transmit in the
upper end of their dynamic range.upper end of their dynamic range.
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upper end of their dynamic range.upper end of their dynamic range.
•• Why is that desirableWhy is that desirable??
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Dynamic Range Dynamic Range (cont.)(cont.)
•• Reverse transmitting devices typically have a Reverse transmitting devices typically have a
Dynamic Output Range of 25 to 60 dBmV (this Dynamic Output Range of 25 to 60 dBmV (this
varies by device).varies by device).
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•• The actual output level of the CPE is The actual output level of the CPE is
determined by the needs at the headend determined by the needs at the headend
receiving device. This is also the reason there receiving device. This is also the reason there
is no AGC necessary in the return amplifiers. is no AGC necessary in the return amplifiers.
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Reverse Tap Port WindowReverse Tap Port Window
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Using Reverse ConditioningUsing Reverse Conditioning
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Transmit Levels Transmit Levels
without Reverse Input PADswithout Reverse Input PADs
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Transmit Levels Transmit Levels Using Reverse Input PADsUsing Reverse Input PADs
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Check your local design and regional policy before
adding or changing system PADing.
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Reverse AlignmentReverse Alignment
•• It is critical to follow equipment and system It is critical to follow equipment and system
design parametersdesign parameters
•• It is critical to understand the test point It is critical to understand the test point
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•• It is critical to understand the test point It is critical to understand the test point
placement within the amplifier design to placement within the amplifier design to
understand the proper injection/telemetry understand the proper injection/telemetry
level to arrive at the hybrid with the proper level to arrive at the hybrid with the proper
levelslevels
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Reverse Alignment Reverse Alignment –– Inputs Inputs
Specified to the Reverse Specified to the Reverse
HybridHybridThis illustrates a possible design flaw due to the Hybrid
requiring 19 dBmV.
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Thermal NoiseThermal Noise
Thermal Noise is the noise energy generated by the Thermal Noise is the noise energy generated by the
random motion of electrons. In HFC networks, most random motion of electrons. In HFC networks, most
thermal noise is produced by active elements, like thermal noise is produced by active elements, like
amplifiers and laser transmitters. The amount of thermal amplifiers and laser transmitters. The amount of thermal
noise in a system is directly proportional to the number of noise in a system is directly proportional to the number of
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noise in a system is directly proportional to the number of noise in a system is directly proportional to the number of
active elements involved, that is, more amplifiers results in active elements involved, that is, more amplifiers results in
more noise.more noise.
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Noise Accumulation: ForwardNoise Accumulation: Forward
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In the forward portion of the HFC network, the total amount In the forward portion of the HFC network, the total amount of noise present is the sum of all the noise contributed by of noise present is the sum of all the noise contributed by each active element through which the signal passes. The each active element through which the signal passes. The C/N ratio for Amplifier #3, in the above diagram, would be C/N ratio for Amplifier #3, in the above diagram, would be based only on the noise contributed by Amplifiers 1, 2, and based only on the noise contributed by Amplifiers 1, 2, and 3. The noise produced by amplifiers #4 and #5 have no 3. The noise produced by amplifiers #4 and #5 have no impact on the output of Amplifier #3. impact on the output of Amplifier #3.
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Energy DistributionEnergy DistributionEnergy DistributionEnergy Distribution
Forward Path SignalForward Path Signal
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Energy AccumulationEnergy AccumulationEnergy AccumulationEnergy Accumulation
Return Path SignalReturn Path Signal
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Noise Accumulation: ReturnNoise Accumulation: Return
Thermal noise and ingress in the return path accumulates Thermal noise and ingress in the return path accumulates
from all of the active elements in a particular network area. from all of the active elements in a particular network area.
The total noise present at the Primary Hub side of Amplifier The total noise present at the Primary Hub side of Amplifier
#1 will be the sum of the noise produced by amplifiers 1, 2, #1 will be the sum of the noise produced by amplifiers 1, 2,
3, 4, and 5.3, 4, and 5.
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3, 4, and 5.3, 4, and 5.
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Clean Noise FloorClean Noise Floor
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Ingress ExamplesIngress Examples
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Laser ClippingLaser Clipping
The screenshot below shows excessive ingress with some common The screenshot below shows excessive ingress with some common path distortions. As technicians in the field become familiar with path distortions. As technicians in the field become familiar with tracking and repairing reverse path ingress they will sometimes see a tracking and repairing reverse path ingress they will sometimes see a pattern of ingress types due to surrounding conditions such as ham pattern of ingress types due to surrounding conditions such as ham radio operators. In a neighborhood, a problem may be addressed one radio operators. In a neighborhood, a problem may be addressed one day only to come back another day with the same signature but from a day only to come back another day with the same signature but from a
174
day only to come back another day with the same signature but from a day only to come back another day with the same signature but from a different cause. Excessive levels of ingress can overdrive (clip) the different cause. Excessive levels of ingress can overdrive (clip) the return laser effecting the entire node.return laser effecting the entire node.
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Common path distortions Common path distortions
(CPD)(CPD)•• Common path distortionCommon path distortion----sometimes called common sometimes called common
path interpath inter--modulation distortion is generally created at a modulation distortion is generally created at a
dissimilar metals interface in the signal path. dissimilar metals interface in the signal path.
•• The downstream carriers passing through this nonThe downstream carriers passing through this non--
linear “diode like” junction create second and third order linear “diode like” junction create second and third order
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linear “diode like” junction create second and third order linear “diode like” junction create second and third order
distortions (beats) that appear in the RF signal path, distortions (beats) that appear in the RF signal path,
especially the upstream. especially the upstream.
•• Downstream RF levels that are too high often will Downstream RF levels that are too high often will
aggravate CPDaggravate CPD----definitely a good reason to keep the definitely a good reason to keep the
forward plant properly aligned!forward plant properly aligned!
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Common Path Distortions Common Path Distortions
(CPD)(CPD)
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Typical plant contact points where Typical plant contact points where
dissimilar metals contribute to CPDdissimilar metals contribute to CPD
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Common Path DistortionsCommon Path Distortions
(CPD) (CPD)
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CPD will generate a spike approximately every 6 MHz.
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Electrical Frequency Electrical Frequency
InterferenceInterference
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Poor Termination or Improper Poor Termination or Improper
PADingPADing•• Poor termination may cause a Poor termination may cause a
reverse path signature like the reverse path signature like the one shown. Be sure to one shown. Be sure to terminate all endterminate all end--ofof--line line coaxial cable as well as coaxial cable as well as unused amplifier ports. This is unused amplifier ports. This is
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unused amplifier ports. This is unused amplifier ports. This is extremely important to extremely important to maintain reverse path services.maintain reverse path services.
•• An elevated noise signature An elevated noise signature such as the one shown may such as the one shown may also indicate improper PADing also indicate improper PADing in the field. Take a reverse in the field. Take a reverse sweep reference at the node sweep reference at the node and balance the RF return.and balance the RF return.
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Diplex Filter Diplex Filter
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The reverse path screenshot shown illustrates poor diplex filter
isolation causing common path distortions.
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Radio Interference Radio Interference
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Signal ImpairmentsSignal Impairments
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Network Effects on Signal Network Effects on Signal
Quality Quality •• Goal is to provide a quality signal to each and Goal is to provide a quality signal to each and
every customer on the network. every customer on the network.
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•• Main source of signal degradation is the Main source of signal degradation is the amplifiers themselves. The amplification amplifiers themselves. The amplification process causes unwanted changes to the process causes unwanted changes to the signal in the form of noise and distortions. signal in the form of noise and distortions.
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Analog Signal ImpairmentsAnalog Signal Impairments
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Carrier to Noise (C/N) RatioCarrier to Noise (C/N) Ratio
CarrierCarrier--toto--noise, expressed as CNR or C/N, is a noise, expressed as CNR or C/N, is a
ratio of the peak of the carrier to the peak of the ratio of the peak of the carrier to the peak of the
noise floor. noise floor. 3dB when double amps in cascade3dB when double amps in cascade
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Carrier to Noise (C/N) Ratio Carrier to Noise (C/N) Ratio (cont.)(cont.)
•• CNR is decreased 3dB every time the cascade CNR is decreased 3dB every time the cascade
doubled. The CNR would decrease by 3dB at doubled. The CNR would decrease by 3dB at
the 2nd, 4th, 8th, 16th, (doubling) etc amplifier the 2nd, 4th, 8th, 16th, (doubling) etc amplifier
and it is not recoverable.and it is not recoverable.
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and it is not recoverable.and it is not recoverable.
•• The FCC requires C/N to be a minimum of 43 The FCC requires C/N to be a minimum of 43
dBc.dBc.
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HeterodyneHeterodyne
In telecommunications In telecommunications heterodyningheterodyning is the is the
generation of new frequencies by mixing two generation of new frequencies by mixing two
or more signals. Mixing two frequencies or more signals. Mixing two frequencies
creates two new frequencies, one at the sum creates two new frequencies, one at the sum
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creates two new frequencies, one at the sum creates two new frequencies, one at the sum
of the two frequencies mixed, and the other at of the two frequencies mixed, and the other at
their difference. A heterodyne receiver is a their difference. A heterodyne receiver is a
telecommunication receiver which uses this telecommunication receiver which uses this
effect to produce frequency shifts.effect to produce frequency shifts.
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Composite Second Order Composite Second Order
Unlike noise, CSO distortion is an organized Unlike noise, CSO distortion is an organized form of signal degradation which consists of form of signal degradation which consists of multiple carrier frequencies which diminish signal multiple carrier frequencies which diminish signal quality. quality.
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Composite Second Order Composite Second Order (cont.)(cont.)
When two or more carriers are passed When two or more carriers are passed
through an amplifier, there is always a certain through an amplifier, there is always a certain
amount of interaction between the carriers. amount of interaction between the carriers.
These beats of interference are a result of the These beats of interference are a result of the
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These beats of interference are a result of the These beats of interference are a result of the
heterodyne process. The amplifier will in heterodyne process. The amplifier will in
some way act like a mixer and will generate some way act like a mixer and will generate
multiples of the signals being amplified.multiples of the signals being amplified.
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Composite Second Order Composite Second Order (cont.)(cont.)
There are literally thousands of second order There are literally thousands of second order
combinations, called beats that occur. CSO, like combinations, called beats that occur. CSO, like
CNR, is also expressed as a ratio of carrier level CNR, is also expressed as a ratio of carrier level
to the level of the beat products. Each to the level of the beat products. Each
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to the level of the beat products. Each to the level of the beat products. Each
combination produces one beat. These beats combination produces one beat. These beats
tend to mass together at the frequencies of the tend to mass together at the frequencies of the
sum and difference of the two carriers in sum and difference of the two carriers in
question. The individual beats form a cluster of question. The individual beats form a cluster of
interfering signals near the video carrier. CSO is interfering signals near the video carrier. CSO is
written as a negative value such as written as a negative value such as --53 dBc. 53 dBc.
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Composite Second Order Composite Second Order (cont.)(cont.)
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Composite Second Order Composite Second Order (cont.)(cont.)
•• CSO affects pictures by causing diagonal CSO affects pictures by causing diagonal
lines to be present in the picture. It does so lines to be present in the picture. It does so
because the beat products fall within the because the beat products fall within the
area of the modulated video carrier. area of the modulated video carrier.
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•• CSO is decreased 3dB every time the CSO is decreased 3dB every time the
cascade is doubled. The CSO would cascade is doubled. The CSO would
decrease by 3dB at the 2nd, 4th, 8th, 16th, decrease by 3dB at the 2nd, 4th, 8th, 16th,
(doubling) etc amplifier and it is not (doubling) etc amplifier and it is not
recoverable.recoverable.
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Composite Triple Beat Composite Triple Beat
•• Composite Triple Beat (CTB) is the same as Composite Triple Beat (CTB) is the same as CSO with the addition of a third frequency CSO with the addition of a third frequency adding and subtracting in the amplification adding and subtracting in the amplification process. process.
•• There are literally thousands of triple beat There are literally thousands of triple beat
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•• There are literally thousands of triple beat There are literally thousands of triple beat combinations that can occur. CTB, like CSO, is combinations that can occur. CTB, like CSO, is also expressed as a ratio of carrier level to the also expressed as a ratio of carrier level to the level of the beat products. Each combination level of the beat products. Each combination produces one beat. These beats tend to mass produces one beat. These beats tend to mass together under the video carrier. The individual together under the video carrier. The individual beats add in power forming the beat product. beats add in power forming the beat product. CTB is written as a negative value such as CTB is written as a negative value such as --53 53 dBc. dBc.
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Composite Triple Beat Composite Triple Beat (cont.)(cont.)
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CTB is a ratio of carrier level to beat products CTB is a ratio of carrier level to beat products power level. The above example shows where the power level. The above example shows where the beats fall for some of the possible combinations of beats fall for some of the possible combinations of frequencies. CTB beats tend to fall directly under frequencies. CTB beats tend to fall directly under the video carrier.the video carrier.
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Composite Triple Beat Composite Triple Beat (cont.)(cont.)
•• Composite triple beat is often a result of Composite triple beat is often a result of
amplifier overdrive. amplifier overdrive.
•• CTB is decreased 6dB every time the cascade CTB is decreased 6dB every time the cascade
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•• CTB is decreased 6dB every time the cascade CTB is decreased 6dB every time the cascade
is doubled. The CTB would decrease by 6dB is doubled. The CTB would decrease by 6dB
at the 2nd, 4th, 8th, 16th, (doubling) etc at the 2nd, 4th, 8th, 16th, (doubling) etc
amplifier and it is not recoverable.amplifier and it is not recoverable.
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Cross Modulation (XMOD)Cross Modulation (XMOD)
•• Cross Modulation (XMOD) is a distortion which Cross Modulation (XMOD) is a distortion which results from the amplitude modulation of one results from the amplitude modulation of one channel superimposing onto another channel. channel superimposing onto another channel.
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•• XMOD simply means a desired channel is XMOD simply means a desired channel is being modulated by another; that is, some of being modulated by another; that is, some of the modulation sidebands on the desired the modulation sidebands on the desired channel are due to another. channel are due to another.
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Cross Modulation (XMOD)Cross Modulation (XMOD)
Excessive XMOD will manifest itself as Excessive XMOD will manifest itself as
spurious signals, as well as the transfer, or spurious signals, as well as the transfer, or
superimposing, of modulation (information) superimposing, of modulation (information)
from one carrier to another. The effect is from one carrier to another. The effect is
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from one carrier to another. The effect is from one carrier to another. The effect is
jittery bars on the picture, generated by the jittery bars on the picture, generated by the
sync pulses of other channels being sync pulses of other channels being
impressed upon the received channel.impressed upon the received channel.
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Hum ModulationHum Modulation
Hum modulation distortions are in effect the Hum modulation distortions are in effect the
transfer of unwanted modulation to the signal transfer of unwanted modulation to the signal
being amplified. Hum is amplitude modulation being amplified. Hum is amplitude modulation
of the carrier by a signal whose frequency is of the carrier by a signal whose frequency is
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of the carrier by a signal whose frequency is of the carrier by a signal whose frequency is
usually a harmonic of the power line frequency. usually a harmonic of the power line frequency.
It can be generated by any number of active It can be generated by any number of active
devices along the coaxial plant. devices along the coaxial plant.
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Digital Signal ImpairmentsDigital Signal Impairments
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Digital Signal ImpairmentsDigital Signal Impairments
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QAM Decision QAM Decision AreasAreas
Decision boundaries for Decision boundaries for common QAM common QAM modulation types are modulation types are shown in the figure. shown in the figure. Notice that the larger Notice that the larger
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Notice that the larger Notice that the larger decision boundary of 16decision boundary of 16--QAM makes it much QAM makes it much more tolerant of signal more tolerant of signal distortions than the distortions than the much smaller much smaller boundaries of 64boundaries of 64-- and and 256256--QAM.QAM.
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Analyzing QAM SignalsAnalyzing QAM Signals
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Constellation Build UpConstellation Build UpOn a test instrument, the locations on the constellation
build up over time, and the shape and distribution can tell
you a great deal about the health of the signal.
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The constellation display on a QAM analyzer gives a visual
indication of how far the noise is moving the signal from ideal
location. The further the signals move from ideal locations,
the poorer the Modulation Error Rate (MER).
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Modulation Error Ratio (MER)Modulation Error Ratio (MER)
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Modulation Error RatioModulation Error Ratio
Digital signals are also susceptible to Digital signals are also susceptible to
signal degradation cause by a variety of signal degradation cause by a variety of
problems. For QAM signal problems. For QAM signal
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problems. For QAM signal problems. For QAM signal
measurements, the Modulation Error Ratio measurements, the Modulation Error Ratio
(MER) summarizes all errors indicated by (MER) summarizes all errors indicated by
a constellation diagram. a constellation diagram.
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Modulation Error Ratio Modulation Error Ratio (cont.)(cont.)
The Modulation Error The Modulation Error Ratio (MER) summarizes Ratio (MER) summarizes all errors indicated by a all errors indicated by a constellation diagram. constellation diagram. For each I/Q pair of a For each I/Q pair of a
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For each I/Q pair of a For each I/Q pair of a constellation diagram constellation diagram there is just one there is just one theoretical target point theoretical target point precisely in the center of precisely in the center of each decision field. But each decision field. But this target is often missed.this target is often missed.
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Bit Error Rate (BER)Bit Error Rate (BER)
•• BER is similar to signalBER is similar to signal--toto--noise ratio in an noise ratio in an
analog system.analog system.
•• BER is the percentage of bits with errors BER is the percentage of bits with errors
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•• BER is the percentage of bits with errors BER is the percentage of bits with errors
divided by the total number of bits that have divided by the total number of bits that have
been transmitted, received or processed over a been transmitted, received or processed over a
given time period. given time period.
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Bit Error Rate (BER) Bit Error Rate (BER) (cont.)(cont.)
•• The rate is typically expressed as 10 to the The rate is typically expressed as 10 to the
negative power. For example, four erroneous negative power. For example, four erroneous
bits out of 100,000 bits transmitted would be bits out of 100,000 bits transmitted would be
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bits out of 100,000 bits transmitted would be bits out of 100,000 bits transmitted would be
expressed as 4 x 10expressed as 4 x 10--5, or the expression 3 x 5, or the expression 3 x
1010--6 would indicate that three bits were in error 6 would indicate that three bits were in error
out of 1,000,000 transmitted. out of 1,000,000 transmitted.
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Power SupplyPower Supply
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Powering Powering ComponentsComponents
•• DC power pack DC power pack
•• Shunts, fuses, power directors, surge Shunts, fuses, power directors, surge
protectorsprotectors
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protectorsprotectors
•• 60/90 vac switch (in some cases )60/90 vac switch (in some cases )
•• Power indicator LEDS Power indicator LEDS
•• Optical nodes used in your system….Optical nodes used in your system….
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System Powering PrinciplesSystem Powering Principles
•• The device that actually couples the 60The device that actually couples the 60--Hz Hz
power onto the cable is called apower onto the cable is called a power power
inserter inserter
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inserter inserter
•• The AC power supplyThe AC power supply
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Application to CATVApplication to CATV
•• The 60The 60--V power supply is considered to V power supply is considered to
be the source E in Ohm’s Law.be the source E in Ohm’s Law.
•• Since individual current draws are Since individual current draws are
already determined by the amplifier’s already determined by the amplifier’s
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already determined by the amplifier’s already determined by the amplifier’s
manufacturer, simply adding the current manufacturer, simply adding the current
draws together gives the total draw from draws together gives the total draw from
the power source (supply). This is the power source (supply). This is
considered the current I. considered the current I.
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Application to CATV Application to CATV (cont.)(cont.)
•• The cable used in a CATV system is the The cable used in a CATV system is the
series resistor. Rating of the cable’s loop series resistor. Rating of the cable’s loop
resistance can be found in the resistance can be found in the
manufacturer’s specifications, usually in manufacturer’s specifications, usually in
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manufacturer’s specifications, usually in manufacturer’s specifications, usually in
1,0001,000--foot increments. These foot increments. These
specifications are rated in ohms per 1,000 specifications are rated in ohms per 1,000
feet. This loop resistance is considered to feet. This loop resistance is considered to
be the R in Ohm’s Law. be the R in Ohm’s Law.
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Application to CATV Application to CATV (cont.)(cont.)
The formula for determining the exact The formula for determining the exact
resistance of a length of cable is the resistance of a length of cable is the
combined resistance of the coaxial cable’s combined resistance of the coaxial cable’s
center conductor and the shield: center conductor and the shield:
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center conductor and the shield: center conductor and the shield:
feetperceresisloopratedxlengthspan
1000tan1000
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Powering System DesignPowering System Design
•• A/C power loses voltage as it travels A/C power loses voltage as it travels
through cable just as RF signal does. through cable just as RF signal does.
•• The effect on 60 Hz power is much less The effect on 60 Hz power is much less
than the higher frequencies used in the RF than the higher frequencies used in the RF
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than the higher frequencies used in the RF than the higher frequencies used in the RF
spectrum.spectrum.
•• Providing active gear in the system with the Providing active gear in the system with the
proper voltage levels is just as important as proper voltage levels is just as important as correct RF levels. correct RF levels.
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Powering System Design Powering System Design (cont.)(cont.)
•• Low voltage levels can cause picture Low voltage levels can cause picture
problems and intermittent outages (flashing).problems and intermittent outages (flashing).
•• Active devices use a set amount of current as Active devices use a set amount of current as
long as the input AC voltage remains above long as the input AC voltage remains above
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long as the input AC voltage remains above long as the input AC voltage remains above
the minimum requirement for the device.the minimum requirement for the device.
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Powering System Design Powering System Design (cont.)(cont.)
•• The current draw of amplifiers downstream The current draw of amplifiers downstream from a section of coax determines the voltage from a section of coax determines the voltage drop across that section of coax. The more drop across that section of coax. The more amplifiers on a coax section, the more voltage amplifiers on a coax section, the more voltage will be lost.will be lost.
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will be lost.will be lost.
•• Coaxial cable has a higher resistance and Coaxial cable has a higher resistance and loses more voltage at higher temperatures. loses more voltage at higher temperatures. Voltage problems that are borderline at low Voltage problems that are borderline at low temperatures may become outages at higher temperatures may become outages at higher temperatures.temperatures.
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Calculating Input Voltage to AmplifiersCalculating Input Voltage to Amplifiers
•• It is necessary to complete five steps to It is necessary to complete five steps to calculate powering:calculate powering:
•• Gather all the necessary specifications.Gather all the necessary specifications.
•• Add the current draws.Add the current draws.
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•• Add the current draws.Add the current draws.
•• Calculate the loop resistance of the first span.Calculate the loop resistance of the first span.
•• Calculate the voltage drop across the first span.Calculate the voltage drop across the first span.
•• Subtract the voltage drop from the source Subtract the voltage drop from the source voltage.voltage.
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Calculating Input Voltage Calculating Input Voltage
to Amplifiersto Amplifiers (cont.)(cont.)
•• To complete Step One, you will need to gather To complete Step One, you will need to gather the following specifications:the following specifications:
•• Determine the loop resistance for all cable Determine the loop resistance for all cable used. used.
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used. used.
•• Determine the current draws from all types of Determine the current draws from all types of amplifiers in the system.amplifiers in the system.
•• Determine the output voltage and amperage Determine the output voltage and amperage rating of the power supply used. (It is probably rating of the power supply used. (It is probably 60 VAC.)60 VAC.)
•• Determine the cable loop resistance.Determine the cable loop resistance.
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Calculating Input Voltage Calculating Input Voltage
to Amplifiersto Amplifiers (cont.)(cont.)
1.4a 1.4a 1.4a 2000 ft 1500 ft
Trunk Amplifier #1
Trunk Amplifier #2
Trunk Amplifier #3
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1.4a 1.4a 1.4a
.7a 60v
2000 ft 1500 ft
500ft
power supply Distribution
Amplifier #1
Cable Section #1 Cable Section #2
Cable Section #3
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Calculation Practice Calculation Practice •• Use the specifications listed below:Use the specifications listed below:
– Trunk cable ft. .76 ohms per thousand
– Distribution cable 1.72 ohms per thousand ft
– Trunk amplifiers 1.4 amperes draw
– Distribution amplifiers .7 amperes draw
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6 0 V A C
2 0 0 0 f t 1 7 5 0 f t 1 9 0 0 f t 1 8 0 0 f t
6 5 0 f t 7 0 0 f t
6 0 0 f t
7 5 0 f t
1 2 3 4 5 1
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Power ModulePower Module
•• Ferroresonant transformerFerroresonant transformer
•• Resonant transformerResonant transformer
•• DualDual--mode temperaturemode temperature--compensating battery compensating battery chargercharger
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chargercharger
•• DC to AC converter (inverter)DC to AC converter (inverter)
•• Transfer isolation relayTransfer isolation relay
•• Main circuit assembly containing the logic Main circuit assembly containing the logic circuitcircuit
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Theory of OperationTheory of Operation
•• AC (line) operationAC (line) operation
•• Inverter (standby) operationInverter (standby) operation
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•• Charger operationCharger operation
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ComplianceCompliance
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FCC Proof of Performance FCC Proof of Performance -- FieldFieldFCC Proofs Performance
SpecImpact on Signal Quality
Minimum
Visual Signal
Level
0 dBmV at the
terminal device
(+3 dB at the
If a given channel signal level is
too low, picture quality may be
affected by an adjacent channel.
225
Level (+3 dB at the
end of 150 feet
of cable)
affected by an adjacent channel.
Shows relative signal intensity.
Terminal
Isolation
18 dB port to
port
Adjacent customer interference
(measured at tap port) isolation
minimizes migration of
interference signals originating
at one subscriber tap port from
an adjacent subscriber tap port.
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FCC Proof of Performance FCC Proof of Performance -- FieldFieldFCC Proofs Performance
SpecImpact on Signal Quality
Low
Frequency
Disturbance
Maximum 3%
of reference
signal
Low frequency disturbances can
produce hum bars (slow
scrolling horizontal lines).
226
Disturbance
(hum)
signal scrolling horizontal lines).
Carrier-to-
Noise (C/N)
Minimum 43
dBc
Below 40 dBc noise is visible as
“snow” on the television.
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FCC Proof of Performance FCC Proof of Performance -- FieldFieldFCC Proofs Performance
SpecImpact on Signal Quality
Cumulative
Leakage
Index (CLI)
Figure of merit
(varies by
measuring
Amount of energy (at
frequencies used by
aeronautical communications)
227
Index (CLI) measuring
technique)
aeronautical communications)
that is leaking out of the system
(may also indicate ingress).
Intermodulatio
n Distortions
(CTB, XMOD,
CSO)
Minimum 51
dBc
Multiple beat patterns result
when levels are too high. (CTB
shows multiple horizontal bars;
XMOD shows multiple pictures
simultaneously; and CSO shows
a diagonal pattern.)
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Performance MeasuresPerformance Measures
•• Adjacent carrier levelsAdjacent carrier levels
•• HumHum
•• CNRCNR
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•• CNRCNR
•• PeakPeak--toto--valleyvalley
•• LeakageLeakage
•• Direct pickupDirect pickup