SCTE Broadband Distribution Specialist Certification Prep

SCTE Broadband SCTE Broadband

Distribution Specialist Distribution Specialist Distribution Specialist Distribution Specialist

Certification PrepCertification Prep

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

HFC Network SegmentsHFC Network Segments

Hub

Hub

Master Headend

TelecomCenterTelecomCenter DistributionDistributionTransportTransport PremisesPremises

Hub

Hub

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)

Broadband Distribution Broadband Distribution Specialist (BDS)Specialist (BDS)

•• System ArchitecturesSystem Architectures

•• Distribution ComponentsDistribution Components

•• Signal TypesSignal Types•• Signal TypesSignal Types

•• Troubleshooting and Troubleshooting and


•• ConstructionConstruction

•• SafetySafety

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


•• Alternative Transport Alternative Transport

SystemsSystems

Hub

Hub

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

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)

Why Certify?Why Certify?

Certification Benefits Both…Certification Benefits Both…•• IndividualsIndividuals

•• Our industryOur industry


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


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

Getting StartedGetting Started

•• Preparing to CertifyPreparing to Certify

•• Getting CertifiedGetting Certified

•• Staying CertifiedStaying Certified•• Staying CertifiedStaying Certified

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

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)

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)

BDS SectionsBDS Sections

Distribution ComponentsDistribution Components

Maintenance & TroubleshootingMaintenance & Troubleshooting

Safety & ConstructionSafety & ConstructionSafety & ConstructionSafety & Construction

Signal TypesSignal Types

System ArchitecturesSystem Architectures

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)

18

(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.

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.

19

•• 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).

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)

HertzHertz

21

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.

22

throughout the United States.throughout the United States.

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

23

wire, satellite and cablewire, satellite and cable

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.

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

25

•• 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.

Typical CATV NetworkTypical CATV Network

Layout DownstreamLayout Downstream

26

Return Path Frequencies Return Path Frequencies

Versus OverVersus Over--thethe--Air UseAir Use

27

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,

28

NTSC requires each channel to be 6 MHz,

divided into separate segments for

Video

Audio

Color

Horizontal sweep information located at specific

points

Digital SignalDigital Signal

Digital refers to a method of encoding

information using a binary system made up

of zeroes and ones.

29

Technology has made it possible to

compress many digital channels into a 6

MHz space.

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

Actual Snapshot of an Analog Actual Snapshot of an Analog

ChannelChannel

31

Network Design and MapsNetwork Design and Maps

32

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.

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

34

•• 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

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:

35

– 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.

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.

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.

HFC Network ModelsHFC Network Models

38

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.

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.

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

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

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

43

•• Impedance of 75 ohms to prevent Impedance of 75 ohms to prevent

ingress/egressingress/egress

•• Unity gain Unity gain

HFC Network Segments

44

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

45

degradation

HFC Network Segments (cont.)

Segment 2 Segment 2 –– Optical DistributionOptical Distribution

Hub-to-node link

Range from 2 to 4 miles

46

Almost exclusively analog amplitude

modulation (AM) laser

Fiber-to-feeder (FTF)

Fiber-to-the-serving area (FSA)

Optical service area (OSA)

Coaxial Distribution Model

47

Optical service area (OSA)

Fiber to the home (FTH)

The coaxial plant consists of two segment

• Express

• Feeder

Coaxial Distribution Model

48

Segment 3 Segment 3 –– Express Coaxial PlantExpress Coaxial Plant

Typical short cascade of amplifiers (1 to 3)


49

Typical covers less than 2000 feet

Key to the future upgradeability of the HFC

network

Segment 4 Segment 4 –– Feeder Coaxial PlantFeeder Coaxial Plant

Line extender amplifier L/E commonly a high

output level amplifier delivers the signals to


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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

Segment 5 Segment 5 –– Subscriber DropSubscriber Drop

The portion from the tap to the customer

premises


51

premises

The portion from the side of the customer

premises to the subscriber terminal

Other ArchitecturesOther Architectures

Fiber DeepFiber Deep

No RF Amplifiers after the node

Fiber is within a few hundred feet of the

52

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

Standard HFC NetworkStandard HFC Network

53

2 power supplies

27 RF amplifiers

1 optical node

595 homes passed 79 HPM

7.49 miles UG

595 Homes per node

Fiber Deep NetworkFiber Deep Network

54

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

FTTH still converts fiber to coax

FTTH takes the fiber to the house demark or

NIU

Fiber To The Home – FTTH

55

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!

Typical NIU used for FTTHTypical NIU used for FTTH

56

Signal TypesSignal Types

57

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

58

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

59

signalsignal

•• Video carriers use amplitude modulationVideo carriers use amplitude modulation

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”

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)

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

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

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.

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.

65

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.

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.

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

68

•• 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

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

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

70

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

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.

72

Cable IssuesCable Issues

Simplest component in the system

Loss increases as signal frequency increases.

Non-Linear cable loss

73

Non-Linear cable loss

• Natural (and unavoidable) characteristic of coax

Equalizers are needed to compensate for this

effect.

73

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.”

7474

contribution.”

• Return Loss

• Flatness

Network IntegrityNetwork Integrity•• ConnectorsConnectors

•• HousingsHousings

•• Cable spansCable spans

7575

•• 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

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

76

Network Integrity Network Integrity (cont.)(cont.)

Resonate peak

• May form as a result of constructive reflected

energy

77

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).

77

Coaxial Cable Coaxial Cable (cont.)(cont.)

Coaxial cable - types

• Armored Sheath

• Flooded / Underground

• Messenger

78

• 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.

78

Skin EffectSkin Effect

Higher frequencies travel closer to the outer diameter or the “skin” of the center conductor.

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center conductor.

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

80

The radii can be obtained in your cable

hand book

Always use an approved bending board

Powers of 10 Powers of 10

81

Positive & Negative Powers Positive & Negative Powers

of 10 of 10

•• Examples of positive powers of 10Examples of positive powers of 10

82

•• Examples of negative powers of 10Examples of negative powers of 10

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.

Characteristics of Scientific Characteristics of Scientific

Notation Notation

•• Converting from scientific to standard Converting from scientific to standard notation notation

84

•• Converting from standard to scientific Converting from standard to scientific notationnotation

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)

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)

86

•• Nano voltage, stated as Nano voltage, stated as nanovoltsnanovolts (nV) (nV)

•• Pico capacitance, stated as Pico capacitance, stated as picofarads picofarads (pf)(pf)

Ratios Ratios

•• Examples of ratios Examples of ratios

87

•• Finding the unknown termFinding the unknown term

Decibels Decibels

•• The Bel The Bel

•• The decibel The decibel

88

•• Definition of the decibel Definition of the decibel

•• Power ratioPower ratio

Basic Electronic PrinciplesBasic Electronic Principles

•• ConductorsConductors

•• VoltageVoltage

89

•• VoltageVoltage

•• ResistanceResistance

•• Ohm’s Law Ohm’s Law

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))

90

•• 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)

Review of Basic CircuitsReview of Basic Circuits

Series CircuitsSeries Circuits

R1+ R2 = Rt

Review of Basic CircuitsReview of Basic Circuits (cont.)(cont.)

Parallel CircuitsParallel Circuits

93

Review of Basic Circuits Review of Basic Circuits (cont.)(cont.)

Series/Parallel CircuitsSeries/Parallel Circuits

94


Voltage DropsVoltage Drops

Calculate the voltage drops and current draw across the Calculate the voltage drops and current draw across the

circuitcircuit

95


•• 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

96

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.

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..

97

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..

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..

98

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

Distribution Cable Loss Distribution Cable Loss

•• Every type of cable affects signal loss Every type of cable affects signal loss differently. differently.

99

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.

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

100

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.

Amplifiers in Conventional Amplifiers in Conventional

Cable ArchitectureCable Architecture Active devices

• Nodes

• Amplifiers

101

• Amplifiers

Trunk amplifier

Bridging amplifier

Line extender (LEs)

101

Physical Description of Physical Description of

a Broadband Amplifiera Broadband Amplifier Push/pull

Feed forward

102

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.

102

Older-style Amplifier Components Newer-style Amplifier Components

Housing Housing

Baseplate (also called a motherboard) A single module

Plug-in modules

The Amplifier HousingThe Amplifier Housing

Lid

Input and output connections

Fins/heat sink

103

Fins/heat sink

Gasket

Mesh/RFI gasket

Bolts

103

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

104

Old-Style interior amplifier components

Newer-style interior amplifier component

104

How an Amplifier WorksHow an Amplifier Works

Note:

Return bandwidth varies by system. Your

system may operate at 5-45 MHz, 5-40 MHz,

105

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.

105

Automatic Gain ControlAutomatic Gain Control

AGC – Automatic gain control

TLC - Thermal level control

ALS – Automatic level and slope control

106

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.

106

Key Components of an Key Components of an

AmplifierAmplifier Hybrids (gain stages)

Diplex filter

RF/AC diplex filter

107

RF/AC diplex filter

Input test point

Output test point

Input and interstage PADs

Input and interstage equalizers

107

Key Components of an Key Components of an

AmplifierAmplifier

Input and interstage equalizers

Power pack

AGC/ASC/ALS

108

AGC/ASC/ALS

Thermal Control

Shunts/fuses/power blocks

108

Coaxial Cable Coaxial Cable

and Broadband Amplifiersand Broadband Amplifiers Characteristics of coaxial cable

• Attenuation

• Tilt

109

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

Coaxial Cable Coaxial Cable

and Broadband Amplifiers and Broadband Amplifiers (cont)(cont)

Unity gain

Amplifier spacing

Using PADs to achieve unity gain

110

Using PADs to achieve unity gain

• Attenuator PADs

110

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.

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.

111

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


to Achieve Unity Gainto Achieve Unity Gain Cable attenuation and frequency

Cable loss ratio

•

112

• The relationship between the cable’s attenuation

of a higher frequency to the attenuation of a

lower frequency.

Equalizer attenuation curve

Equalizer function

112


to Achieve Unity Gainto Achieve Unity Gain PAD and equalizer practice

Summary – Balancing an amplifier with manual gain and slope controls

113

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

System Sweep ProcessSystem Sweep Process

Definition

Equipment

Procedures

114

Procedures

Installing the sweep transmitter

114

System Sweep Process System Sweep Process (cont.)(cont.)

Reverse fiber receivers

Sweeping a fiber node

Sweep and balance

115

• Balancing the node

• Taking references

• Raw sweep (forward path)

• Referencing (forward path)

• Balance and sweep forward path

• Sweep the return 115

System Sweep Process System Sweep Process (cont.)(cont.)

Analyzing a sweep trace

Suckout

Roll-off – low end of the passband

116

Roll-off – low end of the passband

Roll-off – high end

Standing waves

116

AmplifiersAmplifiers

Frequency response

AC power direction

Amplifier power direction

117

Amplifier power direction

Setting up and amplifier for proper power

direction

117

Amplifiers Amplifiers (cont.)(cont.)

Fusing an amplifier output

Blocking power

Checking an active device’s “vital signs”

118

Checking an active device’s “vital signs”

• Check for signal leakage

• Check the physical characteristics

• Measure AC and DC voltage

• Measure RF signal

118

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

119

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.

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.

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

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.

122

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.

123

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.

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.

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

125

Bypass BarBypass Bar

126

Socket for Return ConditionerSocket for Return Conditioner

127

RF Integrity Gasket and RF Integrity Gasket and

Rubber Weather GasketRubber Weather Gasket

128

Seizure Screw CorrosionSeizure Screw Corrosion

129

Voltage Measurement from Voltage Measurement from

TapTap

130

Current Measurement from Current Measurement from

TapTap

131

Physical CharacteristicsPhysical Characteristics

of Power Insertersof Power Inserters

132

Types of Taps Types of Taps

Feed-Through and Terminating Taps

133

Application Criteria Application Criteria

Selecting theSelecting the Number of Tap PortsNumber of Tap Ports

134

Selecting Tap Value Selecting Tap Value

Calculating Tap Signal Levels Calculating Tap Signal Levels

135

Return PathReturn Path

136

Frequency AllocationFrequency Allocation

137

Services using the ReturnServices using the Return

138

• Telephone • High-speed Data (HSD) • IPPV (Impulse Pay-per-View) • Status monitoring• VOD (Video on Demand) • IPG (Interactive Program Guide)

Upstream Allocations

5 MHz 12 MHz

13 MHz

20 MHz 42 MHz

50 MHz

26.975 MHz

29.75 MHz

139

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

OffOff--air Signals Using air Signals Using

Return Path FrequenciesReturn Path Frequencies

140

Ham RadioHam Radio

141

CB RadioCB Radio

142

Impulse/Electrical NoiseImpulse/Electrical Noise

143

Ingress/Noise Over TimeIngress/Noise Over Time

144

Return Path Signal FormatsReturn Path Signal Formats

Telephone Signal on the Return PathTelephone Signal on the Return Path

145

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

146

•• 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

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

147

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

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.

Review of Return Path Setup Review of Return Path Setup (cont.)(cont.)

149

Unity Gain on the HFC Unity Gain on the HFC

NetworkNetwork

150

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.

Unity Gain Reference Points Unity Gain Reference Points (cont.)(cont.)

152

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.

Raw Sweep (Reverse Path) Raw Sweep (Reverse Path) (cont.)(cont.)

154

Referencing Reverse PathReferencing Reverse Path

155

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.

156

•• 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.

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

Exercise Exercise –– Modem Output Modem Output

Level Level (cont.)(cont.)

158

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.

159

upper end of their dynamic range.upper end of their dynamic range.

•• Why is that desirableWhy is that desirable??

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).

160

•• 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.

Reverse Tap Port WindowReverse Tap Port Window

161

Using Reverse ConditioningUsing Reverse Conditioning

162

Transmit Levels Transmit Levels

without Reverse Input PADswithout Reverse Input PADs

163

Transmit Levels Transmit Levels Using Reverse Input PADsUsing Reverse Input PADs

164

Check your local design and regional policy before

adding or changing system PADing.

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

165

•• 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

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.

166

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

167

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.

Noise Accumulation: ForwardNoise Accumulation: Forward

168

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.

Energy DistributionEnergy DistributionEnergy DistributionEnergy Distribution

Forward Path SignalForward Path Signal

169

Energy AccumulationEnergy AccumulationEnergy AccumulationEnergy Accumulation

Return Path SignalReturn Path Signal

170

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.

171

3, 4, and 5.3, 4, and 5.

Clean Noise FloorClean Noise Floor

172

Ingress ExamplesIngress Examples

173

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.

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

175

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!

Common Path Distortions Common Path Distortions

(CPD)(CPD)

176

Typical plant contact points where Typical plant contact points where

dissimilar metals contribute to CPDdissimilar metals contribute to CPD

Common Path DistortionsCommon Path Distortions

(CPD) (CPD)

177

CPD will generate a spike approximately every 6 MHz.

Electrical Frequency Electrical Frequency

InterferenceInterference

178

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

179

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.

Diplex Filter Diplex Filter

180

The reverse path screenshot shown illustrates poor diplex filter

isolation causing common path distortions.

Radio Interference Radio Interference

181

Signal ImpairmentsSignal Impairments

182

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.

183

•• 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.

Analog Signal ImpairmentsAnalog Signal Impairments

184

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

185

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.

186

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.

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

187

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.

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.

188

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

189

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.


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

190

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.


191


•• 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.

192

•• 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.

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

193

•• 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.

Composite Triple Beat Composite Triple Beat (cont.)(cont.)

194

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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….

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

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.

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.

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

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.

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.

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.

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.

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.

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

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

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

Theory of OperationTheory of Operation

•• AC (line) operationAC (line) operation

•• Inverter (standby) operationInverter (standby) operation

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•• Charger operationCharger operation

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.

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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.



Low

Frequency

Disturbance

Maximum 3%

of reference

signal

Low frequency disturbances can

produce hum bars (slow

scrolling horizontal lines).

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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.



Cumulative

Leakage

Index (CLI)

Figure of merit

(varies by

measuring

Amount of energy (at

frequencies used by

aeronautical communications)

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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.)

Performance MeasuresPerformance Measures

•• Adjacent carrier levelsAdjacent carrier levels

•• HumHum

•• CNRCNR

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•• CNRCNR

•• PeakPeak--toto--valleyvalley

•• LeakageLeakage

•• Direct pickupDirect pickup

SCTE Broadband Distribution Specialist Certification Prep

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