Cable Television System Measurements Handbook NTSC Systems
Cable Television SystemMeasurements HandbookNTSC SystemsFebruary 1994
HCable Television SystemMeasurements HandbookNTSC SystemsFebruary 1994 Copyright Hewlett-Packard Company 19941400 Fountain Grove Parkway, Santa Rosa, California, USA.
Table of ContentsChapter 1.TV Signal and CATV DistributionTV Broadcast Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1The Cable Television Distribution System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4Chapter 2.Measurement ParametersSignal Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2Signal Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15Ingress and Co-Channel Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15Low Frequency and Coherent Disturbances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15Measuring Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19Channel Frequency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20Depth of Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21System Frequency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23Interference Outside the System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23In Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26Chapter 3.Test InstrumentationNetwork and Signal Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1In Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6Chapter 4.Performance Measurements with a Spectrum AnalyzerAbsolute and Relative Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1Accuracy Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2Suggested Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2Before you Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3Full System Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4Visual and Aural Carrier Level and Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4Measuring C/N with the Spectrum Analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7Corrections Required to Measure Noise Power Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7Measuring and Calculating Carrier to Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10Computing C/N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11Quick Look C/N Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12Co-Channel and Ingress Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13Low Frequency Disturbances (Hum) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15Coherent Disturbances: CSO and CTB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17Crossmodulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19In-Channel Frequency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20Using Program Video and VITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22Depth of Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-25System Frequency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27Appendix A.Reference Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1Appendix B.Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1Appendix C.Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1
INTRODUCTIONAt the time of the first edition of this handbook (1977)the number of cable television systems was growingrapidly and regulations were being enforced. Growth hasnot abated. With over 10,000 systems in North America,both subscriber base and the channels per systemcontinue to grow. Then, as now, these pressures requiresystem maintenance and testing with increasedefficiency. Better test equipment helps. So does yourunderstanding of the measurement principles.This handbook refreshes the measurement concepts andupdates the use of the modern spectrum analyzer formaking proof-of-performance measurements.February 1994
Chapter 1TV Signal and CATV DistributionThis chapter reviews the signal and distribution methods used in cabletelevision systems as background for instrumentation and measurementdiscussions that follow.TV Broadcast SignalThe television broadcast signal, whether it be NTSC, PAL or SECAM, isthe most complex signal used in commercial communications; comprisedof amplitude, frequency, phase and pulse modulation fitted into a 6 MHzchannel with a single sideband transmission process called vestigialsideband.Figure 1.1 shows the relationship of the RF carrier's modulation to a TVraster. The numbers relate to the NTSC standard, but the methods applyto PAL and SECAM as well. In Figure 1.1(a), the amplitude modulation isshown as an envelope on the RF carrier, symmetrically about a zerovoltage amplitude. When a TV receiver looks at this carrier, it picks offonly the envelope and discards the RF carrier. Figure 1.1(b) expands aportion of this envelope to show the vertical scan as frame sync pulse.The square sync pulse provides bursts of RF energy at the peak carrieramplitude. This repetitive burst synchronizes vertical scan on the TVreceiver at a 59.94 Hz rate (60 Hz for B/W).Figure 1.1(c) is a 1:100 time domain magnification of the waveform inFigure 1.1(a). It shows the horizontal sync pulses and luminanceinformation on two of the 525 horizontal lines that make up a singleframe. These sync pulses, which run at a 15,734.264 Hz rate, also havetheir tops at the peak RF carrier level. For color transmission this pulseincludes a 3.579545 MHz burst on its trailing side, or "back porch." Thisburst of 3.58 MHz is still an amplitude modulation envelope of thecarrier; that is, for the duration of the burst the amplitude of the RFcarrier increases and decreases at a 3.58 MHz rate.WAVEFORM MONITORREADS SIGNALENVELOPE59.94 Hz RATE(60 Hz FOR BW)MOST OF THE ENERGYIS IN THE SYNCPULSESFigure 1.1(d) shows the TV picture that results from these amplitudemodulation (AM) signals. The area not viewed by a TV receiver is alsoshown in the figure. The horizontal black bar at the bottom of the screen,the vertical interval, usually contains test signals used by the broadcastsystem for on-line performance tests that will not interfere with theregular programming.The audio information in a TV channel is a frequency modulated carrierplaced 4.5 MHz above the visual carrier at less than 1/8 of its power.Figure 1.1 (a) doesn't show the aural carrier. The aural signal frequencymodulates onto the RF carrier, thus becoming its sideband.1-1TV VIDEO AUDIO COLOR
AMPLITUDE MODULATIONOF RF CARRIERSEE FIGURE (b)UNMODULATEDCARRIER LEVELFROMa) Television video is amplitude modulatedon the RF carrier and received by theantenna. The TV broadcast carriercontains the information for luminance(black and white), chrominance (color),and synchronizing (format) signalsrequired by the TV receiver.TO0 VOLTSANTENNARECEIVER55.25 MHz(CH.2)b) Amplitude envelope of the signal showsthe vertical scan frame sync pulses at a59.94 Hz rate which establish the verticalframe in the TV screenTIME(a) CARRIER VOLTAGE ON ANTENNA LEADVERTICALSYNCHORIZONTAL SYNC PULSEVERTICALBLANKINGSEE FIGURE (c)COLOR BURST AT 3.58 MHzBLACKWHITE63.56 µSEC15734 HzRATE16.7 mSEC, 59.94 Hz RATETIMETIMELUMINENCE AND CHROMA FOR ONE LINE(c) TWO LINES OF HORIZONTAL SCAN(b) SINGLE FRAME OF VERTICAL SCANHORIZONTAL BLANKING525LINES485LINESSCAN MOTIONVERTICAL BLANKINGc) Horizontal sync pulses and luminanceinformation on two of the 525 horizontallines for a single frame TV frame.d) The resulting TV picture with areasoutside the picture used to transmitsynchronizing and test informationVERTICAL SYNCRECEIVER FRAME(RASTER)(d) TELEVISION PICTURE FORMATFigure 1.1. TV broadcast carrier modulation parameters for NTSC standards.1-2
AMPLITUDEFigure 1.1 shows the broadcast signal in the time domain, as on anoscilloscope. Additional information is available with a display of thesignal's amplitude versus frequency instead of time. Such a display iscalled the frequency domain or frequency spectrum.FREQUENCYSPECTRUM OR DOMAINFigure 1.2 shows a frequency domain display of a single TV channel. Thevertical axis is scaled to the power of the signal, in units relative to amillivolt. (Chapter 2 covers units and power.) The modulation shown inFigure 1.1 in the time domain is now shown in the frequency domain.Since the visual signal contains most of the transmitted power includingaural and color information which is modulated onto it, it is the carrier.The sidebands generated would be symmetrical to the carrier exceptthat, on the lower frequency side (to the left of the carrier), the sidebandsbeyond 0.75 MHz are trapped, or filtered, prior to transmission. Thisvestigial sideband technique is used to conserve frequency spectrum.The TV receiver uses the full upper sideband and the appended lowersideband to reconstruct the TV video.VISUALAURALCOLORFREQUENCYThe color burst is 3.579545 MHz, or 3.58 MHz, above the carrier. Thissignal contains the picture's color or chroma signal. Each horizontal syncpulse has a 3.58 MHz burst to calibrate the TV receiver's color circuitryfor each horizontal line. The color information is phase modulated.1-3THE VISUAL SIGNAL ISTHE CARRIER
Visual CarrierColor SubcarrierAural Carrier0 10Signal Amplitude in dBmV 20 30 40 50 60 70 80LowerChannelBoundary3.584.56.0Frequency, MHzUpperChannelBoundaryFigure 1.2. In the frequency spectrum, the TV channel energy separates into its major signal components.The aural carrier is placed 4.50 MHz above the visual carrier (or 250 kHzfrom the upper edge of the channel). It is an FM signal with a 50 kHzbandwidth.The Cable Television Distribution SystemCATV COMMUNITY CABLE TVEarly television cable distribution systems were established to servecommunities where a majority of the residents could not receiveover-the-air programming because of geographical interference. The termCATV, for community antenna television, has long since been extendedto mean any region wired for the reception of broadcast programming,whether or not good residential antenna reception is available.Subscribers to these systems generally pay a monthly fee for the service,which usually includes increased channel selection, for-pay and locallyoriginated programming.1-4
ON SITEREMOTEFM/UHF/VHFFM/UHF/VHFANTENNATRUNK LINE Radiating out from the headend are trunk lineswhich carry the main CATV signal to be distributed. Opticaltechnology is growing as a wide-band media for long distancetrunk lines.ANTENNASIGNALLEVELSMICROWAVELINKLOCALIN dBmVCABLE 75 ohm coaxial cable is used for most signaldistribution because of its convenient center conductor toshield cross sectional ratio. Losses from cable are fromthe resistance of the copper wire and the frequency dependentlosses caused by radiation and the dielectric capacitance.CABLE TERMINATION The ends of cables mustmatch the cable impedanceor signal reflections willcause distortion.CARS1000 2000STUDIOFEET 30 10 30 30 1075ohmsFEEDER ( DISTRIBUTION )LINES Feeder lines arecoax cables and amplifierswhich bring the CATV signalinto the subscriber'sneighborhood.TVROHEADEND The headend is the source forall signals distributed throughout the systemas well as the collection point for all signalsources. Headend equipment formats allthese incoming signals into a frequency bandsuitable for distribution and home reception.TRUNK AMPLIFIERS The amplifiers alongthe trunk line maintain signal strength with lowdistortion, low noise and suitable gain. Distortion caused by an amplifier will be increasedby following amplifiers. 44 22 30 24TAP Draws off a portionof the feeder line signal forthe subscriber, therebyreducing the line's signallevel (increased insertionloss). The more taps at afeeder, the less power 22each tap canprovide. 29Trunk amplifiers compensate for cable losseswith automatic slope control ( ASC ) and automatic gain control ( AGC ). 4 dBmVBRIDGER AMPLIFIER This amplifier providestwo to four branching lines, or feeders, fordistribution of the signals to subscribers.DISTRIBUTION ( EXTENDER ) AMPLIFIER The amplifier boosts signal to make up forcable and tap losses. Amplifier distortion isnot critical as in the trunk amplifier.75ohms 6SYSTEM LOSS CATV distributionsystem must compensate for cableand device losses. System losses,at the highest operating frequency,are referred to as "dB of cable"without reference to specific cablesize or device losses.DROP is the cable andhardware from tap to subscriber, including splittersor couplers to serve morethan one subscriber. Thelevel at the subscriber'sTV must be between 6 and 14 dBmV to provideacceptable reception.Figure 1.3. A typical CATV coaxial distribution system with signal levels in dBmV given along one complete distribution branch.1-5
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Chapter 2Measurement ParametersService and repair of faulty equipment is one important aspect of theoperator's distribution system responsibilities. The other is preventivemaintenance, the so called "proof-of-performance" testing which qualifiesa system for governmental agency approval.For a complete understanding of proof-of-performance measurements,let's take an overview of electronic measurement techniques. Whetherthe electronics is a circuit board in a trunk amplifier or an entiredistribution system, it can be thought of as a black box with one or moreconnectors for access.Two approaches can be taken to determine how this mysterious blackbox functions. First, monitor each of the connectors while the boxperforms in its normal capacity. Or, secondly, feed a known signal in oneconnector and compare this signal very accurately with the output atanother connector. The first procedure is called signal analysis. Thesecond, because it tells specifically how much the black box circuitchanges a signal, is called network analysis. See Figure 2.1.ALL MEASUREMENTSARE EITHER OF SIGNALSOR OF NETWORKSa) Network AnalysisNetwork Analysis is characterizing a circuit by displaying thephase and amplitude changes on a known input kAnalyzerPhaseDisplayAmplitudeFrequencyb) Signal AnalysisSignal analysis displays the amplitude spectrum of a test tudeFigure 2.1. Network analysis and signal analysis are techniques for analyzing the behavior of electronic circuits.2-1
SPECTRUM: WHATSIGNAL IS ON THECABLE?NETWORK: WHAT DOESCIRCUIT DO TO ASIGNAL?MEASUREMENT'S BASICELEMENTS:FREQUENCYAMPLITUDESignal analysis measures both amplitude and frequency. Measuring thedc voltages of a bridge's power supply, the frequency of a converted UHFchannel at the headend and the system noise level at a subscriber dropare examples of signal analysis.Network analysis measurements offer more information about a circuitor system, but the techniques and equipment are more complicated thanin signal analysis. Group delay is an example of a network analysismeasurement. Equipment which can provide a test signal as well asmeasure frequency, amplitude, phase and their combinations arenetwork analyzers.The output from signal and network analyzers can take many forms: CRTdisplays, meters, data files, and modem signals to name a few.As you can see, the common denominator in these measurementtechniques are the parameters of frequency, amplitude, phase andtheir various combinations. Let's summarize how these parameters arebest qualified for the CATV industry.Signal FrequencySYSTEM FREQUENCYACCURACY MOSTIMPORTANTAccuracy is critical. Inaccurate carrier frequencies or signal spacing cancause serious distortions and interference as vital sidebands areabsorbed by passive bandpass filters or infringe upon adjacent channels.Frequency accuracy is expressed as a percent of the RF frequency, partsper million or Hertz. The accuracy figure gives the limits of thetolerance range. For example, a television carrier at 193.25 MHz must bewithin 100 parts in 10 6 for a broadcast power of less than or equal to 100watts or 1000 Hz for a power of greater than 100 watts. Each can beexpressed in Hz or as a percent: 100watts 100wattsSTABILITY AFFECTSACCURACY193.25 MHz (193.25 MHz 100 10 6 ) 193.25 MHz 19.325 kHzor193.25 MHz 0.01%193.25 MHz 1000 Hzor193.25 MHz 0.00052%Frequency stability refers to the tendency of signal sources to driftwith age, temperature, electrical interference and mechanical vibration.Short term frequency deviation is called residual FM (frequencymodulation) and long term change is called drift. If the residual FM is100 Hz peak to peak for a carrier in ten seconds, the carrier frequencymay not go above or below its nominal frequency by more than 100 Hz inany one 10 second period. A drift spec may be 100 parts per million in 122-2
hours, which means for a carrier, f c, the frequency change, fc, will beless than 1006 f c Hz (where f c is in Hz)10in 12 hours.For the measurement of frequencies whose accuracy and stability aresuspect, the measurement instrument should have at least a factor of 3better frequency accuracy and stability than the spec. In your CATVsystem, such an instrument could pinpoint carrier and pilot inaccuracies,assure correct channel and sideband spacing, and identify unwantedsignals that may be interfering with the system.(a)Channel 2FromStationf f fLOIF2DownConverterf2UpConverterChannel 2To CATVSystemSignalProcessffLOfLO2 f fLOIFLocalOscillator(b)fDownChannel 44FromStationIFf 44 fLO1 f44Channel 8To CATVSystemProcessffLO1LO2f 8 f LO2 f IF2nd L.O.1st L.O.(c)MicrowaveLinkUpChannel 9FromStationUPf c f LO2 f IFDownSignalProcessf9fChannel 6To CATVSystemf LO2LO1fRF fLO1 fgMicrowaveL.O.MicrowaveL.O.Figure 2.2. Frequency accuracy and stability of the broadcast signal in a CATV system depends upon t
The audio information in a TV channel is a frequency modulated carrier placed 4.5 MHz above the visual carrier at less than 1/8 of its power. Figure 1.1 (a) doesn't show the aural carrier. The aural signal frequency modulates onto the RF carrier, thus becoming its sideband. 1 - 1 Chapter 1 TV Signal and CATV Distribution WAVEFORM MONITOR READS .
Catalogue 2020-21 Life Line Plus S3 (HRFR) Cable Life Guard (FR-LSH) Cable Life Shield (HFFR) Cable Multicore Round Cable Shielded Cables Flat Submersible Cable Telephone Switch Board Cable LAN Cable CCTV Cable Co-Axial TV Cable Speaker Cable Presenting Domestic Cable Range for Safer, Securer Homes.
instrumentation tray cable 10 general purpose cable 12 instrumentation tray exposed run direct burial cable 14 power tray exposed run direct burial cable 16 industrial ethernet cable 18 fieldbus technology cable 20 extremelife cable 22 flexlife cable 24 weldlife cable 26 armorfast instrumentation cable 28 flexible service cable
3. Cable television network not to be operated except after registration.- No person shall operate a cable television network unless he is registered as cable operator under this Act. Provided that a person operating a cable television network, immediately before the commencement of this Act may continue to do so for a period of ninety days from
RJ45 Port: Data cable, Ethernet cable, Cat5e, Cat6, Cat6a, Cat7, Cat7a. F-Connector Port: Video cable, coaxial cable, RG6/RG6Q cable, RG59 cable. RJ11/12 Port: Voice cable, POTS (plain old televoice service) cable, 4-wire cable, 6-wire cable, 2 twisted-pair cables, 3 twisted-pair cables, Cat3. VDV SCOUTTM PRO 3 TESTER LOCATION ID REMOTES
Coaxial cable quick reference guide Author: CommScope Subject: Quick reference guide for coaxial cables for hardline trunk, distribution and drop cable applications. Keywords: coaxial cable, hfc network, hybrid fiber coaxial, P3 cable, QR cable, XPRESSPREP cable, BrightWire, hardline cable, trunk cable, drop cable, CATV, CO-112310.1-EN Created Date
DVI and D-sub cable, the DVI cable must be connected along side the rib on the power cord side (Figure 4). 5. For successful cable management, place the cables in this order into the cable management: audio cable (NXM only), power cable, and DVI cable (Figure 5). 6. Place DVI cable, audio cable (NXM only), and power cable into the specific hooks
The Transition to Digital Television: Is America Ready? Congressional Research Service 1 Introduction After June 12, 2009, households with over-the-air analog-only televisions will no longer be able to receive full-power television service unless they either (1) buy a digital-to-analog converter box to hook up to their analog television set; (2) acquire a digital television or an analog television
Cable section: 25: 25mm2 cable 2 35: 35mm cable 50: 50mm2 cable 70: 70mm2 cable Cable length: LXXXX: Cable length (Unit in mm) Remarks: To find the suitable cable for your model, please refer to the in
