Broadcast

BroadcastBasicsWeek13ICS620BROADCASTBASICSICS620Week13IntroductionVideoBasics(AnalogSystems)TransmissionSystems•Wireless(terrestrial)•Wired(cabletelevision)DigitalVideo(TwoWeeks)VideoStandards•StandardsandPrincipals–PersistenceofVisionTherapidpresentationofframesofvideoinformationtogiveyoutheillusionofsmoothmotion.FrequencyStandardsFrameFrequency•16FramesperSecond(fps)BlackandWhite•24fpsSOF•ContinuityofAction•ProblemofFlicker–ThegrossalterationoflightanddarkFrequencyStandardsFieldFrequency•FrameFrequencyx2•ContinuityofIlluminationFilmVs.Video•Film-Projectacompletepicture•Video-Scan,linebyline,atahighrateofspeed-6millionbitspersecondHowdowedescribeapicture?•Apictureelement(“pel”or“pixel”)oneatatime•Foreachpelweneedtosomehowdescribe:–Brightness(luminance)–Hue(phase,“tint”)–Saturation(colorintensity,“chroma”)VerticalResolution•Thepicturequalityassociatedwiththenumberofdots(pixels)usedtoconstructthepicture.–367,000dots–on525rows(vertical)Filmvs.NTSCSpecsAspectRatioCameraTubesEarlyCameraTubesImageOrthiconElectronicScan(CameraPickupTube)VideoSignalElectronBeamTargetLensObjectScanning•Progressive•Interlace/OffsetInterlaceExampleNTSC:525lines,30frames/sec,60fields/secPictureTubePictureTubePictureTubeScanningaFocusedImageProgressiveScanningInterlaceScanningSyncPulsesDifferencesBetweenHorizontalandVerticalSynchPulsesRateDurationVertical59.94/sec1:3Horizontal15,734.264/sec3:1WaveformSketchofaVideoSignalAsimplevideowaveformOneLineWaveformofSyncPulsesIREMeasurementScaleVerticalBlankingInterval(VBI)•Lines1-21ofeachfieldVerticalIntervalTestSignal(VITS)VerticalIntervalReferenceSignal(VIRS)Lines1-9V-syncandEqualizingPulsesLines12-14SMPTETimeCodeLines17-19VITSandVIRSLine20NetworkSourceCode(field1)Line21Closedcaptioning(field1)KellFactorTheRatioofeffectiveresolutiontothetheoreticalresolutionisknownastheKellFactor.VerticalResolutionSummary•MaxLines/Frame=525•LostforVerticalBlanking=42(21linesperfield)•Visible=525-42=483•KellFactor=72.5%•EffectiveResolution=350linesHorizontalResolutionSummary(4.2MHzVideoBandwidth)=4.2cyclespermicrosecondx52microseconds(activescan)x2pixelspercycle=436pixelsperlineTelevisionTransmission•PictureInformation•Blankingpulses•Syncpulses•AudioinformationWhataboutColor?ComponentNatureofColorRGBVideoColorPaletteColorTelevisionR=RedG=GreenB=BlueB+G=CyanG+R=YellowB+R=MagentaNTSCColorBarsBlockDiagramofColorCameraGammaGAmeasurementofcontrast,gammacorrectionisrequiredbecausethebrightnessoutputofacameradoesnotcorrespondtothebrightnessrecognitionofthehumaneye.CompositeColor•Y=LuminanceSignalY=30%red+59%green+11%blue•C=ChrominanceSignalC=IQMatrixColorMatrix•Saturation=AmplitudeoftheIandQsignals•Hue=PhasedevelopedbythedifferenceinamplitudebetweentheIandQsignalsTransmitterTubeColorTVTransmitterTVFrequencyAllocations2-4VHF-Lo54MHz-72MHz5-6VHF-Lo76MHz-88MHz7–13VHF-Hi174MHz–216MHz14–59UHF470MHz–746MHzNOTE:Naturalbreaksoccurbetweenchannels4and5;channels6and7;andchannels13and14.Eachchannelis6MHzwide.NTSCBandpassCharacteristics(BlackandWhite)ColorTVSignalNTSCBandpassCharacteristics(Color)ColorTVSignalWorldwideStandards•NationalTelevisionSystemCommittee-NTSC(1953)•PhaseAlternationLine-PAL(1967)•SequentielCouleurAvecMemoire-SECAM(1967)WorldTVStandardsWorldTVStandardsPrincipalTVSystemsFMStereoTransmitterTransmitterOutput•MainChannel(L+R)•StereoChannel(L-R)•19kHzPilotSub-carrierStereoMultiplexing•L+RSignal(MainChannel)•L-RSignal(StereoChannel)•19kHzPilotSubcarrier(FM)TheMath(L+R)+(L-R)=2L(L+R)+(-L+R)=2RFMStereoReceiverTelevisionStereo•Multi-channelTelevisionSound(MTS)•UsedtoprovideStereoonconventionalNTSCTVbroadcast(TVhasbeenFMmonoformostofit’shistory)TelevisionTransmissionSystemsOver-theAirTerrestrialBroadcastingAntennaSystems•RadioEnergyinSpace–300millionmeterspersecond•E=MC2•SpeedofLightSpectrumWavelength•Lambda(meters)•Velocity(300,000,000meters/sec.)•Frequency(Hz)=v/fTVStationWTHR-TVWTHR-TVCh.13(210-216MHz)WAVELENGTHIN:A.MetersB.MilesC.FeetWTHRTelevision-Channel13Indianapolis,Indiana•Channel13(210-216MHz)•316kwvisual•63.2kwaural•980t/1,039gTelevisionFactbook47CFR73.603WavelengthExampleWTHRTelevisionMeters:Lambda=300/211.25=1.46metersMiles:Lambda=.186/211.25=.00088milesFeet:1meter=3.28feetLambda=1.46metersx3.28=4.79feetAMStation•WhatistheheightofthisAMstationantennatoweroperatingat540kHz,inmetersandfeet?Propagation•RadiationPatterns(Contours)•AM-TowerastheAntenna•FM/TV-AntennaonTowerTVPropagationTVPropagationMapFMPropagationMapKFMD-FMDenverAMTowerSideviewTopviewAMDirectionalTowersAMDirectionalPropagationIrregularGeographicalPatterns•Refraction•Reflection•Absorption•InterferenceWhyDirectionalArrays?•Co-Channel•AdjacentChannel•OtherTypesofWaves•DirectWaves(FM/TV)•GroundWaves(AM)–Radials•SwampySoilvs.SandyTerrain•SkyWaves(AMatnight)TypesofWavesDirectWavesTheprimarypathofthedirectwaveisfromthetransmittingantennatothereceivingantenna.So,thereceivingantennamustbelocatedwithintheradiohorizonofthetransmittingantenna.Becausedirectwavesarerefractedslightly,evenwhenpropagatedthroughthetroposphere,theradiohorizonisactuallyaboutone-