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Broadcast Basics Week 13 ICS 620. BROADCAST BASICS ICS 620 Week 13.

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Presentation on theme: "Broadcast Basics Week 13 ICS 620. BROADCAST BASICS ICS 620 Week 13."— Presentation transcript:

1 Broadcast Basics Week 13 ICS 620

2 BROADCAST BASICS ICS 620 Week 13

3 Introduction Video Basics (Analog Systems) Transmission Systems Wireless (terrestrial) Wired (cable television) Digital Video (Two Weeks)

4 Video Standards Standards and Principals –Persistence of Vision The rapid presentation of frames of video information to give you the illusion of smooth motion.

5 Frequency Standards Frame Frequency 16 Frames per Second (fps) Black and White 24 fps SOF Continuity of Action Problem of Flicker –The gross alteration of light and dark

6 Frequency Standards Field Frequency Frame Frequency x 2 Continuity of Illumination

7 Film Vs. Video Film - Project a complete picture Video - Scan, line by line, at a high rate of speed - 6 million bits per second

8 How do we describe a picture? A picture element (pel or pixel) one at a time For each pel we need to somehow describe: –Brightness (luminance) –Hue (phase, tint) –Saturation (color intensity, chroma)

9 Vertical Resolution The picture quality associated with the number of dots (pixels) used to construct the picture. – 367,000 dots – on 525 rows (vertical)

10 Film vs. NTSC Specs Aspect Ratio

11 Camera Tubes

12 Early Camera Tubes

13 Image Orthicon

14 Electronic Scan (Camera Pickup Tube) Video Signal Electron Beam TargetLensObject

15 Scanning Progressive Interlace/Offset Interlace Example NTSC: 525 lines, 30 frames/sec, 60 fields/sec

16 Picture Tube

17

18

19 Scanning a Focused Image

20 Progressive Scanning

21 Interlace Scanning

22 Sync Pulses

23 Differences Between Horizontal and Vertical Synch Pulses Rate Duration Vertical59.94/sec 1:3 Horizontal 15, /sec 3:1

24 Waveform Sketch of a Video Signal

25 A simple video waveform One Line

26 Waveform of Sync Pulses

27 IRE Measurement Scale

28 Vertical Blanking Interval (VBI) Lines 1-21 of each field Vertical Interval Test Signal (VITS) Vertical Interval Reference Signal (VIRS) Lines 1-9V-sync and Equalizing Pulses Lines 12-14SMPTE Time Code Lines 17-19VITS and VIRS Line 20Network Source Code (field 1) Line 21 Closed captioning (field 1)

29 Kell Factor The Ratio of effective resolution to the theoretical resolution is known as the Kell Factor.

30 Vertical Resolution Summary Max Lines/Frame = 525 Lost for Vertical Blanking = 42 (21 lines per field) Visible = = 483 Kell Factor = 72.5% Effective Resolution = 350 lines

31 Horizontal Resolution Summary (4.2 MHz Video Bandwidth) = 4.2 cycles per microsecond x 52 microseconds (active scan) x 2 pixels per cycle = 436 pixels per line

32 Television Transmission Picture Information Blanking pulses Sync pulses Audio information

33 What about Color?

34 Component Nature of Color R GB

35 Video Color Palette

36 Color Television R = Red G = Green B = Blue B + G = Cyan G + R = Yellow B + R = Magenta

37 NTSC Color Bars

38 Block Diagram of Color Camera

39 Gamma A measurement of contrast, gamma correction is required because the brightness output of a camera does not correspond to the brightness recognition of the human eye.

40 Composite Color Y = Luminance Signal Y =30% red + 59% green + 11% blue C = Chrominance Signal C = I Q Matrix

41 Color Matrix Saturation = Amplitude of the I and Q signals Hue = Phase developed by the difference in amplitude between the I and Q signals

42 Transmitter Tube

43 Color TV Transmitter

44 TV Frequency Allocations 2 - 4VHF-Lo 54 MHz - 72 MHz 5 - 6VHF-Lo 76 MHz - 88 MHz 7 – 13VHF-Hi174 MHz – 216 MHz 14 – 59UHF470 MHz – 746 MHz NOTE: Natural breaks occur between channels 4 and 5; channels 6 and 7; and channels 13 and 14. Each channel is 6 MHz wide.

45 NTSC Bandpass Characteristics (Black and White)

46 Color TV Signal

47 NTSC Bandpass Characteristics (Color)

48 Color TV Signal

49 Worldwide Standards National Television System Committee - NTSC (1953) Phase Alternation Line -PAL (1967) Sequentiel Couleur Avec Memoire - SECAM (1967)

50 World TV Standards

51

52 Principal TV Systems

53 FM Stereo Transmitter Transmitter Output Main Channel (L + R) Stereo Channel (L - R) 19 kHz Pilot Sub-carrier

54 Stereo Multiplexing L+R Signal (Main Channel) L-R Signal (Stereo Channel) 19 kHz Pilot Subcarrier (FM) The Math (L + R) + (L - R) = 2 L (L + R) + (- L + R) = 2 R

55 FM Stereo Receiver

56 Television Stereo Multi-channel Television Sound (MTS) Used to provide Stereo on conventional NTSC TV broadcast (TV has been FM mono for most of its history)

57 Television Transmission Systems Over-the Air Terrestrial Broadcasting

58 Antenna Systems Radio Energy in Space –300 million meters per second E = MC 2 Speed of Light

59 Spectrum

60 Wavelength Lambda (meters) Velocity (300,000,000 meters/sec.) Frequency (Hz) = v/f

61 TV Station WTHR-TV Ch.13 ( MHz) WAVELENGTH IN: A.Meters B.Miles C.Feet

62 WTHR Television - Channel 13 Indianapolis, Indiana Channel 13 ( MHz) 316 kw visual 63.2 kw aural 980t/1,039g Television Factbook 47 CFR

63 Wavelength Example WTHR Television Meters: Lambda = 300/ = 1.46 meters Miles: Lambda =.186/ = miles Feet: 1 meter = 3.28 feet Lambda = 1.46 meters x 3.28 = 4.79 feet

64 AM Station What is the height of this AM station antenna tower operating at 540 kHz, in meters and feet?

65 Propagation Radiation Patterns (Contours) AM - Tower as the Antenna FM/TV - Antenna on Tower

66 TV Propagation

67 TV Propagation Map

68 FM Propagation Map KFMD-FM Denver

69 AM Tower Side viewTop view

70 AM Directional Towers

71 AM Directional Propagation

72 Irregular Geographical Patterns Refraction Reflection Absorption Interference

73 Why Directional Arrays? Co-Channel Adjacent Channel Other

74 Types of Waves Direct Waves (FM/TV) Ground Waves (AM) – Radials Swampy Soil vs. Sandy Terrain Sky Waves (AM at night)

75 Types of Waves

76 Direct Waves The primary path of the direct wave is from the transmitting antenna to the receiving antenna. So, the receiving antenna must be located within the radio horizon of the transmitting antenna. Because direct waves are refracted slightly, even when propagated through the troposphere, the radio horizon is actually about one-third farther than the line-of-sight or natural horizon.

77 Direct Waves

78 Ground Waves The Earth has one refractive index and the atmosphere has another, thus constituting an interface that supports surface wave transmission. These refractive indices are subject to spatial and temporal changes.

79 Ground Waves

80 Sky Waves Sky waves, often called ionospheric waves, are radiated in an upward direction and returned to Earth at some distant location because of refraction.

81 Sky Waves

82 Questions and Answers


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