Broadcasting, Cable, the Internet and Beyond

Broadcasting, Cable, the Internet and BeyondChapter 3

Quick Facts

Bandwidth of an FM channel: 200 kilohertz

Bandwidth of a digital television channel: 6 megahertz

First high-definition TV broadcasts: 1998

Cost of 51” digital HDTV set (1999): $5,000

Cost of 51” digital HDTV set (2006): $1,699

Percent of dads hoping for a consumer electronics gift on Father’s Day, 2006: 42


Basic Principle of Media Technology

Facsimile Technology - All modes of mass communication based on this process

Fidelity - a way to describe how faithfully a facsimile represents the original High Fidelity is reproduction that closely

approximates the original signalRadio waves can be used to transmit facsimiles

of pictures and sounds


Transduction

Transduction - the process of changing one form of energy into another form

Both analog and digital broadcasting involves different kinds of transductions

Noise in the transmission reduces the fidelity of the signal Analog transmission loses fidelity at each phase of the process Digital technology reduces lose of fidelity in the transduction

process. Television and radio signals begin as physical energy

Commonly referred to as light waves or sound waves More and more broadcast signals are now in digital form


Examples of transduction

Capturing sound of a bird chirping using a microphone involves the transduction of sound waves into electricity Making a recording of the bird involves making a facsimile of the original

sound

Transmitting the sound of the chirping involves the transduction of the electrical energy into electromagnetic energy The audio of a bird chirping is superimposed on the carrier wave of the

broadcast channel

At home, our antenna detects the transmitted signal and begins to reverse the transduction process


Signal and Noise

Signal - an electrical impulse or amount of power

Noise - the amount of unwanted interference

Signal to noise ratio - the amount of pure signal present compared to the amount of unwanted noise

Analog signals are subject to varying amounts of noise As signal goes farther away from the transmitter, more noise is added

Digital signals are subject to less noise interference than analog signals


Digital Transmission

Digital technology uses binary codes Binary codes use sequences of 0s and 1s - called bytes

Today, both digital radio and television signals have been approved for broadcasting

Digital transmission - sending binary data to receivers capable of converting this data back into audio or video signals Digital television (DTV) is growing in popularity in the U.S. Two different digital radio systems exist. One uses satellites, the

other involves sending a terrestrial signal by the local broadcaster


Oscillation and the Waveform

Oscillation - a basic concept of audio and video signal processing

Examples - vibration of air produced by our mouths makes the sounds we hear and vibration of light make up all the images

we see Electromagnetic waves are subject to oscillation

The oscillations of a radio wave defines its frequency Waveform - the footprint or image of an oscillation we use

to visualize the presence of the invisible


Frequency and Amplitude

A radio wave may be described in terms of frequency and amplitude

Frequency - the number of waves that pass a given point in a given time

Frequency is usually measured in hertz (Hz) The higher the frequency the shorter the wavelength Amplitude (power) - the height or depth of the wave from

its normal position


Frequency Response

Frequency Response - range of frequencies that a radio set is capable of receiving Example : How well a radio reproduces a range of audio

frequencies

The ear can hear a frequency range of approximately 10 octaves, from a low of 20 Hz to a high of 20,000 Hz

CDs can reproduce the entire range of audio frequencies that the human ear can hear


Steps in Signal Processing

Step One - Signal Generation

Mechanical methods of reproducing sound Microphones Phonograph records Tape recorders

Digital methods of reproducing sound Digital Audio Tape (DAT) Compact Discs (CDs) and Digital Versatile Disks (DVDs) Minidiscs (MD) Computer files (MP3s)


Video Signal Generation (NTSC)

Television’s ability to transmit images is based on the technology of scanning

Analog U.S. television scans a television picture using two fields of information for a total of 525 lines

Each field consists of 262 1/2 horizontal scanning lines The two fields interlace to combine to form a single

picture called a frame


Video Signal Generation (Digital television DTV) (Cont.)

Digital television has several standards High Definition Television (HDTV) represents the best

picture quality HDTV uses either 480, 720 or 1080 scanning lines, 480

being the lowest range, 720 medium, and 1080 being the highest

Digital television channels are free of noise and look better than comparable analog television


Step 2 - Signal Amplification and Processing

Audio Signal Processing

Amplifiers boost or modify electrical signals

Mixing consoles and control boards are used to input, select, control, mix, combine, route, and process signals

Today many signal processing functions can be accomplished using a computer (Desktop Audio)


Step 2 - Signal Amplification and Processing (Cont.)

Video Amplification and Processing

Video signals are mixed using a switcher Special effects generators provide keying and

chromakey effects to a television picture Digital Video Effects provide special effects that can

manipulate the size and position of a picture Computers are being used today to manipulate and

edit video images (Desktop Video)


Step 3 - Signal TransmissionElectromagnetic Spectrum is very large

Radio and television signals occupy a portion of the electromagnetic spectrum Radio and television stations are assigned specific frequencies Carrier wave - the signal produced by a station’s transmitter

AM - The carrier wave is modulated FM - The frequency is modulated

Only a small part of the electromagnetic spectrum is utilized for AM and FM broadcasting AM and FM radio stations use different portions of the spectrum


Radio Bands in the Electromagnetic Spectrum

Medium Wave Band - 107 AM channels, air and marine radio High Frequency Band - International Shortwave, CB, and Ham

radio Very High Frequency (VHF) - FM radio, police radio, airline

navigation systems, and TV channels 2 - 13 Ultra High Frequency (UHF) - UHF and DTV channels 14 - 38,

police and taxi mobile radio, radar and weather satellites Super High Frequency (SHF) - Ku and C band satellites, Microwave

transmission, air navigation Extremely High Frequency (EHF) -special military communications


Spectrum management - the process of defining and keeping track of what frequencies will be assigned and licensed for special purposes

The FCC decides who gets a broadcast license is

Radio Classifications AM Radio - 117 Channels assigned between 540 and 1700 Khz

Each AM channel occupies 10 Hz of bandwidth

FM Radio - 100 Channels assigned between 88 and 108 Mhz Each FM channel occupies 200 Khz of bandwidth

Commercial FM is divided into three zones covering the US

January 2000, new low-powered FM was created

Digital Radio (HD) - approved for broadcasters to create digital services in addition to analog broadcasts.


Signal Transmission (cont.) Spectrum Management -Television and satellite channels

Television Classifications and Basics Each television channel occupies 6 Mhz of bandwidth

VHF television - Channels 2 - 13 UHF television - Channels 14 - 83UHF channel assignments include new digital television

channels (DTV) Satellite TV - Direct Broadcast Satellite (DBS) uses the Super

High Frequency band (SHF)


Wired Communication

Cable TV uses coaxial cable as a transmission medium

Coaxial cable is capable of transmitting a large number of channels through the wire Digital compression increases channel capacity even more

Addressability - the ability to send a program to some households but not others. Addressability is used for pay-per-view (PPV) TV

Fiber Optics uses digital technology - almost unlimited bandwidth Fiber can carry television, telephone and broadband information


Step 4: Signal Reception - Radio

AM radio is ideal for car radios Signals travel long distances, especially at night AM is subject to static interference and limited frequency response.

Receiver quality is often poor FM radio is a full fidelity medium but is limited to line of

sight transmission FM requires a long antenna Signals tend to be blocked by buildings or moving objects Radio Broadcast Data Systems or ‘Smart’ radios provide some

functionality Satellite radios need a special antenna and receiver Satellite services are pay services


Signal Reception - Television

Large Screen Televisions and HDTVs gaining in acceptance

Digital sets incorporate new features such as a picture-in-picture option.

LCD and plasma screen televisions are changing the size and shape of television


Step 5: Storage and Retrieval

Analog audio storage Phonograph records Cassette and reel-to-reel tapes

Digital audio storage Compact Discs (CDs) and Audio DVDs Computer hard drives (MP3s) Digital Audio Tape (DAT)


Video Storage

Analog video storage Early standards included 2” and 3/4” videotape 1/2” VHS consumer video tape recorder

Digital video Digital Versatile Disc (DVD) Digital Video Recorder (DVRs) personal video

recorder


Webcasting: Audio and Video Streaming

Streaming - web-based technology that allows computers to receive audio and video signals over the Internet Computers buffer video playback but accumulating some of the

date before it starts to playback Web sites also compress (shrink) the size of the signals it

streams Playing sounds and moving images on the web requires

multimedia capability Buffering is a technique used to help stream media


End of Chapter 3

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Broadcasting, Cable, the Internet and Beyond