Broadcasting, Cable, the Internet and Beyond

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Broadcasting, Cable, the Internet and Beyond

Chapter 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

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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 signal


Radio waves can be used to transmit facsimiles
of pictures and sounds

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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


Broadcasting, Cable, the Internet and Beyond

Chapter 3


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


Broadcasting, Cable, the Internet and Beyond

Chapter 3


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


Broadcasting, Cable, the Internet and Beyond

Chapter 3


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

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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



Broadcasting, Cable, the Internet and Beyond

Chapter 3


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)

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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


Broadcasting, Cable, the Internet and Beyond

Chapter 3


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



Broadcasting, Cable, the Internet and Beyond

Chapter 3


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)


Broadcasting, Cable, the Internet and Beyond

Chapter 3


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)


Broadcasting, Cable, the Internet and Beyond

Chapter 3


Step 3
-

Signal Transmission


Electromagnetic 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

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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


Broadcasting, Cable, the Internet and Beyond

Chapter 3



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.

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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
-

83


UHF channel assignments include new digital television
channels (DTV)


Satellite TV
-

Direct Broadcast Satellite (DBS) uses the Super
High Frequency band (SHF)


Broadcasting, Cable, the Internet and Beyond

Chapter 3


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

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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

Broadcasting, Cable, the Internet and Beyond

Chapter 3


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)


Broadcasting, Cable, the Internet and Beyond

Chapter 3


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


Broadcasting, Cable, the Internet and Beyond

Chapter 3


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

Broadcasting, Cable, the Internet and Beyond

Chapter 3



End of Chapter 3