Dr. Janet McMullen  Fall 2001  MWF 10:00

Updated: 09/30/01

Key words are placed in bold, but supporting information under them may not be. The rule of thumb is that if I put it in this document you need to know it!

Electromagnetic Spectrum:

• like a keyboard; different types of energy
• subdivisions called bands
• different services are allocated to specific bands/frequencies

Specific stations are assigned to specific frequency is a specific geographical area.

A group of frequencies assigned to a stations constitutes a channel.

[See diagrams in book]

Radio Waves:

Radio waves are like sound waves in that they share the properties of waves:

• pressure = strength or amplitude
• frequency = amount of oscillations over a specific period of time or distance

• Radio waves are measured in Hertz (Hz)
• Hertz = the number of oscillations per second

• speed = how fast the waves travel through whatever medium

• sound waves travel at different rates through different media (air, wood, water, etc.)
• radio waves travel at a constant speed = 186,000 mi/sec. [which is the speed of light]

Radio waves are NOT sound waves. They do not exert pressure like sound waves do. They are electromagnetic.

Wave lengths: have important characteristics

• the shorter the wave length, the more easily small objects block their path
• longer wave lengths tend to bend more easily and work around small objects
• lower sounds have longer waves
• the lower the channel on the spectrum, the longer the waves
• therefore, just as you can hear the bass on a stereo in the next room, an AM station which is lower on the dial will have a larger and more stable coverage area than a station higher on the dial or spectrum

Know definitions of the following:

• phase
• cycle
• Hertz (kilo=100; mega = million; giga = billion)
• attenuation
• carrier wave
• modulation
• transducer
• side bands: adjacent frequencies affected by modulation of the carrier wave; used for other things in multiplexing

AM: (Amplitude Modulation)[ know what is done to the carrier wave to get AM]

• in MF band
• 535 - 1705 KHz (as of 1991)
• each AM channel 10 kHz apart
• 117 channels
• channels extend 5 kHz above and below assignment
• frequency 530 kHz is actually 535-545 kHz
• stations may modulate beyond the 5 kHz if they can without interfering other stations
• AM divided into 3 channel classes (see text)
• local (6 channels)
• regional (41 channels)
• clear (60 channels)

Also divided into 4 classes:

• class I : dominant station on clear channels
• class II: secondary station on clear channels
• class III: regional (46% of total Ams)
• class IV: local (22% of AM total)

Maximum power: 50,000 watts (50 kilowatts) on clear channels

AM Propagation: dependent upon (know all of this and properties of sky waves)

• conductivity of the soil (moist is most conductive; sand is least)
• ground waves
• sky wave

IONOSPHERE: 40-600 miles above the surface of the earth

Related terms to know:

Coverage area:

Directionality:

antenna gain

Disadvantages of AM: interference

• adjacent channel
• co-channel
• static: man-made and natural

AM stations need to be 20 times as strong as competing signals to over come them.

FM (Frequency Modulation)

• Propagation: based on

• direct waves (know how they work)

• height of tower
• power
• FM signal only has to be twice as strong to over come a competing signal
• VHF band
• First 20 channels reserved for non-commercial / educational use
• Country divided into FM Zones
• Stations divided into classes A, B, C, D based on

• power
• antenna height
• A = coverage area radius of 15 mi (approx)
• B = coverage area radius of 30 mi (approx)
• C = coverage area radius of 60 mi (approx)
• D = very low power (10 watts)

Short Wave:

Used for overseas communication

high Frequency band

6-25 mHz

dependent upon ionosphere

• ionosphere is undependable/ frequencies change
• signals must be adjusted for that

New services:

DAB: Digital Audio Broadcasting

Satellite DAB: satellite radio service

• single digital signal adjusted for time zone
• delivered by satellite to dishes on cars, homes, etc.
• will deliver strong national signal
• threat to local broadcasters

Terrestrial DAB:

• digital signal but broadcast from local antenna
• broadcasters like this one better
• maintains local character and service

Concern: will consumers get the new radios/satellites?

RDBS: sometimes called RDS: Radio Data (broadcasting) Service

• provides data delivery to your radio
• can deliver coupons
• weather reports
• sports, etc.
• also tells you exactly what station you're listening to
• can provide other info about the station, such as song title, etc.
• WYZP one of the first RDS broadcasters in Alabama
• Few vehicles have receivers

Know the difference between ANALOG and DIGITAL

TELEVISION

Much of this information is covered in Com 240. If you didn't already have it there, be SURE you understand this stuff before you leave this class. It is absolutely VITAL that you understand how television works.

Any highlighted terms in your text you should know, even if they're not on this sheet.

Flicker:

• 16 fps = illusion of natural motion
• 24 fps = necessary for sound reproduction
• 48 fps = necessary for sound and absence of flicker

camera components:

• pickup tube
• target plate
• frame
• deflection coils or magnets
• 30 fames/60 fields per second
• pixels

Level of resolution:

• NTSC = 525
• HDTV = 1080
• SDTV = 720
• ATV = 560

There are two other systems which are used in other parts of the world:

• PAL
• SECAM
• both operate on 50 fps and 625 lines

Location on the spectrum:

• 12 VHF channels: 2-13 (located in three different blocks of the spectrum)
• 56 UHF channels: 14-69

Note the role of the following:

• synch generator
• ERP
• ghost image

Transmission of Television:

• TV PICTURE is VHF or UHF waves which are both direct waves
• Both of these are easily bent or blocked (which causes the ghost image)
• TV AUDIO is AM which uses ground waves which are lower on the spectrum and stronger
• Therefore, video component needs to be 20 times stronger than the audio component

 Know the definition and function of the following from Chapters 3, 4 and 5

• phosphors
• primary colors (NOT the book or movie!)
• CRT
• kinescope
• Grade A Contour (reception good 90% of the time)
• Grade B Contour (reception good 50% of the time)
• Ancillary signals
• VBI: vertical blanking interval (what is it; how is it used?)
• teletext
• closed captioning
• alternate audio (stereo, bilingual)
• translators
• ENG (electronic news gathering)
• SNG (satellite news gathering)
• EFP (electronic field production)
• remote vehicles
• time-base corrector
• PIP
• LCD
• frames
• fields
• progressive scanning
• interlaced scanning
• DTV
• NTSC
• compatibiliity 
• analogue
• kinescope
• pixel
• phosphor
• liquid crystal display
• plasma display panel
• fiber-optic cable
• cable converter box
• addressable converter
• STB
• Web TV, TiVo, Replay TV
• DAB
• DARS
• RBDS

• syndication
• networking
• broadcast network: two or more stations connected to each other so they can put identical programs on the air in more than one market SIMULTANEOUSLY.
• Convergence
• stylus
• laser
• CD magnetic recording DAT
• cart
• kinsescope recording
• slanted track
• digital videotape
• VCR
• camcorders
• laser video
• remote pickups
• relay links
• pirates
• unwired networks: organizations which provide programs to groups of stations but without interconnection to those stations
• coaxial cable
• delivery circuits
• relay circuits
• microwave relays
• fibre-optics
• LEDs
• communication satellites
• footprint
• geostationary orbit (possible at 22,000 mi. above the equator)
• C band
• KU band (newer, more powerful, used for DBS)
• transponder
• cross-strapping
• global beams
• hemispheric beams
• spot beam
• TVRO
• thrusters
• orientation
• spin stabilization
• rebroadcasting
• DBS
• hybridization
• translators
• LPT
• coaxial cable
• CARS
• head-end
• trunk cable
• drop cable
• feeder cable
• super turnk
• tree and branch
• amplifiers
• PPV
• pay channels
• encryption
• addressability
• interactivity
• niche services
• MATV
• MDS
• down converted
• MMDS

Again, let me remind you that this is just a key word list. Most of this stuff you probably know from having been around electronic media a long time. Good luck.

Copyright, 2001

Dr. Janet McMullen