Topic 3.1 Skeletal Outline - Broadcast Media Basics
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2733
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Jun 10, 2024
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Module 3: Topic 3.1 Broadcast Media – Basics Print out this skeletal outline to take notes on key elements discussed in the lecture. Note, please look
over the entire slideshow. However, this is to help you with the most important topics to prepare you
for the module 1 exam. Course Objectives:
CLO1 – Identify key historical aspects related to communication technologies, including economic, political, societal, and cultural aspects.
CLO2 – Identify modern digital communication trends.
CLO3 – Explain historical and/or modern aspects of communication technologies. Module Overview:
In this module, you will learn about the basic principles of broadcast media (e.g., over-the-air radio). You
will also learn the history, underlying technical principles, and regulation of broadcast radio.
By the end of this module, you will be able to:
LO3.1: Identify the basic principles of airwave broadcasting (supports CLO1)
LO3.2: Identify the basic principles of radio broadcasting (supports CLO1)
LO3.3: Identify the key technologies and people involved with early radio (supports CLO1)
LO3.4: Explain historical and/or modern aspects of broadcasting (supports CLO3)
Main Questions to Be Answered by the end of the Module:
Make sure you can answer the following questions by the end of this module:
1.
What is electromagnetic energy?
2.
What are the properties of radio waves?
3.
What is Frequency Measurement?
4.
What is wave propagation?
5.
What is the Radio Frequency Spectrum?
6.
What are Radiators?
7.
What are the different types of antennas?
8.
What are Long vs. Short Wavelengths?
_____________________________________________________________________________________
Basic Principles of Electronic Media (see Radio Wave Basics lecture video)
Define electromagnetic energy? (Write out the information needed in the space provided below):
Define the electric part:
o
Electric – Alternative Current/Direct Current
Alternative Current – electrical currents repeatedly and regularly alternating (i.e..: changes)
Direct Current – electrical current flowing continuously in one direction/1D
o
AC/DC went electrical
Define the magnetic part:
COM 2733 - SKELETAL OUTLINE NOTES
o
Magnetic portion
AC is used and creates radiation
More alternations = more radiation
This type of radiation is called “Radio Waves”
Radio Waves – the alternating current creates a bit of radiation around the source that radiates through the air
Lamp analogy
o
The electrons flow straight from the source to the lamp (direct current electricity). Electrons are engaged when you turn the lamp on, but with alternating current, the power goes back and forth on the wire. Those alternations create radiation that radiates away from the source. That principle is what is used for
radio waves.
Radio Tower
o
A metal conductor running electricity on the radio wave tower. If you want to transmit out AM radio to listen to in your car, what is done is the electricity runs up and down the wire. When it's being done, that would create radiation around the tower, and the radiation would gradually go away from the tower, go through the air, and be picked up by your car. This is true for all radio transmissions and happens with cell phone towers sending out information signals if you have internet working on your cellphone. Properties of Radio Waves (see Measurement and Propagation lecture video)
List the 2 properties of radio waves. (Write out the information needed in the space provided below):
First property of radio waves
o
Power – the amount of electrical current put into the radio waves (e.g., a little to a lot or
vise versa)
Has bigger waves and more amplitude
The more power you put into it, the further that wave in going to travel.
Second property of radio waves
o
Frequency – the rate of the alternating current (e.g., slow to fast, or vise versa)
Has faster waves
Power is the amount of electricity put into it. Frequency is the speed of electricity.
Car analogy
COM 2733 - SKELETAL OUTLINE NOTES
o
The cars on the road and the speed of the cars on the road. Power is the # of electrons that are allowed to flow on the wire. You can have one electron or increase the number of electrons you have, like increasing the # of cars that you have on the roads. More cars
+ more power. o
Frequency is the speed or the rate of the flowing electrons; you can have a few # of the electrons flowing relatively slowly, or you can have a few # of electrons going very fast. You can change the # of electrons in the speed; you can have a few electrons at a low power with a high frequency or a low frequency, or you can increase the # number of electrons drawn to increase the power further. Still having it relatively slow rate or you can have that go at a faster rate. NOTE: power and frequency are independent of each other. Frequency Measurement (see Radio Wave Basics lecture video)
Explain Frequency Measurement (Write out the information needed in the space provided below):
Frequency Measurement
o
A complete cycle
Alternation of a radio wave from momentary 0, through the +, through the -, then back to zero.
o
Frequencies are measured by Hertz (Hz)
# of complete wave cycles in 1 second
More cycles = more Hertz
Wave Propagation (see Radio Wave Basics lecture video)
Identify and describe components of the wave propagation. (Write out the information needed in the space provided below):
Recall: radio waves are made of electricity and magnetism
Magnets of like polarity repel each other
The + and – aspects of the wave act like the poles on a magnet(ex. North and North while South and South repel each other, opposites attract.)
As each radio wave is emitted, it repels (or propels) the preceding wave before it
o
Once the radio tower creates one radio wave and sends it off in the air, it would die away if there were no continuous radio waves being sent out. By having the electrons go
up and down on the antenna, you create another radio wave, which then pushes the first one. Then you continue with the electricity that creates another radio wave which then pushes the second one.
Radio wave propagation = radio transmission
COM 2733 - SKELETAL OUTLINE NOTES
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o
By propagating that wave, which is one wave pushing the one before it and pushed by the one behind it, which is how radio waves transmit.
o
North and North magnets while South and South magnets repel each other, opposites attract
Radio Frequency Spectrum (see The EM Spectrum lecture video)
List each application of each Radio Frequency Band:
Note on EHF & SHF
o
Due to earth having trees, buildings, and mountains, both frequencies only compatible with what they are compatible for. The way 5G technology for cell phones works is by having lots and lots of different transmission points that you’re always very near to. A cell phone tower might be 30miles away from the individual location, but 5G towers are going to be every couple of hundred feet down a major road. They are really small transmitters that don’t take up very much power and they are EVERYWHERE. Which is why we have higher bandwidth on our cell phones by having new technology where the very very high frequency waves that aren’t going far, but you don’t need them to go far bc you’re always going to have a transition point somewhere that’s 10-50 feet away.
EHF/Extremely High Frequency:
o
Frequency: 30 – 300 GHz
o
Application: Satellite
Satellite
Molecules in the air can interfere with transmission of these waves.
SHF/Super High Frequency:
o
Frequency: 30 – 30 GHz
o
Application: Satellite
Earth
Cant send anything very far, if you want to transmit from one part of the planet to another with SHF, all building and mountains are in the way which causes interference and signal would never go through. (ex.: satellite TV would go out if
there is a major thunderstorm due to higher electromagnetic interference in the
clouds)
Only good for going through the atmosphere with nothing in the way.
UHF/Ultra High Frequency:
o
Frequency: 300 MHz – 3 GHz
o
Application: TV, cellular
Basic cell phone capability comes from
VHF/Very High Frequency:
o
Frequency: 30 – 300 MHz
o
Application: FM, TV, pagers
HF/High Frequency:
o
Frequency: 3 – 30 MHz
o
Application: Shortwave radio
Can bounce signals around the world
MF/Medium Frequency:
o
Frequency: 300 kHz – 3 MHz
o
Application: AM radio
Low frequency, very robust radio signals. Can travel very far as lower frequency signals are stronger than higher frequency signals.
COM 2733 - SKELETAL OUTLINE NOTES
LF/Low Frequency:
o
Frequency: 30 – 300 kHz
o
Application: Maritime navigation
Low radio waves can travel great distances so they can go around the curvature of the earth. Radiators (i.e., Antennas)
Explain Antennas (Write out the information needed in the space provided below):
Antennas
o
Electrical conductors with Alternating Current (AC)
o
Waves travel from broadcast antennas to receiver antennas
o
Radio antennas are most efficient when antenna height = radio wavelength being broadcasted
E.g., AM radio station operating at 600 kHz (600,000 Hz). That wavelength is 500
meters long, so the broadcast tower should be 500 meters tall. o
It is not practical to build radio station towers that high
Many AM stations are built at ½, ¼, or 1/8 of the desired wavelength.
low-frequency radio towers would have to be EXTREMELY TALL
Frequency
Wavelength
300
Hz
1,000,000
meters
3,000
Hz
100,000
meters
30,000
Hz
10,000
meters
300,000
Hz
1,000
meters
3,000,000
Hz
100
meters
30,000,000
Hz
10
meters
300,000,000
Hz
1
meters
3,000,000,000
Hz
0.10
meters
Understanding the Antenna (see Wave Transmission lecture video)
Describe each group of antennas (Write out the information needed in the space provided below):
LF, MF, HF Antennas: o
Do not need line of sight to transmit
o
Almost always used all-steel towers
The whole tower radiates the waves
IRL ex.: on the San Antonio riverwalk, close to the middle of downtown, theres a WOAI right in the middle of the parking lot, they have a big gigantic tower that operates that way. The whole tower radiates that type of wave that are good at going long distances, cutting through buildings, mountains, and going around the curvature of the earth. These are low, medium, and high frequencies are very strong and robust, and very low frequencies waves can go very far. The higher you go in the EM spectrum, the smaller the waves become and don’t go quite as far nor work as well.
Usually built at a fourth of the height of the wavelength
VHF, UHF Antennas: COM 2733 - SKELETAL OUTLINE NOTES
o
Works great with “line of sight” transmission (“line of sight” = very few barriers as possible, nothing in the way between the source and you)
Ex.: the wifi router. The more walls between the router and the electronic device, the slower and worse the signal is going to be. (some apartments have a hidey hole for the router, and it’s a dumb design if you’re WFH or doing school 100% remote)
o
Antenna placed on the roof, hill, or supported tower
o
Antenna does not need to be as tall
SHF, EHF Antennas:
o
Also the best with the line of sight
o
Parabolic dish used to focus radio waves onto an antenna in the middle
Ex.: DirecTV or Dish Network satellite dish. If there is a small antenna in the middle, the dish operates very well the same way rain dish would, gathers rain as its falling. Need to have big, wide dish to gather rain as its falling to get as many water droplets as possible. Same idea works with your satellite dish for the home TV.
Frequencies are very scattered, all over the place and you need to get a lot of them in one place to have enough strength to figure out what the signal is. Long vs. Short Wavelengths (see Wave Transmission lecture video)
Describe the difference between long and short wavelengths (Write out the information needed in the space provided below):
Long Wavelengths
o
They are at a lower frequency
o
The wave seemingly follows the curvature of the earth
That’s how they were originally thought these waves were doing back when they were first discovered. You could transmit radio transmissions from NYC to the middle of the Atlantic ocean.
In actuality, it was blasting right through the earth and coming out the other side. You’re transmitting in NYC, blasting through the ocean and coming out on the other side to get the naval vessel. Water conducts electrical eaves that’s being sent and goes right though. Doesn’t transmit well if being sent from NYC to L.A
o
These powerful waves can penetrate mountains and buildings.
With AM radio, when driving to Austin, the AM radio station is going to stay on a lot longer and will be a long time before that transmission goes away. Why? Because as you’re going over and around the curvature of the earth, going from San Antonio to Austin, that wave is going right through there.
Short Wavelengths
o
They are at a higher frequency
o
They cant penetrate the earth, mountains, nor buildings. Can’t go far
o
The wave travels in a straight line away from the earth
Reason why you put the tower up on top of the building rather than on the ground. If its on the ground, radio wave wouldn’t go very far but can go a distance and keeps going until it dissipates and can’t be picked up anymore. COM 2733 - SKELETAL OUTLINE NOTES
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_____________________________________________________________________________________
Summary:
-
The basic principles of electronic media
o
Electromagnetic energy
o
Power, frequency, frequency measurement
o
Wave propagation
-
The electromagnetic spectrum
o
The radio frequency spectrum
-
Radiators (i.e., antennas)
o
Understanding the Antenna
o
Long wavelengths versus short wavelengths
COM 2733 - SKELETAL OUTLINE NOTES