Radio and Electricity

1
Radio and Electricity

• Radio works because of electricity, so to
  understand radio, you have to know a little bit
  about electricity. In this group, well get some
  of the basics of electricity out of the way.
  There are three units we will study related to
  electricity in this group voltage, current, and
  power. By the time you are ready for your test,
  you will be very familiar with all of them.

2
Static Electricity

• If you have ever shuffled across a carpet and
  touched a doorknob on a cold dry day, you
  probably got a nice little shock.
• You probably also heard the crackle of an
  electric spark at your fingertip. If the room was
  dark, you may have even seen the spark. You may
  have seen the same thing when you combed your
  hair, pulled off a sweater, or slid across a
  cloth car seat.
• This is called static electricity.

3
The Source of Static Electricity

• To understand where static electricity comes
  from, we first have to learn (or review) just a
  little bit of chemistry.
• All the stuff around us solids, liquids and
  gases is called matter. All matter is made
  of extremely tiny particles called atoms.
  Atoms are far too small to be seen, even with the
  best microscopes, but we still know quite a bit
  about them.

4
The Helium Atom

• Take a look at the helium atom. It has two
  protons and two neutrons in its nucleus, with two
  electrons spinning around the nucleus.

5
Atoms

• Like the helium atom, all atoms are made of a
  tightly packed center called a nucleus that is
  made up of even smaller particles called
  protons and neutrons. The proton has a
  positive charge and the neutron has a neutral
  charge. Buzzing around this nucleus of protons
  and neutrons are particles that are many times
  smaller than even the protons and neutrons.
  These particles are called electrons and have a
  negative charge. Electrons circle around the
  nucleus in paths that are called orbits.
• Dont worry too much about all this charge
  business just yet, but do try to remember that
  protons have a positive charge, electrons have a
  negative charge, and neutrons have a neutral
  charge

6
Kinds of Atoms

• The number of protons in an atom determines
  what kind of atom it is. For example, a copper
  atom, shown here in diagram form, has exactly 29
  protons represented by the in the nucleus or
  center. A typical copper atom will also have 34
  neutrons, but that number can vary. The 29
  protons are matched by 29 electrons in the shells
  or orbits surrounding the nucleus.

7
Electron Charges Static Electricity

• A long time ago, people figured out that if you
  rubbed certain substances together - such as fur
  and rubber - a charge would be produced, just
  like the charge produced by your shuffle across a
  carpet on a cold day.

8
Electron Charges

• It turns out that this charge is simply a bunch
  of loose electrons that have no place to go. In
  some atoms, electrons are not held very tightly
  and can easily be removed. When a rubber rod is
  rubbed with fur, electrons are removed from the
  fur and build up on the rubber rod as static
  electricity.

9
Static Electricity

• So static electricity is just a bunch of
  electrons looking for some place to go. When you
  shuffle across a carpet, you pick up loose
  electrons. When you get to a metal doorknob,
  these electrons are attracted to that metal and
  ZAP!

10
Cute, But No Good For Radio

• Static electricity is interesting to play with.
  Its fun to shock someone else instead of the
  doorknob. (Come on, admit it. You know youve
  done that!) It is also interesting to see the
  sparks fly when you pull off your sweater in a
  darkened room. And it is really cool to watch
  the ultimate static electricity spark a
  lightning bolt!
• However, static electricity is no good for
  radio. So why did we bother with it? Because
  you need to understand that electricity is
  electrons. Let me say that again. Electricity
  is electrons!
• So lets get on to electricity we can use!

11
The Humble Flashlight

• A simple flashlight is nothing more than a
  bulb, one or more batteries, and a switch to turn
  it on or off.

12
Inside the Flashlight

• Look inside the flashlight and you will see
  that the end of the bulb tip touches the tip of
  one battery, and that the side of the bulb
  touches metal usually the metal reflector.
  This reflector comes in contact with the switch.
  If you look carefully, you will see that the this
  switch is connected to the bare metal spring at
  the bottom of the flashlight, and that spring
  touches the bottom of the other battery.
  Finally, the tip of the bottom battery touches
  the bottom of the top battery.

13
Flashlight Schematic Diagram

• If you diagram the flashlight, it looks
  something like this

14
Schematic Diagram

• Notice the symbols that are used to represent
  the switch, bulb and batteries. These are
  schematic symbols.
• Also notice that there is a continuous loop
  from the bulb to the switch to the batteries and
  back to the bulb. This loop is called a circuit.
  
• When the switch is open, the circuit is broken.
  We call that an open circuit. When the switch
  is closed, there is an unbroken loop. We say
  that the circuit is now closed because of this
  unbroken loop.
• When the circuit is closed, electricity can
  begin to move through this closed loop from the
  batteries, through the bulb, through the closed
  switch, and back to the batteries at the other
  end.

15
Simple Light Circuit

• This may be a little bit easier to see if we
  connect everything together with wires. Here you
  see a bulb from a Christmas tree light set
  connected to two batteries and a crude switch.
  As pictured, the switch is open and the light is
  off.

16
Simple Light Circuit

• Press the switch and the light comes on.

17
So whats Happening?

• When you press the switch, the circuit is
  closed and electricity (electrons) begins to flow
  from the negative (-) end of the battery where
  they are stored up, through the wire loop to the
  bulb, and back into the positive () end of the
  other battery where the battery is hungry for all
  those extra electrons. As the electricity flows
  through the bulb, some of the energy of this flow
  lights up the bulb.
• Unlike static electricity, which is just a
  bunch of electrons that will jump ship and make a
  spark at the first chance they get, this kind of
  electricity is a nice flow of electrons through a
  circuit that can actually do some useful work.

18
Conductors

• Some substances, including most metals, provide
  an easy path for electrons to move through them.
  Any substance that allows electrons to flow
  freely through it is called a conductor. One
  excellent conductor is copper. Shown below is a
  piece of stranded copper wire. (Stranded means
  that the wire is actually made up of a number of
  smaller wires twisted together.)

19
Insulators

• Other substances do not allow electrons to flow
  through them. They are called insulators. One
  excellent electrical insulator is glass. Other
  insulators include rubber, wood and plastic.
  Insulators, such as the black plastic shown here
  surrounding the copper wire, helps to prevent
  electric shock by not allowing electrons to pass
  through.

20
Current

• Now with all of that information, here is the
  first big idea. This orderly flow of electrons
  in an electric circuit is called current. It is
  this electric current that is the workhorse of
  radio and electronics!

21
Current Is Measured In Amperes (Or Amps)

• We need to measure just how much current we
  have flowing through a circuit. Electrical
  current is measured in a unit called amperes.
  This unit is often abbreviated to amps.

22
How Do We Measure Amps?

• The instrument used to measure the flow of
  current in an electrical circuit is called an
  ammeter. The one shown here measures in
  milliamperes (milliamps) or thousandths of an
  ampere

23
Voltage and Volts

• Sometimes we need to know just how hard current
  is being pushed through a circuit. Imagine a
  water hose, and imagine that the water in that
  hose is like electrons flowing through a wire.
  Now suppose this hose passes a gallon of water
  every minute. If you squeeze the hose, it will
  still pass the same amount of water, but it will
  pass it out in a smaller and sharper stream. You
  havent changed the amount of water flowing, but
  you have changed the pressure.

24
Voltage and Volts

• Electric current is like that as well. Without
  changing the number of electrons flowing in the
  circuit, we can change the pressure on those
  electrons. The pressure placed on those
  electrons is called voltage. It is also
  sometimes called electromotive force or EMF.
  Regardless of what it is called, it is measured
  in units called volts.

25
How Do We Measure Volts?

• The instrument used to measure Electromotive
  Force (EMF) (or voltage) between two points such
  as the poles of a battery is called a voltmeter.

26
Batteries

• We often see batteries measured in volts. A
  typical AA, AAA, C or D cell produces an
  electrical pressure of about 1.5 volts. If the
  cells are stacked together end to - end, we
  can add their voltage. So the total voltage in
  our flashlight, as well as the simple light
  circuit, was about three volts.

27
Batteries for Hams

• The most useful battery for hams for field work
  is the automobile battery because it can supply
  the voltage needed for most amateur radios we
  might want to run in our vehicles. The typical
  automobile battery usually supplies about 12
  volts.

28
Gel Cell Rechargeables

• Today, many hams also use high capacity 12
  volt gel cell batteries such as the one shown
  here. They are relatively inexpensive, but care
  must be taken to charge them properly!

29
Power - Watts

• We still have a few more terms to go. We
  measure the total electric power used or produced
  with a unit called watts. One good example is
  the light bulb. Light bulbs are classified based
  on the number of watts they use. (This also
  gives some indication of how bright the bulb will
  be. Well learn more about power in a bit, but
  for now, remember that electrical power is
  measured in watts.

30
Resistance Is Futile!

• Only if you are the Borg! In electricity,
  resistance is very useful. Consider our simple
  light circuit. When electricity flows through a
  metal wire, the electrons zip along with very
  little to slow them down. But when these
  electrons hit something like the tiny filament
  inside a bulb, it resists the flow of these
  electrons. This resistance changes some of the
  electrical energy into the light we wanted in the
  first place.

31
Resistance - Ohms

• There are some materials, such as the filament
  in the light bulb, that oppose current flow. The
  term used to describe opposition to current flow
  is called resistance.
• This resistance can also be measured, and it is
  very useful to do so. The basic unit of
  resistance is the ohm.

32
The Multimeter

• For the Technician exam, you have to know that
  the ammeter measures current (amps), and the
  voltmeter measures electromotive force (or
  voltage). You do not have to know that the
  ohmmeter is used to measure resistance.
  Actually, all three of these can be measured with
  a single meter called a multimeter. A good
  multimeter is very inexpensive and extremely
  useful to have around.

33
The Multimeter

• Here is a typical multimeter that will measure
  voltage, current and resistance. It costs less
  than ten dollars, and is a very useful tool that
  no ham should ever be without!

34
Direct Current

• In our simple light circuit, electricity leaves
  the batteries from one end, flows through the
  wire in one direction, and enters the other end
  of the batteries. In other words, the electron
  flow (or current) is in one direction only.
  Current that flows only in one direction is
  called direct current, and is abbreviated DC.

35
Alternating Current

• Electric current in your home works almost the
  same way, but not quite. Because of the way
  household electricity is produced, it does not
  flow in the same direction all the time. In
  fact, it is constantly reversing direction. As
  far as doing useful work, it doesnt matter
  whether the electrons are moving in the same
  direction all the time or constantly changing
  direction. As long as the electrons are moving,
  the work will get done.
• When an electric current reverses direction on
  a regular basis, it is called alternating
  current, and it is abbreviated AC.

36
Representing AC

• We can represent the flow of alternating
  current using a wavy line like this one, called a
  sine wave. (Dont worry about why its called a
  sine wave. Theres a good reason, but you dont
  need to know it for the Technician test.)

37
An Electron Roller Coaster

• Now imagine a tiny electron riding along this
  sine wave, kind of like a roller coaster. When
  the electron goes up the curve, it is traveling
  in one direction. When it goes back down the
  curve, it has reversed itself and is traveling in
  the opposite direction.

38
Cycle

• Lets say we start at the point on the roller
  coaster labeled A and time how long it takes
  for the electron to get to B on the roller
  coaster. If you look carefully, youll see that
  the electron went up, then all the way down, and
  all the way back up. In other words, it went
  through one complete curve of this roller
  coaster. We call this complete trip down in one
  direction and all the way back in the other one
  cycle

39
Frequency

• With any good roller coaster ride, the faster
  the better! So lets suppose we want to measure
  how fast our little alternating current electron
  is going up and down this roller coaster. We
  want to know how many times our electron is
  reversing directions in one second. If we time
  the reverses of direction in U.S. household
  alternating current, it turns out that it
  reverses about sixty times per second. Since
  each complete reversal is one cycle, we say that
  alternating household current reverses at sixty
  cycles per second.

40
Frequency Definition

• Frequency is the measure of the number of
  cycles per second an alternating current
  reverses. It is measured in a unit called the
  hertz. One hertz is equal to one cycle per
  second, and the Hertz is the standard unit of
  frequency.
• Based on this, the AC current in a U.S.
  household is 60 Hertz.
• Whew! That was a lot of stuff to remember. If
  you are not sure you understand it, go back over
  this section until you do.

41
Check-Up Time!

• Now lets try the questions from this group.
• You should make a note of any that you miss for
  later review.

42
T4A01

• Electrical current is measured in which of the
  following units?
• A. Volts
• B. Watts
• C. Ohms
• D. Amperes

43
T4A01 Answer - D

• Current is measured in amperes (or more
  commonly amps). It is a measure of the amount of
  electrical energy. Power supply capacity is
  often rated by the number of amps it can produce
  at a given voltage.

44
T4A02

• Electrical Power is measured in which of the
  following units?
• A. Volts
• B. Watts
• C. Ohms
• D. Amperes

45
T4A02 Answer - B

• Overall electrical power is generally measured
  in watts. Transmitter power output is often
  measured in watts. So are many common home
  appliances and light bulbs.

46
T4A03

• What is the name for the flow of electrons in an
  electric circuit?
• A. Voltage
• B. Resistance
• C. Capacitance
• D. Current

47
T4A03 Answer - D

• Current is the amount of electron flow in a
  circuit. The greater the amount of electron
  flow, the higher the current.

48
T4A04

• What is the name of a current that flows only in
  one direction?
• A. An alternating current
• B. A direct current
• C. A normal current
• D. A smooth current

49
T4A04 Answer - B

• Direct current flows through a circuit in one
  direction only.

50
T4A05

• What is the standard unit of frequency?
• A. The megacycle
• B. The Hertz
• C. One thousand cycles per second
• D. The electromagnetic force

51
T4A05 Answer - B

• The basic unit of frequency is the Hertz. One
  Hertz equals one cycle per second.

52
T4A06

• How much voltage does an automobile battery
  usually supply?
• A. About 12 volts
• B. About 30 volts
• C. About 120 volts
• D. About 240 volts

53
T4A06 Answer - A

• Most amateur equipment is designed to be
  powered by a 12 volt supply. This is so
  primarily because most car batteries are 12 volt
  batteries.

54
T4A07

• What is the basic unit of resistance?
• A. The volt
• B. The watt
• C. The ampere
• D. The ohm

55
T4A07 Answer - D

• Resistance is the opposition to current flow
  and it is measured in ohms. Whenever electricity
  passes through a wire or any other component and
  it either begins to glow or generate heat or
  both, that is due to resistance.

56
T4A08

• What is the name of a current that reverses
  direction on a regular basis?
• A. An alternating current
• B. A direct current
• C. A circular current
• D. A vertical current

57
T4A08 Answer - A

• Alternating current flows first in one
  direction and then in the opposite direction,
  usually in a very regular cycle. The alternating
  current in U.S. households changes direction 120
  times per second. Each two changes in direction
  (down and back up) is one cycle, creating 60
  complete cycles every second, so we say that
  electric current has a frequency of 60 cycles per
  second or 60 Hertz.

58
T4A09

• Which of the following is a good electrical
  conductor?
• A. Glass
• B. Wood
• C. Copper
• D. Rubber

59
T4A09 Answer - C

• Metals are generally good conductors of
  electricity. A conductor is a substance that
  allows electrons to flow through it easily.

60
T4A10

• Which of the following is a good electrical
  insulator?
• A. Copper
• B. Glass
• C. Aluminum
• D. Mercury

61
T4A10 Answer - B

• Non-metals do not allow electrons to move
  through them very readily, so they make good
  insulators.

62
T4A11

• What is the term used to describe opposition to
  current flow in ordinary conductors such as
  wires?
• A. Inductance
• B. Resistance
• C. Counter EMF
• D. Magnetism

63
T4A11 Answer - B

• Even the best conductors offer some resistance
  to current flow, but this resistance is not
  enough to make much difference unless the
  conductor is very long, such as a long strand of
  wire.

64
T4A12

• What instrument is used to measure the flow of
  current in an electrical circuit?
• A. Frequency meter
• B. SWR meter
• C. Ammeter
• D. Voltmeter

65
T4A12 Answer - C

• If you remember that current is measured in
  amps, the answer to this question should be easy!

66
T4A13

• What instrument is used to measure Electromotive
  Force (EMF) between two points such as the poles
  of a battery?
• A. Magnetometer
• B. Voltmeter
• C. Ammeter
• D. Ohmmeter

67
T4A13 Answer - B

• Electromotive force is the fancy name for
  voltage, and voltage is measured with a voltmeter.

68
Group T4B

• Group T4B covers the relationship between
  frequency and wavelength, identification of
  amateur radio bands, names of frequency ranges,
  and types of radio waves .

69
Radio Waves

• Radio waves are a kind of energy that carries
  your voice and data from your transmitter to
  another hams receiver. We cant see a radio
  wave, but we dont have to actually see it to
  understand it.
• Remember our electron roller coaster, better
  known as a sine wave? It turns out that a sine
  wave is a pretty good model to explain radio
  waves, so lets take a closer look.

70
Waves

• If you have ever dropped a stone into a pool or
  pond, you know what happens. You get a series of
  ripples that spread out in circles. The energy
  from that falling rock is transferred to the
  water and spreads out in the form of these little
  ripples or waves.

71
Waves A Closer Look
72
Wave Form

• If you look at the cross section of the waves
  on the diagram in the previous slide, you can see
  that it looks a lot like our sine wave. Thats
  because it is a sine wave, and you can imagine
  the moving curve as the waves spread out from
  where the stone was dropped. Unlike our electron
  roller coaster, it is the wave that moves, and
  not something moving along the wave.

73
Wavelength

• Here is a plain sine wave. If we measure from
  Point A to Point B, the distance is the length of
  one complete wave or cycle. We call this the
  wavelength. The name for the distance a radio
  wave travels during one complete cycle is
  wavelength.

74
Frequency

• Remember that the frequency of alternating
  current is a measure of the number of cycles per
  second that alternating current reverses. So the
  number of times that an alternating current flows
  back and forth per second is its frequency.

75
Measuring Frequency

• As you saw in the last group of questions,
  frequency is measured in a unit called the Hertz.
  Hertz is the standard unit of frequency, and one
  hertz is equal to one cycle per second.
• Since the frequency of AC house current is 60
  Hertz, we say it goes through 60 cycles per
  second.

76
Radio Waves

• Now 60 cycles per second (or 60 Hertz) seems
  pretty fast. But imagine the ripples on the pond
  moving out at a speed of 20,000 times a second.
  Thats 20,000 waves lapping up against the shore
  every single second.
• Obviously, water waves cannot do that, but
  radio waves can. They are waves of energy that
  act a little like electric waves, and a little
  like magnetic waves. Radio waves are types of
  waves known as electromagnetic waves. Radio
  waves oscillate (or reverse direction) at a
  frequency of at least 20,000 Hertz.
• Electromagnetic waves that oscillate more than
  20,000 times per second as they travel through
  space are generally referred to as radio waves.

77
How Fast Do Radio Waves Move?

• If radio waves oscillate more than 20,000 times
  a second, just how fast do they move? It turns
  out they move pretty darn fast. In fact, radio
  waves travel through space at the speed of light.
  And in case you didnt know, the speed of light
  is (approximately) a whopping 186,000 miles per
  second. At that speed a light beam will cover a
  distance equal to over seven times around the
  world in less than a second!

78
Wavelength, Frequency and the Speed of Light

• The wavelength and frequency are directly
  related to each other and to the speed of light.
  We wont bore you with the stuff you dont need
  to know about that. However, there are some
  things you are going to have to know to
  understand this stuff, so lets get to it.

79
Wavelength Revisited

• Take another look at the diagram of the sine
  wave. You should remember that the distance from
  Point A to Point B is the wavelength. In the
  radio world, wavelength is measured in meters.

80
Frequency Revisited

• You should also remember that the frequency of
  a wave is the measure of the number of cycles it
  completes in one second. One cycle per second is
  one Hertz.
• But we saw that the lowest frequency of a radio
  wave is 20,000 Hertz, and it goes way up from
  there. Radio wave frequencies can go into the
  millions of Hertz!

81
So how do we Handle the Big Numbers?

• Lets take the lowest frequency radio wave at
  20,000 Hertz. It is sometimes easier to use
  larger units to deal with numbers as large as
  this. In the radio business, we use two
  different units to help us deal with large
  numbers.

82
Kilohertz (KHz)

• The first unit we use is the kilohertz. One
  kilohertz is equal to 1000 Hertz. Kilohertz is
  abbreviated KHz.
• Using this unit, 20,000 Hertz equals 20
  Kilohertz (or 20 KHz).
• It may not be any simpler, but it is a little
  shorter.

83
Megahertz (MHz)

• When the frequency of a radio wave gets into
  the millions, the numbers get really big. One
  popular amateur band, the 2 meter band, starts at
  a frequency of 144,000,000 Hertz. As you can
  see, 144 million is a pretty large number, so we
  use our second unit to make things a little
  easier to manage.
• So the second unit we use is the megahertz.
  One megahertz equals 1,000,000 Hertz. Megahertz
  is abbreviated MHz.
• Using this unit, 144,000,000 Hertz becomes 144
  megahertz (or 144 MHz).

84
Is Your Head Spinning Yet?

• We promised we would explain a little more
  about the amateur bands, so here goes. You now
  know that the 2 meter band begins at 144 MHz. Do
  you know why the call it the 2 meter band?
• Heres a hint. Remember that the wavelength of
  a radio wave measured in meters.

85
Aha!

• Thats right! This band is called the 2 meter
  band because 2 meters is the approximate
  wavelength of the waves in this band.
• Thats the same reason we call the other ham
  bands what we do. The 6 meter band has radio
  wavelengths of about 6 meters, the 1.25 meter
  band has radio wavelengths of about 1.25 meters,
  and the 70 centimeter band has radio wavelengths
  of about .7 meters. (Sneaked that last one in on
  you, didnt we?)
• So remember that the property of a radio wave
  often used to identify the different bands
  amateur radio operators use is the physical
  length of the wave, or simply the wavelength

86
Formulas to Forget

• OK, were going to give you two formulas that
  show you how frequency and wavelength are
  related, and here they are...
• 300
• Wavelength (in meters) -----------------
• Frequency (in MHz)
• 300
• Frequency (in MHz) ---------------------
• Wavelength (in meters)

87
Whats Important!

• These two formulas show the math whizzes among
  us what the rest of us will just have to
  memorize. The wavelength of a radio wave
  relates to its frequency in that the wavelength
  gets shorter as the frequency increases, and the
  wavelength gets longer as the frequency
  decreases. The same is true for frequency.

88
Frequency Ranges of Several Bands

• OK, now that you know all about how frequency
  and wavelength are related, and you also know
  that amateur bands are often described by their
  average wavelength, its time to learn some
  really useful stuff. Below are the frequency
  ranges of several ham bands that you can use as a
  Technician. Theres no way around it, youll
  need to memorize them to ace the exam!
• Frequency range of the 2 meter band in the U.S.
  - 144 to 148 MHz
• Frequency range of the 6 meter band in the U.S.
  - 50 to 54 MHz
• Frequency range of the 70 centimeter band in the
  U.S. - 420 to 450 MHz

89
Sound Waves

• Sound also travels in waves, but unlike radio
  waves, sound waves cannot travel through space.
  Sound waves can only travel through air or some
  other type of matter. However, like radio waves,
  sound waves also have a range of frequencies as
  well.
• Generally, the higher the frequency, the higher
  pitched the sound.
• Sound waves in the range between 300 and 3000
  Hertz are the frequencies of the average human
  voice. These frequencies are important because
  hams are trying to transmit their voices all the
  time, and they want to use microphones that have
  a good frequency response in the human voice
  range.

90
Check-Up Time!

• Now lets try the questions from this group.
• You should make a note of any that you miss for
  later review.

91
T4B01

• What is the name for the distance a radio wave
  travels during one complete cycle?
• A. Wave speed
• B. Waveform
• C. Wavelength
• D. Wave spread

92
T4B01 Answer - C

• The distance a radio wave travels in one cycle
  is its wavelength. Amateur bands are often
  identified by the average wavelength of the radio
  waves within that band, such as the 2 meter band,
  or more often, just "2 meters."

93
T4B02

• What term describes the number of times that an
  alternating current flows back and forth per
  second?
• A. Pulse rate
• B. Speed
• C. Wavelength
• D. Frequency

94
T4B02 Answer - D

• Frequency is the number of times an alternating
  current, such as a radio wave, travels back and
  forth in one second. Each cycle is one Hertz.
  In the case of AC house current, the frequency is
  relatively low only 60 cycles per second.
• However, as you will soon see, the frequencies
  of radio waves are much higher, and depending on
  the frequency, they are measured in either
  kilohertz (1000 hertz) or megahertz (1 million
  hertz).

95
T4B03

• What does 60 hertz (Hz) mean?
• A. 6000 cycles per second
• B. 60 cycles per second
• C. 6000 meters per second
• D. 60 meters per second

96
T4B03 Answer - B

• Hertz means "cycles per second."

97
T4B04

• Electromagnetic waves that oscillate more than
  20,000 times per second as they travel through
  space are generally referred to as what?
• A. Gravity waves
• B. Sound waves
• C. Radio waves
• D. Gamma radiation

98
T4B04 Answer - C

• Radio waves are waves of electromagnetic energy
  that have a frequency of more than 20,000 hertz
  (or 20 kilohertz). An electromagnetic wave is a
  wave of energy with electrical and magnetic
  components.

99
T4B05

• How fast does a radio wave travel through space?
• A. At the speed of light
• B. At the speed of sound
• C. Its speed is inversely proportional to its
  wavelength
• D. Its speed increases as the frequency increases

100
T4B05 Answer - A

• All electromagnetic waves travel through space
  at the speed of light - about 186,000 miles per
  second!

101
T4B06

• How does the wavelength of a radio wave relate
  to its frequency?
• A. The wavelength gets longer as the frequency
  increases
• B. The wavelength gets shorter as the frequency
  increases
• C. There is no relationship between wavelength
  and frequency
• D. The wavelength depends on the bandwidth of the
  signal

102
T4B06 Answer - B

• As frequency increases, the wavelength gets
  shorter. As frequency decreases, the wavelength
  gets shorter. For you math whizzes, frequency
  and wavelength are inversely proportional. (No,
  thats not on the test.)

103
T4B07

• What is the formula for converting frequency to
  wavelength in meters?
• A. Wavelength in meters equals frequency in Hertz
  multiplied by 300
• B. Wavelength in meters equals frequency in Hertz
  divided by 300
• C. Wavelength in meters equals frequency in
  megahertz divided by 300
• D. Wavelength in meters equals 300 divided by
  frequency in megahertz

104
T4B07 Answer - D

• 300
• Wavelength ---------------
• (Meters) Frequency (MHz)

105
T4B08

• What are sound waves in the range between 300
  and 3000 Hertz called?
• A. Test signals
• B. Ultrasonic waves
• C. Voice frequencies
• D. Radio frequencies

106
T4B08 Answer - C

• Knowing where the voice frequencies are
  concentrated is very useful when adjusting for
  the best possible audio from your microphone.

107
T4B09

• What property of a radio wave is often used to
  identify the different bands amateur radio
  operators use?
• A. The physical length of the wave
• B. The magnetic intensity of the wave
• C. The time it takes for the wave to travel one
  mile
• D. The voltage standing wave ratio of the wave

108
T4B09 Answer - A

• Amateurs often refer to the various bands by
  their approximate wavelength, such as 80 meters,
  20 meters, 10 meters or 2 meters.

109
T4B10

• What is the frequency range of the 2 meter band
  in the United States?
• A. 144 to 148 MHz
• B. 222 to 225 MHz
• C. 420 to 450 MHz
• D. 50 to 54 MHz

110
T4B10 Answer - A

• You will almost certainly get at least one
  question on your exam about the frequency of a
  particular band or sub-band. The bad news is
  they just have to be memorized. The good news is
  that this is information you will use as long as
  you are a ham.

111
T4B11

• What is the frequency range of the 6 meter band
  in the United States?
• A. 144 to 148 MHz
• B. 222 to 225 MHz
• C. 420 to 450 MHz
• D. 50 to 54 MHz

112
T4B11 Answer - D

• Next to 2 meters, 6 meters is probably the most
  popular band for Technician licensees. When this
  band is open, you can work some real DX (long
  distance contacts)!

113
T4B12

• What is the frequency range of the 70 centimeter
  band in the United States?
• A. 144 to 148 MHz
• B. 222 to 225 MHz
• C. 420 to 450 MHz
• D. 50 to 54 MHz

114
T4B12 Answer - C

• There are really only three bands youll need
  to know the frequencies for 6 meters, 2 meters,
  and 70 centimeters. They are important to you
  because they are all bands open to you as a
  Technician licensee.

115
Group T4C

• Group T4C covers how radio works. It also covers
  receivers, transmitters, transceivers,
  amplifiers, power supplies, and types of
  batteries and their service life .

116
Radio Equipment

• After all of that heavy theory about radio
  waves, were going to take a look at some very
  basic information about what different radio
  components do.

117
Radio Receiver

• The radio receiver is a device used to convert
  radio signals into sounds we can hear. You
  should be very familiar with radio receivers.
  You use them to listen to your favorite radio
  stations. The receivers hams use do the very
  same thing, except we use them to listen to other
  hams.

118
Radio Transmitter

• A radio transmitter is used to convert sounds
  from our voice into radio signals that are then
  sent out over the air to the other hams radio
  receiver.

119
Transceiver

• Back in the early days of amateur radio, every
  ham had to have two separate pieces of equipment
  a transmitter and a receiver. The transmitter
  was used to generate the signal sent out over the
  air, and the receiver was used to receive the
  other hams signal. However, for many years now,
  the transmitter and receiver have been combined
  into a single unit called a transceiver

120
Transceiver

• In a transceiver, the transmitter and receiver
  are combined into a single unit. This eliminates
  the need for having to have the two separate
  units and it makes tuning much easier as well.

121
Power Supply

• Most modern radios require 12 volts DC as a
  power source. This allows them to be operated
  mobile using car batteries. The voltage coming
  from the plugs in U.S. homes is 110-120 volts AC.
  To get the proper voltage to use these radios in
  your home, you need a device called a power
  supply. The power supply is a device is used to
  convert the alternating current from a wall
  outlet into low-voltage direct current. The
  output of a power supply used for amateur radio
  is usually about 12 volts.

122
RF Amplifier

• Sometimes a ham may need or want more output
  power than the radio is capable of generating.
  An RF (radio frequency) amplifier is used to
  increase the output of a radio to a higher power.
  For example, you could use an amplifier to boost
  the power of a 10 watt radio to 100 watts.

123
Batteries

• Most handhelds are powered by batteries, and
  there are a number of different types. For
  example, there are lead-acid batteries, alkaline
  batteries, nickel-cadmium batteries and
  lithium-ion batteries. Of these, the lithium-ion
  battery offers the longest life when used with a
  hand-held radio, assuming each battery is the
  same physical size. You probably already know
  this if you use a digital camera.

124
Nickel-Cadmium Batteries

• Most fully charged AA, AAA, C or D batteries
  have a charge of about 1.5 volts. However, a
  fully charged nickel-cadmium battery has a
  nominal voltage per cell of about 1.2 volts.
  This voltage is lower than most other types of
  batteries, but the advantage of a nickel-cadmium
  cell is that it is relatively inexpensive and
  rechargeable, and that can save a lot of money.

125
Carbon-Zinc Batteries

• Carbon-zinc batteries are the common AA, AAA, C
  or D batteries you find at the local store. They
  are usually the most inexpensive batteries, but
  they have one distinct disadvantage that makes
  them fairly expensive in the long run. Unlike
  nickel-cadmium, lead-acid or, lithium-ion
  batteries, carbon-zinc batteries are not designed
  to be re-charged.

126
Battery Care

• As a Technician, you will almost certainly use
  some sort of rechargeable batteries with your
  equipment. Regardless of the type of
  rechargeable you use, there are several things
  you should do to keep rechargeable batteries in
  good condition and ready for emergencies.
• They should be inspected for physical damage
  and replaced if necessary
• They should be stored in a cool and dry
  location
• They must be given a maintenance recharge at
  least every 6 months

127
Battery Use

• Regardless of the kind of battery you use, the
  best way to get the most amount of energy from a
  battery is to draw current from the battery at
  the slowest rate needed. This will help your
  battery to last much longer.

128
Check-Up Time!

• Now lets try the questions from this group.
• You should make a note of any that you miss for
  later review.

129
T4C01

• What is used to convert radio signals into
  sounds we can hear?
• A. Transmitter
• B. Receiver
• C. Microphone
• D. Antenna

130
T4C01 Answer - B

• Radio signals are received and changed into
  sound by a receiver. Radio signals are produced
  by a transmitter. When the transmitter and
  receiver are combined into a single unit, as is
  almost always the case with modern radios, the
  combination is called a transceiver.

131
T4C02

• What is used to convert sounds from our voice
  into radio signals?
• A. Transmitter
• B. Receiver
• C. Speaker
• D. Antenna

132
T4C02 Answer - A

• Radio signals are produced by a transmitter.
  Radio signals are received and changed into sound
  by a receiver. When the transmitter and receiver
  are combined into a single unit, as is almost
  always the case with modern radios, the
  combination is called a transceiver.

133
T4C03

• What two devices are combined into one unit in a
  transceiver?
• A. Receiver, transmitter
• B. Receiver, transformer
• C. Receiver, transistor
• D. Transmitter, deceiver

134
T4C03 Answer - A

• In the early days of amateur radio, even up to
  the 1960s, the transmitter and receiver were
  usually two separate units. However, beginning
  in the mid 1960s, the two units were combined to
  make a transceiver. Almost all commercially
  produced amateur gear is of the transceiver type,
  with the exception of a few simple kits.

135
T4C04

• What device is used to convert the alternating
  current from a wall outlet into low-voltage
  direct current?
• A. Inverter
• B. Compressor
• C. Power Supply
• D. Demodulator

136
T4C04 Answer - C

• Most amateur gear requires 12 volts direct
  current (DC). When amateur gear is used in the
  home, a power supply is required to convert the
  110 volt alternating current (AC) from the wall
  socket to the 12 volt direct current (DC)
  required (or any other DC voltage that may be
  required).

137
T4C05

• What device is used to increase the output of a
  10 watt radio to 100 watts?
• A. Amplifier
• B. Power supply
• C. Antenna
• D. Attenuator

138
T4C05 Answer - A

• An amplifier is a device that is used to
  amplify or increase the power of a signal. An
  amplifier may be used to increase RF (radio
  frequency) power. Other amplifiers may be used
  to increase the power of a sound signal such as a
  guitar amplifier.

139
T4C06

• Which of the battery types listed below offers
  the longest life when used with a hand-held
  radio, assuming each battery is the same physical
  size?
• A. Lead-acid
• B. Alkaline
• C. Nickel-cadmium
• D. Lithium-ion

140
T4C06 Answer - D

• Lithium-ion batteries have a high storage
  capacity for their size, so they last longer.
  They are generally more expensive. (You may
  already know that lithium-ion digital camera
  batteries last longer than any other kind. If
  you do, you also already know they are more
  expensive.)

141
T4C07

• What is the nominal voltage per cell of a fully
  charged nickel-cadmium battery?
• A. 1.0 volts
• B. 1.2 volts
• C. 1.5 volts
• D. 2.2 volts

142
T4C07 Answer - B

• Although nickel-cadmium batteries, more
  commonly known as nicads, have a lower voltage
  than a typical alkaline battery of the same type,
  the difference is not that great, and they are
  rechargeable many times. For that reason, most
  handheld radios use nicads as a power source.

143
T4C08

• What battery type on this list is not designed
  to be re-charged?
• A. Nickel-cadmium
• B. Carbon-zinc
• C. Lead-acid
• D. Lithium-ion

144
T4C08 Answer - B

• Carbon-zinc batteries are the least expensive
  batteries, and they are the most common.
  However, they are designed for only a single use,
  and generally cannot be recharged.

145
T4C09

• What is required to keep rechargeable batteries
  in good condition and ready for emergencies?
• A. They must be inspected for physical damage and
  replaced if necessary
• B. They should be stored in a cool and dry
  location
• C. They must be given a maintenance recharge at
  least every 6 months
• D. All of these answers are correct

146
T4C09 Answer - D

• Amateur operators are often called on to
  provide communications in an emergency. Many
  emergencies result in a loss of commercial power.
  If you want to help, you need to insure that
  your batteries are properly stored, charged and
  maintained so that you can be ready to deploy at
  a moment's notice.

147
T4C10

• What is the best way to get the most amount of
  energy from a battery?
• A. Draw current from the battery as rapidly as
  possible
• B. Draw current from the battery at the slowest
  rate needed
• C. Reverse the leads when the battery reaches the
  1/2 charge level
• D. Charge the battery as frequently as possible

148
T4C10 Answer - B

• Drawing only the current you need will make the
  most of your battery's charge. Whatever you do,
  NEVER, NEVER, NEVER reverse the leads on a
  battery. This can seriously damage your
  equipment!

149
Group T4D

• Group T4D covers the most important Ohms Law
  relationships .

150
Important (But Confusing) Abbreviations

• Were about to look at something called Ohms
  law. Ohms law is a very important mathematical
  formula that shows how voltage, current and
  resistance are related to each other. But before
  we can study the law, we need to look at the
  abbreviations for each of these values, and they
  are not what you would expect. They are
• Voltage E
• Current I
• Resistance R
• You would expect that voltage should be
  abbreviated V and current should be C, but they
  are not. Youll need to learn these three for
  what comes next.

151
Ohms Law

• Ohms law ties voltage, current and resistance
  all together in one neat package. If you know
  any two of them, you can easily figure out the
  third. If you know a little algebra, youll only
  need to remember one formula. If you dont,
  youll either need to remember three formulas or
  a little memory aide youll see in just a bit.

152
Ohms Law Voltage Unknown

• Remember our little flashlight circuit?
  Suppose you know the current and resistance in
  that circuit and you want to know the voltage.
  Use this formula
• Voltage (E) equals current (I) multiplied by
  resistance (R)
• If you use the abbreviations, it is simply
• E I x R
• Well see how you actually use this in just a
  bit.

153
Ohms Law Current Unknown

• Using the same circuit, suppose you know the
  voltage and the resistance, but you dont know
  the current. If so, the formula you use is
• Current (I) equals voltage (E) divided by
  resistance (R)
• Using just the abbreviations, the formula is
• E
• I ---
• R
• Well use this one shortly, too!

154
Ohms Law - Resistance Unknown

• Finally, using the same flashlight circuit one
  more time, suppose you know the current and the
  voltage, but you need to know the resistance. If
  so, the formula is
• Resistance (R) equals voltage (E) divided by
  current (I)
• Using just the abbreviations, the formula is
• E
• R ---
• I

155
A Simple Solution!

• If you know algebra, you can take E I x R and
  come up with the other two equations. But, if
  you dont know algebra and you dont want to
  remember three different equations, there is
  another solution - its the Ohms Law Circle!

156
Ohms Law Circle

• The Ohms Law circle is really easy to use.
  Draw it out on a piece of paper and keep it
  handy.
• To use the circle, you will cover the value you
  dont know with your hand. If the two values you
  know are beside each other, you multiply them
  together. If one is over the other, divide the
  lower value into the upper value.
• (Dont panic! All will be explained)

157
Ohms Law Problems

• We promised all would be explained, so here
  goes. Grab a piece of paper and lets rumble!
• OK, all these formulas and this circle might
  seem a little confusing, so lets see how they
  work by going through a few problems. That
  should clear up any confusion you might have.
• Well work each problem two ways. First, well
  show you how to do it using the formula, and then
  well work the same problem using the circle. It
  doesnt matter which one you use to get the
  answer, so long as you can get the right answer.

158
Ohms Law Problem 1 Voltage Unknown

• What is the voltage across the resistor if a
  current of 0.5 amperes flows through a 2 ohm
  resistor?
• Solution
• E I x R
• E 0.5 x 2 1 volt
• Or...

159
Ohms Law Problem 1 Voltage Unknown

• Using the circle, cover the E. You now have to
  multiply I times R to get the right answer of 1
  volt.

160
Ohms Law Problem 2 Voltage Unknown

• What is the voltage across the resistor if a
  current of 1 ampere flows through a 10 ohm
  resistor?
• Solution
• E I x R
• E 1 x 10 10 volts
• Or, using the circle, cover the E. You now
  have to multiply I times R to get the right
  answer of 10 volts.

161
Ohms Law Problem 3 Voltage Unknown

• What is the voltage across the resistor if a
  current of 2 amperes flows through a 10 ohm
  resistor?
• Solution
• E I x R
• E 2 x 10 20 volts
• Or, using the circle, cover the E. You now
  have to multiply I times R to get the right
  answer of 20 volts.

162
Ohms Law Problem 4 Current Unknown

• What is the current flow in a circuit with an
  applied voltage of 120 volts and a resistance of
  80 ohms?
• Solution
• E
• I ---
• R
• 120
• I --- 1.5 amps
• 80
• Or...

163
Ohms Law Problem 4 Current Unknown

• Using the circle, cover the I. You now have to
  divide E by R to get the right answer of 1.5 amps.

164
Ohms Law Problem 5 Current Unknown

• What is the current flowing through a 100 ohm
  resistor connected across 200 volts?
• Solution
• E
• I ---
• R
• 200
• I --- 2 amps
• 100
• Or, using the circle, cover the I. You now
  have to divide E by R to get the right answer of
  2 amps.

165
Ohms Law Problem 6 Current Unknown

• What is the current flowing through a 24 ohm
  resistor connected across 240 volts?
• Solution
• E
• I ---
• R
• 240
• I --- 10 amps
• 24
• or, using the circle, cover the I. You now
  have to divide E by R to get the right answer of
  10 amps.

166
Ohms Law Problem 7 Resistance Unknown

• What is the resistance of a circuit when a
  current of 3 amperes flows through a resistor
  connected to 90 volts?
• Solution
• E
• R ---
• I
• 90
• R --- 30 ohms
• 3
• Or...

167
Ohms Law Problem 7 Resistance Unknown

• Using the circle, cover the R. You now have to
  divide E by I to get the right answer of 30 ohms.

168
Ohms Law Problem 8 Resistance Unknown

• What is the resistance in a circuit where the
  applied voltage is 12 volts and the current flow
  is 1.5 amperes?
• Solution
• E
• R ---
• I
• 12
• R --- 8 ohms
• 1.5
• Or, using the circle, cover the R. You now
  have to divide E by I to get the right answer of
  8 ohms.

169
Check-Up Time!

• Now lets try the questions from this group.
• You should make a note of any that you miss for
  later review.

170
T4D01

• What formula is used to calculate current in a
  circuit?
• A. Current (I) equals voltage (E) multiplied by
  resistance (R)
• B. Current (I) equals voltage (E) divided by
  resistance (R)
• C. Current (I) equals voltage (E) added to
  resistance (R)
• D. Current (I) equals voltage (E) minus
  resistance (R)

171
T4D01 Answer - B

• There are three possible equations for Ohm's
  Law. There is also a great memory aid for those
  who don't like to remember equations. Well look
  at that later. First, here is the Ohms Law
  equation to find current (I)
• E
• I ---
• R

172
T4D02

• What formula is used to calculate voltage in a
  circuit?
• A. Voltage (E) equals current (I) multiplied by
  resistance (R)
• B. Voltage (E) equals current (I) divided by
  resistance (R)
• C. Voltage (E) equals current (I) added to
  resistance (R)
• D. Voltage (E) equals current (I) minus
  resistance (R)

173
T4D02 Answer - A

• Here is the Ohms Law equation for determining
  voltage
• E I x R

174
T4D03

• What formula is used to calculate resistance in
  a circuit?
• A. Resistance (R) equals voltage (E) multiplied
  by current (I)
• B. Resistance (R) equals voltage (E) divided by
  current (I)
• C. Resistance (R) equals voltage (E) added to
  current (I)
• D. Resistance (R) equals voltage (E) minus
  current (I)

175
T4D03 Answer - B

• Here is the Ohms Law equation to solve for
  current
• E
• R ---
• I

176
T4D04

• What is the resistance of a circuit when a
  current of 3 amperes flows through a resistor
  connected to 90 volts?
• A. 3 ohms
• B. 30 ohms
• C. 93 ohms
• D. 270 ohms

177
T4D04 Answer - B

• You can solve this by using this formula
• E
• R ---
• I
• E 90
• R --- --- 30 Ohms
• I 3

178
Or You Can Use the Ohms Law Circle
179
For Resistance...

• Cover the R (resistance), and divide E
  (voltage) by I (current)

180
T4D05

• What is the resistance in a circuit where the
  applied voltage is 12 volts and the current flow
  is 1.5 amperes?
• A. 18 ohms
• B. 0.125 ohms
• C. 8 ohms
• D. 13.5 ohms

181
T4D05 Answer - C

• You can solve this by using this formula
• E
• R ---
• I
• E 12
• R --- --- 8 Ohms
• I 1.5

182
Or for Resistance...

• Cover the R (resistance), and divide E
  (voltage) by I (current)

183
T4D06

• What is the current flow in a circuit with an
  applied voltage of 120 volts and a resistance of
  80 ohms?
• A. 9600 amperes
• B. 200 amperes
• C. 0.667 amperes
• D. 1.5 amperes

184
T4D06 Answer - D

• You can solve this one by using the formula
• E
• I ---
• R
• E 120
• I --- --- 1.5 amperes
• R 80

185
Or for Current...

• Cover the I (current), and divide E (voltage)
  by R (resistance)

186
T4D07

• What is the voltage across the resistor if a
  current of 0.5 amperes flows through a 2 ohm
  resistor?
• A. 1 volt
• B. 0.25 volts
• C. 2.5 volts
• D. 1.5 volts

187
T4D07 Answer - A

• You can solve this one by using the formula
• E I x R
• E I x R 0.5 x 2 1 volt

188
Or for Voltage...

• Cover the E (voltage), and multiply I (current)
  times R (resistance)

189
T4D08

• What is the voltage across the resistor if a
  current of 1 ampere flows through a 10 ohm
  resistor?
• A. 10 volts
• B. 1 volt
• C. 11 volts
• D. 9 volts

190
T4D08 Answer - A

• You can solve this one by using the formula
• E I x R
• E I x R 1 x 10 10 volts

191
Or for Voltage...

• Cover the E (voltage), and multiply I (current)
  times R (resistance)

192
T4D09

• What is the voltage across the resistor if a
  current of 2 amperes flows through a 10 ohm
  resistor?
• A. 20 volts
• B. 0.2 volts
• C. 12 volts
• D. 8 volts

193
T4D09 Answer - A

• You can solve this one by using the formula
• E I x R
• E I x R 2 x 10 20

194
Or for Voltage...

• Cover the E (voltage), and multiply I (current)
  times R (resistance)

195
T4D10

• What is the current flowing through a 100 ohm
  resistor connected across 200 volts?
• A. 20,000 amperes
• B. 0.5 amperes
• C. 2 amperes
• D. 100 amperes

196
T4D10 Answer - C

• You can solve this one by using the formula
• E
• I ---
• R
• E 200
• I --- --- 2 amperes
• R 100

197
Or for Current...

• Cover the I (current), and divide E (voltage)
  by R (resistance)

198
T4D11

• What is the current flowing through a 24 ohm
  resistor connected across 240 volts?
• A. 24,000 amperes
• B. 0.1 amperes
• C. 10 amperes
• D. 216 amperes

199
T4D11 Answer - C

• You can solve this one by using the formula
• E
• I ---
• R
• E 240
• I --- --- 10 amper