Technician License Course Chapter 4 Propagation, Antennas and Feed Lines

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Technician License CourseChapter 4Propagation,
Antennas and Feed Lines
Lesson Plan Module 10 Practical Antennas
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The Dipole

• Most basic antenna.
• Two conductive, equal length parts.
• Feed line connected in the middle.
• Total length is ½ wavelength (½ l ).
• Length (in feet) 468 / Frequency (in MHz).

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The Dipole
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The Ground-Plane

• Simply a dipole that is oriented perpendicular to
  the Earths surface (vertical) .
• One half of the dipole is replaced by the
  ground-plane.
• Earth
• Car roof or trunk lid or other metal surface.
• Radial wires.
• Length (in feet) 234 / Frequency (in MHz).

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The Ground-Plane
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Loop Antennas Variations

• Quad
• Delta
• Horizontal

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Directional (Beam) Antennas

• Beam antennas focus or direct RF energy in a
  desired direction.
• Gain
• An apparent increase in power in the desired
  direction (both transmit and receive).
• Yagi (rod-like elements TV antennas).
• Quad (square shape, wire loop elements).

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Directional (Beam) Antennas
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Directional (Beam) Antennas

• All beam antennas have parts called elements.
• Driven element is connected to the radio by the
  feed line.
• Reflector element is on the back side.
• Director element is on the front side toward the
  desired direction.

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Feed Line Devices

• Balun
• Duplexer
• Antenna switch
• SWR meter
• Antenna analyzer
• Antenna tuner

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Coax Feed Lines

• RG-58
• RG-8
• RG-213
• RG-174
• Hardline

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Coax

• Most common feed line.
• Easy to use.
• Matches impedance of modern radio equipment (50
  ohms).
• Some loss of signal depending on coax quality
  (cost).

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Coax Connectors

• SO-239/PL-259
• BNC
• N
• SMA

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Nothing is Perfect

• Although the goal is to get 100 of your radio
  energy radiated into space, that is virtually
  impossible.
• What is an acceptable level of reflected power or
  SWR?
• 11 SWR is perfect.
• 21 SWR should be the max you should accept (as a
  general rule).
• Modern radios will start lowering transmitter
  output power automatically when SWR is above 21.
• 31 is when you need to do something to reduce
  SWR.

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Test and Matching Equipment

• Proper impedance matching is important enough to
  deserve some simple test equipment as you develop
  your station repertoire.
• Basic test equipment SWR meter.
• Matching equipment Antenna tuner.

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Standing Wave Ratio (SWR)

• If the antenna and feed line impedances are not
  perfectly matched, some RF energy is not radiated
  into space and is returned (reflected) back to
  the source.
• Something has to happen to this reflected energy
  generally converted into heat or unwanted radio
  energy (bad).

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Antenna Tuner

• One way to make antenna matching adjustments is
  to use an antenna tuner.
• Antenna tuners are impedance transformers (they
  actually do not tune the antenna).
• When used appropriately they are effective.
• When used inappropriately all they do is make a
  bad antenna look good to the transmitterthe
  antenna is still bad.

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How to use an Antenna Tuner

• Monitor the SWR meter.
• Make adjustments on the tuner until the minimum
  SWR is achieved.
• The impedance of the antenna is transformed to
  more closely match the impedance of the
  transmitter.

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SWR Meter

• The SWR meter is inserted in the feed line and
  indicates the mismatch that exists at that point.
• You make adjustments to the antenna to minimize
  the reflected energy (minimum SWR).

20
Antenna Supports

• Trees.
• Towers or masts.
• Covenants and antenna restrictions must be
  considered.

21
What antenna polarization is normally used for
long-distance weak-signal CW and SSB contacts
using the VHF and UHF bands? (T3A03)

• A. Right-hand circular
• B. Left-hand circular
• C. Horizontal
• D. Vertical

22
What antenna polarization is normally used for
long-distance weak-signal CW and SSB contacts
using the VHF and UHF bands? (T3A03)

• A. Right-hand circular
• B. Left-hand circular
• C. Horizontal
• D. Vertical

23
When using a directional antenna, how might your
station be able to access a distant repeater if
buildings or obstructions are blocking the direct
line of sight path? (T3A05)

• A. Change from vertical to horizontal
  polarization
• B. Try to find a path that reflects signals to
  the repeater
• C. Try the long path
• D. Increase the antenna SWR

24
When using a directional antenna, how might your
station be able to access a distant repeater if
buildings or obstructions are blocking the direct
line of sight path? (T3A05)

• A. Change from vertical to horizontal
  polarization
• B. Try to find a path that reflects signals to
  the repeater
• C. Try the long path
• D. Increase the antenna SWR

25
What is the primary purpose of a dummy load?
(T7C01)

• A. To prevent the radiation of signals when
  making tests
• B. To prevent over-modulation of your
  transmitter
• C. To improve the radiation from your antenna
• D. To improve the signal to noise ratio of your
  receiver

26
What is the primary purpose of a dummy load?
(T7C01)

• A. To prevent the radiation of signals when
  making tests
• B. To prevent over-modulation of your
  transmitter
• C. To improve the radiation from your antenna
• D. To improve the signal to noise ratio of your
  receiver

27
Which of the following instruments can be used to
determine if an antenna is resonant at the
desired operating frequency? (T7C02)

• A. A VTVM
• B. An antenna analyzer
• C. A Q meter
• D. A frequency counter

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Which of the following instruments can be used to
determine if an antenna is resonant at the
desired operating frequency? (T7C02)

• A. A VTVM
• B. An antenna analyzer
• C. A Q meter
• D. A frequency counter

29
What instrument other than an SWR meter could you
use to determine if a feedline and antenna are
properly matched? (T7C08)

• A. Voltmeter
• B. Ohmmeter
• C. Iambic pentameter
• D. Directional wattmeter

30
What instrument other than an SWR meter could you
use to determine if a feedline and antenna are
properly matched? (T7C08)

• A. Voltmeter
• B. Ohmmeter
• C. Iambic pentameter
• D. Directional wattmeter

31
Which of the following is the most common cause
for failure of coaxial cables? (T7C09)

• A. Moisture contamination
• B. Gamma rays
• C. The velocity factor exceeds 1.0
• D. Overloading

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Which of the following is the most common cause
for failure of coaxial cables? (T7C09)

• A. Moisture contamination
• B. Gamma rays
• C. The velocity factor exceeds 1.0
• D. Overloading

33
Why should the outer jacket of coaxial cable be
resistant to ultraviolet light? (T7C10)

• A. Ultraviolet resistant jackets prevent
  harmonic radiation
• B. Ultraviolet light can increase losses in the
  cables jacket
• C. Ultraviolet and RF signals can mix together,
  causing interference
• D. Ultraviolet light can damage the jacket and
  allow water to enter the cable

34
Why should the outer jacket of coaxial cable be
resistant to ultraviolet light? (T7C10)

• A. Ultraviolet resistant jackets prevent
  harmonic radiation
• B. Ultraviolet light can increase losses in the
  cables jacket
• C. Ultraviolet and RF signals can mix together,
  causing interferance
• D. Ultraviolet light can damage the jacket and
  allow water to enter the cable

35
What is a disadvantage of air core coaxial
cable when compared to foam or solid dielectric
types? (T7C11)

• A. It has more loss per foot
• B. It cannot be used for VHF or UHF antennas
• C. It requires special techniques to prevent
  water absorption
• D. It cannot be used at below freezing
  temperatures

36
What is a disadvantage of air core coaxial
cable when compared to foam or solid dielectric
types? (T7C11)

• A. It has more loss per foot
• B. It cannot be used for VHF or UHF antennas
• C. It requires special techniques to prevent
  water absorption
• D. It cannot be used at below freezing
  temperatures

37
Which of the following types of solder is best
for radio and electronic use? (T7D08)

• A. Acid-core solder
• B. Silver solder
• C. Rosin-core solder
• D. Aluminum solder

38
Which of the following types of solder is best
for radio and electronic use? (T7D08)

• A. Acid-core solder
• B. Silver solder
• C. Rosin-core solder
• D. Aluminum solder

39
What is the characteristic appearance of a cold
solder joint? (T7D09)

• A. Dark black spots
• B. A bright or shiny surface
• C. A grainy or dull surface
• D. A greenish tint

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What is the characteristic appearance of a cold
solder joint? (T7D09)

• A. Dark black spots
• B. A bright or shiny surface
• C. A grainy or dull surface
• D. A greenish tint

41
What is a beam antenna? (T9A01)

• A. An antenna built from aluminum I-beams
• B. An omnidirectional antenna invented by
  Clarence Beam
• C. An antenna that concentrates signals in one
  direction
• D. An antenna that reverses the phase of
  received signals

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What is a beam antenna? (T9A01)

• A. An antenna built from aluminum I-beams
• B. An omnidirectional antenna invented by
  Clarence Beam
• C. An antenna that concentrates signals in one
  direction
• D. An antenna that reverses the phase of
  received signals

43
Which of the following describes a simple dipole
mounted so the conductor is parallel to the
earths surface? (T9A03)

• A. A ground wave antenna
• B. A horizontally polarized antenna
• C. A rhombic antenna
• D. A vertically polarized antenna

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Which of the following describes a simple dipole
mounted so the conductor is parallel to the
earths surface? (T9A03)

• A. A ground wave antenna
• B. A horizontally polarized antenna
• C. A rhombic antenna
• D. A vertically polarized antenna

45
What is a disadvantage of the rubber duck
antenna supplied with most handheld radio
transceivers? (T9A04)

• A. It does not transmit or receive as
  effectively as a full-sized antenna
• B. It transmits a circularly polarized signal
• C. If the rubber end cap is lost it will unravel
  very quickly
• D. All of these choices are correct.

46
What is a disadvantage of the rubber duck
antenna supplied with most handheld radio
transceivers? (T9A04)

• A. It does not transmit or receive as
  effectively as a full-sized antenna
• B. It transmits a circularly polarized signal
• C. If the rubber end cap is lost it will unravel
  very quickly
• D. All of these choices are correct.

47
How would you change a dipole to make it resonant
on a higher frequency? (T9A05)

• A. Lengthen it
• B. Insert coils in series with radiating wires
• C. Shorten it
• D. Add capacity hats to the ends of the
  radiating wires

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How would you change a dipole to make it resonant
on a higher frequency? (T9A05)

• A. Lengthen it
• B. Insert coils in series with radiating wires
• C. Shorten it
• D. Add capacity hats to the ends of the
  radiating wires

49
What type of antennas are the quad, Yagi, and
dish? (T9A06)

• A. Non-resonant antennas
• B. Loop antennas
• C. Directional antennas
• D. Isotropic antennas

50
What type of antennas are the quad, Yagi, and
dish? (T9A06)

• A. Non-resonant antennas
• B. Loop antennas
• C. Directional antennas
• D. Isotropic antennas

51
What is a good reason not to use a rubber duck
antenna inside of your car? (T9A07)

• A. Signals can be significantly weaker than when
  it is outside of the vehicle
• B. It might cause your radio to overheat
• C. The SWR might decrease, decreasing the signal
  strength
• D. All of these choices are correct

52
What is a good reason not to use a rubber duck
antenna inside of your car? (T9A07)

• A. Signals can be significantly weaker than when
  it is outside of the vehicle
• B. It might cause your radio to overheat
• C. The SWR might decrease, decreasing the signal
  strength
• D. All of these choices are correct

53
What is the approximate length, in inches, of a
quarter-wavelength vertical antenna for 146 MHz?
(T9A08)

• A. 112
• B. 50
• C. 19
• D. 12

54
What is the approximate length, in inches, of a
quarter-wavelength vertical antenna for 146 MHz?
(T9A08)

• A. 112
• B. 50
• C. 19
• D. 12

55
What is the approximate length, in inches, of a 6
meter ½-wavelength wire dipole antenna? (T9A09)

• A. 6
• B. 50
• C. 112
• D. 236

56
What is the approximate length, in inches, of a 6
meter ½-wavelength wire dipole antenna? (T9A09)

• A. 6
• B. 50
• C. 112
• D. 236

57
In which direction is the radiation strongest for
a half-wave dipole antenna in free space? (T9A10)

• A. Equally in all directions
• B. Off the ends of the antenna
• C. Broadside to the antenna
• D. In the direction of the feedline

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In which direction is the radiation strongest for
a half-wave dipole antenna in free space? (T9A10)

• A. Equally in all directions
• B. Off the ends of the antenna
• C. Broadside to the antenna
• D. In the direction of the feedline

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What does an antenna tuner do? (T9B04)

• A. It matches the antenna system impedance to
  the transceivers output impedance
• B. It helps a receiver automatically tune in
  weak stations
• C. It allows the antenna to be used on both
  transmit and receive
• D. It automatically selects the proper antenna
  for the frequency band being used

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What does an antenna tuner do? (T9B04)

• A. It matches the antenna system impedance to
  the transceivers output impedance
• B. It helps a receiver automatically tune in
  weak stations
• C. It allows the antenna to be used on both
  transmit and receive
• D. It automatically selects the proper antenna
  for the frequency band being used

61
Which of the following connectors is most
suitable for frequencies above 400 MHz? (T9B06)

• A. A UHF (PL-259/SO-239) connector
• B. A Type N connector
• C. An RS-213 connector
• D. A DB-23 connector

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Which of the following connectors is most
suitable for frequencies above 400 MHz? (T9B06)

• A. A UHF (PL-259/SO-239) connector
• B. A Type N connector
• C. An RS-213 connector
• D. A DB-23 connector

63
Which of the following is true of PL-259 type
coax connectors? (T9B07)

• A. They are good for UHF frequencies
• B. They are water tight
• C. They are commonly used at HF frequencies
• D. They are a bayonet type connector

64
Which of the following is true of PL-259 type
coax connectors? (T9B07)

• A. They are good for UHF frequencies
• B. They are water tight
• C. They are commonly used at HF frequencies
• D. They are a bayonet type connector

65
Why should coax connectors exposed to the weather
be sealed against water intrusion? (T9B08)

• A. To prevent an increase in feedline loss
• B. To prevent interference to telephones
• C. To keep the jacket from becoming loose
• D. All of these choices are correct

66
Why should coax connectors exposed to the weather
be sealed against water intrusion? (T9B08)

• A. To prevent an increase in feedline loss
• B. To prevent interference to telephones
• C. To keep the jacket from becoming loose
• D. All of these choices are correct

67
What electrical difference exists between the
smaller RG-58 and larger RG-8 coaxial cables?
(T9B10)

• A. There is no significant difference between
  the two types
• B. RG-58 cable has less loss at a given
  frequency
• C. RG-8 cable has less loss at a given frequency
• D. RG-58 cable can handle higher power levels

68
What electrical difference exists between the
smaller RG-58 and larger RG-8 coaxial cables?
(T9B10)

• A. There is no significant difference between
  the two types
• B. RG-58 cable has less loss at a given
  frequency
• C. RG-8 cable has less loss at a given frequency
• D. RG-58 cable can handle higher power levels