Technician Licensing Class

Technician Licensing Class
Technician Licensing Class
Antennas
Antennas
•
A simple dipole mounted so the conductor is parallel to
the Earth's surface is a horizontally polarized antenna.
T9A3
• Polarization is referenced to the Earth’s surface
• Horizontal or Vertical
Simple Dipole
Three element beam
Antennas
•
•
The strongest radiation from a half-wave dipole
antenna in free space is broadside to the antenna.
T9A9 The approximate length of a 6 meter 1/2-wavelength
wire dipole antenna is 112 inches.
T9A10
112 inches
468
Length of vertical in feet = _______
f (MHz)
(for half-wave dipole)
Feet = 468/50 =
9.36
9.36 x 12 = 112.3 inches
Six Meter ½ Wavelength Dipole
Antennas
•
•
You would change a dipole antenna to make it resonant on a
higher frequency by making it shorter.
T9A2 The electric field of vertical antennas is perpendicular to
the Earth.
T9A5
Vertical and Horizontal Polarization
H & V Polarized Antennas
Antennas
•
The approximate length of a quarter-wavelength
vertical antenna for 146 MHz is 19 inches.
T9A8
Length of vertical in feet =
(for quarter-wave dipole)
(2-meters is 144-148 MHz)
______
234
f (MHz)
Feet = 234/146 = 1.6
1.6 x 12 = 19 inches
19”
Radiation Pattern of an Antenna Changes as Height Above Ground is Varied
Antennas
•
T9A6
Directional antennas are the quad, Yagi, and dish.
Highest concentration of power
•
Directional Radiation Pattern of a Yagi Beam
T9A1
A beam antenna concentrates signals in one direction
A Beam Antenna – The Yagi Antenna
Antennas
•
Radio direction finding methods are used to locate
sources of noise interference or jamming.
T8C1
2-element Yagi DF Antenna
3-element Quad DF Antenna
Antennas

A directional antenna would be useful for a hidden
transmitter hunt.
T8C2
Hidden Transmitter
Hunts are called Fox
Hunting
All ages participate in a Fox Hunt
Antennas
•
When using a directional antenna, your station might
be able to access a distant repeater if buildings or
obstructions are blocking the direct line of sight path by
finding a path that reflects signals to the repeater.
T3A5
Directional Antenna
used to bounce signal
to reach repeater
blocked by building
Antennas

The gain of an antenna is the increase in signal
strength in a specified direction when compared to a
reference antenna.
T9A11
Isotropic Radiator Pattern

“Gain” of an antenna
Horizontal antenna polarization is normally used for
long-distance weak-signal CW and SSB contacts using the
VHF and UHF bands.
T3A3
Antennas
•
Signals could be significantly weaker if the antennas at
opposite ends of a VHF or UHF line of sight radio link are
not using the same polarization.
T3A4
Transmitter to Receiver – Radio waves from transmitting
antennas induce signals in receiving antennas as they pass by
Element 2 Technician Class Question
Pool
Antennas
Valid July 1, 2010
Through
June 30, 2014
T9A03
Which of the following describes a simple
dipole mounted so the conductor is parallel
to the Earth's surface?
A. A ground wave antenna
B. A horizontally polarized antenna
C. CA rhombic antenna
D. A vertically polarized antenna
T9A10
In which direction is the radiation
strongest from a half-wave dipole
antenna in free space?
A. Equally in all directions
B. Off the ends of the antenna
C. Broadside to the antenna
D. In the direction of the feedline
T9A09
What is the approximate length, in
inches, of a 6 meter 1/2-wavelength wire
dipole antenna?
A. 6
B. 50
C. 112
D. 236
T9A05
How would you change a dipole antenna to
make it resonant on a higher frequency?
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
T9A02
Which of the following is true regarding
vertical antennas?
A. The magnetic field is perpendicular to
the Earth
B. The electric field is perpendicular to
the Earth
C. The phase is inverted
D. The phase is reversed
T9A08
What is the approximate length, in inches,
of a quarter-wavelength vertical antenna
for 146 MHz?
A. 112
B. 50
C. 19
D. 12
T9A06
What type of antennas are the quad, Yagi,
and dish?
A. Non-resonant antennas
B. Loop antennas
C. Directional antennas
D. Isotropic antennas
T9A01
What is a beam antenna?
A. An antenna built from aluminum Ibeams
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
T8C01
Which of the following methods is used
to locate sources of noise interference
or jamming?
A. Echolocation
B. Doppler radar
C. Radio direction finding
D. Phase locking
T8C02
Which of these items would be useful for a
hidden transmitter hunt?
A. Calibrated SWR meter
B. A directional antenna
C. A calibrated noise bridge
D. All of these choices are correct
T3A05
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?
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
T9A11
What is meant by the gain of an antenna?
A. The additional power that is added to the
transmitter power
B. The additional power that is lost in the antenna
when transmitting on a higher frequency
C. The increase in signal strength in a specified
direction when compared to a reference antenna
D. The increase in impedance on receive or transmit
compared to a reference antenna
T3A03
What antenna polarization is normally used
for long-distance weak-signal CW and SSB
contacts using the VHF and UHF bands?
A. Right-hand circular
B. Left-hand circular
C. Horizontal
D. Vertical
T3A04
What can happen if the antennas at
opposite ends of a VHF or UHF line of sight
radio link are not using the same polarization?
A. The modulation sidebands might
become inverted
B. Signals could be significantly weaker
C. Signals have an echo effect on voices
D. Nothing significant will happen
Technician Licensing Class
Feed Me with
Some Good Coax!
Feed Me with Some Good Coax!
•
•
A common use of coaxial cable is to carry RF signals
between a radio and antenna.
T9B3 Coaxial cable is used more often than any other
feedline for amateur radio antenna systems because it is
easy to use and requires few special installation
considerations.
T6D11
Copper Wire
Outside Insulation
•
Mesh
Insulation
50 ohms is the impedance of the most commonly used
coaxial cable in typical amateur radio installations.
T9B2
Feed Me with Some Good Coax!
•
As the frequency of a signal passing through coaxial
cable is increased the loss increases.
T9B5
• The Higher the frequency the more the loss
•
PL-259 type coax connectors are commonly used at HF
frequencies.
T9B7
BNC, Type N, and PL 259 Connectors
•
A Type N connector is most suitable for frequencies
above 400 MHz?
T9B6
Feed Me with Some Good Coax!
N
Male
N
Female
Male VHF
PL-259
Male
BNC
Male
SMA
Female
SMA
Female
BNC
Understand the type of connector on your radio
You may need an adapter from your coax connector to your radio
Never buy cheap coax, connectors, or
adapters
Female
SO-239
Feed Me with Some Good Coax!
•
A disadvantage of "air core" coaxial cable, when
compared to foam or solid dielectric types is that it
requires special techniques to prevent water absorption.
T7C11
Smaller Heliax
Large coax, with hollow center conductor, low loss
Feed Me with Some Good Coax!
•
The most common cause for failure of coaxial cables is
moisture contamination.
T7C9
• Regular BNC, Type N, and PL259 connectors are not water-tight.
•
•
•
Coax connectors exposed to the weather should be
sealed against water intrusion to prevent an increase in
feedline loss.
T7C10 The outer jacket of coaxial cable should be resistant
to ultraviolet light because UV light can damage the jacket
and allow water to enter the cable.
T9B10 Electrical differences exists between the smaller RG58 and larger RG-8 coaxial cables in that RG-8 cable has
less loss at a given frequency.
T9B8
Coax Cable Type, Size, and Loss per 100 feet
Coax Type
RG-58U
RG-8X
RG-8U
RG-213
Hardline
Size
Loss @ 100 MHz
Small
Medium
Large
Large
Large, Rigid
4.3 dB
3.7 dB
1.9 dB
1.9 dB
0.5 dB
Loss @ 400 MHz
9.4
8.0
4.1
4.5
1.5
dB
dB
dB
dB
dB
Feed Me with Some Good Coax!
Feed Me with Some Good Coax!
•
•
•
•
The lowest loss feedline at VHF and
UHF is an Air-insulated hard line.
T7C2 An antenna analyzer can be used to
determine if an antenna is resonant at the
desired operating frequency.
T7C3 In general terms, standing wave ratio
(SWR) is a measure of how well a load is
matched to a transmission line.
T9B1 It is important to have a low SWR in an
antenna system that uses coaxial cable
feedline to provide efficient transfer of
power and reduce losses.
T9B11
MFJ-269 SWR Analyzer
Impedance Mismatch Causes Reflected Wave
Feed Me with Some Good Coax!
•
A “1 to 1” reading on an SWR meter indicates a perfect
impedance match between the antenna and the feedline.
T7C4
SWR Reading
1:1
1.5:1
2:1
3:1
4:1
Antenna Condition
Perfectly Matched
Good Match
Fair Match
Poor Match
Something definitely Wrong
A battery operated SWR analyzer for tower antenna work
Feed Me with Some Good Coax!
•
•
•
2 to 1 is the approximate SWR value above which the
protection circuits in most solid-state transmitters begin to
reduce transmitter power.
T7C6 An SWR reading of 4:1 means there is an impedance
mismatch.
T9B9 A loose connection in an antenna or a feedline might
cause erratic changes in SWR readings.
T7C5
Make sure all coax connections are
tight to help minimize interference
Feed Me with Some Good Coax!
•
Other than an SWR meter you could use a directional
wattmeter to determine if a feedline and antenna are
properly matched.
T7C8
Dual/Twin Needle
Single Needle
Feed Me with Some Good Coax!
•
•
Power lost in a feedline is converted into heat.
T9B4 An antenna tuner matches the antenna system
impedance to the transceiver's output impedance.
T7C7
MFJ-971 Portable QRP
200 Watt Tuner
Palstar 1500 Watt Auto-Tuner
Icom 7000 with LDG
7000 Auto-Tuner
Miracle QPak 50 Watt
Manual Tuner
MFJ-994B 1500 Watt Auto-Tuner
Feed Me with Some Good Coax!
•
If figure T5 represents a transceiver in which block 1 is
the transmitter portion and block 3 is the receiver portion,
the function of block 2 is a transmit-receive switch.
T7A7
1
2
Transmitter
T/R Switch
Figure T5
3
Receiver
Feed Me with Some Good Coax!
•
The primary purpose of a dummy load is to prevent the
radiation of signals when making tests.
T7C1
• Prevents signals from being sent out over the air
• Allows observation of signal on Spectrum Analyzer
300 Watt Dry
Dummy Load
Dummy Load-Can
1kw with oil
Dry Dummy Load
Element 2 Technician Class Question
Pool
Feed Me with
Some Good Coax!
Valid July 1, 2010
Through
June 30, 2014
T6D11
Which of the following is a common use
of coaxial cable?
A. Carry dc power from a vehicle battery to a
mobile radio
B. Carry RF signals between a radio and
antenna
C. Secure masts, tubing, and other cylindrical
objects on towers
D. Connect data signals from a TNC to a
computer
T9B03
Why is coaxial cable used more often than
any other feedline for amateur radio antenna systems?
A. It is easy to use and requires few special
installation considerations
B. It has less loss than any other type of
feedline
C. It can handle more power than any other
type of feedline
D. It is less expensive than any other types of
feedline
T9B02
What is the impedance of the most
commonly used coaxial cable in typical
amateur radio installations?
A. 8 ohms
B. 50 ohms
C. 600 ohms
D. 12 ohms
T9B05
What generally happens as the
frequency of a signal passing through
coaxial cable is increased?
A. The
B. The
C. The
D. The
apparent SWR increases
reflected power increases
characteristic impedance increases
loss increases
T9B07
Which of the following is true of PL-259
type coax connectors?
A. They are good for UHF frequencies
B. They are water tight
C. The are commonly used at HF frequencies
D. They are a bayonet type connector
T9B06
Which of the following connectors is most
suitable for frequencies above 400 MHz?
A. A UHF (PL-259/SO-239) connector
B. A Type N connector
C. An RS-213 connector
D. A DB-23 connector
T7C11
A. It
B. It
C. It
D. It
What is a disadvantage of "air core" coaxial
cable when compared to foam or solid
dielectric types?
has more loss per foot
cannot be used for VHF or UHF antennas
requires special techniques to prevent water absorption
cannot be used at below freezing temperatures
T7C09
Which of the following is the most common
cause for failure of coaxial cables?
A. Moisture contamination
B. Gamma rays
C. The velocity factor exceeds 1.0
D. Overloading
T9B08
Why should coax connectors exposed to the
weather be sealed against water intrusion?
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
T7C10
Why should the outer jacket of coaxial
cable be resistant to ultraviolet light?
A. Ultraviolet resistant jackets prevent
harmonic radiation
B. Ultraviolet light can increase losses in
the cable’s 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
T9B10
What electrical difference exists
between the smaller RG-58 and larger
RG-8 coaxial cables?
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
T9B11
Which of the following types of feedline has
the lowest loss at VHF and UHF?
A. 50-ohm flexible coax
B. Multi-conductor unbalanced cable
C. Air-insulated hard line
D. 75-ohm flexible coax
T7C02
Which of the following instruments can be
used to determine if an antenna is resonant
at the desired operating frequency?
A. A VTVM
B. An antenna analyzer
C. A “Q” meter
D. A frequency counter
T7C03
What, in general terms, is standing wave
ratio (SWR)?
A. A measure of how well a load is
matched to a transmission line
B. The ratio of high to low impedance in
a feedline
C. The transmitter efficiency ratio
D. An indication of the quality of your
station’s ground connection
T9B01
Why is it important to have a low SWR
in an antenna system that uses coaxial
cable feedline?
A To reduce television interference
B To allow the efficient transfer of
power and reduce losses
C To prolong antenna life
D All of these choices are correct
T7C04
What reading on an SWR meter indicates a
perfect impedance match between the
antenna and the feedline?
A. 2 to 1
B. 1 to 3
C. 1 to 1
D. 10 to 1
T7C05
What is the approximate SWR value above which
the protection circuits in most solid-state transmitters begin to
reduce transmitter power?
A. 2 to 1
B. 1 to 2
C. 6 to 1
D. 10 to 1
T7C06
What does an SWR reading of 4:1 mean?
A. An antenna loss of 4 dB
B. A good impedance match
C. An antenna gain of 4
D. An impedance mismatch
T9B09
What might cause erratic changes in
SWR readings?
A. The transmitter is being modulated
B. A loose connection in an antenna or a
feedline
C. The transmitter is being overmodulated
D. Interference from other stations is
distorting your signal
T7C08
What instrument other than an SWR meter
could you use to determine if a feedline
and antenna are properly matched?
A. Voltmeter
B. Ohmmeter
C. Iambic pentameter
D. Directional wattmeter
T7C07
What happens to power lost in a feedline?
A. It increases the SWR
B. It comes back into your transmitter
and could cause damage
C. It is converted into heat
D. It can cause distortion of your signal
T9B04
What does an antenna tuner do?
A. It matches the antenna system impedance
to the transceiver's output impedance
B. It helps a receiver automatically tune in
weak stations
C. It allows an antenna to be used on both
transmit and receive
D. It automatically selects the proper antenna
for the frequency band being used
T7A07
If figure T5 represents a transceiver in which block
1 is the transmitter portion and block 3 is the
receiver portion, what is the function of block 2?
1
2
3
Transmitter
Receiver
Figure T5
A. A
B. A
C. A
D. A
balanced modulator
transmit-receive switch
power amplifier
high-pass filter
T7C01
What is the primary purpose of a
dummy load?
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
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