Technician Licensing Class
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1
Technician Licensing Class
Antennas
Valid July 1, 2014
Through
June 30, 2018
2
Amateur Radio Technician Class
Element 2 Course Presentation
 ELEMENT 2 SUB-ELEMENTS (Groupings)
•
•
•
•
•
•
•
•
•
•
About Ham Radio
Call Signs
Control
Mind the Rules
Tech Frequencies
Your First Radio
Going On The Air!
Repeaters
Emergency!
Weak Signal Propagation
3
Amateur Radio Technician Class
Element 2 Course Presentation
 ELEMENT 2 SUB-ELEMENTS (Groupings)
• Talk to Outer Space!
• Your Computer Goes Ham Digital!
• Multi-Mode Radio Excitement
• Run Some Interference Protection
• Electrons – Go With the Flow!
• It’s the Law, per Mr. Ohm!
• Go Picture These!
 Antennas
• Feed Me With Some Good Coax!
• Safety First!
4
Antennas
• T9A03 Plenty of new Technician Class operators, looking to work
some skywaves on 6- and 10-meters, create their own halfwave
dipole antennas. The dipole antenna is usually mounted parallel to
the Earth’s surface to transmit horizontal waves.
Dipole Antenna
5
Antennas
• T9A10 If the dipole is erected east-to-west, the energy will go out
mostly north-to-south, broadside to the antenna. Slightly droop the
dipole ends if you wish more energy in other directions.
• T9A09 To calculate the length, end to end, of a 6-meter, halfwave
wire dipole antenna, we first need to convert 6 meters over to
megahertz. Remember that formula, 300 divided by the frequency
in megahertz to equal meters? Three hundred divided by 6 equals
approximately 50 MHz, and now apply the formula for a halfwave
dipole: 468  frequency in MHz = a halfwave dipole in feet.
Calculator: 468  50 = 9.36 feet. Now multiply 9.36 x 12 to
convert feet to inches, and you get 112.3 inches. You’re a regular
whiz on that keypad!
6
Antennas
• T9A05 You can approximate what band a ham is transmitting on
by looking at their dipole. The dipole is usually one-half the
wavelength length of the meter band of operation. For instance, I
can spot a brand new 6 -meter Technician Class dipole as
approximately 3 meters long, end to end, with coax feeding to it in
the center. To increase the antenna’s resonant frequency, shorten it
by twisting back a couple of inches of wire at each end and it will
work at a slightly higher frequency.
7
Antennas
• T9A02 If an antenna element is perpendicular to the Earth’s
surface, it is standing straight up and down – it is a vertical antenna
and will radiate vertical electric field radio waves. To get started,
consider a dual-band 2 meter/440 MHz vertical home antenna,
available for under $100. Just add coax cable between the ventmounted antenna and your transceiver and you’re on the air. No
tuning required for your little handheld or mobile 2 band radio.
These antennas are usually white fiberglass with internal 2-band
copper elements. Some are one section, some two section, and you
can get a tall three-section dual-band antenna, too, if you live in an
extremely remote area and need the most gain. Usually, the one- or
two-section antenna, standing less than 10 feet tall, will do the trick
nicely. Get the antenna up on your roof, be careful in how you get
the antenna placed, watch out for wires, and enjoy great range on 2
meters and 440 MHz.
8
Antennas
9
Antennas
• T9A08 We calculate the length, in feet, of a quarter-wavelength
vertical antenna by dividing 234 by the antenna’s operating
frequency in megahertz. Let’s try the calculator on this one: Clear
Clear 234  146 = 1.6 feet. Since they want the answer in inches,
no big deal. Multiply 1.6 x 12 = 19 inches approximately. To
convert feet and fractions of a foot to inches, multiple by 12.
19”
Radiation Pattern of an Antenna Changes as Height Above Ground is Varied
10
Antennas
• T9A06 Once you are on the air with your dual-band equipment,
you may wish to reach out a little further in one specific direction.
Antennas like the quad, the Yagi, and the microwave dish are all
highly directional – they beam your signal in one specific direction.
11
Antennas
• T9A01 The beam antenna is much like that new digital television
over-the-air antenna on the roof – elements all in line with one
another, with the shorter elements in the front. This antenna will
concentrate signals in one direction. The beam antenna is subject
to the universal principle of NFL – no free lunch. While it
concentrates energy in one direction, it subtracts energy in other
directions. The total energy radiated by an antenna is always the
same, regardless of the gain. The beam antenna is excellent for
satellite and weak-signal work, but not necessary for talking around
town on 2 meters and 70 centimeters, the 440 MHz band.
12
Antennas
A Beam Antenna – The Yagi Antenna
Beam Antenna on a tower
13
Antennas
• T8C01 You just added some home office equipment and notice
there is a steady, no-voice carrier sitting right on your favorite
repeater channel. You know it’s coming from your house because
your handheld out on the street is just fine. Practice your radio
direction finding skills by going into your home office, tuning in
the steady “dead carrier,” and start switching off different pieces of
equipment and pulling the plug from the power cord. Remember,
some pieces of office equipment will still continue to transmit
phantom signals on ham bands, although turned off, yet still
plugged in. When you pull the plug that drops the signal. Time to
replace that particular piece of equipment with another brand that
will hopefully not cause interference. Worst offenders in the home
office? FAX machines, printers, and older telephone modems.
14
Antennas
W6JAY practices his fox hunt
direction-finding skills
15
Antennas
• T8C02 A very exciting sport is called “fox hunting.” A ham will
hide a low-power transmitter on the 2-meter band, usually
transmitting around 146.565. Expert transmit hunters will use a
directional antenna to home into the general signal direction. The
closer they get to the transmitter the stronger the signal appears on
their handheld. When they get relatively close, they pull off the
directional antenna, and then start “sniffing” around with their
handheld with maybe just a paperclip stuck in the antenna socket.
16
Antennas
17
Antennas
 T9A11 The reference antenna with zero gain is called an isotropic
radiator. While an isotropic radiator cannot exist in real life, it is an
extremely useful measuring stick or ideal. An antenna with gain is
one that takes energy from somewhere within the antenna pattern
and radiates the signal in the desired direction of transmission. Got
it? It’s like taking a reflector to a plain old light bulb, and taking
wasted energy going up, and redirecting it with combined energy
down at street level. Your mobile VHF and UHF 2 meter and 440
MHz antennas all have a little bit of omni-directional gain, taking
energy that would normally go straight up, and radiating it down
close toward the horizon.
18
Antennas
Isotropic Radiator Pattern
“Gain” of an antenna
19
Antennas
 T3A03 As a new Technician Class ham radio operator, your first
radio will likely be a dual-band handheld, operating FM (frequency
modulation) with a vertical antenna. If you enjoy talking with a lot
of other hams about anything and everything, the dual band
handheld will get you going in grand style! If you are interested in
propagation, and are fascinated with how radio waves bounce off
the ionosphere and get from here to there, you may wish to
consider a high frequency transceiver that includes 6 meters, 2
meters and 440 MHz bands. On VHF and UHF (2 meters and 440
MHz), that big mobile or base station will most likely have single
sideband capabilities as well, for these VHF/UHF frequencies.
SSB lets you work hundreds of miles and farther, called “weak
signal” work. When you switch over to SSB from FM, you’ll also
need to switch antennas – almost all weak signal work is
accomplished with an antenna that is horizontally polarized.
20
Antennas
• T3A04 Almost all repeater stations throughout the world use
vertical polarization for transmit and receive. This means you must
use the same polarization of your handheld antenna, whether it be a
tiny rubber duck or a long element flexible whip. Keep your
handheld and antenna straight up and down, perpendicular to the
Earth, for best reception. If you transmit with the handheld antenna
horizontal to the Earth, your received signal could be as much as
100 times weaker through that distant repeater. Now you wouldn’t
want that, would you?
21
Antennas
Transmitter to Receiver – Radio waves from transmitting
antennas induce signals in receiving antennas as they pass by
22
Antennas
• T9A12 A 5/8 wave antenna has a more “squashed” pattern than the
normal “doughnut” pattern of a quarter wave antenna. It has
slightly higher gain than a quarter wave antenna, but it is still
omnidirectional. It is not always the best solution however; its
lower radiation angle may cause it to “undershoot” another station
at a high altitude. Like any antenna installation, some
experimentation is usually in order to find the best arrangement.
23
Antennas
• T9A13 A typical quarter wave antenna relies on the roof to form
the ground plane of the antenna, which should extend about a
quarter wavelength in any direction from its base. If it is mounted
near the edge of the roof, it tends to act more like a quarter wave
antenna with one radial, which gives it a major lobe in the direction
of the “most roof,” but at a rather high angle, often more than 45
degrees above the horizon. Mount your antenna in the center of the
roof for a uniform radiation pattern!
24
Antennas
• T9A14 For some reason, most hams have too little space for their
antennas, rather than too much. Antennas are often shorter than
they need to be for best performance. An antenna that’s shorter
than its resonant length can be made resonant by adding inductance
in series with the antenna; this inductance is generally known as a
loading coil. It is never the perfect solution for a too-short
antenna, but in many cases the loss of performance is minimal
when compared to a full-sized antenna.
25
Antennas
26
Element 2 Technician Class
Question Pool
Antennas
Valid July 1, 2014
Through
June 30, 2018
27
T9A03
Which of the following describes a simple dipole
mounted so the conductor is parallel to the Earth's
surface?
A.
B.
C.
D.
A ground wave antenna
A horizontally polarized antenna
A rhombic antenna
A vertically polarized antenna
28
T9A10
In which direction is the radiation strongest from
a half-wave dipole antenna in free space?
A.
B.
C.
D.
Equally in all directions
Off the ends of the antenna
Broadside to the antenna
In the direction of the feedline
29
T9A09
What is the approximate length, in inches, of a 6
meter 1/2-wavelength wire dipole antenna?
A.
B.
C.
D.
6
50
112
236
30
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
31
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
32
T9A08
What is the approximate length, in inches, of a
quarter-wavelength vertical antenna for 146
MHz?
A.
B.
C.
D.
112
50
19
12
33
T9A06
What type of antennas are the quad, Yagi, and
dish?
A.
B.
C.
D.
Non-resonant antennas
Loop antennas
Directional antennas
Isotropic antennas
34
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
35
T8C01
Which of the following methods is used to locate
sources of noise interference or jamming?
A.
B.
C.
D.
Echolocation
Doppler radar
Radio direction finding
Phase locking
36
T8C02
Which of these items would be useful for a
hidden transmitter hunt?
A.
B.
C.
D.
Calibrated SWR meter
A directional antenna
A calibrated noise bridge
All of these choices are correct
37
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
38
T3A03
What antenna polarization is normally used for
long-distance weak-signal CW and SSB contacts
using the VHF and UHF bands?
A.
B.
C.
D.
Right-hand circular
Left-hand circular
Horizontal
Vertical
39
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
40
T9A12
What is a reason to use a properly mounted 5/8
wavelength antenna for VHF or UHF mobile
service?
A. It offers a lower angle of radiation and more
gain than a 1/4 wavelength antenna and usually
provides improved coverage
B. It features a very high angle of radiation and is
better for communicating via a repeater
C. The 5/8 wavelength antenna completely
eliminates distortion caused by reflected signals
D. The 5/8 wavelength antenna offers a 10-times
power gain over a 1/4 wavelength design
41
T9A13
Why are VHF or UHF mobile antennas often
mounted in the center of the vehicle roof?
A. Roof mounts have the lowest possible SWR
of any mounting configuration
B. Only roof mounting can guarantee a
vertically polarized signal
C. A roof mounted antenna normally provides
the most uniform radiation pattern
D. Roof mounted antennas are always the
easiest to install
42
T9A14
Which of the following terms describes a type of
loading when referring to an antenna?
A. Inserting an inductor in the radiating portion
of the antenna to make it electrically longer
B. Inserting a resistor in the radiating portion of
the antenna to make it resonant
C. Installing a spring at the base of the antenna
to absorb the effects of collisions with other
objects
D. Making the antenna heavier so it will resist
wind effects when in motion
43