Transcript Technician License Class

Technician
License Class
Gordon West
Technician Class Manual
Pages 115-121
Weak Signals
Presented by
Heart Of Texas
Amateur Radio Club
(HOTARC)
Let’s Review…Frequency
Remember:
– kilo- means 1,000 (thousand), as in kHz
– Mega- means 1,000,000 (million), as in MHz
– Giga- means 1,000,000,000 (billion), as in GHz
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Frequency
MF (Medium Freq.): 300 kHz – 3 MHz
HF (High Freq.): 3 MHz – 30 MHz
VHF (Very High Freq): 30 MHz – 300 MHz
UHF (Ultra High Freq): 300 MHz – 3 GHz
“Microwaves”: generally above 500 MHz (or 0.5 GHz)
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Radio Frequencies
The FCC allows amateur radio operators to
transmit only in 27 specific “windows.”
Most Technicians primarily use their voice
privileges in VHF and UHF.
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Radio Signals
Pages 115 – 119…
Key words:
– Curvature of the earth
Let’s look at this “curvature of the earth”
thing…
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How Radio Waves Travel
Line-of-sight: the antennas can “see” each other. Your
radio signals are heard!
Beyond about 7-8 miles, signals are blocked by the
curvature of the earth…the “radio horizon.”
YOU
Yes!
Waco
Bellmead
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How Radio Waves Travel
To talk to a station beyond the radio horizon,
beyond the line-of-sight, a “repeater” mounted
up high can relay your radio signals.
YOU
Yes!
Waco
Dallas
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How Radio Waves Travel
Some radio waves can reflect off the ionosphere
(about 100-200 miles up) and travel hundreds of
miles.
YOU
Ionosphere
Yes!
Waco
Memphis
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How Radio Waves Travel
Radio waves can even reflect more than once
and sometimes travel long distances around the
world!
YOU
Ionosphere
Yes!
Paris
Waco
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How Radio Waves Travel
Signals can also be relayed by satellite or even reflected
off of the moon!
Reflection off the ionosphere is affected by
radiation from
Ionosphere
the sun. So,
Solar radiation
radio operators
often monitor the
solar conditions,
and note the time
of day.
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T9 B04 (pg 115)
What is the radio horizon?
A. The point where radio signals between two points
are blocked by the curvature of the Earth
B. The distance from the ground to a horizontally
mounted antenna
C. The farthest point you can see when standing at the
base of your antenna tower
D. The shortest distance between two points on the
Earth's surface
Notice the similar point is stressed in the next
question (B11).
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T9B11 (pg 115)
Why do VHF and UHF Radio signals usually
travel about a third farther than the visual line of
sight distance between 2 stations?
A. Radio signals move somewhat faster than the
speed of light and travel farther in the same amount
of time
B. Radio waves are not blocked by dust particles
C. The Earth seems less curved to radio
waves than to light
D. Radio waves are blocked by dust particles
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VHF and UHF
See pages 117 – 119…
Key words:
– Shorter wavelengths (penetrating power)
– Single Sideband
Let’s think again about those upper frequency
bands that you can use…
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VHF & UHF Bands
1240
1300
UHF
902
420
435
438
Satellite
928
450
5 MHz repeater frequency separation (Split)
219
220
Digital
Mssging
144 144.1
CW
222
Closer to
“microwavelengths”
225
VHF
148
600 kHz repeater frequency separation (Split)
50
UHFshorter
wavelengths
50.1
CW
More energy—
”punches” right
through the
atmosphere
54
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T9 B06 (pg 117)
Why do UHF signals often work better inside of
buildings than VHF signals?
A. VHF signals lose power faster over distance
B. The shorter wavelength of UHF signals
allows them to more easily penetrate
urban areas and buildings
C. This is incorrect; VHF works better than UHF inside
buildings
D. UHF antennas are more efficient than VHF
antennas
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Propagation
Reflection and Multi-path Interference
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T9 B10 (pg 117)
What term is commonly used to describe the
rapid fluttering sound sometimes heard from
mobile stations that are moving while
transmitting?
A. Flip-flopping
B. Picket fencing  Just
remember
C. Frequency shifting
this
D. Pulsing
unusual
answer!
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T9B02 (pg 117)
What might be happening when we hear a VHF
signal from long distances?
A. Signals are being reflected from outer space
B. Someone is playing a recording to us
C. Signals are being reflected by
lightning storms in our area
D. A possible cause is
sporadic E reflection from
a layer in the ionosphere
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T6 A04 (pg 118)
Which type of voice modulation is most often
used for long distance and weak signal contacts
on the VHF and UHF bands?
A. FM
B. AM
 Single Sideband!
C. SSB
D. PM
Let’s look at what we mean by sideband…
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What is Meant by “Sideband?”
AM stands for Amplitude Modulation
AM signals are almost 10 kHz wide—lots of spectrum.
– Carrier in the middle
(e.g., 1230 kHz for KRZI)
– Upper and lower sidebands
(identical, but mirrored)
To create “Single SideBand”
– Carrier is suppressed
– One sideband is suppressed
(usually the lower one)
– More power can be sent in
the much narrower signal.
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T6 A07 (pg 118)
Which sideband is normally used for VHF and
UHF SSB communications?
A. Upper sideband
B. Lower sideband
C. Suppressed sideband
D. Inverted sideband
Note: Above 10 MHz, always use USB (upper).
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T5D11 (pg 118)
What may be the problem if another operator
reports that your SSB signal is very garbled and
breaks up?
A. You have the noise limiter turned on
B. The transmitter is too hot and needs to cool off
C. RF energy may be getting into the
microphone circuit and causing feedback
D. You are operating on lower sideband
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T9B01 (pg
119)
Why are VHF/UHF signals not normally heard
over long distances?
A. They are too weak to go very far
B. FCC regulations prohibit them from going more than
50 miles
C. VHF and UHF signals are usually not
reflected by the ionosphere
D. They collide with trees and shrubbery and fade out
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T1C09 (pg 120)
What do the FCC rules mean when an amateur
frequency band is said to be available on a
secondary basis?
A. Secondary users of a frequency have equal rights
to operate
B. Amateurs are only allowed to use the frequency at
night
C. Amateurs may not cause harmful
interference to primary users
D. Secondary users are not allowed on amateur bands
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Grid Square Map
Waco, TX  EM11
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T7A09 (pg 120)
What is a grid locator?
A. A letter-number designator assigned to a
geographic location
B. Your azimuth and elevation
C. Your UTC location
D. The 4 digits that follow your ZIP code
Waco, TX Is EM11
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T7A11 (pg 120)
What is the maximum power allowed when
transmitting telecommand signals to radio
controlled models?
A. 500 milliwatts
B. 1 watt
C. 25 watts
D. 1500 watts
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T7A12 (pg 121)
What is the station identification requirement
when sending commands to a radio control
model using amateur frequencies?
A. Voice identification must be transmitted every 10
minutes
B. Morse code ID must be sent once per hour
C. A label indicating the licensee's call sign
and address must be affixed to the
transmitter
D. There is no station identification requirement for this
service
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