SUBELEMENT T3 Radio wave characteristics: properties of radio waves; propagation modes [3 Exam...
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Transcript of SUBELEMENT T3 Radio wave characteristics: properties of radio waves; propagation modes [3 Exam...
SUBELEMENT T3
Radio wave characteristics: properties of radio waves; propagation modes
[3 Exam Questions - 3 Groups]
1Radio Waves 2014
T3A - Radio wave characteristics: how a radio signal travels; fading; multipath; wavelength vs. penetration; antenna orientation
T3B - Radio and electromagnetic wave properties: the electromagnetic spectrum; wavelength vs. frequency; velocity of electromagnetic waves; calculating wavelength
T3C - Propagation modes: line of sight; sporadic E; meteor and auroral scatter and reflections; tropospheric ducting; F layer skip; radio horizon
2Radio Waves
HF PropagationIt is the unpredictable nature of HF propagation that makes the HF bands so much fun.
Long distance communication (DX) is accomplished by the reflection of radio waves by the ionosphere, the upper layers of the atmosphere ionized by ultraviolet radiation from the sun.
3Radio Waves
Solar Effects on the Atmosphere
4Radio Waves
Radio Propagation
Propagation is the path radio waves travel from one station to another.Three basic types of propagation:
• Line of Sight.• Ground Wave.• Sky Wave.
5Radio Waves
Ground Wave Propagation
Ground waves travel along the ground Higher power, farther travel
6Radio Waves
Sky Wave Propagation• At HF frequencies radio
waves can be reflected by the Ionosphere.
• At VHF and higher frequencies the waves usually pass through the ionosphere.
7Radio Waves
Sporadic “E” Propagation
Small areas of the “E” Region can become highly ionizedAllows long distance sky-wave propagation on the VHF bandsMost likely to occur on the 6 meter band in the summertimeBy its name, it is “sporadic”.
8-Radio Waves 2014
Solar Effects
•Sun Spots –Sunspots look darker because they’re cooler than surrounding areas but emit ultraviolet light that charge the Ionosphere. More sunspots mean improved upper HF and lower VHF propagation.
•Sun Spot Cycle–Sunspots tend to come and go from minimum to maximum to minimum in an 11 year cycle. Different cycles have different maximums.
•Solar Emissions–Electromagnetic emissions like ultraviolet and x-rays arrive at the earth in only 8 minutes. Particle emissions can take 20-40 hours to arrive at the earth where they are pulled to the poles by the earth’s magnetic field.
•Solar Rotation–The sun rotates every 28 days (a solar day)
9 Radio Waves 9
Sunspots
10Radio Waves
Sunspots peak during 11-year cycles.The higher the sunspot count, the more the
atmosphere is ionized.Thus, higher sunspot counts support a higher
Maximum Usable Frequency (MUF).
Propagation Ionosphere Layers
The Atmosphere is divided into layers A,B,C,D,E,F The Ionosphere consist of layers D, E, and F The D layer absorbs low frequencies The F layer typically reflects radio waves < 30
MHz Refraction
E layer refraction can be 1200 miles The higher altitude F layer refraction can be 2500
miles Balancing Absorption and Refraction
D layer absorption defines Lowest Usable Frequency (LUF)
E and F layer refraction determine Maximum Usable Frequency (MUF)
11 Radio Waves
Solar Particles and the Magnetosphere
Solar particle emissions are largely deflected by the earth’s magnetic field. Some are drawn to the poles and generate auroras.
12 Radio Waves
Critical Angle
13 Radio Waves
PropagationReflection and Multi-path Interference
14Radio Waves
Tropospheric Ducting
•Radio waves are refracted between the earth and transition in the duct. This is primarily a VHF phenomena and allows propagation for hundreds or thousands of miles. The 2m distance record is between California and Hawaii via a tropo duct
•Ducts can be formed during temperature inversions in very stable weather conditions.
•Ducts are common in the midwest and along the coast (over open water) during summer
15Radio Waves
T3A01 - What should you do if another operator reports that your station’s 2
meter signals were strong just a moment ago, but now they are weak or distorted
A. Change the batteries in your radio to a different typeB. Turn on the CTCSS toneC. Ask the other operator to adjust his squelch controlD. Try moving a few feet or changing the direction of your antenna if possible, as reflections may be causing multi-path distortion
16Radio Waves
T3A01 - What should you do if another operator reports that your station’s 2
meter signals were strong just a moment ago, but now they are weak or distorted
A. Change the batteries in your radio to a different typeB. Turn on the CTCSS toneC. Ask the other operator to adjust his squelch controlD. Try moving a few feet or changing the direction of your antenna if possible, as reflections may be causing multi-path distortion
17Radio Waves
T3A02 - Why are UHF signals often more effective from inside buildings than VHF
signals?
A. VHF signals lose power faster over distanceB. The shorter wavelength allows them to more easily penetrate the structure of buildingsC. This is incorrect; VHF works better than UHF inside buildingsD. UHF antennas are more efficient than VHF antennas
18Radio Waves
T3A02 - Why are UHF signals often more effective from inside buildings than VHF
signals?
A. VHF signals lose power faster over distanceB. The shorter wavelength allows them to more easily penetrate the structure of buildingsC. This is incorrect; VHF works better than UHF inside buildingsD. UHF antennas are more efficient than VHF antennas
19Radio Waves
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 circularB. Left-hand circularC. HorizontalD. Vertical
20Radio Waves
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 circularB. Left-hand circularC. HorizontalD. Vertical
21Radio Waves
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 invertedB. Signals could be significantly weakerC. Signals have an echo effect on voicesD. Nothing significant will happen
22Radio Waves
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 invertedB. Signals could be significantly weakerC. Signals have an echo effect on voicesD. Nothing significant will happen
23Radio Waves
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
polarizationB. Try to find a path that reflects signals
to the repeater C. Try the long pathD. Increase the antenna SWR
24Radio Waves
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
polarizationB.Try to find a path that
reflects signals to the repeater
C. Try the long pathD. Increase the antenna SWR
25Radio Waves
T3A06 - What term is commonly used to describe the rapid fluttering sound
sometimes heard from mobile stations that are moving while transmitting?
A. Flip-floppingB. Picket fencingC. Frequency shiftingD. Pulsing
26Radio Waves
T3A06 - What term is commonly used to describe the rapid fluttering sound
sometimes heard from mobile stations that are moving while transmitting?
A. Flip-floppingB. Picket fencingC. Frequency shiftingD. Pulsing
27Radio Waves
T3A07 - What type of wave carries radio signals between transmitting and
receiving stations?
A. ElectromagneticB. ElectrostaticC. Surface acousticD. Magnetostrictive
28Radio Waves
T3A07 - What type of wave carries radio signals between transmitting and
receiving stations?
A. ElectromagneticB. ElectrostaticC. Surface acousticD. Magnetostrictive
29Radio Waves
T3A08 - Which of the following is a likely cause of irregular fading of signals received by ionospheric reflection?
A. Frequency shift due to Faraday rotationB. Interference from thunderstormsC. Random combining of signals arriving via different paths D. Intermodulation distortion
30Radio Waves
T3A08 - Which of the following is a likely cause of irregular fading of signals received by ionospheric reflection?
A. Frequency shift due to Faraday rotationB. Interference from thunderstormsC. Random combining of signals arriving via different paths D. Intermodulation distortion
31Radio Waves
T3A09 Which of the following results
from the fact that skip signals refracted from the ionosphere are elliptically
polarized?A. Digital modes are unusableB. Either vertically or horizontally polarized antennas may be used for transmission or receptionC. FM voice is unusableD. Both the transmitting and receiving antennas must be of the same polarization
32Radio Waves
T3A09 Which of the following results
from the fact that skip signals refracted from the ionosphere are elliptically
polarized?A. Digital modes are unusableB. Either vertically or horizontally polarized antennas may be used for transmission or receptionC. FM voice is unusableD. Both the transmitting and receiving antennas must be of the same polarization
33Radio Waves
T3A10 - What may occur if data signals propagate over multiple
paths?A. Transmission rates can be increased by a factor equal to the number of separate paths observedB. Transmission rates must be decreased by a factor equal to the number of separate paths observedC. No significant changes will occur if the signals are transmitting using FMD. Error rates are likely to increase
34Radio Waves
T3A10 - What may occur if data signals propagate over multiple
paths?A. Transmission rates can be increased by a factor equal to the number of separate paths observedB. Transmission rates must be decreased by a factor equal to the number of separate paths observedC. No significant changes will occur if the signals are transmitting using FMD. Error rates are likely to increase
35Radio Waves
T3A11 - Which part of the atmosphere enables the propagation
of radio signals around the world?
A. The stratosphereB. The troposphereC. The ionosphereD. The magnetosphere
36Radio Waves
T3A11 - Which part of the atmosphere enables the propagation
of radio signals around the world?
A. The stratosphereB. The troposphereC. The ionosphereD. The magnetosphere
37Radio Waves
T3B - Radio and electromagnetic wave properties
the electromagnetic spectrum; wavelength vs. frequency; velocity of electromagnetic waves; calculating
wavelength
38Radio Waves
Wavelength vs Frequency• The distance a radio wave travels in one cycle is called
wavelength• The number of cycles per second is frequency• The maximum displacement of wave from reference value is
amplitude
39 Radio Waves
One WavelengthOne Wavelength
TimeTime
V+V+
VV--
0V0V
One CycleOne Cycle
AmplitudeAmplitude
T3B01 - What is the name for the distance a radio wave travels during
one complete cycle?
A. Wave speedB. WaveformC. WavelengthD. Wave spread
40Radio Waves
T3B01 - What is the name for the distance a radio wave travels during
one complete cycle?
A. Wave speedB. WaveformC. WavelengthD. Wave spread
41Radio Waves
T3B02 - What property of a radio wave is used to describe its
polarization?
A. The orientation of the electric fieldB. The orientation of the magnetic fieldC. The ratio of the energy in the magnetic field to the energy in the electric fieldD. The ratio of the velocity to the wavelength
42Radio Waves
T3B02 - What property of a radio wave is used to describe its
polarization?
A. The orientation of the electric fieldB. The orientation of the magnetic fieldC. The ratio of the energy in the magnetic field to the energy in the electric fieldD. The ratio of the velocity to the wavelength
43Radio Waves
T3B03 - What are the two components of a radio wave?
A. AC and DCB. Voltage and currentC. Electric and magnetic fieldsD. Ionizing and non-ionizing radiation
44Radio Waves
T3B03 - What are the two components of a radio wave?
A. AC and DCB. Voltage and currentC. Electric and magnetic fieldsD. Ionizing and non-ionizing radiation
45Radio Waves
T3B04 - How fast does a radio wave travel through free space?
A. At the speed of lightB. At the speed of soundC. Its speed is inversely proportional to its wavelengthD. Its speed increases as the frequency increases
46Radio Waves
T3B04 - How fast does a radio wave travel through free space?
A. At the speed of lightB. At the speed of soundC. Its speed is inversely proportional to its wavelengthD. Its speed increases as the frequency increases
47Radio Waves
Frequency to Wavelength Conversion
• To convert from frequency to wavelength in meters:
48Radio Waves
300300Freq (Freq (MHzMHz))Wavelength =Wavelength =
Frequency and wavelength are inversely proportional – as one increases, the other decreasesLonger (wavelength) – Lower (frequency)
T3B05 - How does the wavelength of a radio wave relate to its frequency?
A. The wavelength gets longer as the frequency increasesB. The wavelength gets shorter as the frequency increasesC. There is no relationship between wavelength and frequencyD. The wavelength depends on the bandwidth of the signal
49Radio Waves
T3B05 - How does the wavelength of a radio wave relate to its frequency?
A. The wavelength gets longer as the frequency increasesB. The wavelength gets shorter as the frequency increasesC. There is no relationship between wavelength and frequencyD. The wavelength depends on the bandwidth of the signal
50Radio Waves
Frequency Calculations•300 is the Speed of Light in free space
–Radio wave travel at the Speed of Light–300,000,000 meters per second–Radio waves moves slower in wire–Velocity Factor is speed in a material divided by the speed of light i.e. .66
•f is frequency in millions (MHz)–The millions of cycles cancel the millions of meters–146,520,000 = 146.53 MHz
•m is Wave length in Meters or the distance of a full cycle
–How far it takes a wave to complete a complete cycle–The higher the frequency the lower the meter (shorter)–The lower the frequency the higher the meters (longer)
51Radio Waves
300
f m
300 = f x m
Frequency Calculations
52
300
f m
300,000,000
Frequency Wave length meters300 is the speed of light
300,000,000 metersper second
F is frequency in MHzM is Wave Length distance in meters of a full cycle at this frequency
To solve for a value, cover it with your finger and solve the remaining formula
Radio Waves 2014
Frequency Calculations
53Electrical Principles 2014
300300ff
MHzmm
freq = 300/m
Meters Calculations
54Electrical Principles 2014
300300
ff mm
meters = 300/f
T3B06 - What is the formula for converting frequency to approximate
wavelength in meters?
A. Wavelength in meters equals frequency in hertz multiplied by 300B. Wavelength in meters equals frequency in hertz divided by 300C. Wavelength in meters equals frequency in megahertz divided by 300D. Wavelength in meters equals 300 divided by frequency in megahertz
55Radio Waves
T3B06 - What is the formula for converting frequency to approximate
wavelength in meters?
A. Wavelength in meters equals frequency in hertz multiplied by 300B. Wavelength in meters equals frequency in hertz divided by 300C. Wavelength in meters equals frequency in megahertz divided by 300D. Wavelength in meters equals 300 divided by frequency in megahertz
56Radio Waves
T3B07 - What property of radio waves is often used to identify the
different frequency bands?
A. The approximate wavelengthB. The magnetic intensity of wavesC. The time it takes for waves to travel one mileD. The voltage standing wave ratio of waves
57Radio Waves
T3B07 - What property of radio waves is often used to identify the
different frequency bands?
A. The approximate wavelengthB. The magnetic intensity of wavesC. The time it takes for waves to travel one mileD. The voltage standing wave ratio of waves
58Radio Waves
One WavelengthOne Wavelength
TimeTime
V+V+
VV--
0V0V
One CycleOne CycleAmplitudeAmplitude
Radio Spectrum
Medium WaveMedium Wave(MF)(MF)
Short WaveShort Wave(HF)(HF)
Very High Very High FrequencyFrequency
(VHF)(VHF)
Ultra High Ultra High FrequencyFrequency
(UHF)(UHF)
59Radio Waves
AM
Bro
adca
st54
0
1630
TV 2
-654 88
FM B
road
cast
108
TV 7
-13
174
216
TV 1
4-69
470
806
300 kHz 3 MHz 30 MHz 300 MHz 3 GHzFrequency
1 Km 100 m 10 m 1 m 10 cmWavelength
Major Amateur Bands in BLUE
T3B08 - What are the frequency limits of the VHF spectrum?
A. 30 to 300 kHzB. 30 to 300 MHzC. 300 to 3000 kHzD. 300 to 3000 MHz
60Radio Waves
T3B08 - What are the frequency limits of the VHF spectrum?
A. 30 to 300 kHzB. 30 to 300 MHzC. 300 to 3000 kHzD. 300 to 3000 MHz
61Radio Waves
T3B09 - What are the frequency limits of the UHF spectrum?
A. 30 to 300 kHzB. 30 to 300 MHzC. 300 to 3000 kHzD. 300 to 3000 MHz
62Radio Waves
T3B09 - What are the frequency limits of the UHF spectrum?
A. 30 to 300 kHzB. 30 to 300 MHzC. 300 to 3000 kHzD. 300 to 3000 MHz
63Radio Waves
T3B10 - What frequency range is referred to as HF?
A. 300 to 3000 MHzB. 30 to 300 MHzC. 3 to 30 MHzD. 300 to 3000 kHz
64Radio Waves
T3B10 - What frequency range is referred to as HF?
A. 300 to 3000 MHzB. 30 to 300 MHzC. 3 to 30 MHzD. 300 to 3000 kHz
65Radio Waves
T3B11 - What is the approximate velocity of a radio wave as it travels
through free space?
A. 3000 kilometers per secondB. 300,000,000 meters per secondC. 300,000 miles per hourD. 186,000 miles per hour
66Radio Waves
T3B11 - What is the approximate velocity of a radio wave as it travels
through free space?
A. 3000 kilometers per secondB. 300,000,000 meters per secondC. 300,000 miles per hourD. 186,000 miles per hour
67Radio Waves
T3C - Propagation modes
line of sight; sporadic E; meteor and auroral scatter and
reflections; tropospheric ducting; F layer skip; radio horizon
68Radio Waves
Aurora Borealis
69Radio Waves
T3C01 - Why are direct (not via a repeater) UHF signals rarely heard from
stations outside your local coverage area?
A. They are too weak to go very farB. FCC regulations prohibit them from going more than 50 milesC. UHF signals are usually not reflected by the ionosphereD. They collide with trees and shrubbery and fade out
70Radio Waves
T3C01 - Why are direct (not via a repeater) UHF signals rarely heard from
stations outside your local coverage area?
A. They are too weak to go very farB. FCC regulations prohibit them from going more than 50 milesC. UHF signals are usually not reflected by the ionosphereD. They collide with trees and shrubbery and fade out
71Radio Waves
T3C02 - Which of the following might be happening when VHF signals are being received from long distances?
A. Signals are being reflected from outer spaceB. Signals are arriving by sub-surface ductingC. Signals are being reflected by lightning storms in your areaD. Signals are being refracted from a sporadic E layer
72Radio Waves
T3C02 - Which of the following might be happening when VHF signals are being received from long distances?
A. Signals are being reflected from outer spaceB. Signals are arriving by sub-surface ductingC. Signals are being reflected by lightning storms in your areaD. Signals are being refracted from a sporadic E layer
73Radio Waves
T3C03 - What is a characteristic of VHF signals received via auroral
reflection?
A. Signals from distances of 10,000 or more miles are commonB. The signals exhibit rapid fluctuations of strength and often sound distortedC. These types of signals occur only during winter nighttime hoursD. These types of signals are generally strongest when your antenna is aimed west
74Radio Waves
T3C03 - What is a characteristic of VHF signals received via auroral
reflection?
A. Signals from distances of 10,000 or more miles are commonB. The signals exhibit rapid fluctuations of strength and often sound distortedC. These types of signals occur only during winter nighttime hoursD. These types of signals are generally strongest when your antenna is aimed west
75Radio Waves
T3C04 - Which of the following propagation types is most commonly associated with
occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands?
A. BackscatterB. Sporadic EC. D layer absorptionD. Gray-line propagation
76Radio Waves
T3C04 - Which of the following propagation types is most commonly associated with
occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands?
A. BackscatterB. Sporadic EC. D layer absorptionD. Gray-line propagation
77Radio Waves
T3C05 - Which of the following effects might cause radio signals to be heard
despite obstructions between the transmitting and receiving stations?
A. Knife-edge diffractionB. Faraday rotationC. Quantum tunneling D. Doppler shift
78Radio Waves
T3C05 - Which of the following effects might cause radio signals to be heard
despite obstructions between the transmitting and receiving stations?
A. Knife-edge diffractionB. Faraday rotationC. Quantum tunneling D. Doppler shift
79Radio Waves
T3C06 - What mode is responsible for allowing over-the-horizon VHF and UHF
communications to ranges of approximately 300 miles on a regular basis?
A. Tropospheric scatterB. D layer refractionC. F2 layer refractionD. Faraday rotation
80Radio Waves
T3C06 - What mode is responsible for allowing over-the-horizon VHF and UHF
communications to ranges of approximately 300 miles on a regular basis?
A. Tropospheric scatterB. D layer refractionC. F2 layer refractionD. Faraday rotation
81Radio Waves
T3C07 - What band is best suited for communicating via meteor scatter?
A. 10 metersB. 6 metersC. 2 metersD. 70 cm
82Radio Waves
T3C07 - What band is best suited for communicating via meteor scatter?
A. 10 metersB. 6 metersC. 2 metersD. 70 cm
83Radio Waves
T3C08 - What causes tropospheric ducting?
A. Discharges of lightning during electrical stormsB. Sunspots and solar flaresC. Updrafts from hurricanes and tornadoesD. Temperature inversions in the atmosphere
84Radio Waves
T3C08 - What causes tropospheric ducting?
A. Discharges of lightning during electrical stormsB. Sunspots and solar flaresC. Updrafts from hurricanes and tornadoesD. Temperature inversions in the atmosphere
85Radio Waves
T3C09 - What is generally the best time for long-distance 10 meter band
propagation via the F layer?A. From dawn to shortly after sunset during periods of high sunspot activityB. From shortly after sunset to dawn during periods of high sunspot activityC. From dawn to shortly after sunset during periods of low sunspot activityD. From shortly after sunset to dawn during periods of low sunspot activity
86Radio Waves
T3C09 - What is generally the best time for long-distance 10 meter band
propagation via the F layer?A. From dawn to shortly after sunset during periods of high sunspot activityB. From shortly after sunset to dawn during periods of high sunspot activityC. From dawn to shortly after sunset during periods of low sunspot activityD. From shortly after sunset to dawn during periods of low sunspot activity
87Radio Waves
T3C10 - What is the radio horizon?
A. The distance over which two stations can communicate by direct pathB. The distance from the ground to a horizontally mounted antennaC. The farthest point you can see when standing at the base of your antenna towerD. The shortest distance between two points on the Earth's surface
88Radio Waves
T3C10 - What is the radio horizon?
A. The distance over which two stations can communicate by direct pathB. The distance from the ground to a horizontally mounted antennaC. The farthest point you can see when standing at the base of your antenna towerD. The shortest distance between two points on the Earth's surface
89Radio Waves
T3C11 - Why do VHF and UHF radio signals usually travel somewhat farther
than the visual line of sight distance between two stations?
A. Radio signals move somewhat faster than the speed of lightB. Radio waves are not blocked by dust particlesC. The Earth seems less curved to radio waves than to lightD. Radio waves are blocked by dust particles
90Radio Waves
T3C11 - Why do VHF and UHF radio signals usually travel somewhat farther
than the visual line of sight distance between two stations?
A. Radio signals move somewhat faster than the speed of lightB. Radio waves are not blocked by dust particlesC. The Earth seems less curved to radio waves than to lightD. Radio waves are blocked by dust particles
91Radio Waves
T3C12 - Which of the following bands may provide long distance
communications during the peak of the sunspot cycle?
A. Six or ten metersB. 23 centimetersC. 70 centimeters or 1.25 metersD. All of these choices are correct
92Radio Waves
T3C12 - Which of the following bands may provide long distance
communications during the peak of the sunspot cycle?
A. Six or ten metersB. 23 centimetersC. 70 centimeters or 1.25 metersD. All of these choices are correct
93Radio Waves
Measuring the Sun
•Solar Flux–A measure of the sun’s noise at 10.7cm
•Solar K-index–The K-index quantifies disturbances in the horizontal component of earth's magnetic field during a 3 hour interval with an integer in the range 0-9 with 1 being calm and 5 or more indicating a geomagnetic storm. The K-index is a measure of short term stability of the Earth’s magnetic field.
•Solar A-index–The A-index provides a daily average level for geomagnetic activity and indicates long term stability of the Earth’s geomagnetic field.94 Radio Waves 2014
G3A08 Which of the following effects can a geomagnetic storm have on radio-wave
propagation?
A. Improved high-latitude HF propagationB. Degraded high-latitude HF propagationC. Improved ground-wave propagationD. Improved chances of UHF ducting
95 Radio Waves 2014
G3A08 Which of the following effects can a geomagnetic storm have on radio-wave
propagation?
A. Improved high-latitude HF propagationB. Degraded high-latitude HF propagationC. Improved ground-wave propagationD. Improved chances of UHF ducting
96 Radio Waves 2014
G3A16 What is a possible benefit to radio communications resulting from periods of high
geomagnetic activity?
A. Aurora that can reflect VHF signalsB. Higher signal strength for HF signals passing through the polar regionsC. Improved HF long path propagationD. Reduced long delayed echoes
97 Radio Waves 2014
G3A16 What is a possible benefit to radio communications resulting from periods of high
geomagnetic activity?
A. Aurora that can reflect VHF signalsB. Higher signal strength for HF signals passing through the polar regionsC. Improved HF long path propagationD. Reduced long delayed echoes
98 Radio Waves 2014
G3B12 What factors affect the Maximum Usable Frequency (MUF)?A. Path distance and locationB. Time of day and seasonC. Solar radiation and ionospheric disturbancesD. All of these choices are correct
99 Radio Waves 2014
G3B12 What factors affect the Maximum Usable Frequency (MUF)?A. Path distance and locationB. Time of day and seasonC. Solar radiation and ionospheric disturbancesD. All of these choices are correct
100 Radio Waves 2014
Backscatter Propagation
101 Radio Waves 2014
G3C07 What makes HF scatter signals often sound distorted?
A. The ionospheric layer involved is unstableB. Ground waves are absorbing much of the signalC. The E-region is not presentD. Energy is scattered into the skip zone through several different radio wave paths
102 Radio Waves 2014
G3C07 What makes HF scatter signals often sound distorted?
A. The ionospheric layer involved is unstableB. Ground waves are absorbing much of the signalC. The E-region is not presentD. Energy is scattered into the skip zone through several different radio wave paths
103 Radio Waves 2014
End ofSUBELEMENT T3
Radio wave characteristics: properties of radio waves; propagation modes
104Radio Waves