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

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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.

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Solar Effects on the Atmosphere

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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.

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Ground Wave Propagation

Ground waves travel along the ground Higher power, farther travel

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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.

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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”.

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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)

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Sunspots

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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)

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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.

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Critical Angle

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PropagationReflection and Multi-path Interference

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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

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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

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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

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 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

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 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

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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

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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

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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

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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

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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

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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

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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

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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

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T3A07 - What type of wave carries radio signals between transmitting and

receiving stations?

A. ElectromagneticB. ElectrostaticC. Surface acousticD. Magnetostrictive

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T3A07 - What type of wave carries radio signals between transmitting and

receiving stations?

A. ElectromagneticB. ElectrostaticC. Surface acousticD. Magnetostrictive

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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

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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

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 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

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 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

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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

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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

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T3A11 - Which part of the atmosphere enables the propagation

of radio signals around the world?

A. The stratosphereB. The troposphereC. The ionosphereD. The magnetosphere

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T3A11 - Which part of the atmosphere enables the propagation

of radio signals around the world?

A. The stratosphereB. The troposphereC. The ionosphereD. The magnetosphere

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T3B - Radio and electromagnetic wave properties

the electromagnetic spectrum; wavelength vs. frequency; velocity of electromagnetic waves; calculating

wavelength

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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

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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

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T3B01 - What is the name for the distance a radio wave travels during

one complete cycle?

A. Wave speedB. WaveformC. WavelengthD. Wave spread

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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

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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

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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

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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

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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

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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

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Frequency to Wavelength Conversion

• To convert from frequency to wavelength in meters:

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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

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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

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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)

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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

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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

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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

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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

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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

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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)

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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

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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

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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

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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

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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

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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

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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

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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

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T3C - Propagation modes

line of sight; sporadic E; meteor and auroral scatter and

reflections; tropospheric ducting; F layer skip; radio horizon

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Aurora Borealis

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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T3C07 - What band is best suited for communicating via meteor scatter?

A. 10 metersB. 6 metersC. 2 metersD. 70 cm

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T3C07 - What band is best suited for communicating via meteor scatter?

A. 10 metersB. 6 metersC. 2 metersD. 70 cm

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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

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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

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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

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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

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 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

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 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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Backscatter Propagation

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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

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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

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End ofSUBELEMENT T3

Radio wave characteristics: properties of radio waves; propagation modes

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