or
Subelement L11
Propagation.
Section L11
What type of propagation usually occurs from one hand-held VHF transceiver to another nearby?
• Tunnel propagation
• Skywave propagation
• Auroral propagation
• Correct Answer
Line-of-sight propagation

key words: VHF, NEARBY. The two antennas "see" one another. 'Line-of-sight' is also known as 'direct waves' in contrast with 'sky wave'.

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How does the range of sky-wave propagation compare to ground-wave propagation?
• It depends on the weather
• Correct Answer
It is much longer
• It is much shorter
• It is about the same

Ground Wave propagation present on long wavelengths (e.g., 160 m and 80 m) is of the order of 200 km. One hop via the E layer of the ionosphere can reach to 2000 km. One hop via the F2 layer can reach to 4000 km. Multiple hops cover greater distances.

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When a signal is returned to Earth by the ionosphere, what is this called?
• Ground-wave propagation
• Earth-Moon-Earth propagation
• Correct Answer
Sky-wave propagation
• Tropospheric propagation

Sky Waves or 'ionospheric waves' rely on refraction in layers of the ionosphere.

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How are VHF signals propagated within the range of the visible horizon?
• By plane wave
• By geometric wave
• Correct Answer
By direct wave
• By sky wave

key words: HORIZON. The two antennas "see" one another. 'Line-of-sight' is also known as 'direct waves' in contrast with 'sky wave'.

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Skywave is another name for:
• ground wave
• inverted wave
• Correct Answer
ionospheric wave
• tropospheric wave

Sky Waves or 'ionospheric waves' rely on refraction in layers of the ionosphere.

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That portion of the radiation which is directly affected by the surface of the Earth is called:
• inverted wave
• Correct Answer
ground wave
• tropospheric wave
• ionospheric wave

key words: SURFACE OF THE EARTH. "A special form of diffraction. Bending results when the lower part of the wave front loses energy due to currents induced in the ground (ARRL Handbook)". Ground Wave propagation present on long wavelengths (e.g., 160 m and 80 m) is of the order of 200 km.

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At lower HF frequencies, radiocommunication out to 200 km, during daytime, is made possible by:
• troposphere
• skip wave
• ionosphere
• Correct Answer
ground wave

"A ground wave is the result of a special form of diffraction that primarily affects longer-wavelength vertically polarized radio waves. It is most apparent in the 80 and 160 meter amateur bands, where practical ground-wave distances may extend beyond 200 km (120 mi). It is also the primary mechanism used by AM broadcast stations in the medium-wave bands. The term ground wave is often mistakenly applied to any short-distance communication, but the actual mechanism is unique to the longer-wave bands. (...) Ground wave is most useful during the day at 1.8 and 3.5 MHz, when D layer absorption makes sky wave propagation more difficult." (ARRL Handbook 2012).

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The distance travelled by ground waves:
• Correct Answer
is less at higher frequencies
• depends on the maximum usable frequency
• is more at higher frequencies
• is the same for all frequencies

"The actual mechanism is unique to longer wavelengths (ARRL Handbook)". Ground Wave (about 200 km) is most apparent on 160 m and 80 m. "A special form of diffraction. Bending results when the lower part of the wave front loses energy due to currents induced in the ground (ARRL Handbook)".

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The radio wave which follows a path from the transmitter to the ionosphere and back to Earth is known correctly as the:
• skip wave
• Correct Answer
ionospheric wave
• F layer
• surface wave

key word: IONOSPHERE. Sky Waves or 'ionospheric waves' rely on refraction in layers of the ionosphere.

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Reception of high frequency (HF) radio waves beyond 4000 km is generally made possible by:
• surface wave
• Correct Answer
ionospheric wave
• ground wave
• skip wave

One hop via the E layer of the ionosphere can reach to 2000 km. One hop via the F2 layer can reach to 4000 km. Multiple hops cover greater distances.

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What causes the ionosphere to form?
• Temperature changes ionizing the outer atmosphere
• Correct Answer
Solar radiation ionizing the outer atmosphere
• Lightning ionizing the outer atmosphere
• Release of fluorocarbons into the atmosphere

Ultraviolet (UV) radiation and particles emanating from the Sun break down molecules in the ionosphere to form charged ions.

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What type of solar radiation is most responsible for ionization in the outer atmosphere?
• Thermal
• Correct Answer
Ultraviolet
• Microwave
• Ionized particles

Ultraviolet (UV) radiation and particles emanating from the Sun break down molecules in the ionosphere to form charged ions.

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Which ionospheric region is closest to the Earth?
• The F region
• The A region
• Correct Answer
The D region
• The E region

Above the troposphere and stratosphere, the layers of the ionosphere are: D, E, F1 and F2 (from lowest to highest).

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Which region of the ionosphere is the least useful for long distance radio-wave propagation?
• The F2 region
• The F1 region
• The E region
• Correct Answer
The D region

The D layer, lowest of the layers, is fairly dense. Once ionized during daylight hours, it ABSORBS lower frequencies ( i.e., 160 m and 80 m ).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What two sub-regions of ionosphere exist only in the daytime?
• Correct Answer
F1 and F2
• Troposphere and stratosphere
• Electrostatic and electromagnetic
• D and E

key word: SUB-REGIONS. The F1 and F2 layers present during the day combine at night to form the F layer. D and E are two distinct layers of their own.

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When is the ionosphere most ionized?
• Dawn
• Midnight
• Dusk
• Correct Answer
Midday

key word: MOST. At midday, with the Sun shining directly at the ionosphere, ionization is most intense. As the Sun sets and throughout the night, ions recombine (how quickly depending on the density of a given layer) so that ionization is minimum right before dawn (sunrise).

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When is the ionosphere least ionized?
• Correct Answer
Shortly before dawn
• Just after noon
• Just after dusk
• Shortly before midnight

key word: LEAST. At midday, with the Sun shining directly at the ionosphere, ionization is most intense. As the Sun sets and throughout the night, ions recombine (how quickly depending on the density of a given layer) so that ionization is minimum right before dawn (sunrise).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Why is the F2 region mainly responsible for the longest distance radio-wave propagation?
• Because it exists only at night
• Because it is the lowest ionospheric region
• Because it does not absorb radio waves as much as other ionospheric regions
• Correct Answer
Because it is the highest ionospheric region

Above the troposphere and stratosphere, the layers of the ionosphere are: D, E, F1 and F2 (from lowest to highest).

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What is the main reason the 160, 80 and 40 metre amateur bands tend to be useful only for short-distance communications during daylight hours?
• Because of a lack of activity
• Correct Answer
Because of D-region absorption
• Because of auroral propagation
• Because of magnetic flux

The D layer, lowest of the layers, is fairly dense. Once ionized during daylight hours, it ABSORBS lower frequencies ( i.e., 160 m and 80 m ).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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During the day, one of the ionospheric layers splits into two parts called:
• D1 and D2
• E1 and E2
• A and B
• Correct Answer
F1 and F2

The F1 and F2 layers present during the day combine at night to form the F layer. The other designations simply do not exist.

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The position of the E layer in the ionosphere is:
• below the D layer
• sporadic
• above the F layer
• Correct Answer
below the F layer

From the Earth up and above the troposphere and stratosphere, the layers of the ionosphere are: D, E, F1 and F2.

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What is a skip zone?
• Correct Answer
An area which is too far away for ground-wave propagation, but too close for sky-wave propagation
• An area which is too far away for ground-wave or sky-wave propagation
• An area covered by sky-wave propagation
• An area covered by ground-wave propagation

The Skip Zone is a zone of silence beyond the reach of the Ground Wave but closer than the nearest point where the Sky Wave returns to Earth.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What is the maximum distance along the Earth's surface that is normally covered in one hop using the F2 region?
• 300 km (190 miles)
• Correct Answer
4000 km (2500 miles)
• None; the F2 region does not support radio-wave propagation
• 2000 km (1250 miles)

One hop via the E layer of the ionosphere can reach to 2000 km. One hop via the F2 layer can reach to 4000 km. Multiple hops cover greater distances.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What is the maximum distance along the Earth's surface that is normally covered in one hop using the E region?
• Correct Answer
2000 km (1250 miles)
• 300 km (190 miles)
• 4000 km (2500 miles)
• None; the E region does not support radio-wave propagation

One hop via the E layer of the ionosphere can reach to 2000 km. One hop via the F2 layer can reach to 4000 km. Multiple hops cover greater distances.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Skip zone is:
• a zone between the antenna and the return of the first refracted wave
• Correct Answer
a zone between the end of the ground wave and the point where the first refracted wave returns to Earth
• a zone of silence caused by lost sky waves
• a zone between any two refracted waves

The Skip Zone is a zone of silence beyond the reach of the Ground Wave but closer than the nearest point where the Sky Wave returns to Earth.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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The distance to Europe from your location is approximately 5000 km. What sort of propagation is the most likely to be involved?
• Sporadic "E"
• Back scatter
• Tropospheric scatter
• Correct Answer
Multihop

One hop via the E layer of the ionosphere can reach to 2000 km. One hop via the F2 layer can reach to 4000 km. Multiple hops cover greater distances.

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For radio signals, the skip distance is determined by the:
• Correct Answer
height of the ionosphere and the angle of radiation
• power fed to the power amplifier
• angle of radiation
• type of transmitting antenna used

How far one hop through the ionosphere reaches depends on the take-off angle of the wave with respect to ground ( the lower, the further ) AND the height of the layer where refraction takes place ( the higher, the further ). One hop via the E layer of the ionosphere can reach to 2000 km. One hop via the F2 layer can reach to 4000 km. Multiple hops cover greater distances.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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The distance from the transmitter to the nearest point where the sky wave returns to the Earth is called the:
• angle of radiation
• maximum usable frequency
• Correct Answer
skip distance
• skip zone

Do not confuse Skip Distance and Skip Zone. Skip Distance is the "nearest point where the sky wave returns". It marks the end of the Skip Zone which extended from beyond the reach of the Ground Wave to the "nearest point where the sky wave returns".

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Skip distance is the:
• the maximum distance a signal will travel by both a ground wave and reflected wave
• Correct Answer
the minimum distance reached by a signal after one reflection by the ionosphere
• the maximum distance reached by a signal after one reflection by the ionosphere
• the minimum distance reached by a ground-wave signal

Skip Distance is the "nearest point where the sky wave returns".

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Skip distance is a term associated with signals from the ionosphere. Skip effects are due to:
• selective fading of local signals
• high gain antennas being used
• local cloud cover
• Correct Answer
reflection and refraction from the ionosphere

The phenomenon which returns certain radio waves to Earth is primarily refraction.

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The skip distance of a sky wave will be greatest when the:
• ionosphere is most densely ionized
• signal given out is strongest
• Correct Answer
angle between the ground and the radiation is smallest
• polarization is vertical

How far one hop through the ionosphere reaches depends on the take-off angle of the wave with respect to ground ( the lower, the further ) AND the height of the layer where refraction takes place ( the higher, the further ). One hop via the E layer of the ionosphere can reach to 2000 km. One hop via the F2 layer can reach to 4000 km. Multiple hops cover greater distances.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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If the height of the reflecting layer of the ionosphere increases, the skip distance of a high frequency (HF) transmission:
• stays the same
• varies regularly
• decreases
• Correct Answer
becomes greater

How far one hop through the ionosphere reaches depends on the take-off angle of the wave with respect to ground ( the lower, the further ) AND the height of the layer where refraction takes place ( the higher, the further ). One hop via the E layer of the ionosphere can reach to 2000 km. One hop via the F2 layer can reach to 4000 km. Multiple hops cover greater distances.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What effect does the D region of the ionosphere have on lower frequency HF signals in the daytime?
• It has little or no effect on 80-metre radio waves
• Correct Answer
It absorbs the signals
• It bends the radio waves out into space
• It refracts the radio waves back to Earth

The D layer, lowest of the layers, is fairly dense. Once ionized during daylight hours, it ABSORBS lower frequencies ( i.e., 160 m and 80 m ).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What causes distant AM broadcast and 160 metre ham band stations not to be heard during daytime hours?
• The presence of ionized clouds in the E region
• The splitting of the F region
• The weather below the ionosphere
• Correct Answer
The ionization of the D region

The D layer, lowest of the layers, is fairly dense. Once ionized during daylight hours, it ABSORBS lower frequencies ( i.e., 160 m and 80 m ).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Two or more parts of the radio wave follow different paths during propagation and this may result in phase differences at the receiver. This "change" at the receiver is called:
• absorption
• skip
• Correct Answer
fading
• baffling

Parts of a wave arriving with difference in phases (Selective Fading) cause a fluctuation in the perceived signal. Signals with large bandwidths are more susceptible to Selective Fading. SSB is less affected. [ "Selective fading: fading which affects unequally the different spectral components of a modulated radio wave" (IEC). ]

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A change or variation in signal strength at the antenna, caused by differences in path lengths, is called:
• Correct Answer
fading
• absorption
• fluctuation
• path loss

Parts of a wave arriving with difference in phases (Selective Fading) cause a fluctuation in the perceived signal. Signals with large bandwidths are more susceptible to Selective Fading. SSB is less affected. [ "Selective fading: fading which affects unequally the different spectral components of a modulated radio wave" (IEC). ]

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When a transmitted radio signal reaches a station by a one-hop and two-hop skip path, small changes in the ionosphere can cause:
• consistent fading of received signal
• consistently stronger signals
• a change in the ground-wave signal
• Correct Answer
variations in signal strength

This effect called 'multipath' (where copies of the same signal arrive with phase differences after travelling different path lengths) causes Rapid Fading.

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The usual effect of ionospheric storms is to:
• produce extreme weather changes
• prevent communications by ground wave
• increase the maximum usable frequency
• Correct Answer
cause a fade-out of sky-wave signals

Ionospheric Storm: exceptional solar activity where greater quantities of particles arrive from the Sun make for more ionization (too much ionization), absorption is increased and may last for days.

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On the VHF and UHF bands, polarization of the receiving antenna is very important in relation to the transmitting antenna, yet on HF bands it is relatively unimportant. Why is that so?
• Greater selectivity is possible with HF receivers making changes in polarization redundant
• Correct Answer
The ionosphere can change the polarization of the signal from moment to moment
• The ground wave and the sky wave continually shift the polarization
• Anomalies in the Earth's magnetic field produce a profound effect on HF polarization but not on VHF & UHF frequencies

As a radio wave travels through the changing layers of the ionosphere and is refracted back to Earth, wave polarization will have changed.

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What causes selective fading?
• Time differences between the receiving and transmitting stations
• Large changes in the height of the ionosphere at the receiving station ordinarily occurring shortly before sunrise and sunset
• Correct Answer
Phase differences between radio wave components of the same transmission, as experienced at the receiving station
• Small changes in beam heading at the receiving station

Parts of a wave arriving with difference in phases (Selective Fading) cause a fluctuation in the perceived signal. Signals with large bandwidths are more susceptible to Selective Fading. SSB is less affected. [ "Selective fading: fading which affects unequally the different spectral components of a modulated radio wave" (IEC). ]

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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How does the bandwidth of a transmitted signal affect selective fading?
• It is the same for both wide and narrow bandwidths
• Only the receiver bandwidth determines the selective fading effect
• It is more pronounced at narrow bandwidths
• Correct Answer
It is more pronounced at wide bandwidths

Parts of a wave arriving with difference in phases (Selective Fading) cause a fluctuation in the perceived signal. Signals with large bandwidths are more susceptible to Selective Fading. SSB is less affected. [ "Selective fading: fading which affects unequally the different spectral components of a modulated radio wave" (IEC). ]

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Polarization change often takes place on radio waves that are propagated over long distances. Which of these does not cause polarization change?
• Passage through magnetic fields (Faraday rotation)
• Refractions
• Correct Answer
Parabolic interaction
• Reflections

key word: NOT. Refraction, reflection and magnetic fields all affect wave polarization as waves travel to and from the ionosphere.

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Reflection of a SSB transmission from the ionosphere causes:
• a high-pitch squeal at the receiver
• Correct Answer
little or no phase-shift distortion
• phase-shift distortion
• signal cancellation at the receiver

Parts of a wave arriving with difference in phases (Selective Fading) cause a fluctuation in the perceived signal. Signals with large bandwidths are more susceptible to Selective Fading. SSB is less affected. [ "Selective fading: fading which affects unequally the different spectral components of a modulated radio wave" (IEC). ]

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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How do sunspots change the ionization of the atmosphere?
• The more sunspots there are, the less the ionization
• Unless there are sunspots, the ionization is zero
• They have no effect
• Correct Answer
The more sunspots there are, the greater the ionization

The number of sunspots visible on the surface of the Sun are related to overall solar activity. The higher the sunspot numbers, the higher the emission of Ultraviolet (UV) and particles. Ionization is directly influenced by the level of radiation.

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How long is an average sunspot cycle?
• 5 years
• 7 years
• Correct Answer
11 years
• 17 years

key word: AVERAGE. The duration of the solar cycles varies from 7 to 17 years but the AVERAGE is 11 YEARS.

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What is solar flux?
• A measure of the tilt of the Earth's ionosphere on the side toward the sun
• The number of sunspots on the side of the sun facing the Earth
• The density of the sun's magnetic field
• Correct Answer
The radio energy emitted by the sun

The Sun's activity can be observed by visually counting sunspots but also by measuring noise at a microwave frequency. Sunspot numbers and solar flux are well co-related. The measurement of the solar flux is reported as a Solar Flux Index.

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What is the solar-flux index?
• A measure of solar activity that is taken annually
• Correct Answer
A measure of solar activity that is taken at a specific frequency
• Another name for the American sunspot number
• A measure of solar activity that compares daily readings with results from the last six months

The Sun's activity can be observed by visually counting sunspots but also by measuring noise at a microwave frequency. Sunspot numbers and solar flux are well co-related. The measurement of the solar flux is reported as a Solar Flux Index.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What influences all radiocommunication beyond ground-wave or line-of-sight ranges?
• The F2 region of the ionosphere
• The F1 region of the ionosphere
• Lunar tidal effects
• Correct Answer
Solar radiation

Because the Sun affects the ionosphere and the troposphere (e.g., temperature inversions), it can be said that it has an influence on all radiocommunications.

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Which two types of radiation from the sun influence propagation?
• Correct Answer
Electromagnetic and particle emissions
• Subaudible and audio-frequency emissions
• Polar region and equatorial emissions
• Infrared and gamma-ray emissions

Ultraviolet (UV) rays, a form of electromagnetic radiation, and particles [namely alpha and beta] are responsible for ionization in the ionosphere.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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When sunspot numbers are high, how is propagation affected?
• High frequency radio signals become weak and distorted
• Correct Answer
Frequencies up to 40 MHz or even higher become usable for long-distance communication
• High frequency radio signals are absorbed
• Frequencies up to 100 MHz or higher are normally usable for long-distance communication

Maximum Usable Frequencies (MUF) in the range of 30 to 50 MHz become possible during solar cycle peaks. Stronger ionization allow upper layers of the ionosphere to refract higher frequencies rather than let them escape into space (as is the case during solar cycle lows).

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All communication frequencies throughout the spectrum are affected in varying degrees by the:
• ionosphere
• aurora borealis
• atmospheric conditions
• Correct Answer
sun

Because the Sun affects the ionosphere and the troposphere (e.g., temperature inversions), it can be said that it has an influence on all radiocommunications.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Average duration of a solar cycle is:
• 1 year
• Correct Answer
11 years
• 3 years
• 6 years

key word: AVERAGE. The duration of the solar cycles varies from 7 to 17 years but the AVERAGE is 11 YEARS.

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The ability of the ionosphere to reflect high frequency radio signals depends on:
• upper atmosphere weather conditions
• Correct Answer
the amount of solar radiation
• the power of the transmitted signal
• the receiver sensitivity

Ionization makes refraction possible. Ultraviolet (UV) rays, a form of electromagnetic radiation, and particles [namely alpha and beta] are responsible for ionization in the ionosphere.

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HF radio propagation cycles have a period of approximately 11:
• centuries
• Correct Answer
years
• months
• days

key word: 11. The duration of the solar cycles varies from 7 to 17 years but the AVERAGE is 11 YEARS.

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What happens to signals higher in frequency than the critical frequency?
• They are absorbed by the ionosphere
• Their frequency is changed by the ionosphere to be below the maximum usable frequency
• They are reflected back to their source
• Correct Answer
They pass through the ionosphere

The 'Critical Frequency' is a measurement of the highest frequency which will be refracted back to Earth when sent straight up at a given time. Above the Critical Frequency, the wave escapes into space. How high the Critical Frequency is, relates to the ionization level.

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What causes the maximum usable frequency to vary?
• The type of weather just below the ionosphere
• Correct Answer
The amount of radiation received from the sun, mainly ultraviolet
• The temperature of the ionosphere
• The speed of the winds in the upper atmosphere

The Maximum Usable Frequency (MUF) is the highest frequency usable for sky wave propagation between two points on the globe. MUF varies with ionization levels (solar cycle, time of the day). Maximum Usable Frequencies (MUF) in the range of 30 to 50 MHz become possible during solar cycle peaks.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What does maximum usable frequency mean?
• Correct Answer
The highest frequency signal that will reach its intended destination
• The lowest frequency signal that will reach its intended destination
• The highest frequency signal that is most absorbed by the ionosphere
• The lowest frequency signal that is most absorbed by the ionosphere

The Maximum Usable Frequency (MUF) is the highest frequency usable for sky wave propagation between two points on the globe. MUF varies with ionization levels (solar cycle, time of the day). Maximum Usable Frequencies (MUF) in the range of 30 to 50 MHz become possible during solar cycle peaks.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What can be done at an amateur station to continue HF communications during a sudden ionospheric disturbance?
• Try a different frequency shift
• Correct Answer
Try a higher frequency band
• Try the other sideband
• Try a different antenna polarization

A Sudden Ionospheric Disturbance is a sudden rise in radiation, due to solar flares, which increases D-layer ABSORPTION for an hour or so. The only option is to "try a higher frequency band" in an attempt to cut through the absorption.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What is one way to determine if the maximum usable frequency (MUF) is high enough to support 28 MHz propagation between your station and western Europe?
• Listen for WWVH time signals on 20 MHz
• Correct Answer
Listen for signals from 10-metre beacon stations
• Listen for signals from 20-metre beacon stations
• Listen for signals from 39-metre broadcast stations

The 10 m band spans 28.0 MHz to 29.7 MHz. 'Beacons' are one-way automated stations maintained by amateurs which operate on known frequencies to permit evaluating propagation conditions.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What usually happens to radio waves with frequencies below the maximum usable frequency (MUF) when they are sent into the ionosphere?
• They pass through the ionosphere
• Correct Answer
They are bent back to the Earth
• They are changed to a frequency above the MUF
• They are completely absorbed by the ionosphere

As Maximum Usable Frequency (MUF) is the highest frequency usable for sky wave propagation between two points on the globe, using lower frequencies are also refracted back to Earth. In fact, the Optimum Working Frequency is somewhat lower than the MUF [85%]. Note that frequencies below the MUF are more subject to absorption and noise so a lower limit does exist. Refraction of a given signal by the ionosphere is dependent on the frequency, the level of ionization and the angle of entry into a layer.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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At what point in the solar cycle does the 20-metre band usually support worldwide propagation during daylight hours?
• Only at the maximum point of the solar cycle
• At the summer solstice
• Correct Answer
At any point in the solar cycle
• Only at the minimum point of the solar cycle

During solar peaks and solar lows, the 20 m band (14.0 MHz to 14.35 MHz) usually support worldwide communications during the day.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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If we transmit a signal, the frequency of which is so high we no longer receive a reflection from the ionosphere, the signal frequency is above the:
• skip distance
• speed of light
• sunspot frequency
• Correct Answer
maximum usable frequency

The Maximum Usable Frequency (MUF) is the highest frequency usable for sky wave propagation between two points on the globe. MUF varies with ionization levels (solar cycle, time of the day). Maximum Usable Frequencies (MUF) in the range of 30 to 50 MHz become possible during solar cycle peaks.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Communication on the 80 metre band is generally most difficult during:
• daytime in winter
• Correct Answer
daytime in summer
• evening in winter
• evening in summer

During the summer, two problems can affect 160 m and 80 m: static from lightning (thunderstorms) and D-layer absorption. The D layer, lowest of the layers, is fairly dense. Once ionized during daylight hours, it ABSORBS lower frequencies ( i.e., 160 m and 80 m ).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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The optimum working frequency provides the best long range HF communication. Compared with the maximum usable frequency (MUF), it is usually:
• double the MUF
• half the MUF
• slightly higher
• Correct Answer
slightly lower

As Maximum Usable Frequency (MUF) is the highest frequency usable for sky wave propagation between two points on the globe, using lower frequencies are also refracted back to Earth. In fact the Optimum Working Frequency is somewhat lower than the MUF [85%]. Note that frequencies below the MUF are more subject to absorption and noise so a lower limit does exist. Refraction of a given signal by the ionosphere is dependent on the frequency, the level of ionization and the angle of entry into a layer.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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During summer daytime, which bands are the most difficult for communications beyond ground wave?
• Correct Answer
160 and 80 metres
• 40 metres
• 30 metres
• 20 metres

During the summer, two problems can affect 160 m and 80 m: static from lightning (thunderstorms) and D-layer absorption. The D layer, lowest of the layers, is fairly dense. Once ionized during daylight hours, it ABSORBS lower frequencies ( i.e., 160 m and 80 m ).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Which ionospheric region most affects sky-wave propagation on the 6 metre band?
• The D region
• Correct Answer
The E region
• The F2 region
• The F1 region

At 50 to 54 MHz, the 6 m band normally escapes into space. However, 'Sporadic E' ( intense but temporary ionization of patches in the upper regions of the E layer ) can provide refraction paths for 6 metres.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What effect does tropospheric bending have on 2-metre radio waves?
• Correct Answer
It lets you contact stations farther away
• It causes them to travel shorter distances
• It garbles the signal
• It reverses the sideband of the signal

key word: BENDING. Tropospheric bending : refraction occurs when a wave travels through masses of differing densities (humidity content) in the troposphere. The wave travels further rather than escape right away into space.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What causes tropospheric ducting of radio waves?
• Correct Answer
A temperature inversion
• Lightning between the transmitting and receiving stations
• An aurora to the north
• A very low pressure area

key word: DUCTING. Wave gets caught between sandwiched masses of different humidity contents (like in a waveguide). A 'temperature inversion', where hot air masses find themselves riding over cooler air, lead to conditions supporting 'Ducting'. Except for 'Tropo Ducting', common troposcatter (scattering through the troposphere) opens VHF paths out to 500 km for well-equipped stations (800 at the most). 'Tropospheric Ducting' permit distances beyond 800 km.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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That portion of the radiation kept close to the Earth's surface due to bending in the atmosphere is called the:
• Correct Answer
tropospheric wave
• inverted wave
• ground wave
• ionospheric wave

key word: BENDING. Tropospheric bending : refraction occurs when a wave travels through masses of differing densities (humidity content) in the troposphere. The wave travels further rather than escape right away into space.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What is a sporadic-E condition?
• A brief decrease in VHF signals caused by sunspot variations
• Correct Answer
Patches of dense ionization at E-region height
• Partial tropospheric ducting at E-region height
• Variations in E-region height caused by sunspot variations

At 50 to 54 MHz, the 6 m band normally escapes into space. However, 'Sporadic E' ( intense but temporary ionization of patches in the upper regions of the E layer ) can provide refraction paths for 6 metres.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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On which amateur frequency band is the extended-distance propagation effect of sporadic-E most often observed?
• 20 metres
• 2 metres
• Correct Answer
6 metres
• 160 metres

At 50 to 54 MHz, the 6 m band normally escapes into space. However, 'Sporadic E' ( intense but temporary ionization of patches in the upper regions of the E layer ) can provide refraction paths for 6 metres.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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In the northern hemisphere, in which direction should a directional antenna be pointed to take maximum advantage of auroral propagation?
• South
• Correct Answer
North
• East
• West

key word: AURORA. The arrival of high-energy particles from the Sun (e.g., after a solar flare) disturbs the Earth's magnetic field (a geomagnetic storm). The resulting unusual ionization of gases in the E layer above the poles produce the visual display known as 'aurora' ("Northern Lights"). Pointing antennas at the aurora front permit oblique paths to distant stations.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Where in the ionosphere does auroral activity occur?
• Correct Answer
At E-region height
• At F-region height
• In the equatorial band
• At D-region height

key word: AURORA. The arrival of high-energy particles from the Sun (e.g., after a solar flare) disturbs the Earth's magnetic field (a geomagnetic storm). The resulting unusual ionization of gases in the E layer above the poles produce the visual display known as 'aurora' ("Northern Lights"). Pointing antennas at the aurora front permit oblique paths to distant stations.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Which emission mode is best for auroral propagation?
• FM
• SSB
• Correct Answer
CW
• RTTY

The unstable front of the aurora and ensuing scattering of the radio wave make for distorted signals, only the smaller bandwidth signals are usable.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Excluding enhanced propagation modes, what is the approximate range of normal VHF tropospheric propagation?
• 1600 km (1000 miles)
• Correct Answer
800 km (500 miles)
• 2400 km (1500 miles)
• 3200 km (2000 miles)

Except for 'Tropo Ducting', common troposcatter (scattering through the troposphere) opens VHF paths out to 500 km for well-equipped stations (800 at the most). 'Tropospheric Ducting' (where a wave gets caught between sandwiched air masses during a 'temperature inversion') permit distances beyond 800 km.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What effect is responsible for propagating a VHF signal over 800 km (500 miles)?
• Faraday rotation
• D-region absorption
• Moon bounce (EME) Earth - Moon - Earth
• Correct Answer
Tropospheric ducting

Except for 'Tropo Ducting', common troposcatter (scattering through the troposphere) opens VHF paths out to 500 km for well-equipped stations (800 at the most). 'Tropospheric Ducting' (where a wave gets caught between sandwiched air masses during a 'temperature inversion') permit distances beyond 800 km.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What kind of unusual HF propagation allows weak signals from the skip zone to be heard occasionally?
• Ducting
• Ground-wave
• Correct Answer
Scatter-mode
• Sky-wave with low radiation angle

Key words: UNUSUAL, WEAK. "Beyond Ground Wave and too close for normal Sky Wave" is the 'Skip Zone', a zone of silence. Out of the choices presented, the only explanation for propagation into the Skip Zone is HF SCATTER. The signals will be weak and distorted.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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If you receive a weak, distorted signal from a distance, and close to the maximum usable frequency, what type of propagation is probably occurring?
• Line-of-sight
• Ducting
• Correct Answer
Scatter
• Ground-wave

key words: WEAK, DISTORTED. Signals propagated via 'HF Scatter' have a characteristic weak and distorted (hollow, echo-like) sound. The distortion is caused by multi-path effects. Unlike simple refraction, where the entire signal changes direction, scattering splits the signal in many directions (thus explaining the weakness).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What is a characteristic of HF scatter signals?
• Reversed sidebands
• High intelligibility
• Correct Answer
Rapid flutter or hollow sounding distortion
• Reversed modulation

key words: FLUTTER, HOLLOW. Signals propagated via 'HF Scatter' have a characteristic weak and distorted (hollow, echo-like) sound. The distortion is caused by multi-path effects. Unlike simple refraction, where the entire signal changes direction, scattering splits the signal in many directions (thus explaining the weakness).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What makes HF scatter signals often sound distorted?
• The state of the E-region at the point of refraction
• Correct Answer
Energy scattered into the skip zone through several radio-wave paths
• Auroral activity and changes in the Earth's magnetic field
• Propagation through ground waves that absorb much of the signal

key words: SCATTER, DISTORTED. Signals propagated via 'HF Scatter' have a characteristic weak and distorted (hollow, echo-like) sound. The distortion is caused by multi-path effects. Unlike simple refraction, where the entire signal changes direction, scattering splits the signal in many directions (thus explaining the weakness).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Why are HF scatter signals usually weak?
• The F region of the ionosphere absorbs most of the signal energy
• Auroral activity absorbs most of the signal energy
• Correct Answer
Only a small part of the signal energy is scattered into the skip zone
• Propagation through ground waves absorbs most of the signal energy

key words: SCATTER, WEAK. Signals propagated via 'HF Scatter' have a characteristic weak and distorted (hollow, echo-like) sound. The distortion is caused by multi-path effects. Unlike simple refraction, where the entire signal changes direction, scattering splits the signal in many directions (thus explaining the weakness).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What type of propagation may allow a weak signal to be heard at a distance too far for ground-wave propagation but too near for normal sky-wave propagation?
• Sporadic-E skip
• Ground wave
• Correct Answer
Scatter
• Short-path skip

"Beyond Ground Wave and too close for normal Sky Wave" is the 'Skip Zone', a zone of silence. Out of the choices provided, the only explanation for propagation into the Skip Zone is HF SCATTER.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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On the HF bands, when is scatter propagation most likely involved?
• When the sunspot cycle is at a minimum and D-region absorption is high
• At night
• When the F1 and F2 regions are combined
• Correct Answer
When weak and distorted signals near or above the maximum usable frequency for normal propagation can be heard over unusual paths

Key words: WEAK, DISTORTED, UNUSUAL PATHS. "Special forms of F layer scattering can create unusual paths within the skip zone. Backscatter and sidescatter signals are usually observed just below the MUF for the direct path and allow communications not normally possible by other means. (...) Backscattered signals are generally weak and have a characteristic hollow sound." (ARRL Handbook 2012)

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Which of the following is not a scatter mode?
• Meteor scatter
• Tropospheric scatter
• Ionospheric scatter
• Correct Answer
Absorption scatter

Key words: IS NOT. Meteor Scatter (bouncing signals off the ionized trails left by meteors), Troposcatter (scattering by layers of varying humidity content in the lower atmosphere) and Ionospheric Scatter (through irregularities, turbulence or stratification in the ionospheric layers) are all known scatter modes.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Meteor scatter is most effective on what band?
• 15 metres
• 160 metres
• Correct Answer
6 metres
• 40 metres

30 MHz to 100 MHz is the range where 'Meteor Scatter' is most effective. This makes the 6 m amateur band (50 MHz to 54 MHz) the band of choice for Meteor Scatter.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Which of the following is not a scatter mode?
• Forward scatter
• Correct Answer
Inverted scatter
• Side scatter
• Back scatter

key word: NOT. Scattering has to do with dispersing in many DIRECTIONS. 'Side Scatter', 'Back Scatter' and ' Forward Scatter' are valid paths.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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In which frequency range is meteor scatter most effective for extended-range communication?
• 10 - 30 MHz
• 3 - 10 MHz
• 100 - 300 MHz
• Correct Answer
30 - 100 MHz

30 MHz to 100 MHz is the range where 'Meteor Scatter' is most effective. This makes the 6 m amateur band (50 MHz to 54 MHz) the band of choice for Meteor Scatter.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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