Canadian Basic Qualification pool, section B-007-008

Subelement B-007

B-007

Section B-007-008

B-007-008-001

What kind of unusual HF propagation allows weak signals from the skip zone to be heard?

A.
Ducting
Correct Answer
B.
Scatter-mode
C.
Ground wave
D.
Sky-wave with low radiation angle

B-007-008-001

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.

Tags: none

B-007-008-002

If you receive a weak, distorted signal close to the maximum usable frequency, what type of propagation is probably occurring?

Correct Answer
A.
Scatter
B.
Line-of-sight
C.
Ground wave
D.
Ducting

B-007-008-002

Key words: WEAK, DISTORTED. Signals propagated via 'HF Scatter' have a characteristic weak and distorted (hollow, echo-like) sound. The distortion is caused by multipath 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.

Tags: none

B-007-008-003

What type of VHF/UHF propagation depends upon small variations in density and water-vapour content?

Correct Answer
A.
Tropospheric scatter
B.
Tropospheric ducting
C.
Ionospheric scatter
D.
Sporadic-E

B-007-008-003

The radio horizon is about 15% further than the visible horizon. The troposphere is the lower part of the atmosphere where we live. Temperature, pressure and water vapour content change gradually with altitude. Hence, the refractive index changes with altitude and leads to the refraction of radio waves. Masses about the size of a wavelength with small differences in temperature, pressure and water vapour content are also found here and there in the troposphere. These masses provoke another effect, namely, tropospheric scatter (troposcatter).

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

Tags: none

B-007-008-004

What makes HF scatter signals often sound distorted?

A.
Auroral activity and changes in the Earth's magnetic field
Correct Answer
B.
Energy scattered into the skip zone through several radio-wave paths
C.
The state of the E-region at the point of refraction
D.
Propagation through ground waves that absorb much of the signal

B-007-008-004

Key words: SCATTER, DISTORTED. Signals propagated via 'HF Scatter' have a characteristic weak and distorted (hollow, echo-like) sound. The distortion is caused by multipath 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.

Tags: none

B-007-008-005

Why are HF scatter signals usually weak?

A.
Auroral activity absorbs most of the signal energy
B.
Propagation through ground waves absorbs most of the signal energy
Correct Answer
C.
Only a small part of the signal energy is scattered into the skip zone
D.
The F region of the ionosphere absorbs most of the signal energy

B-007-008-005

Key words: SCATTER, WEAK. Signals propagated via 'HF Scatter' have a characteristic weak and distorted (hollow, echo-like) sound. The distortion is caused by multipath 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.

Tags: none

B-007-008-006

What type of propagation may allow a weak high frequency (HF) signal to be heard at a distance too far for ground-wave propagation but too near for normal sky-wave propagation?

Correct Answer
A.
Scatter
B.
Sporadic-E skip
C.
Tropospheric scatter
D.
Short-path skip

B-007-008-006

"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.

Tags: none

B-007-008-007

On the HF bands, when is scatter propagation most likely involved?

A.
At night when propagation is poor
B.
When the sunspot cycle is at a minimum and D-region absorption is high
C.
When the F1 and F2 regions are combined
Correct Answer
D.
When you receive weak and distorted signals near the maximum usable frequency (MUF)

B-007-008-007

Key words: WEAK, DISTORTED. "Special forms of F region 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.

Tags: none

B-007-008-008

Tropospheric scatter frequently explains VHF/UHF communications well beyond the radio horizon. What makes this propagation mode possible?

A.
Increased daytime ionization of the D region
Correct Answer
B.
Small variations in the properties of the lower atmosphere
C.
Local cloud cover
D.
Ionized patches in the troposphere

B-007-008-008

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

Tags: none

B-007-008-009

Meteor scatter is most effective on what band?

A.
40 metres
Correct Answer
B.
6 metres
C.
160 metres
D.
15 metres

B-007-008-009

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.

Tags: none

B-007-008-010

What is the effect of scattering on a radio wave?

Correct Answer
A.
The wave gets redirected in many directions
B.
A portion of the wave abruptly changes direction
C.
The wave is gradually bent
D.
The wave is absorbed by the medium

B-007-008-010

When a wave is split and redirected in multiple directions after hitting a rough surface or propagating through a medium with masses of varying densities, this is scattering. Refraction and reflection are distinct phenomena.

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

Tags: none

B-007-008-011

In which frequency range is meteor scatter most effective for extended-range communication?

A.
100 MHz to 150 MHz
B.
10 MHz to 30 MHz
Correct Answer
C.
30 MHz to 100 MHz
D.
3 MHz to 10 MHz

B-007-008-011

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.

Tags: none

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