Canadian Basic Qualification pool, section B-007-006

Subelement B-007

B-007

Section B-007-006

B-007-006-001

Observatories probe the ionosphere at vertical incidence. What term describes the highest frequency that a region can reflect at the time?

Correct Answer
A.
Critical frequency
B.
Optimum working frequency
C.
Maximum usable frequency
D.
Doppler frequency

B-007-006-001

The 'Critical Frequency' is a measurement of the highest frequency that 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.

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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B-007-006-002

What causes the maximum usable frequency to vary?

Correct Answer
A.
The amount of radiation received from the sun
B.
The temperature of the ionosphere
C.
The type of weather just below the ionosphere
D.
The speed of the winds in the upper atmosphere

B-007-006-002

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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B-007-006-003

What does maximum usable frequency mean?

A.
The lowest frequency that is most absorbed by the ionosphere
B.
The highest frequency that is most absorbed by the ionosphere
Correct Answer
C.
The highest frequency at which a signal will reach a given destination
D.
The lowest frequency at which a signal will reach a given destination

B-007-006-003

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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B-007-006-004

Why is communication possible between two continents at a frequency above the local critical frequency?

A.
Ionization is not uniform around the globe
B.
A higher frequency cuts through absorption more easily
Correct Answer
C.
The signal enters the ionosphere at an oblique (inclined) angle
D.
The sun's relative position differs between the two locations

B-007-006-004

he 'Critical Frequency' is a measurement of the highest frequency which will be refracted back to Earth when sent straight up at a given time. If a wave enters the ionosphere at a lower angle, a useful refraction may have time to materialize.

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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B-007-006-005

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?

Correct Answer
A.
Listen for 10-metre beacon stations
B.
Listen for WWVH time signals on 15 MHz
C.
Listen for 20-metre beacon stations
D.
Listen for 31-metre broadcast stations

B-007-006-005

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.

Tags: none

B-007-006-006

What usually happens to radio waves with frequencies below the maximum usable frequency (MUF) when they are sent into the ionosphere?

A.
They are changed to a frequency above the MUF
B.
They are completely absorbed by the ionosphere
C.
They pass through the ionosphere
Correct Answer
D.
They are bent back to the Earth

B-007-006-006

As Maximum Usable Frequency (MUF) is the highest frequency usable for sky wave propagation between two points on the globe, 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 the ionosphere.

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

Tags: none

B-007-006-007

At what point in the solar cycle does the 20-metre band usually support worldwide propagation during daylight hours?

A.
Only at the minimum point of the solar cycle
B.
Only at the maximum point of the solar cycle
Correct Answer
C.
At any point in the solar cycle
D.
At the beginning of the solar cycle

B-007-006-007

During solar peaks and solar lows, the 20-metre band (14.0 MHz to 14.35 MHz) usually supports 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.

Tags: none

B-007-006-008

What happens daily when the solar UV radiation increases?

A.
The atmospheric noise level decreases
B.
Ground wave propagation decreases
Correct Answer
C.
The maximum usable frequency increases
D.
Weather in the ionosphere changes

B-007-006-008

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

Tags: none

B-007-006-009

When is propagation on the 80-metre band generally the LEAST effective?

A.
Evening in summer
B.
Evening in winter
Correct Answer
C.
Daytime in summer
D.
Daytime in winter

B-007-006-009

During the summer, two problems can affect 160 m and 80 m: static from lightning (thunderstorms) and D-region absorption. The D region, lowest of the regions, 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.

Tags: none

B-007-006-010

The optimum working frequency provides the best long-range HF communication. Compared with the maximum usable frequency (MUF), it is usually:

A.
half the MUF
B.
double the MUF
Correct Answer
C.
slightly lower
D.
slightly higher

B-007-006-010

As Maximum Usable Frequency (MUF) is the highest frequency usable for sky wave propagation between two points on the globe, 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 the ionosphere.

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

Tags: none

B-007-006-011

During summer daytime, which bands are the most difficult for communications beyond ground wave?

A.
30 metres
B.
20 metres
Correct Answer
C.
160 metres and 80 metres
D.
40 metres

B-007-006-011

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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