Canadian Basic Qualification pool, section B-007-004

Subelement B-007

B-007

Section B-007-004

B-007-004-001

What effect does the D region of the ionosphere have on lower frequency HF waves in the daytime?

Correct Answer
A.
It absorbs the waves
B.
It bends the radio waves out into space
C.
It refracts the radio waves back to Earth
D.
It distorts the waves

B-007-004-001

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.

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B-007-004-002

Why can you not hear distant 160-metre and AM broadcast stations during daytime hours?

A.
The presence of ionized clouds in the E region
Correct Answer
B.
The ionization of the D region
C.
The weather below the ionosphere
D.
The splitting of the F region into two sub-regions

B-007-004-002

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.

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B-007-004-003

A radio transmission may follow two or more different paths during propagation, and this may result in phase differences at the receiver. What is the effect at the receiver?

A.
Intermodulation
B.
Absorption
Correct Answer
C.
Fading
D.
Wavering

B-007-004-003

Parts of a wave arriving with differences in phase (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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B-007-004-004

While using a 2-metre hand-held transceiver in an urban setting, you notice that moving less than one metre can severely attenuate your received signal. What is the likely cause?

A.
Underground conduits change ground conductivity
B.
Overhead power lines create a Faraday cage
C.
Passing vehicles absorb the radio signals
Correct Answer
D.
Signals arriving on different paths cancel one another

B-007-004-004

When copies of a radio signal arrive at your receiver after following different paths, different distances can lead to phase differences (multipath propagation). Copies of a signal with opposing phases cancel one another.

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-007-004-005

A transmitted radio signal reaches a receiver by both one-hop and two-hop skip paths. What can small changes in the ionosphere cause?

A.
Consistently weaker signals
B.
A shift in signal frequency
C.
Consistently stronger signals
Correct Answer
D.
Variations in signal strength

B-007-004-005

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

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-007-004-006

What can be done to continue HF communications during a sudden ionospheric disturbance (SID)?

Correct Answer
A.
Try a higher frequency band
B.
Try a different antenna polarization
C.
Try the other sideband
D.
Try a different frequency shift

B-007-004-006

A Sudden Ionospheric Disturbance is a sudden rise in radiation, due to solar flares, which increases D-region 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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B-007-004-007

On the VHF and UHF bands, the polarization of the receiving antenna in relation to the transmitting antenna is very important, yet on HF bands it is relatively unimportant. Why is that so?

A.
The refraction forces the wave's polarization to vertical
B.
The polarization of ground waves and ionospheric waves continually varies
Correct Answer
C.
The refraction in the ionosphere changes the wave's polarization
D.
The polarization of ionospheric waves varies depending on the entry angle into the refracting region

B-007-004-007

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

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

Tags: none

B-007-004-008

What causes selective fading?

A.
Small changes in directional antenna heading at the receiving station
Correct Answer
B.
Phase differences between radio wave components of the same transmission, as experienced at the receiving station
C.
Time differences between the receiving and transmitting stations
D.
Large changes in the height of the ionosphere at the receiving station ordinarily occurring shortly before sunrise and sunset

B-007-004-008

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-007-004-009

How does the bandwidth of a transmitted signal affect selective fading?

A.
It is the same for both wide and narrow bandwidths
Correct Answer
B.
It is more pronounced at wide bandwidths
C.
Only the receiver bandwidth determines the selective fading effect
D.
It is more pronounced at narrow bandwidths

B-007-004-009

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

Tags: none

B-007-004-010

What effect do refraction, reflection and Faraday rotation have on a radio wave?

A.
Change the wavelength
Correct Answer
B.
Change the polarization
C.
Increase the speed of propagation
D.
Increase the occupied bandwidth

B-007-004-010

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

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

Tags: none

B-007-004-011

If a radio transmission follows two or more different paths during propagation, the received signal may degrade due to fading. What other type of degradation can occur?

Correct Answer
A.
Phase-shift distortion
B.
Frequency shift
C.
Heterodyne squeal
D.
Higher noise floor

B-007-004-011

"Phase shift distortion, also known as 'envelope delay distortion', is where the propagation time of different frequencies through an audio communications link varies. For example, a 1 kHz frequency may take 0.5 ms to propagate through a radio link while a 2 kHz may take 1.5 ms to propagate through the same link. This plays havoc with a digital signal waveform, as all associated harmonics become distorted." [Practical Radio Engineering and Telemetry for Industry, David Bailey, Elsevier, 2003]

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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