G3A: Sunspots and solar radiation; ionospheric disturbances; propagation forecasting and indices
G3A01:
What can be done at an amateur station to continue communications during a sudden ionospheric disturbance?
Try a higher frequency
Try the other sideband
Try a different antenna polarization
Try a different frequency shift
G3A02:
What effect does a Sudden Ionospheric Disturbance (SID) have on the daytime ionospheric propagation of HF radio waves?
It disrupts signals on lower frequencies more than those on higher frequencies
It disrupts higher-latitude paths more than lower-latitude paths
It disrupts communications via satellite more than direct communications
None, because only areas on the night side of the Earth are affected
G3A03:
How long does it take the increased ultraviolet and X-ray radiation from solar flares to affect radio-wave propagation on the Earth?
Approximately 8 minutes
28 days
Several hours depending on the position of the Earth in its orbit
20 to 40 hours after the radiation reaches the Earth
G3A04:
What is measured by the solar flux index?
The radio energy emitted by the sun
The density of the sun's magnetic field
The number of sunspots on the side of the sun facing the Earth
A measure of the tilt of the Earth's ionosphere on the side toward the sun
G3A05:
What is the solar-flux index?
A measure of solar activity at 10.7 cm
A measure of the highest frequency that is useful for ionospheric propagation between two points on the Earth
A count of sunspots which is adjusted for solar emissions
Another name for the American sunspot number
G3A06:
What is a geomagnetic disturbance?
A significant change in the Earth's magnetic field over a short period of time
A sudden drop in the solar-flux index
A shifting of the Earth's magnetic pole
Ripples in the ionosphere
G3A07:
Which latitudes have propagation paths that are more sensitive to geomagnetic disturbances?
Those greater than 45 degrees North or South latitude
Those between 5 and 45 degrees North or South latitude
Those at or very near to the equator
All paths are affected equally
G3A08:
What can be an effect of a geomagnetic storm on radio-wave propagation?
Degraded high-latitude HF propagation
Improved high-latitude HF propagation
Improved ground-wave propagation
Improved chances of UHF ducting
G3A09:
What is the effect on radio communications when sunspot numbers are high?
Long-distance communication in the upper HF and lower VHF range is enhanced
High-frequency radio signals become weak and distorted
Frequencies above 300 MHz become usable for long-distance communication
Long-distance communication in the upper HF and lower VHF range is diminished
G3A10:
What is the sunspot number?
A measure of solar activity based on counting sunspots and sunspot groups
A 3 digit identifier which is used to track individual sunspots
A measure of the radio flux from the sun measured at 10.7 cm
A measure of the sunspot count based on radio flux measurements
G3A11:
How long is the typical sunspot cycle?
Approximately 11 years
Approximately 8 minutes
Between 20 and 40 hours
Approximately 28 days
G3A12:
What is the K-index?
A measure of the short term stability of the Earth's magnetic field
An index of the relative position of sunspots on the surface of the sun
A measure of the stability of the sun's magnetic field
An index of solar radio flux measured at Boulder, Colorado
G3A13:
What is the A-index?
An indicator of the long term stability of the Earth's geomagnetic field
An index of the relative position of sunspots on the surface of the sun
The amount of polarization of the sun's electric field
An index of solar radio flux measured at Boulder, Colorado
G3A14:
How are radio communications usually affected by the charged particles that reach the Earth from solar coronal holes?
HF communications are disturbed
HF communications are improved
VHF/UHF ducting is improved
VHF/UHF ducting is disturbed
G3A15:
How long does it take charged particles from Coronal Mass Ejections to affect radio-wave propagation on the Earth?
20 to 40 hours
28 days
14 days
The effect is instantaneous
G3A16:
What is a possible benefit to radio communications resulting from periods of high geomagnetic activity?
Aurora that can reflect VHF signals
Higher signal strength for HF signals passing through the polar regions
Improved HF long path propagation
Reduced long delayed echoes
G3A17:
At what point in the solar cycle does the 20 meter band usually support worldwide propagation during daylight hours?
At any point in the solar cycle
At the summer solstice
Only at the maximum point of the solar cycle
Only at the minimum point of the solar cycle
G3A18:
If the HF radio-wave propagation (skip) is generally good on the 24-MHz and 28-MHz bands for several days, when might you expect a similar condition to occur?
28 days later
7 days later
14 days later
90 days later
G3A19:
Which frequencies are least reliable for long distance communications during periods of low solar activity?
Frequencies above 20 MHz
Frequencies below 3.5 MHz
Frequencies near 3.5 MHz
Frequencies at or above 10 MHz
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