B-007
B-007
Section B-007-005
How do sunspots change the ionization of the atmosphere?
The number of sunspots visible on the surface of the Sun is 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.
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 solar flux?
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 is the solar-flux index?
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?
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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What effect of the sun's activity influences ionospheric propagation on a daily basis?
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?
Maximum Usable Frequencies (MUF) in the range of 30 to 50 MHz become possible during solar cycle peaks. Stronger ionization allows upper regions of the ionosphere to refract higher frequencies rather than let them escape into space (as is the case during solar cycle lows).
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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All communication frequencies throughout the spectrum are affected in varying degrees by:
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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The ability of the ionosphere to refract high frequency radio signals depends on:
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.
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 major cause of cyclical changes in HF propagation?
Apart from daily variations in solar radiation, HF propagation is impacted by the solar cycles. The duration of the solar cycles varies from 7 to 17 years but the AVERAGE is 11 YEARS.
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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