HF propagation conditions refer to the factors influencing the behavior and propagation of high-frequency (HF) radio waves globally or within a specific region. Understanding the differences between global and regional HF propagation conditions is important for optimizing HF radio communications and ensuring reliable transmission over long distances.
Global propagation conditions encompass the overall factors affecting HF radio waves on a global scale, including solar and geomagnetic indices, but exclude regional MUF between specific locations. The banner below shows the overall conditions that affect HF radio waves on a global scale.
A banner courtesy of Paul L Herrman, N0NBH.
It shows Solar and geomagnetic indices that influence the global conditions.
Glossary of terms on this banner
- SFI (Solar Flux Index): A measure of solar radio emissions at a wavelength of 10.7 cm, indicating solar activity levels
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- SN (Daily Sunspot Number).
- A is an index indicating the average level for geomagnetic activity; good conditions A < 10
- Kp (K planetary) is an index that indicates disturbances in the Earth’s magnetic field, ranging from 0 (calm) to 9 (severe storm).
Good conditions possible when Kp is less than 3.
- X-ray is the solar flare class that may cause D-region absorption.
- 304A is the solar radiation measured by SEM (Solar EUV Monitor). It affects F-region ionization.
- Ptn Flx: proton flux and Elc Flx: electron flux in the solar wind
- Aurora
refers to auroral activity, which can affect radio wave propagation .
- MUF Boulder is the highest frequency at which HF communication is possible via skywaves over Boulder, Colorado (updated every 15 minutes).
MUF means Maximum Usable Frequency.
- GeoMag Field indicates the activity of the Earth's magnetic field is based
on the Kp-Index.
Possible values: INACTIVE, VERY QUIET, UNSETTLED, ACTIVE, MINOR STORM, MAJOR STORM, SEVERE STORM, or EXTREME STORM. Higher indications can cause HF blackouts and auroral events. Updated every three hours.
- Sig Noise Lvl is the background noise (in S-units) being generated by interaction between the solar wind and the geomagnetic activity. A more active and disturbed solar wind, the greater the noise. Updated every ½ hour.
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Regional HF propagation conditions are the local conditions that affect HF radio waves within a particular area or region. These conditions can vary significantly from the global conditions due to the regional ionospheric state, local topography, tropospheric weather, and other factors. For example, mountain ranges or bodies of water can cause reflection and refraction of HF radio waves, which can affect the angle of incidence and propagation. Similarly, weather phenomena such as thunderstorms and precipitation can cause attenuation or scattering of HF radio waves.
Because regional HF propagation conditions can vary significantly, it's important to consider these factors when planning HF radio communications within a particular region. This may involve selecting the best frequency and mode of propagation for the specific conditions, as well as accounting for any local factors that may affect the behavior of the radio waves.
Conclusion: Both global and regional HF propagation have unique characteristics and challenges. Understanding these differences helps amateur radio operators optimize their communication strategies.
See also an index of terms for HF Radio Propagarion.
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