↳ ↑ Global versus Regional
HF Propagation Conditions

This page is part of the project "Understanding HF Propagation."
by Doron Tal, 4X4XM

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 popular banner courtesy of Paul L Herrman, N0NBH.
Figure 1: Solar and geomagnetic indices that influence the global conditions.
This banner is divided into three panels:
  1. The left panel displays solar indices (SFI, SN, X-Ray, and 304Å @SEM), geomagnetic indices (A&K Plntry), space weather indices (Ptn Flx, Elc Flx), Aurora, and the MUF above Boulder, CO. Glossary of these terms:
    • SFI (Solar Flux Index): A measure of solar radio emissions at a wavelength of 10.7 cm, indicating solar activity levels ↗.
    • 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 current solar flare class (enhances the 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).
    2.  
  2. In the middle, there is a "red" image of the current solar corona that represents radiation strength at 304 Ångstrom.
    3.  
  3. The right side of the banner displays the calculated global HF conditions on eight ham bands.
    The calculated conditions are just an estimate and quite different from real-world conditions.
    4. The last two indicators on the right panel are
    * The GeoMag Field: Reflects the current activity level of Earth's magnetic field, based on the Kp-Index.
    Possible values include INACTIVE, VERY QUIET, UNSETTLED, ACTIVE, MINOR STORM, MAJOR STORM, SEVERE STORM, and EXTREME STORM. This indicator updates every three hours. Storm-level readings are typically associated with high-frequency (HF) radio fadeouts and auroral phenomena.
    * Sig Noise Lvl: Represents the background noise level (measured in S-units) caused by interactions between the solar wind and geomagnetic activity. Increased solar wind activity leads to higher noise levels. This data refreshes every 30 minutes.

Why do the regional conditions vary significantly from the calculated values shown in Figure 1?

T Index Map
Figure 2: Online T Index Map ↗ courtesy of ASWFC; Updates every 15 minutes

Click on Figure 2 to read explanations.

Regional HF propagation conditions are the local conditions that affect HF radio waves within a particular area or region.


Figure 3: Animated MUF 3000 km propagation map in the last 24 hours courtesy of Roland Gafner, HB9VQQ
Figure 3 illustrates dynamically how the HF conditions vary significantly from the global conditions. 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.

The project "Understanding HF Propagation" focuses on near-real-time indicators and explains what they mean.
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