HF Radio Propagation Predictions
and Space Weather
HF radio propagation predictions based on the „ITU method“ (ITU-R P.533-11) must be calculated using the 13-month sliding average SIDC Sunspot number (formerly called the Zurich Sunspot number). The reason is that the original theory and underlying data in the ITU predictions are based on exactly this number and thus alternative measures of the solar activity (actual sunspot numbers, Boulder Sunspot numbers, solar flux, etc.) will not yield correct results. On the bottom of this page regularly updated predictions of the Sunspot Numbers can be downloaded.
It must be remembered that the predictions are monthly medians, i.e. on 15 days of the month “conditions“ will be better and on the remaining 15 days “conditions“ will be worse than predicted.`