# HF Radio Propagation Predictions

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HF radio propagation predictions based on the "ITU method" (ITU-R P.533)
must be calculated using the 12-month sliding average SIDC Sunspot number
(formerly called 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 monthy meadians, i.e. on
15 days of the month "conditions" will be better and on the remaining
15 days "conditions" will be worse than predicted.

Download predicted sunspot numbers