2 posts tagged with "propagation"

Every conversation about HF conditions comes down to four numbers: SFI, SSN, the K index and the A index. They get passed on the air, printed in forecasts and written in logs — but not everyone can read them.

In short: the first two say how much the Sun is giving out (and therefore how dense the ionosphere is), and the last two say how quiet the Earth's magnetic field is (and therefore whether a storm is choking that ionosphere).

Below is a full account of each index: what it means physically, how to read it, what it affects and when it is worth getting on the air. Beside each section there is a live gauge that pulls the current value from NOAA and shows where we stand.

Throughout August 2026 the award “35th anniversary of Ukraine's independence” was on the air. Over 31 days the activators made 17,387 contacts with 8,226 different stations in 99 countries. Every line of the log carries a time, a frequency, a band, a mode, the other station's callsign, its locator and a report. Together they make a fairly rare thing: a month of continuous observation of the short waves, made not by an instrument but by people.

What follows is what can be seen in it. Not “the award was a success” but concrete numbers: when the bands opened, why Saturdays weigh more than the Sun, how far FT8 reaches compared with SSB, and why amateur radio remains a hobby of wealthy countries.