G4NSJ – 10 metres propagation geomagnetic storms WSPR

20/4/25. Strange 10 metre propagation:

During the last week or so, propagation on the higher HF bands, particularly 10 metres, has been affected by severe geomagnetic storms, peaking at G4. This was the reason for low maximum usable frequencies which made DX contacts on the higher HF bands very difficult, if not impossible. You can see on the WSPR Map below that most stations transmitting on 10 metres were not being heard.

For two consecutive days, no one heard my 10m WSPR signals. I thought I had a problem with the antenna. However, on the 17th April, things began to change. My signal was heard by one station, DP0GVN, down in the Antarctic.

Broadcast Bands:

I’ve noticed that the higher frequency broadcast bands have been unusually quiet recently. The 21, 19 and 16 metre bands are usually lively during the day but, not of late. Even the 31 metre band has been dead during the last 7 days.

Update 22/5/25:

The 10 metre band is worse than ever! We are just about at the sunspot maximum but you wouldn’t think so. So, what’s this all about?

The K INDEX:

A low K-index of 0 to 3 signifies quiet geomagnetic conditions, ideal for HF radio propagation. This is particularly good on the higher bands like 20 metres up to 10 metres. Under these stable conditions, signal paths remain consistent, absorption is minimal, and long-distance DX contacts are more reliable, including those via polar and trans-equatorial routes.

When the K-index rises to 4 or 5, geomagnetic activity becomes unsettled. This leads to increased signal absorption, especially on lower bands such as 160m and 80m. Signal fading, particularly along polar paths.

At high K-index values, 6 to 9, geomagnetic storms can severely impact HF communications. Absorption on low bands often becomes extreme, rendering 160m and 80m virtually unusable. Polar blackouts disrupt transpolar DX routes, while bands above 20m become increasingly unreliable, plagued by deep fades and fluctuating signals.