Radio wave propagation forecast

Real-Time HF Propagation & Solar Forecast

Radio wave propagation on the Shortwave (HF) bands is entirely dependent on the Sun. Solar activity ionizes the Earth's upper atmosphere (the ionosphere), acting like a giant mirror for radio signals. To plan your DX (long-distance) contacts, you need to know the current "space weather."

Live Solar Data & Band Conditions

Below is the real-time space weather widget provided by N0NBH, utilizing live data from NOAA and the Space Weather Prediction Center. This is the gold standard used by ham radio operators worldwide.

Data updates automatically. Provided by Paul L Herrman (N0NBH).

How to Read the Forecast

For a beginner, the numbers on the banner might look confusing. Here is a simplified guide to the most important indicators you need to check before turning on your transceiver:

Indicator	Meaning	What to Look For
SFI (Solar Flux Index)	Measures the total radio emission from the sun. Higher SFI means better ionization.	Above 100 is good. Above 150 means excellent conditions on higher bands (15m, 12m, 10m).
SN (Sunspot Number)	The number of visible sunspots. They emit ultraviolet radiation that charges the ionosphere.	The higher, the better. Above 100 provides great worldwide propagation.
A-Index & K-Index	Measure the stability of the Earth's magnetic field. Solar flares disrupt it, causing radio blackouts.	Lower is better! K-Index < 3 and A-Index < 10 mean stable, quiet bands with low noise.
MUF (Max Usable Frequency)	The highest frequency that can bounce off the ionosphere at a given moment.	If the MUF is 22 MHz, the 20m (14 MHz) and 15m (21 MHz) bands will be open, but the 10m (28 MHz) band will be closed.

Day vs. Night Bands

The bottom section of the widget shows calculated conditions for Day and Night across different wavelengths. A "Fair" or "Good" status means you have a high chance of making DX contacts.

• Daytime Bands (20m, 17m, 15m, 12m, 10m): These rely on the D and E layers of the ionosphere, which are heavily energized by direct sunlight. They usually "close" shortly after sunset.
• Nighttime Bands (160m, 80m, 40m, 30m): Lower frequencies experience high absorption during the day. When the sun goes down, the absorbing D-layer disappears, allowing signals to reach the higher F-layer and bounce across continents.

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