Broadcast via WWV and WWVH at 18 and 45 minutes past the hour. This message is updated every 3 hours.
Reports current Solar-terrestrial indinces, Solar Flux, A-index, K-Index, forecast for space weather storms.
Prepared by the US Dept. of Commerce, NOAA, Space Environment Center
WM5R presentation of Introduction to Long-delaye echoes and theories among this propagation effect.
Ionospheric HF Radio Propagation Theory in a Nutshell by Rick Johnson, AE3C
T index explained BY NOAA
History, activity, glossary and modern reseach about suspots
Report of solar & geophysical activity
Online professional-grade high-frequency (3-30 MHz) propagation predictions
This article will help to unravel some of the mysteries as well as giving useful operating tips to maximize your chances of working that rare station by G4UCJ
overview of radio signals and radiowave propagation and how different areas of the atmosphere affect radio communications.
Web based VHF-UHF RF planning powered by SPLAT! and Google Maps. Access via website, Android App or dynamic Google Earth interface.
The Five Most Likely Explanations for Long Delayed Echoes
Solar Flux, Geomagnetic Activity indexes and interpreting their relation
W0RW article that guide you to using beacons to determine dead bands or upcoming propagation openings.
Article on propagation basics. The ground wave used for radio communications signal propagation on the long, and medium wave bands for local radio communications
Flash Movie describing HF (shortwave) radio propagation to beginners. Very helpful aid in understanding.
About greyline propagation in HF bands
Concise guides to radio signal propagation including topics such as the ionosphere, troposhere, ionospheric refraction, E layer, D, layer etc.
Live space weather and propagation data, in RSS (XML) format.
These pages provide general propagation advice for HF communicators. Information available includes inferred global propagation conditions, real time HF fadeout coverage charts, regional ionospheric vertical MUF maps and Hourly Area Prediction charts for Astralia and Asia, Europe and North America
Optimal Working Frequencies (MHz) for High Frequency (HF) / Shortwave Radio. By region, updated monthy.