Understanding 11-Metre Propagation
Why 27 MHz sometimes reaches across countries and continents—and why the band can suddenly go quiet.
The short version
Radio propagation is how a signal travels between stations. At 27 MHz, contacts can be local by ground wave or travel much farther when ionospheric conditions support skywave propagation.
Sporadic-E
Sporadic-E involves patches of unusually strong ionisation in the E region of the ionosphere. It can support unexpected openings, especially during warmer months in many mid-latitude regions. It is variable and cannot be guaranteed.
F-layer and solar conditions
The ionosphere’s higher regions can support long-distance HF paths when conditions are suitable. Solar activity influences the ionosphere, but a high solar index does not guarantee a good opening on a particular path or at a particular time.
Use indicators carefully
Solar flux, sunspot numbers and planetary Kp describe different aspects of solar and geomagnetic conditions. NOAA explains that Kp measures geomagnetic disturbance; its effect on an individual 11-metre path is not a simple yes/no prediction.
What to record
Log date and UTC time, your location, the station heard, frequency, mode, signal quality and whether the contact was completed. Repeated observations are more useful than a single forecast.
Further reading
Always check current rules for the country and radio service you are using. A community convention or software feature is not proof that a transmission is authorised.
This guide is educational and may need updating as regulations, software and community information change. Check linked primary sources before relying on technical or regulatory details.