How the signal actually got here
Notes from listening in Telford — what the signal sounds like, then the weather or solar physics that usually goes with it.
Strong, steady signals with little fading. They can sit there for hours.
A temperature inversion: air above hotter than air below. Two common stacks:
| Scenario 1 | Scenario 2 |
|---|---|
| Upper troposphere | |
| Warmer & drier | Normal temperature |
| Colder & wetter | Warmer & drier |
| Warmer & drier | Colder & wetter (fog) |
| Ground | |
Relative barometric pressure at or above 1020 hPa is typical when tropo shows up.
E-layer reflections are often over in minutes. They build to a strong signal and fade as quickly as they arrived.
The notes below are patterns from watching what seems to trigger Es — not a textbook.
Notable daytime windows, May–September:
Can be triggered by intense thunderstorms. The mid-point between two DX stations is often where the storm is. X marks storm activity:
Can follow a sudden rise in barometric pressure — around 20 hPa in two days:
Similar to sporadic E, except the signals flutter in strength rather than fading in and out.
Solar flares energising the E layer.