| Time (ET) | Receiver | Distance (mi) | SNR (dB) |
|---|---|---|---|
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Analysing propagation data…
snr + 20·log₁₀(d/d_med)), then bin receivers by bearing — each receiver contributes one vote per bin, regardless of how many spots they sent you.
The number shown is the bin's deviation in dB from your all-bearing mean. Positive lobes = stronger than average; negative dips suggest an antenna null or propagation asymmetry.
Not a pure antenna pattern — receiver site quality, day/night and magnetic-field effects still bleed in, but most stations' antenna patterns dominate.
What is the gray line? (click to expand)
The gray line (also called the terminator) is the boundary between the sunlit and dark sides of Earth, sweeping around the globe as it rotates. At any point on the gray line it is simultaneously sunrise on one edge and sunset on the other.
During daylight, the D-layer of the ionosphere absorbs HF radio signals — this is why long-distance propagation on 30m and 40m is limited during the day. At sunrise, the D-layer evaporates rapidly within minutes. At sunset, it disappears as the sun sets. During these brief windows the absorption vanishes while the F-layer (which reflects signals to distant stations) is still present and dense.
The result: a 30–60 minute window of dramatically enhanced long-distance propagation at dawn and again at dusk. Signals that are normally absorbed can suddenly travel thousands of kilometers farther.
On this chart: the blue line shows median spot distance for each half-hour of the day averaged over the past 7 days. The dashed line is the baseline average (excluding gray-line hours). The gold shaded bands show the ±1.5 hour windows around computed sunrise and sunset. A peak in the blue line that rises above the baseline inside a gold band is a gray-line enhancement event.