Wednesday 15th April 2020. This was one of those days where it seemed to be extremely quiet on 28 MHz. As usual, I had left the radio on the FT8 frequency of 28.074 MHz all day monitoring.
When I checked at the end of the day, I had heard a few European stations possibly via meteor scatter or possibly via aircraft reflections for the closer ones.
However when I checked the WSJT-X programme, I had two decodes as well from Africa, 9J2BS in Zambia and ZS1DX in Cape Twon, South Africa.
152600 -20 -2.3 1920 ~ KC3LEE 9J2BS -07
154230 -17 -0.4 2436 ~ IT9IHB ZS1DX RR73
I had decoded just one 15-second transmission from each station and as can be seen from the signal levels... -20dB and -17dB, the signals were buried well into the noise and well below a level I could hear by ear.
Propagation... When I checked who else had heard ZS1DX, I got the map shown top right above. Notice the footprint in the UK. It is a long narrow corridor and it seems to have been around the same time as when I heard ZS1DX, i.e. 15:30 UTC.
As for what happened? I suspect there was either a F2 or TEP opening to from Cape Town to the southern part of Europe. There was probably a weak Sporadic-E cloud somewhere over the western part of France where the MUF got up as high as 28 MHz for a while to allow the ZS1DX signal to extend from southern Europe up into the UK.
As with a lot of Sporadic-E openings, the Sporadic-E cloud was small so the footprint in the UK was small.... or at least narrow and elongated as I'd expect.
As to how I heard ZS1DX, it was possible just one lucky meteor burst over the Bay of Biscay to the south. This allowed me to hear for 15 seconds what the stations in Spain were hearing to the south. It's also possible that there was some weak Sporadic-E that got intense enough for a very short period to allow propagation of 28 MHz signals.
As for 9J2BS, there was no similar opening to the UK or northern Europe for him according to the PSK Reporter website.
Very interesting! I think both your options for what happened are entirely plausible. But which one it was? Who can say?
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