Monday, 21 August 2017

Solar Eclipse - WSPR Results

Despite being across the Atlantic, the great US eclipse of August 21 2017 was an opportunity to test for any propagation peculiarities into the EU that arise from temporary darkness.

I had a long thought about which band to listen out on for this event.  There was a lot of ignoring to do - not of reason, but of opinion flooding out from the US which, understandably enough, was heavily biased towards the low bands.

I settled on 20m.

Interestingly, there did seem to be a marked, transient change in propagation from the US west coast.  As soon as totality hit Oregon (17:16UT), W6BSD (a long way off the totality line) and, a few moment later, K7RE (also way off totality), popped up from nowhere.  W6BSD was very weak at -28dB S/N, but K7RE hit -15dB at 17:3UT, dropping off a cliff to -24dB ten minutes later.  K7RE did not appear again for another two hours, when the eclipse effects were well over and very shallow-angle local sunset propagation briefly took over.

How MUF ought to have worked out inthe absence of an eclipse.

It's clear that essentially no station directly in the path of totality was heard during the eclipse, even though many stations prior to the eclipse were being heard well.  The propagation prediction in terms of MUF confirms the experience that signals from the US ought to have been strong until the eclipse ended around UK sunset time.  That they were not suggests strongly that transient darkness was suppressing the MUF and, therefore, the received signals.

KG6MC, a station just off the totality path, was heard before, through, and after the eclipse. The overall pattern was quite noisy but did show a distinct reduction in signal strength when it could have been expected to be increasing.

N4EFS was the best example I heard, in that he was received steadily for hours running up to the eclipse, and then vanished about 45 minutes before totality.  Again, that is not expected by reference to experience of propagation or the MUF forecast.

I'm sure there will be a more robust and detailed assessment of any effects in the US, where they can be expected to be strong down to the low bands.  It remains to be seen if anyone had any interest in a proper assessment across to the EU.

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