During an extensive Sporadic-E opening in Australia on the 15th of December 2020, WSPR signals from John VK2IJM and David VK2DVM in Sydney were heard by Peter VK6KXW near Perth in Western Australia.
Timestamp UTC Call MHz SNR Drift Grid Pwr Reporter RGrid km az Mode
2020-12-15 10:36 VK2DVM 144.490519 -25 0 QF56og 10 VK6KXW OF87jr 3199 263 2
2020-12-15 10:16 VK2IJM 144.490507 -8 0 QF56ni 10 VK6KXW OF87jr 3192 263 2
2020-12-15 10:36 VK2DVM 144.490519 -25 0 QF56og 10 VK6KXW OF87jr 3199 263 2
2020-12-15 10:16 VK2IJM 144.490507 -8 0 QF56ni 10 VK6KXW OF87jr 3192 263 2
The path was in the region of 3200 kms which is way beyond the usual 2300km or so one hop distance from Sporadic-E. It seems likely that on this occasion, the most likely propagation mode was double hop Sporadic-E which is very rare at 144 MHz.
It looks as if just one WSPR transmission from each of the VK2 stations was decoded at 10:16 and 10:36 UTC. This was about an hour after sunset in Sydney which is 11 hours ahead of UTC.
It's also worth pointing out that the reports from the WSPRnet website say that the VK2 stations were running just 10 watts.
Tropo?... As the path cross the Great Australian Bight, it's always worth checking to see if that was a factor.
The forecast was for some weak tropo across the Bight but nothing special and it doesn't seem to extend inland.
VK6CPU in Perth was also heard by VK5AYD in Adelaide at around the same time over a distance of 2149 kms which was likely to be via Sporadic-E.
Timestamp UTC Call MHz SNR Drift Grid Pwr Reporter RGrid km az Mode
2020-12-15 10:56 VK6CPU 144.490510 -24 3 OF78wb 5 VK5AYD PF97ja 2149 99 2
It would seem as if double hop Sporadic-E was the most likely mode of propagation.
Update: Just to clarify that when I say double hop Sporadic-E, I am referring to two areas of ionisation that are capable of supporting 144 MHz propagation. The signal may well be chordal i.e. Ground to cloud to cloud to ground ... as opposed to reflecting off the ground at some mid way point.
Links...
1) More info about long distance openings on 144 MHz can be seen on my 144 Page... https://ei7gl.blogspot.com/p/144-mhz.html
