Hi all,
there I am posting another interesting comment from Peter, G3PLX about the GL phenomenon. The original article I posted already here on the blog:
http://60mband.blogspot.com/2011/02/sunset-watchers-on-5mhz-by-peter-g3plx.html
Petr:
I have not done any study of greyline propagation so I cannot say much about it, but I am sure that there is nothing 'magic' about the exact local sunset time, since the path is not at ground-level but high in the sky. In the case of long distance paths, there will be a big effect of the D-layer absorption, and the D-layer is much lower than the F-layer so the D-layer sunset will be only about half an hour later than at the ground and not an hour or more as it is at the F-layer height.
But, as I said in my posting, that's not the whole story and there is no sudden 'best time' at sunset, even at D-layer sunset. The D-layer absorption is getting lower and lower, starting well before the sun sets and it doesn't reach the minimum absorption until some time after sunset, so it's not clear how the 'best greyline time' will relate to the exact sunset time. If your experience is that there is a peak in the signals, then that must mean that there is another effect which is making the signals weaker AFTER darkness comes, and the peak that you experience is the overlap between (or the gap between..) the two effects. For the higher bands it may be that this second effect is the F-layer MUF dropping through the band, but I don't think this
can be true for 160m dx, so I cannot guess the answer.
But for sure there is no good reason to set your clock too accurately!
Start listening well before sunset and keep listening until much later!
73,
Peter, G3PLX
It will be very helpful to get some comments from another DXers regarding the SS/SR effect on the propagation specially on the LF and mainly over here on 60m band.
Do not hesitate to pot Your comment below or let me know by email I can post it on the blog to share with all of us.
73 - Petr, OK1RP
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