From Dave G3YMC

Markus, DF6NM wrote:

But maybe the scattering centers are not only the rocks themselves: Bob
Brown, NM7M, had a fascinating article in QST 12/99 "Bubbles in the Ozone
Layer", suggesting that turbulent air-flow over mountain ranges could cause
bubbles affecting the ultraviolet irradiation to the D-Layer before

sunrise.

I also found the QST article fascinating.  For those who haven't seen it it
concerned reception of a commercial station on 55.5kHz in California by the
author in Washington state.  He observed an interesting pattern to the
signal strength of this station around dawn caused he surmised by enhanced
propogation in the ozone layer over the Rocky Mountains to the east.  My
first thoughts were that this was probably not relevant to us in Europe, but
perhaps it may well be the very mechanism which causes the big signal
changes we are seeing on Toni's signal close to the Alps, and some of the
73kHz effects.

I don't know whether the article is available on the ARRL site, it is
actually 3 pages so would be a bit big to send as an attachment.

Congratulations to all involved in the recent 73 activity.  It has convinced
me I am wasting my time there when I only hear s4 signals from the locals!
I assume local noise is the limiting factor, but I did use to hear a lot
better a couple of years ago.

73s Dave
[email protected]
http://ourworld.compuserve.com/homepages/sergeantd