On Wed, 20 Aug 2003 22:09:58 +0200, "Keith Olivier"
wrote:

Peter

I used to know the proper description for this, but I'm a bit rusty on
amateur radio now. Basically what happens is that in mid summer, under the
influence if intense solar radiation the MUF (maximum upper frequency) which
can be reflected of the ionosphere increases. It can reach such high levels
that signals at the 120-160Mhz level can be reflected back down to earth
(normally they would go straight out into space) and can then be heard by
people a considerable distance away.

Back in the CB radio craze days of the 1970's this phenominon was
called "skip" from the signal "skipping" off the ionosphere and
travelling in a reflected angle path instead of line-of-sight.