On Thu, 24 Jan 2008 07:21:21 +0000, Mark Carver
wrote:

Don Pearce wrote:

Most of the time yes, but I've studied an awful lot of anomalous
propagation over the years and particularly around sunset it is not
unusual to get signals coming through from much further at high
strength for a few seconds.

Yes, my radio has been unable to decode the BBC and D1 muxes for spells during
severe 'lift' conditions. The metering menus showed 100% signal, but 0%
quality, normally it's 100/100. I remember one day in August 2003, DAB was
unusable, as was FM, as as DTT, the only stable reception was D-Sat, (and AM :-) )

Spot on! The satellite signals come down at such a steep angle that
they don't get trapped in the atmospheric waveguide ducts that form.
And AM wavelengths are just too big to fit. It is just the daily rise
and fall of the ionosphere that dictates how far that goes.

d

--
Pearce Consulting
http://www.pearce.uk.com