Thank you Richard, and the others, for digging out and presenting the
information from which I can deduce a ball-park figure.

My original figure of 5 dB per hop for a ground reflection was
slightly too high. It's nearer to 3.5 dB. I'm still thinking about
it. But 4 dB is near enough. Not that it matters very much.

I deduced 5 dB from my experience of signal strengths received from
such places as the antipodes and the Western US states. It's not
surprising hopping across just the North Atlantic results in zero dB
loss.

The excess path loss, over and above spreading loss, must be due to
ground reflection losses. Just calculate backwards from received
signal strength, path distance and the probable number of hops.

It's easy to do this with dedicated computer programs.

For very long distance paths assume that half the ground reflections
are due to sea/ocean water and the other half is due to land masses
and you won't go far wrong. Ground reflection losses at the
transmitting and receiving sites can be ignored. Or such losses can
be lumped together to constitute another complete hop.

I needed the information to include in a simple program which predicts
(approximately) path loss for multi-hop propagation. Program users
cannot be expected to know incidence angles, ground conductivity and
permittivity, Brewster angles etc, for every hop along a route. Some
guesswork is needed on the part of the programmer to make a program
useful.

Despite your continuing abuse of the English language I know you are
quite capable of understanding the foregoing waffle.

I'm on South Eastern Australian Merlot tonight. Hic!

I think the Chinese will be coming along shortly with their own high
quality stuff. They are not just becoming adept with their high
technology. Californian wine growers should look to their laurels.
But no doubt you are all more immediately concerned with the price of
oil, the gas in your tanks, and from where it may be obtained. Iraq
and Iran for example.
----
Reg, G4FGQ