Hi Carl,
I'm afraid SnapMAX is just no help at all on that one. The IFRB
etc. data gives me no basis in there for extrapolation. It's an empirical
approach in which the data is all from the non-interfering broadcast
station regime and that sure doesn't head out to anywhere near 12000 km.
The curves go to 3500 km, and I'd cheerfully push to 4000 and might not
blink too hard at 5000, but 12000?? Can't see it, unfortunately.
But having said that, let's do it anyway <grin>. The curves look as if
they might be settling down, and I'd not know why, to what looks, on the
face of it, as if it could become a steady fall-off in remote field
strength, rather larger than we'd attribute to pure reciprocal distance.
Making the enormous assumption of a continued straight line of the same
slope and ignoring noise, as you were doing, and for 1 Kw and verticals,
it looks as if a semi-reasonable extrapolation would give us a field
strength of 1 uV/m at 4500 km. Now, moving steadfastly on to a totally
unreasonable extrapolation, that could take us out to a field strength of
20 dB down on 1 uV/m at 7000 km and 40 dB down on 1 uV/m (!!!!) at let's
say around 10,000 km. Scientific it sure ain't, but can you do anything
with that?
I'll rapidly restate that that's not SnapMAX, but just an ad hoc look at
the curves that I based SnapMAX MF signal losses on. I shudder a little at
what I just did, but what's the point of hamming if we don't push the
envelope a tad!!
73 de Crawford WA3ZKZ, VP8CMY, ex G4ARR jcbmck@udel.edu
"If a man will begin with certainties, he shall end in doubts;
but if he will be content to begin with doubts he shall
end in certainties." Francis Bacon
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