Hello all,
Further to the comment by Marek SQ5BPM
""But,
surprisingly, the path from Greece, southern Spain and Portugal to New
Zealand is ca. 3/4 over the sea. Especially Portugal is interesting as the
path is very close to 20000km and is mostly over the sea in both directions.
Shortest paths on a sphere are not very intuitive hi.""
I would like to draw attention to another factor which comes into play at
least in the case of the Iberian Peninsula.
Porto is almost exactly diametrically opposite to Wellington. The sunrise
in Porto is almost exactly the same and locked to the sunset time in
Wellington,
giving around 5m greyline, and the sunset in Porto is similarly locked to
the sunrise
in Wellington giving no greyline at all. This I believe to be true for the
whole yearly
cycle. If a significant dark path is necessary as it would appear from the
recently
reported captures of DCF39 in New Zealand, I postulate that it is not
possible under
"normal" conditions to achieve longwave communication over the
~20,000km. However
all is not lost as previous experience with 160m showed that sporadic but
very infrequent
communication was possible over this path and at signal strengths that need
some explaining.
Perhaps someone with better understanding of this phenomenon (and better
maths than mine)
could calculate the diameter of the effective "cone of silence" around
diametrically situated stations
and suggest a strategy to exploit whatever phenomenon assisted
communication on 160m.
Please discuss. Plots of Sunrise and Sunset are below.
http://homepage.esoterica.pt/~brian/NZSunRiseSet_1.htm
http://homepage.esoterica.pt/~brian/NZSunRiseSet_2.htm
73, Brian CT1DRP
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