[HCDX] Re: Antipodal Focusing
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[HCDX] Re: Antipodal Focusing
Sorry to break this to you, but Thailand is nowhere near antipodal from the
US. For starters both are in the Northern Hemisphere... Unfortunately there
is little land on the opposite side of the globe from the USA --- in the
Indian Ocean.
73, Glenn Hauser
Yes Radio Thailand on 7260 kc at my local sunrise sure is stable here in
Central Florida, even more so then R. Australia on 9580 kc. There is a
propagation mode called anti-podal focusing. If you are at or very near the
opposite side of the planet from the station you are receiving from and the
aurora ovals are retracted, the RF signal can travel on all available
geometric (GC) great circle paths, all coming together at the opposite side
of the planet and adding up to a big signal. Antipodal focusing may explain
Radio Thailand's big signal here in the U.S. Antipodal focusing is best at
the fall/spring equinox of which we are fast approaching.
A neat HF propagation project would be to keep track of Radio Thailand's
7260 kc signal every morning at local sunrise here in the U.S. for 365 days
and plot it's signal strength versus the Ap index.
73,
Thomas F. Giella, KN4LF
Plant City, FL, USA
EL87WX
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