Yuri, K3BU wrote:
"Recent studies found efficiency of various polarizations based on
geographical location, related to geomagnetic fields (gyrofrequency).

Do antenna modelimg programs adjust for gyrofrequencies? I can readily
see that soil conductivity at a geographical location would affect
efficiency and perhaps the polarization choice.

John H. Nelson, RCA Short-Wave Radio Propagation Analyst, found that
those signals which pass through or close to the auroral zone suffer the
greatest degradation. If the signal must take a great circle route over
the North Polar region, problems increase.

Nelson also found that propagation here on the earth correlated with the
relative positions of the planets in the solar system. Be this astronomy
or astrology, it allowed Nelson to make pretty good radio propagation
forecasts. See: "The Propagation Wizard`s Handbook", a "73" publication
by J.H. Nelson.

Best regards, Richard Harrison, KB5WZI