Interesting thread, one poster mentioned work by John Wang / FCC on MF-AM
field strength prediction curves.
I don't recall sighting that work, but prior to the 1975 Regional
Administrative Broadcasting Conference in Geneva (Regions 1 & 3) there was
considerable work done, both theory and measurements, on "excess
polarization coupling loss" which is a non-reciprocal phenomenon in
propagation, dependent, amongst other things, upon the angle of propagation
with respect to the geomagnetic equator and proximity to the gyrofrequency.
While there was much dispute as to magnitude, the existence of the
phenomenon was always accepted and an algorithm was ultimately agreed.
That algorithm was also accepted in the 1981 RABC in Rio de Janeiro for
Region 2, although for international coordination purposes the value was set
to 0.
I seem to recall that Phil Knight of the BBC Research Department led much of
that work and the RD reports are all now on-line.
The algorithms have also been incorporated into the ITU-R P series
recommendations for MF-AM Skywave field strength prediction. Do a google on
"excess polarization coupling loss" also polarisation.
Regards
Sam Dellit formerly VK4ZSS now Canberra, Australia
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