Jose,
I am only presenting the possibility that if the ionosphere (where 160 propagation happens) isn't uniformly smooth and instead consists of "warps, wrinkles and tilts" that in a *dynamic ionosphere*, this could be at least one reason we are experiencing slow fades. Elliptical polarization, assuming that it is ever changing, could provide yet another degree of selective fading. I'm don't think I *totally* understand why KL7AJ says that "at HF the ionosphere forbids the propagation of linearly polarized signals". If at the magnetic equator, and signals were East to West to equal the earth magnetic tilt of the signals, it seems that at an instance in time that a linear polarized signal could happen. But that may be nit picking. Jim - KR9U From: JC N4IS [mailto:n...@comcast.net] Sent: Wednesday, February 05, 2014 10:45 PM To: jbw...@comcast.net; 'Tom W8JI'; he...@vitelcom.net; topband@contesting.com Subject: RE: Topband: circular polarization on 160m James You brought a good article about HF propagation, however the behavor on 160m is different from HF. If you check on the KL7A arcticle figure 1 what is happening between 1 and 2 MHz you can see that the green and red does not behaivor the same way as above 2 MHz. This subject is more complex because there us no shirt answer, actualy between 1 and 2 MHz. the ionosphere does not support linear polariration wave. The wave are actualy eliptical and not circular for most directions. You can check the long answer on the "must read book" from NM7M . R Brown 'The Big Gun's Guied to Low Band Propagation" . Magneto-iomic Theory pag 47 to 56 ; and Power coupling pag 57. Thanks to Karl. K9LA, the book is available on his also must read site on the 160m link http://k9la.us/html/160m.html Regards JC N4IS _________________ Topband Reflector Archives - http://www.contesting.com/_topband