Carl I learned that polarization is not predictable after the first ionospheric bounce.
73 Mark K3MSB On Thu, Mar 29, 2018 at 1:30 PM, Carl Luetzelschwab < [email protected]> wrote: > Polarization - As Jerry K4SAV stated, the electron gyro-frequency plays an > important role on 160m since our ionosphere is immersed in a magnetic field > - it also affects ionospheric absorption and refraction. For those of us at > mid to high latitudes, vertical polarization on 160m is *theoretically* > optimum since it couples the most energy to the limiting polarization at > the entrance to the ionosphere. I don't understand Mark K3MSB's comment > about the polarization terms disappearing unless it has to do with that > fact that the polarization going up to the ionosphere has nothing to do > with the polarization going thru the ionosphere (which is dictated by the > ionosphere). > > Elevation angles - Ray tracing shows that elevation angles up to about 10 > degrees are E hops since there is still enough E region ionization at night > to refract 160m. I don't know how important these E hops are - probably > okay for short distance, but the losses (absorption and ground reflection) > add up quickly for the longer distances. Above 15 degrees or so we get F > hops. From 10-15 degrees is where ducting occurs in the electron density > valley above the nighttime E region. Ducting in the valley likely requires > shallow angles. But when a signal gets dumped out of the duct, that > suggests a higher down-coming angle. > > K4SAV said it best: ". . . and the real world on 160 is very complicated." > > Carl K9LA > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > _________________ Topband Reflector Archives - http://www.contesting.com/_topband
