In message , "Jim, K7JEB"
writes

Land mobile and aircraft radios almost invariably
use vertically polarized antennas. That wave
polarization is generally maintained under conditions
of reflection and refraction over short- and long-
distance paths. For polarization rotation to occur
during propagation, the medium generally must be
birefringent (eg: the ionosphere). This rarely occurs
with terrestrial waves.

The local 2m beacon ( about 80 miles north and shielded by a local hill
) here is horizontally polarised. However if I beam south it is much
stronger on vertical polarisation. I have no idea why.

Brian GM4DIJ
--
Brian Howie