> >In my experience, cross-polarized antenna systems (those with
> >simultaneous in-phase vertical and horizontal components)
>
> Isn't that just diagonal polarization? You can't have multiple linear
> polarization orientations; that's the whole point of circular
> polarization.
>
> Bob NO6B
Very astute question there Bob, and there are actually two schools of
thought (and the associated debates) on that very matter. If the two
radiators could be considered point sources that are coincident, then yes,
you'd have slant polarization due to the E&M fields adding directly. If you
don't assume them to be coincident sources, then you just have two
orthogonal linear polarizations that can be treated separately. That's the
simplified version of the way most seem to view the topic, but the grey area
comes when you try to gauge "how close is close enough to consider them to
be concicident".
In most dual-polarization (non-circular, non-elliptical) FM arrays, there is
little attention paid to coincidence of the radiators, and due to pattern
distortion caused by the mounting structure, or even due to intentionally
combining a non-directional radiator of one polarization with a directional
radiator of another polarization, treating them as separate Hpol and Vpol
radiators/fields is likely a more realistic approximation. As such, Steve's
comment about mixed linear polarizations yielding less predicable results
than true Cpol/Epol are on the money.
--- Jeff WN3A
