Hi Mark,
Very true on the HF bands. but not true on 160 meters at mid to
high latitudes.
On 160 meters both entry and exit polarization tend to be vertically
polarized at mid to high latitudes. This also applies to the exit from
the ionosphere and re-entry into the ionosphere of intermediate hops
over land and sea at mid to high latitudes.
Horizontal polarization is much more efficiently reflected by intermediate
hops over land, both polarizations are efficiently reflected over sea.
Unfortunately, horizontal polarization doesn't exit and re-enter the ionosphere
efficiently on 160 meters at mid to high latitudes, so most of the energy
re-entering the ionosphere after an intermediate hop is inefficiently
reflected vertical polarization at mid and high latitudes.
This means that long distance propagation over the North Atlantic
on 160 meters is much more efficient from W1 and VE1 where the first
intermediate hop is over the Atlantic Ocean, while propagation from the
other US and VE call areas has its first hop over a much less efficient land.
160 meter long distance propagation is much more efficient to the south
73
Frank
W3LPL
----- Original Message -----
From: "Mark K3MSB" <mark.k3msb@gmail.com>
To: "Carl Luetzelschwab" <carlluetzelschwab@gmail.com>
Cc: "topBand List" <topband@contesting.com>
Sent: Thursday, March 29, 2018 10:20:11 PM
Subject: Re: Topband: 160m polarization and elevation angles
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 <
carlluetzelschwab@gmail.com> 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
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