Re: wave polarisation


<wimabctel@xxxxxxxxx> wrote news:2d223e1f-4f8d-43b6-854d-f77febc7b633@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On 9 mayo, 20:34, Szczepan BiaĹ?ek <sz.bia...@xxxxx> wrote:
 <wimabc...@xxxxxxxxx> wrotenews:c2a4968f-da6c-49ee-9887-9c3a53d33ceb@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On 9 mayo, 10:02, Szczepan BiaŠŠek <sz.bia...@xxxxx> wrote:



> U¢¯ytkownik <wimabc...@xxxxxxxxx> napisaŠø w
> wiadomo¢�cinews:e1617758-86bf-4564-bcc8-8784d70cd9d5@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> On 8 mayo, 10:35, Szczepan BiaŠøek <sz.bia...@xxxxx> wrote:

> >> I start reading about acoustic analogy.
> > I found that: "Over long distances, the atmosphere can cause the
> > polarization of a radio wave to fluctuate, so the distinction between
> > horizontal and vertical becomes less significant."
> > From:http://whatis.techtarget.com/definition/0,,sid9_gci843762,00.html

> >> The my question are:
> > 1. What means "long distances" in km (or miles),
> > 2. What is the best orientation of the antenna for long distances.
> >> S*
> >Hello,
> >Under normal circumstances, polarization change in line-off-site

> conditions (think of max 40 mile) is not that much, so antenna
> polarization does matter (unless you use at least circular
> polarization on one side).

> >In a propagation path that is dominated by multi-path effects

> (reflection at buildings, hills, foliage, etc), you get almost random
> polarization and then the polarization is not that important. Your
> cell phone and indoor WIFI are examples.

> >Extreme weather conditions can also lead to polarization changes or a

> random polarization component (ducting superrefraction).

> >For sea water up to VHF, reflection depends on polarization. For

> ground-ground links (for example ship shore) mostly vertical
> polarization is used (as the sea water helps in this case). So if you
> want to receive these communication, you use a vertical polarized
> antenna.

> >The largest change in polarization you will get when the waves have to

> travel through the ionosphere. At HF (ground-ground link via
> ionosphere), the polarization vector rotates many times. This is due
> to Faraday rotation. Â Also ground-satellite links suffer from this
> effect. The higher the frequency, the less the change in polarization.
> For example at 100 MHz you should think about 30 full rotations (that
> is more then 10k degrees), while at 10 GHz the change in polarization
> will be about 1 degree. Circular polarization may help to mitigate the
> influence of Faraday rotation.

> >At HF sky wave (100....>1000 mile via ionosphere) polarization of the

> antenna matters. This is not because of the polarization change of the
> waves due to Faraday rotation, but because of the reflection
> characteristics of mother earth. In HF antennas, reflection on mother
> earth is used (in combination with antenna height) to get the required
> elevation radiation pattern of the antenna. Reflection on earth
> depends on polarization.

> >Hopefully this helps you a bit.

>> You do not use the words "transversal" and "EM". The only evidence of
> polarization is antenna directional sensitivity.
>You talked about radiowaves, that are EM waves. In free space, only

progapation mode is transversal (that means both E- and H-field are
perpendicular to the direction of energy propagation. With regards to
audio, in gas, only lossless propagation mode is longitudinal
(molecule movement and pressure vectors are parallel to the direction
of energy propagation) .

EM is the hydraulic analogy (by Heaviside). It is a "piece to teach" a field
method.
In that time the electricity was incompressble and massles. Now the
electrons are compressible and have mass.
We need a new analogy. It can be call the Gas analogy or Acoustic analogy.
Inwww.tetech.nlis wrote that are many analogies for EM.

>> In the acoustic analogy a radio waves are normal spherical electric >> waves
> emitted from the two sources (ends of the dipole).
> So the sources are polarised, not the waves. Waves interfere. Do you
> agree?
>Not agree, the waves are also polarized, that can be physically

measured. Polarization is determined by the E-field vector.

A dipole has the E-field (in electrostatics). The equations are by Gauss.
The same equations we can use for the Hertz dipole. The E-field will be
alternate.
At long distances the frequency in receiving antennas will be twice more.

>> See my topic "frequency doubling" . I am only a science hobyist.

>> The second question was: " What is the best orientation of the antenna
>> for
> long distances?
> For old radio antennas. Very long horizontal wire.
>On UHF (for example 2450 MHz), long distance can be 20 km, but on HF

500 km is not called long distance. So the meaning of long distance
depends on the frequency band.

>You should distinguish between the actual polarization of the antenna

and the physical appearance. depending on how you feed it, a very long
horizontal wire can be sensitive to vertical or horizontal polarized
waves.

>Though the equations for acoustical waves look similar to those of EM

waves, the orientation of the field components is completely
different. Â When you require a more specific answer, you should make
your question more specific. I tried to give you a general answer for
the various forms of radio wave propagation.

Now is XXI century. EM is a beautiful theory from XIX century. In Tetech
products no incompressible massless fluid.
So the most specific and important question is:
How is frequency in receiving antenna. Is it doubled?

 Best regards, and sorry for my style
 S*

Hello Szczepan,

You are right, charge is compressible. The charge that is required to
charge (for example) a sphere seems

Seems or unquestionable?

to break the coninuity equition as
is used for incompressible fluid in hydraulics.

Continuity in electromagnetism is regained by introducing the D-field
(dielectric displacement). The D-field is responsible for the
capacitive current in case of varying E-field.

So in your products is the dielectric displacement or compressed electrons?

Regarding frequency doubling. We can be lucky. Antennas and
propagation behaves in virtually all cases linearly. From linear
systems you might know that input and output frequency are the same,
so no doubling in frequency.

Try understand me. Your Hertz dipole emits electrc waves from the TWO ends (opposite phases). So the electrons in a receiving antenna are kicked twice more frequent.

In case of non-linear parts in a system (for example a corroded
connector in an antenna cable that is used by two or more
transmitters, that may behave as a semiconductor), you might get so
called mixer products (sum frequencies, harmonics, difference
frequencies, etc).

Harmonics may be the reason that nobody have seen the Phenomenon.

If you would like to know more about EM-fields related to antennas and
electronics, just start with classical EM theory. This is a solid
tool, existing over 100 years and is used by many people with succes
to predict behaviour of circuits and antennas. If this will change of
today, I will close my business activities next monday.

EM existing over 100 years and will be used the next as the "piece to teach".
Your business base on experiments.
Now You have the opportunity to make the most famous experiment in the history.
If the result will be null I will change my hobby.

Best regards,
S*

.

Relevant Pages

  • Re: Circular polarization... does it have to be synchronous??
    ... It is commonly understood that polarization of electromagnetic waves may be either linear or circular. ... The two extreme special cases of this are linear and circular. ... For example most common linear amateur antennas produce and/or respond to waves of linear polarization, and these antennas produce either either horizonally or vertically polarized waves depending upon the orientation of the antenna with respect to the earth's surface. ...
    (rec.radio.amateur.antenna)
  • Re: wave polarisation
    ... What is the best orientation of the antenna for long distances. ... Under normal circumstances, polarization change in line-off-site ... You talked about radiowaves, that are EM waves. ... the various forms of radio wave propagation. ...
    (rec.radio.amateur.antenna)
  • Re: Photons shapeshifting to wave prior to measurement
    ... >>The left and right circularly polarized waves will not interfere ... >>a 180 flipping of polarization of one wavelet wrt the other. ... there is a fundamental law called *superposition*. ... > I wonder if any store is selling a double slit kit. ...
    (sci.physics)
  • Re: wave polarisation
    ... polarization of a radio wave to fluctuate, ... What is the best orientation of the antenna for long distances. ... In the acoustic analogy a radio waves are normal spherical electric waves emitted from the two sources. ...
    (rec.radio.amateur.antenna)
  • Re: Through a glass darkly
    ... | way the amplitude vector for the electric field depends on time: ... | we refer to this case as plane polarization. ... |> | independent of the source, taking the form of spherical waves. ... |> vacuum causes frequency shift ...
    (sci.physics.relativity)
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