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From: Archimedes Plutonium on 4 Jun 2010 01:53


Archimedes Plutonium wrote:
> Enrico wrote:
>
> >
> > http://www.copradar.com/preview/chapt2/ch2d1.html
> >
> > Police traffic radar emits an unmodulated continuous wave (CW) and
> > measures' reflections (echoes). Reflections are frequency shifted
> > (Doppler shift) if the target is moving; the faster the target is
> > traveling, the more the frequency shifts. A target traveling toward
> > the radar shifts the frequency higher while a target traveling away
> > from the radar shifts the frequency lower (compared to transmit
> > frequency). The radar, by design, simultaneously transmits a
> > continuous signal while receiving continuous signal echoes.
> >
> >
> > Enrico
>
> Enrico, it is an unfortunate use of the words "Doppler shift" because
> the
> radar is not measuring a doppler shift. The radar is giving you back
> "echoes"
> of distance 1 and time 1 then it gives you distance 2 and time 2, all
> at the
> speed of light. The calculation is then, making use of d_1, t_1 and
> d_2, t_2.
>
> Somehow, somewhere, novices are throwing in the words "Doppler shift"
> when
> they never should be throwing in such.
>
> And I see that Wikipedia on some of its Doppler pages is erroneous on
> this
> physics also.
>
> So this is what happens when you have a culture of fake physics of a
> Doppler
> shift.
>
> Enrico, do you actually believe that the radar is "picking up a
> Doppler shift of the
> radar wave?"
>
> When I was in the Navy, we routinely did Maneuvering Boards or Mo
> Boards of radar
> on distant ships to tell their speed and direction of motion. Enrico,
> do you actually
> believe that we were doing a Doppler shift on a distant ship?
>
> This is what happens when fakeness enters physics, in that it seems to
> spread
> into other corridors and avenues and pollutes the minds of students of
> physics.
>

Here is my hunch of what happened. A manufacturer of the hand held
radars
named the company as Doppler Radars. Or they advertized their product
as
a Doppler radar.

Or, they had a greenhorn spokesperson trying to explain to potential
sales
customers of how the device worked. And they really did not know so
they
introduced Doppler shift when that was all wrong.

Or, someone just added Doppler shift to the explanation of how it
works
and others just spread it. For the Internet, when a mistake is
committed
has a tendency to multiply that mistake all over the place.

The short and simple is that radar devices function to gather distance
_1 and
time_1 in one echo and then distance_2 and time_2 in a second echo and
then
it compute the speed of the object.

Radar devices do not measure a Doppler shift because the speeds of
cars
or ships is so slow, even a fast car is so slow compared to the speed
of radar
which is the speed of light, that there is nothing of a shift to
measure.


Archimedes Plutonium
http://www.iw.net/~a_plutonium/
whole entire Universe is just one big atom
where dots of the electron-dot-cloud are galaxies
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