Re: GPS 'GR Correction' Myth.


"Paul B. Andersen" <paul.b.andersen@xxxxxxxxxxxxxxxx> wrote in message
news:dddnsj$17i$1@xxxxxxxxxxxxxxxxxxx
| Henri Wilson wrote:
| > On 9 Aug 2005 04:08:08 -0700, "Randy Poe" <poespam-trap@xxxxxxxxx>
wrote:
| >> Henry Wilson wrote:
| >>>On the other hand, the 3gig signal has such a short wavelength that
| >>>its phasing, after reflection, would be all over the place.
|
| Correct. It is.
|
| >>As a vehicle is rigid, no such thing happens. If there is
| >>a second reflection point of distance d from the first, then
| >>the reflected signal from that point has a phase of 2*pi*d/lambda
| >>relative to the first. This remains constant in time. The sum
| >>of two sinusoids of frequency f and different, constant phase
| >>relationship, is another sinusoid of frequency f.
| >
| >
| > Glad to see you are learning from me.
| > Now, what if the signals are 180 out?
| > Can you not see that the reflected beam would have a very small
amplitude?
|
| Of course it would.
| If the phase difference it is anything but zero,
| the amplitude will be zero.


HAHAHAHAHAHAHAHAHAHA!
Ooops, I farted :-)
If the phase difference it is exactly pi,
the amplitude will be zero.
a)
|/\/\/\/\/\|
|\/\/\/\/\/| = |--------|
b)
|/\/\/\/\/\|
|/\/\/\/\/\| = ??



Henri has a computer model created now, he can
suddenly change the direction of the wave and look
at the waveform's phase.




| But that doesn't mean that the wave is cancelled
| out, it only means that it is going in another direction.
|
| Remember what we are talking about.
| The reflection of a plane EM-wave off a target.
| The phase relationships will determine in which
| direction the wave is reflected.

Back to the cop's radar gun, I hope.
Not much point otherwise :-)
The phase is a function of distance.
The frequency is a function of speed.
Move the car VERY slowly and you'll see why.

Man, what ARE you doing in an educational establishment?
Oh well... those that can, do. Those that can't, become
teaching assistants.


| If the target is a plane surface perpendicular to
| the incident EM-wave, all will be reflected back
| to the source.

That's the general idea... This is a cop's radar gun, remember,
it's not aimed at a B2 or F117, or even intended to be.
http://www.simviation.com/pageimages/b2a.jpg

| But if the plane surface has any angle but perpendicular,
| the reflected wave will go in another direction,
| and nothing will go back to the source.

Yeah, stealth really works. I've got a stealth windshield
on my car in case there's a cop around. :-)


| The wave will always go in the direction where
| the phases add. That's why the perpendiculars to
| the direction of propagation are called
| "planes of equal phase".
|
| So if your car consists of only perfectly plane
| metallic surfaces, you have a stealth car.
| The probability for any plane to be exactly perpendicular
| to the direction to the radar gun is practically zero,
| and the radar wouldn't see you.
| http://www.jetplanes.co.uk/f117.html
|
| But cars are not like that. They have curved surfaces.


Cop bait.
http://ourworld.compuserve.com/homepages/jeep_man/ab5.jpg




| But you are right. When the EM-wave hits the car,
| the phases are indeed "all over the place",
| which means that the wave will be reflected in
| just about every direction.
| Only a small fraction of the wave will be reflected
| back to the radar gun. This is because there will
| always be some part of the car's surface that is
| perpendicular to the direction to the gun.
|
| You can find this discussed in more detail here:
| http://www.aerospaceweb.org/question/electronics/q0168.shtml
|
| The basic principle of a traffic radar isn't
| different from any radar, and you know that
| a car would show up on a radar, don't you?
|
| Paul
More cop bait:
http://www.42fordgpw.com/images/jill/CRW_3674_800px.jpg
Androcles.

.

Relevant Pages

  • Re: GPS GR Correction Myth.
    ... |>suddenly change the direction of the wave and look ... |>| The reflection of a plane EM-wave off a target. ... |>Move the car VERY slowly and you'll see why. ... This is a cop's radar gun, remember, ...
    (sci.physics.relativity)
  • Re: GPS GR Correction Myth.
    ... a second reflection point of distance d from the first, then the reflected signal from that point has a phase of 2*pi*d/lambda relative to the first. ... But that doesn't mean that the wave is cancelled ... it will be a plane wave. ... So if your car consists of only perfectly plane ...
    (sci.physics.relativity)
  • Re: GPS GR Correction Myth.
    ... a second reflection point of distance d from the first, then the reflected signal from that point has a phase of 2*pi*d/lambda relative to the first. ... But that doesn't mean that the wave is cancelled ... So if your car consists of only perfectly plane ... and the radar wouldn't see you. ...
    (sci.physics.relativity)
  • Re: GPS GR Correction Myth.
    ... a second reflection point of distance d from the first, then the reflected signal from that point has a phase of 2*pi*d/lambda relative to the first. ... But that doesn't mean that the wave is cancelled ... So if your car consists of only perfectly plane ... and the radar wouldn't see you. ...
    (sci.physics.relativity)
  • Re: Standing-Wave Current vs Traveling-Wave Current
    ... It has also caused conceptual difficulties because of the perfect source's -1 reflection coefficient. ... When we initially connect or turn on the voltage source, the source/resistance combination sees Z0 looking into the line. ... voltage of the perfect voltage source and Rs is the 150 ohm source resistance, until the reflection of the original forward wave returns. ...
    (rec.radio.amateur.antenna)
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