electromagnetic transmission power relativistic effects

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Google phil hobbs antenna

Surely you can do that much.

All I want to do is get things right. You seem to be arguing some yourself.

I personally don't have much interest in RF, but I know that rectennas can be over 80% efficient, so they can't reflect back half of the incident power. I furnished links.

John

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It seems like all the loss-less impedance matching scheme's that I know about involve a certain time delay and energy storage. (L's and C's) The 'art' is in getting all the energy into the load. But if ya just need to go 'brute force' and can waste power then R source =3D R load is the place to start.

George H.

Even if the receive antenna reflected a microwatt of RF, only a tiny bit of that would hit the transmit antenna. Most would be lost to space.

And there's still no reason why a receiver that absorbs a microwatt from the far-field pattern would reflect a microwatt. I might reflect a tenth of a microwatt. I might reflect a watt. The transmitter has no way of knowing how much was absorbed.

The original question includes an invalid premise.

John

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I think that 'in principle' you could design a 'can' around your antenna so that it would capture most of the energy at some certain wavelength from some certain direction. Perhaps not the best radio antenna.

George H.

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Yeah, I feel like I'm an order of magnitude stupider than Phil.

George H.

It's okay to budget them after photodetection--that's where they actually show up. You can see them on a scintillator, and count them with a PMT.

Cheers

Phil Hobbs

A tornado doesn't exist. It's just properties of something else.

Actually, that's probably true.

John

When one's been by, nothing much is left in existence either. Brr. :(

(Prayers for the people of Joplin MO.)

Cheers

Phil Hobbs

...and Tuscaloosa, and Birmingham, and Huntsville, and...

Hi,

I was talking with a Ph.D candidate in optics a couple years back about light traveling through space from a star to a telescope, and if I am remembering correctly he said he believed the light doesn't actually travel as a wave, but is instead a probability wave that collapses when a photon is absorbed by the telescope, and the photon is emitted at the same time as it is received, and not emitted unless something does end up receiving it. So this transactional view of quantum mechanics is where the premise of a receiver having a measurable effect on the transmission power comes from.

cheers, Jamie

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On a sunny day (Tue, 24 May 2011 17:24:22 -0700) it happened John Larkin wrote in :

I am glad he does not. Photon is nothing more than Planck's constant x frequency, a MATHEMATICAl concept. It is NOT an object (that flies past you LOL).

On a sunny day (Wed, 25 May 2011 00:04:05 -0700) it happened Jamie wrote in :

Right, I have read that too, and found it an inspiring view that would explain some things. There is some repeated posting in sci.physics about the 2 slit experiment, where De Broglie once stated that this 'probability wave', or better the point where we think the wave 'top' is (in time and space), is really just that, probability, and that once we get a better understanding then we will find an accompanying wave in an 'ether', one that passes through the 2 slits ahead of that what we call photon, and causes it to deflect one way or the other, sort of a field at a much finer structure. Of course that breaks Einsteins 'nothing faster than c' dogma. So, I personally adhere to that view. Einsteins dogma will have to go so we can move on.

They sure behave as if they do. That's good enough for most engineering applications.

John

On a sunny day (Wed, 25 May 2011 06:55:20 -0700) it happened John Larkin wrote in :

No they dont. What you enjeneerun?

Not the issue at all. The outgoing wave starts with 1000 W outgoing, and ends with 999,999999 W outgoing, and the reason is that the receiver's antenna is ANOTHER radiator, and the outgoing waves of both antennae sum to the lesser power. It isn't about 'reflection' per se, but about destructive interference.

That's what it means when any antenna absorbs energy.

That destructive interference causes, on the quantum mechanical level, an increased rate/probability of photon emission at the transmitter, which (in the macroscale) means a bit of impedance fluctuation as compared to the impedance of an antenna in truly free space.

Hey, Jamie -

That sounds about right. You can get more info on that by checking out QED from your local library which is authored by Richard Feynman. I think you may enjoy reading it.

Cheers & 73, John

Ya it seems like a strange way to think about light traveling! I am glad I never took any quantum mechanics courses, IMO its all a bunch of garbage that is being taught :D

cheers, Jamie

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Doesn't that just blow causality all to heck?

-- Les Cargill