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Old April 10th 07, 04:49 AM posted to rec.radio.amateur.antenna
Cecil Moore[_2_] Cecil Moore[_2_] is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default Constructive interference in radiowave propagation

Jim Kelley wrote:
Then your observation was unrelated to the topic of discussion, which
was your claim that 2 Joules per second could be obtained from a 1 watt
laser.


You know that I never claimed that, Jim. As bright a guy
as you are, why do you have to stoop to falsifying what
I have said?

If the average intensity is one watt per square inch
and we cause interference, the intensity of one particular
square inch can go to zero in the case of total destructive
interference. Since that energy has to go somewhere, it
goes into constructive interference in some other square
inch. If it is total constructive interference, we will
indeed double the average intensity to two watts per square
inch. The total power is still the same but the power
density has doubled in half the area while going to zero
in the other half of the area.

Hint: (2 watts/in^2 + 0 watts/in^2)/2 in^2 = 1 watt

It's certainly an impressive meter reading. It is your contention then
that interference caused a 250 Joule per second increase in the amount
of energy being produced by your radio?


Of course not. That's another false implication of yours.
The interference causes the forward power to be 250 watts
higher than the output of the source. Such is the nature
of constructive interference. The reflected power is 250
watts. |Forward power| = |source power| + |reflected power|

You can't average power 'going' one direction with power 'going' in some
other direction.


I didn't know we had two directions in the laser example.
I thought both beams were going the same direction. If the
beams are going in opposite directions, we get standing
waves and that changes things. If your split beams were
going in opposite directions, I misunderstood the example
and you can forget everything I have said about it.

If you integrate all
of the energy, from all the bright fringes it still doesn't exceed the
energy coming from the source.


That's what I have said all along, Jim. You are obviously
trying to set up some sort of straw man. The energy in the
bright fringes exceeds the average energy. That is all
I have ever said.

There is no amount of hand waving that can cause a one watt laser to
deliver 2 Joules of energy per second.


Of course not and I never said it would. Please stop trying
to imply that I said something that I never said. It is
downright unethical to debate in such an unfair manner.

Born and Wolf doesn't discuss power and interference, and they certainly
don't interchange intensity and power in their discussions like you do.


Intensity is power density. I have a habit of saying power
when I should have said power density. For that I apologize
and will try to break myself of that habit. But you can
always tell by the context that I was talking about power
density.

There can be no more 'power gain' along a transmission line than there
can be along a beam of light.


On the contrary, reflection gain from a tuner is an
accepted concept within the wave reflection model.

But even with all the interference and power
averaging taken into consideration, the radiated power will still not
exceed the input power.


Nobody believes the conservation of energy principle can be
violated so that is just another one of your straw men. Go
ahead, be my guest, and knock it down if it makes you feel
better. Nobody cares.

You can't get 400 watts to a load using two 100 watt PA's no matter how
much interfering and averaging you do, Cecil. How can you even make
that claim with a straight face?


I didn't make that claim. I said that Keith would have to prove
it was possible before his assertions made any sense. I challenged
Keith to prove that was possible. I certainly have never made that
claim. You usual lack of ethics is showing. If you are forced to
lie to make your point, your point is not worth making.
--
73, Cecil http://www.w5dxp.com