Constructive interference in radiowave propagation
 

On Apr 10, 4:41 pm, Cecil Moore wrote:
Keith Dysart wrote:
Now just above, you started with 100W + 100W and ended with
400W. And you wonder why readers think you advocate this
position.

100W + 100W is not all we started with. Somewhere
else is 100W + 100W of destructive interference
that adds up to zero.

This is very much like the equation in Born and Wolf.

Itotal = 4I1 where I1 = I2 = 100 watts/unit-area

Such is the nature of constructive interference. That
you are ignorant of such is noted.

Does this not cause you some discomfort? It clearly
violates conservation of energy.

I see no connection between what you have posted above and what
you posted below.

Above: Itotal = 4I1
Below: nothing with a factor of 4

Above: 100 + 100 becomes 400
Below: 200 + 200 becomes 400
but then you compute a 100 and claim some relationship

Absolutely NOT! There is 200 watts of destructive
interference somewhere else. Here is a real-world
example:

---291.4 ohm line---+---1/2WL 50 ohm line---291.4 ohm load
Pfor1=200W-- Pfor2=400W--
--Pref1=0W --Pref2=200W

On the load side of point '+':
P1 = Pfor1(1-rho^2) = 100W
P2 = Pref2(rho^2) = 100W

P1 + P2 + 2*SQRT(P1*P2) = Pfor2 = 400W
(200W of constructive interference)

Now once again you have assumed that there are only positive roots.

On the source side of point '+':
P3 = Pfor1(rho^2) = 100W
P4 = Pref2(1-rho^2) = 100W

P3 + P4 - 2*SQRT(P3*P4) = Pref1 = 0W
(200W of destructive interference)

And positive roots here again, but this time it is subtracted.
Isn't that the same as adding the negative root?
So the two equations are identical, they just use the different roots.

But how do you know which to use?

Enquiring minds...

....Keith

Constructive interference in radiowave propagation
 

Keith Dysart wrote:
Above: Itotal = 4I1
Below: nothing with a factor of 4

Look again. P1=100W, Pfor2=400W

Above: 100 + 100 becomes 400

No, above: 100 + 100 + 2*SQRT(100*100) becomes 400
That's the nature of constructive interference.

There is 200W of destructive interference on the source
side of the Z0-match which is supplying the 200W of
constructive interference on the load side.

Now once again you have assumed that there are only positive roots.

Since there is no such thing as negative power, the negative
root is discarded as not representing reality. The sign of
the interference comes from cos(0) for constructive interference
and cos(180) for destructive interference.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

On Apr 10, 10:14 pm, Cecil Moore wrote:
Keith Dysart wrote:
Now once again you have assumed that there are only positive roots.

Since there is no such thing as negative power, the negative
root is discarded as not representing reality.

Isn't negative power just power that is going the other way?

....Keith

Constructive interference in radiowave propagation
 

On Apr 10, 9:17 pm, Cecil Moore wrote:
Keith Dysart wrote:
Are you sure there are different rules for ham radio sources
than for all the other ones? Something different about them?
Something that makes them not amenable to the techniques used
for others?

You are using the rules of superposition in your examples.
I don't know if the rules of superposition apply to those
other sources but I do know that a ham transmitter, like
my IC-706, is not linear enough to abide by the rules of
superposition. How is superposition supposed to handle
foldback?

One of the principles of superposition is that you can apply
it to non-linear systems as long as they remain linear in the
operating range that is of interest.

Ham transmitters cannot willy-nilly be shorted and opened
in order to ascertain their linear model characteristics.

Read
http://www.w2du.com/R2ch19.pdf and
http://www.w2du.com/R3ch19a.pdf
for descriptions on how to do so without needing to short or
open the output. These articles argue that at least the
amateur transmitters examined are linear over the operating
range of interest.

If that is true, why hasn't anyone ever solved them,
published the results, and ended the arguments?

The problems presented in the examples are solvable and
have been solved in public on this group.

The
"solutions" produce different results depending upon
whose brain is being used. Nobody has ever *solved*
the problem and therefore the argument still continues
to rage.

The continuing argument is more a reflection on the people
involved than on the problems. For the most part, the various
approaches produce the same answer to the questions, except
that some approaches provide no answer to some of the questions.
Those who support those approaches then declare those questions
unanswerable rather than exploring the approaches that do answer
the questions.

An interesting question is why do people reject the approaches
that work without examination? I am sure that there must be
some opportunities for psychological study there.

....Keith

Constructive interference in radiowave propagation
 

Keith Dysart wrote:

Isn't negative power just power that is going the other way?

I'm leery of the concept of propagating power (especially after seeing
the morass it's led its adherents into), but most certainly negative
power is the time rate of movement of energy that's going the other way.
If we make a simple circuit of sine wave source and load where the load
is anything but pure resistance, we can see that the energy goes one way
for part of the cycle, the other way for the rest of half the cycle,
then repeats the movement in alternate directions during the second half
of the cycle. The powers (observed at a single point) during the
movement in the two directions are positive and negative. Which
direction of energy flow represents positive and which represents
negative is entirely a matter of choice.

The constant mixing of and confusion between power and energy is one of
the tools used to keep the discussion's rational participants off
balance, and it has been shown to work quite well. A real analysis of
energy flow involves calculating the power at various points and times
in the circuit or transmission line of interest. This gives a view of
energy flow very different from the bouncing waves of average power;
flurry of s-parameter gobbledigook; virtual shorts, opens, photons, and
reflection coefficients; and vague parallels to optical phenomena that
unceasingly issue forth. But the view that comes from calculation is
correct, while the alternative is just so much smoke and noise.

Roy Lewallen, W7EL

Constructive interference in radiowave propagation
 

Keith Dysart wrote:
Isn't negative power just power that is going the other way?

That is just a mathematical convention. If we say
left to right is positive, then right to left
becomes negative. If we say right to left is
positive, then left to right becomes negative.
Same for up/down or down/up or 45 degrees vs
225 degrees. It is a purely arbitrary mathematical
convention. True negative power just doesn't exist.
Negative energy would violate the conservation of
energy principle.

Is a Poynting vector pointing toward Alpha Centauri
positive or negative?

Since true negative power is impossible, the negative
power result of a square root process is discarded
as an artifact.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Keith Dysart wrote:
One of the principles of superposition is that you can apply
it to non-linear systems as long as they remain linear in the
operating range that is of interest.

One of the assumptions in your model is that the source
impedance remains constant with varying degrees of
incident reflected energy. That assumption is false for
an IC-706. Variable constant source impedances are not
allowed by the rules of superposition.

The problems presented in the examples are solvable and
have been solved in public on this group.

:-) Then publish the results in QEX and settle it once
and for all. :-) I predict that QEX will refuse to publish
your ideas. The problems "solved in public on this group"
are simple-minded and bear no resemblance to reality.
They are akin to: Assume a lossless transmission line.
Therefo There are no losses in transmission lines.
In classical logic, your "solution" is known as
petitio principii.

An interesting question is why do people reject the approaches
that work without examination?

Translation: Why would anyone disagree with me and be
wrong when they could agree with me and be right? :-)

I am sure that there must be
some opportunities for psychological study there.

It's already been done. It's in the psychotic
section under "delusions of grandeur". :-)
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Roy Lewallen wrote:
A real analysis of
energy flow involves calculating the power at various points and times
in the circuit or transmission line of interest.

Here's what I said years ago in my energy analysis
article:

"The term "power flow" has been avoided in favor of
"energy flow". Power is a measure of that energy flow
per unit time through a plane. Likewise, the EM fields
in the waves do the interfering. Powers, treated as
scalars, are incapable of interference."

Seems you are still trying to influence people through
false innuendo.

... flurry of s-parameter gobbledigook;

There you have it, folks. Everyone give up on your
S-Parameter analysis. It's only "gobbledigook" (sic).

But the view that comes from calculation is correct, while
the alternative is just so much smoke and noise.

One wonders why that smoke and noise yields the same results
as your short-cut methods plus the tracking of energy through
the system. Could it be that the wave reflection model is a
super-set of your simplified model?
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Roy Lewallen wrote in news:131pgo519itfm24
@corp.supernews.com:

....
I'm leery of the concept of propagating power (especially after seeing
the morass it's led its adherents into), but most certainly negative
power is the time rate of movement of energy that's going the other
way.
If we make a simple circuit of sine wave source and load where the load
is anything but pure resistance, we can see that the energy goes one
way
for part of the cycle, the other way for the rest of half the cycle,
then repeats the movement in alternate directions during the second
half
of the cycle. The powers (observed at a single point) during the
movement in the two directions are positive and negative. Which
direction of energy flow represents positive and which represents
negative is entirely a matter of choice.

Roy, one of the questions I continue to ask myself is why certain
explanations of transmission line / load behaviour seem inconsistent with
basic AC circuit theory as it applies at 50Hz or 60Hz, why the
explanations hinge on a restriction that forward power and reflected
power are purely real when in the general sense, a load may be reactive
and therefore there is real and reactive power at the line-load
interface, and similarly, depending on the transformed impedance, the
source-line interface.

One can only guess at the motivation for all the obfuscation that we see
here. The invention of new terms, multiple meanings for terms,
inconsistent properties for entities, switching in and out of optics,
photon explanations, changing dimensions of quantities for convenience,
construction of special cases to demonstrate assertions and that don't
even qualify as inductive inferences, etc, are all part of a vast array
of obfuscation.

Thankfully, textbooks are not as confusing.


Owen

Constructive interference in radiowave propagation
 

Owen Duffy wrote:
Roy, one of the questions I continue to ask myself is why certain
explanations of transmission line / load behaviour seem inconsistent with
basic AC circuit theory as it applies at 50Hz or 60Hz, ...

That's an easy one, Owen. The wavelength is so long at
60 Hz (5,000,000 meters) that the lumped circuit model
usually works just fine. As you probably know, the lumped
circuit model is a sub-set of the distributed network model.
If the lumped circuit model worked for RF, the distributed
network model (wave reflection model) would have been
abandoned long ago.

100m of transmission line is 0.00002 wavelengths at 60 Hz.
Distributed network effects are negligible.

100m of transmission line is 10 wavelengths at 30 MHz.
Distributed network effects are at a 100% level. Current
in the loop is flowing in opposite directions at ten
points around the loop at the same time.

Somewhere in between 60 Hz and 30 MHz, that old patched-up
lumped circuit model must necessarily be discarded.

One can only guess at the motivation for all the obfuscation that we see
here.

Sorry, but the actual obfuscation seems to me to originate
with trying to use an inadequate, patched-up, lumped circuit
model on distributed network problems. When the lumped circuit
model yields correct results, the distributed network model
yields the same results. When the lumped circuit model yields
incorrect results, the distributed network model yields
correct results.

Again, the challenge is for you guys to generate standing-
waves in the complete absence of reverse traveling waves.
Until you provide a valid example of that, the reverse
traveling waves continue to exist (in spite of all your
hand-waving). They obey the rules of the wave reflection
model and the principles of superposition and conservation
of energy.

The principle of superposition gives us permission to treat
forward traveling waves and reverse traveling waves
separately and then superpose the results. We get the
correct answer every time.

If you fail at generating standing waves without reverse
traveling waves, then for what you guys say to be true,
you must be able to generate traveling waves that contain
zero energy.

It appears that some people have been using mashed potato
short-cuts for so long, they have lost track of the basic
principles underlying the component wave behavior. Anyone
who believes an S-Parameter analysis is "gobbledigook" (sic)
falls into that category.
--
73, Cecil http://www.w5dxp.com