Constructive interference in radiowave propagation
 

On Apr 11, 7:41 am, Cecil Moore wrote:
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.

Which is, of course, why all my examples explicitly state the
construction of the generator to be one that is guaranteed
linear. But if the behaviour for this kind of simple case
can not be understood, there is no hope for understanding
a real transmitter. The argument "since I can not understand
a real transmitter, there is no value in understanding a
linear generator" seems weak.

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.

I would hope so. The ideas are quite basic, not mine, and can
be found in any standard text book on transmission lines and
circuit analysis. No need to publish in QEX. Or perhaps I
misunderstand QEX's audience and it is appropriate for them.
But then I suspect that more capable writers than myself would
be the appropriate authors.

Have you considered putting optics aside for a moment (after
all, we are trying to understand circuits, especially in the
transmitter), and cracking open any textbook that deals directly
with the subjects at hand?

....Keith

Constructive interference in radiowave propagation
 

Owen Duffy wrote:
One can only guess at the motivation for all the obfuscation that we see
here.

Here's a list of questions for you and everyone else.

1. Is the distributed network model valid? If not,
please explain where it is invalid.

2. Is the wave reflection model valid? If not,
please explain where it is invalid.

3. Is the base of knowledge and laws of physics
from the field of optics valid? If not, please
explain where they are invalid.

4. Is an S-Parameter analysis valid? If not,
please explain where it is invalid.

5. Does the principle of superposition give us
permission to analyze the forward wave and
reflected wave separately and then superpose
the results? If not, please explain why not.

6. Does the conservation of energy principle
work for forward and reflected waves? If not,
why not?

7. Does the label of "obfuscation" really apply
to items 1-6?

8. Do you and other gurus already know everything
there is to know or does every person have holes
in his/her limited knowledge base?
--
73, Cecil, w5dxp.com

Constructive interference in radiowave propagation
 

"Cecil Moore" wrote in message
t...
Owen Duffy wrote:
One can only guess at the motivation for all the obfuscation that we see
here.

Here's a list of questions for you and everyone else.

1. Is the distributed network model valid? If not,
please explain where it is invalid.

2. Is the wave reflection model valid? If not,
please explain where it is invalid.

3. Is the base of knowledge and laws of physics
from the field of optics valid? If not, please
explain where they are invalid.

4. Is an S-Parameter analysis valid? If not,
please explain where it is invalid.

5. Does the principle of superposition give us
permission to analyze the forward wave and
reflected wave separately and then superpose
the results? If not, please explain why not.

6. Does the conservation of energy principle
work for forward and reflected waves? If not,
why not?

7. Does the label of "obfuscation" really apply
to items 1-6?

8. Do you and other gurus already know everything
there is to know or does every person have holes
in his/her limited knowledge base?
--
73, Cecil, w5dxp.com

I have no beef with above, and would like to thank you and Walt for
persisting in defending, explaining and trying to correct some "wrongos" out
there.

Seems that the unbelievers are in the same camp with those who could not
digest the behavior of loading coils in standing wave antenna circuit. Seems
it would be much nicer if the discussions were more in the line "oh, yea,
why?" rather than "you fool, you know notin'" ...or something like that.

I have experienced special case of interference between two antennas, fed
from the same transmitter and separate amplifiers. The result was distorted
signal on SSB, seems was a bit wider and modulation being raspy. It appears
that part of the "other" RF was picked up by other antenna and amp,
"processed" and retransmitted. I have observed this effect on one YU
station, alerted him to it, asked to switch one PA-ANT off, and signal
became "crystal" clean.
Let the "it can't be" games begin :-)

So it seems that if I want transmit the same signal in two or three
different directions- antennas, they should not "see" each other, or they
will interfere (until they go through atmo/ionosphere "massaging") and lose
their correlating identity?

Thanks Cecil and Walt!

73 Yuri, K3BU.us

Constructive interference in radiowave propagation
 

Yuri Blanarovich wrote:
Seems that the unbelievers are in the same camp with those who could not
digest the behavior of loading coils in standing wave antenna circuit. Seems
it would be much nicer if the discussions were more in the line "oh, yea,
why?" rather than "you fool, you know notin'" ...or something like that.

If you remember, two of those gurus tried to use standing-
wave current to measure the phase shift through a loading
coil apparently not realizing that their simple-minded model
wouldn't accomplish that task because the phase of standing-
wave current is essentially unchanging all up and down the
mobile antenna. Last I heard, they were rabidly defending
those obviously flawed measurements because, of course,
gurus know everything and never make mistakes. :-)
--
73, Cecil, w5dxp.com

Constructive interference in radiowave propagation
 

On Apr 11, 4:14 am, Cecil Moore wrote:

True negative power just doesn't exist.
Negative energy would violate the conservation of
energy principle.

Correct. Therefore 2*sqrt(P1*P2)cos(180) is impossible as well as
ridiculous.

Since true negative power is impossible, the negative
power result of a square root process is discarded
as an artifact.

But what is TRUE negative power, and how does it differ from other
types of negative power? :-)

ac6xg

Constructive interference in radiowave propagation
 

On Apr 11, 9:02 am, Cecil Moore wrote:
Again, the challenge is for you guys to generate standing-
waves in the complete absence of reverse traveling waves.

I do recall a textbook derivation of the voltages and currents
on a trasmission line that used the distributed model and
differential equations. It expressed the result in terms
of x (distance along the line) and t (time). It was messy.

It then followed this with a proof showing that thinking of
the system as having a forward and reverse wave produced the
same result. This was much simpler.

But which one was real?

In the end, it is the actual distributed voltage and current on
the line that are real, not the means of describing them.

Both methods accurately describe these, but I certainly prefer
the latter since I can do the math for it.

Still, just because I like to think of it that way, just because
it gives me the right answers, does not mean that that is the way
it is.

Reality is the distributed voltage and current.

Use the analysis technique of your choice, but only as long as
it gives you the correct answers.

....Keith

Constructive interference in radiowave propagation
 

Jim Kelley wrote:

Cecil Moore wrote:
True negative power just doesn't exist.
Negative energy would violate the conservation of
energy principle.

Correct. Therefore 2*sqrt(P1*P2)cos(180) is impossible as well as
ridiculous.

That's the interference term, Jim. Hecht, Born, and Wolf
all agree that the interference term can be negative.
Suggest you take a refresher course and alleviate the
ignorance you are displaying for everyone to observe.

Remember that P1 and P2 are Poynting vectors, i.e. power
densities and the negative sign simply denotes the
decrease in power density due to destructive interference.
The negative destructive interference subtracts from the
P1+P2 power and the result of that subtraction can *never*
be negative. The interference term has NO separate existence
aside from the existence of the power density components of
P1 and P2.

Please tell Hecht, Born, and Wolf that they are ridiculous.

2SQRT(I1*I2)cos(A)

That's the third term in equation (15) page 259, 4th
edition of "Principles of Optics".

If cos(A) is 180 degrees, the interference term becomes
negative and subtracts from the I1+I2 sum.

Born and Wolf continue, "... and minima of intensity

Imin = I1 + I2 - 2*SQRT(I1*I2)"

Exactly the same equations appear in "Optics", by Hecht,
4th edition, page 388.

"Imin = I1 + I2 - 2*SQRT(I1*I2)"

Note that I is intensity or irradiance, the dimensions
of which are watts/unit-area, exactly the same dimensions
as the Poynting vectors, P1 and P2 above.

In "Fields and Waves in Modern Radio", Ramo and Whinnery
subtract Poynting vectors that are 180 degrees out of
phase to obtain the net Poynting vector?

Since true negative power is impossible, the negative
power result of a square root process is discarded
as an artifact.

But what is TRUE negative power, and how does it differ from other
types of negative power? :-)

The sign on a power term denotes a decrease in power level
but never to a negative level. Thus, reflected power subtracts
from the forward power to obtain power delivered to the load.
Destructive interference power subtracts from average power
to allow for constructive interference power. In no case does
the net power go negative.
--
73, Cecil, w5dxp.com

Constructive interference in radiowave propagation
 

Keith Dysart wrote:
But which one was real?

That's a metaphysical question. First please prove
that you are real. :-)

Use the analysis technique of your choice, but only as long as
it gives you the correct answers.

It has in every case so far. Other techniques, like
using standing-wave current to try to measure the
phase shift through a loading coil, have failed
miserably.
--
73, Cecil, w5dxp.com

Constructive interference in radiowave propagation
 

On Apr 11, 11:54 am, Cecil Moore wrote:
Keith Dysart wrote:
But which one was real?

That's a metaphysical question.

So it is settled then. There is no NEED for a forward OR reverse
travelling wave. Differential equations rule.

First please prove that you are real. :-)

It doesn't matter if I am real as long as you think I am.

Use the analysis technique of your choice, but only as long as
it gives you the correct answers.

It has in every case so far.

Well, except for the inability to explain where the "reflected
power" goes in the transmitter. Of course this is not an issue
for carefully selected examples where no "reflected power" reaches
the transmitter. A more general analysis technique would not
require such careful selection of examples.

....Keith

Constructive interference in radiowave propagation
 

Keith Dysart wrote:

...
Well, except for the inability to explain where the "reflected
power" goes in the transmitter. Of course this is not an issue
for carefully selected examples where no "reflected power" reaches
the transmitter. A more general analysis technique would not
require such careful selection of examples.

...Keith


When I fire up the big russian 3.5KW linear into a high swr, I don't
have to guess about where the reflected power is going at the xmitter,
the nice red glow on the plates are an excellent indication when they
begin dumping unknown amounts of power as infrared radiation ... when I
grab the coax (150 ft. run) and feel its warmth, I even wonder about how
much power it takes to elevate it's temp!

JS