Constructive interference in radiowave propagation
 

Cecil, W5DXP wrote:
"Antenna gain over isotropic is an application of constructive
interference."

Yes. An often offered annalog is an inflated spherical balloon. It
contains the same amount of air no matter how it is squeezed. Sqeeze it
one place and it bulges elsewhere.

An isotropic antenna, could one be constructed, would radiate equally
well in all directions. As a radiation pattern becomes lopsided, the
bulge is filled with the energy squeezed from elsewhere.

Directive gain of an antenna is a power ratio. It`s the power that you
would have to put into an isotropic wersus the power you have to put
into the gain antenna to lay the same signal on a point in the preffered
direction.

Other things equal, if a gain antenna radiates twice the power in the
preferred direction as an isotropic, it has a gain of 3 dBi.

Best regards, Richard Harrison, KB5WZI

Constructive interference in radiowave propagation
 

Cecil Moore wrote:
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?

So now you start with the accusations, and here's why (from
yesterday):

"If it were total constructive interference, two 1/2W
beams would yield an intensity of 2 watts."

It was pointed out to you that that notion violates conservation of
energy, but rather than admit that you were incorrect, you attempt to
revise history. Then there was this:

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

:-) Actually, it's a beam of light that subtends a solid angle of
less than one degree. Let's call it a degree just to be
conservative. That would leave 719 other solid degrees where there is
0 watts, so according to Cecil's theory of spacial power averaging,
the answer could also be 2 watts+0+0+0... / 719 = 2.78 milliwatts.
But apparently those values don't give the answer you were going for.

Others have made points along these lines quite eloquently. Excellent
comments in this thread from Roy, Keith, Owen, Gene, Tom, et al.

73, Jim AC6XG

Constructive interference in radiowave propagation
 

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.

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)

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)
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Keith Dysart wrote:
Any example where reflected energy is allowed to
reach the source cannot be analyzed in any valid
real-world way.

A strange assertion. Consider two wire phone lines; transmitter
and receiver at each end. Consider cable modems; ditto. Consider
computer busses; ditto.

We are discussing ham radio sources, Keith, which are
none of the above. How many hams use cable modems for
their RF transmissions? Please get real.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Jim Kelley wrote:

w5dxp wrote:
If it were total constructive interference, two 1/2W
beams would yield an intensity of 2 watts.

That should have been 2 watts per unit-area. Note that
I did NOT say two 1/2W beams would yield a power of 2
watts. The correct dimensions of intensity would be
2 watts/unit-area, a power density, not a power. I have
already apologized for that goof in dimensions.

It was pointed out to you that that notion violates conservation of
energy, but rather than admit that you were incorrect, you attempt to
revise history. Then there was this:

No, that notion *DOES NOT* violate the conservation of energy
principle which cannot be violated. That notion relies upon
one watt per unit area of total destructive interference
occurring somewhere else. The one watt of destructive
interference causes a flat black area. The energy from that
flat black area is redistributed to the area of constructive
interference and causes that area to be twice as bright as
the average area. Born and Wolf's equation is valid.

Itotal = 4I1 where I1 = I2 = 0.5W

2 watts/unit-area = 4(0.5) watts/unit-area

Again, I ask you to please cease from trying to twist my
words into a violation of the conservation of energy
principle. If you think I have uttered such words, you
are mistaken. Next time you are confused, instead of your
arrogant ASSumptions, please just ask me what I meant.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

"K7ITM" wrote in
ps.com:

Hi Owen,

I had a quick look at your article. Though I didn't try to proof-read
it for accuracy, I was reminded that the equations I posted those long
years ago said that if you know the _instantaneous_ voltage and
current at a point on a line, and know its impedance (as a frequency-
independent quantity), the equations apply, and you can resolve that
instantaneous pair of values into forward and reverse. That's
something that's not immediately obvious when people think only about
sine waves.

Tom,

Something else that follows from the derivation is that whilst the
indicated Pf and Pr do not have stand along meaning, Pf-Pr does have
meaning irrespective of the nominal R for which the instrument is
calculated.

For example, if we cascade a 100W source, 50 ohm directional wattmeter, a
75 ohm directional wattmeter and a 100+j0 load, the instrument readings
should be:
- 75 ohm: Pf=112.4, Pr=12.4, P=100
- 50 ohm: Pf=104.1, Pr=4.1, P=100

This of course assumes that the instruments do not significantly disturb
the thing they are measuring, in this case the V/I conditions at the 100
ohm load.

So, while you can nominate any reference Zo for a Pf or Pr value (and so
vary those values), the power passing the instrument (Pf-Pr) is indicated
correctly irrespective of the calibration R.

(The article explains that the result of Pf-Pr is only meaningful if the
calibration impedance is purely real.)

Owen

Constructive interference in radiowave propagation
 

On Apr 10, 4:13 am, "Keith Dysart" wrote:



Why don't you analyze my example:

(Since the Grand PoohBah Power Master seems unwilling, here, for your
consideration, I give you...)


Generator with
291.4 Ohm ------------ 291.4 Ohm line ---- 50 Ohm load
Source Impedance Pfor2=100w--
--Pref2=50w

What is the power emitted by the generator into the line?
-- Assuming lossless line, 50W of course; 50V@1A at the load.

Where does Pref2=50W go?
-- Into satisfying the boundary conditions at the generator
to line interface. We have way to little info to
determine if the generator dissipates more, or less, or
the same, as if it were terminated in 291.4 ohms.

Are there ghosts?
-- Some people believe in them. I've never seen on--Oh not
THAT kind of ghost. Well, not at the load, but certainly
at the generator, if the generator is putting out a signal
that's an interesting enough function of time. TDRs really
do work.

What is the magnitude?
-- Of what? We have enough info to resolve Vf, If, Vr and Ir
on the line, and if we knew the line length and
the excitation, we could be a lot more definitive about
things, but since steady-state excitation doesn't
produce ghosts... but the reflection coefficient at the
line-load interface is -1/sqrt(2), so that's the voltage
ratio we'll see between the forward and reverse waves.

What power would the generator emit if the line was terminated
with 291.4 Ohms?
-- "100 watts, of course." For those who don't immediately see
that, it's not difficult to go through some math to show that
the power delivered to a load is independent of the load
impedance so long as magnitude((Zload-Rgen)/(Zload+Rgen)) is
constant--that is, so long as the magnitude of the reflection
coefficient is constant--as it is along a lossless line...
and from that, find the Thevenin or Norton equivalent of the
source in this example ... and from that, figure the power
that source will deliver to a matched load.

Please do not modify the example for analysis since this may change
the results.

There is much to be learned by trying examples that may challenge
your expectations.

:-) This reminds me of some thoughts I posted a long time ago about
lines whose Zo is somewhat reactive. For example, if a linear
sinusoidal source of impedance Zo is connected to a line also of
impedance Zo, what load maximizes the power in the load? If you keep
magnitude((Zload-Zo)/(Zload+Zo)) constant, is the power dissipated in
the load independent of the phase angle of (Zload-Zo)/(Zload+Zo)?

...Keith

Cheers,
Tom

Constructive interference in radiowave propagation
 

On Apr 10, 4:46 pm, Cecil Moore wrote:
Keith Dysart wrote:
Any example where reflected energy is allowed to
reach the source cannot be analyzed in any valid
real-world way.

A strange assertion. Consider two wire phone lines; transmitter
and receiver at each end. Consider cable modems; ditto. Consider
computer busses; ditto.

We are discussing ham radio sources, Keith, which are
none of the above. How many hams use cable modems for
their RF transmissions? Please get real.

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?

If that is so, I am surprised at your claim that ham radio
sources have something in common with light bulbs and lasers
such that knowledge of those subjects can help analysis, while
any knowledge of the behaviour of other electrical circuits is
for naught.

Seriously though, it does all work. The problems are solvable.
You don't need to throw up your hands and say: "too tough."
And then rationalize this response by calling them "too
different" or saying "insufficient information".
Much can be learned by solving the problems set using more
controlled examples. Try it. Using the regular techniques will
produce the same answer for all the problems you can currently
solve, as well as allowing you to solve ones you currently
declare as unsolvable.

....Keith

Constructive interference in radiowave propagation
 

On Apr 10, 5:30 pm, "K7ITM" wrote:
On Apr 10, 4:13 am, "Keith Dysart" wrote:

Why don't you analyze my example:

(Since the Grand PoohBah Power Master seems unwilling, here, for your
consideration, I give you...)



Generator with
291.4 Ohm ------------ 291.4 Ohm line ---- 50 Ohm load
Source Impedance Pfor2=100w--
--Pref2=50w

What is the power emitted by the generator into the line?

-- Assuming lossless line, 50W of course; 50V@1A at the load.

Where does Pref2=50W go?

-- Into satisfying the boundary conditions at the generator
to line interface.

This is a different way of expressing it. But I like it.

We have way to little info to
determine if the generator dissipates more, or less, or
the same, as if it were terminated in 291.4 ohms.

Are there ghosts?

-- Some people believe in them. I've never seen on--Oh not
THAT kind of ghost. Well, not at the load, but certainly
at the generator, if the generator is putting out a signal
that's an interesting enough function of time. TDRs really
do work.

What is the magnitude?

-- Of what?

I was think of the ghost, for those who believe in them, mostly
to force some computation. If there is one, it must be quantifiable.

We have enough info to resolve Vf, If, Vr and Ir
on the line, and if we knew the line length and
the excitation, we could be a lot more definitive about
things, but since steady-state excitation doesn't
produce ghosts... but the reflection coefficient at the
line-load interface is -1/sqrt(2), so that's the voltage
ratio we'll see between the forward and reverse waves.

What power would the generator emit if the line was terminated
with 291.4 Ohms?

-- "100 watts, of course." For those who don't immediately see
that, it's not difficult to go through some math to show that
the power delivered to a load is independent of the load
impedance so long as magnitude((Zload-Rgen)/(Zload+Rgen)) is
constant--that is, so long as the magnitude of the reflection
coefficient is constant--as it is along a lossless line...
and from that, find the Thevenin or Norton equivalent of the
source in this example ... and from that, figure the power
that source will deliver to a matched load.

There is much to be learned by trying examples that may challenge
your expectations.

:-) This reminds me of some thoughts I posted a long time ago about
lines whose Zo is somewhat reactive. For example, if a linear
sinusoidal source of impedance Zo is connected to a line also of
impedance Zo, what load maximizes the power in the load? If you keep
magnitude((Zload-Zo)/(Zload+Zo)) constant, is the power dissipated in
the load independent of the phase angle of (Zload-Zo)/(Zload+Zo)?

Hmmmmmm. I'll have to think on this. Perhaps after I work out whether
the source impedance of a properly tuned amateur transmitter is the
complex conjugate of the load impedance.

....Keith

Constructive interference in radiowave propagation
 

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?

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

A signal generator equipped with a circulator load solves
all the experimental problems but doesn't act like a ham
transmitter.

Seriously though, it does all work. The problems are solvable.

If that is true, why hasn't anyone ever solved them,
published the results, and ended the arguments? 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.
--
73, Cecil http://www.w5dxp.com

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

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

Constructive interference in radiowave propagation
 

Cecil Moore wrote:
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.

Ah, but the ignorance being seen by all is all yours, sir. You
continue to ignore a significant detail, Cecil. See if you can find
it. Hint: people who write physics books know that power does not
interfere.

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

I agree with them, and they don't post here. But if they did, they'd
be telling you the same thing as everyone else here.

ac6xg

Constructive interference in radiowave propagation
 

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

Yes, it is settled in your own mind. In my mind,
there is certainly a need for forward and reverse
traveling waves without which standing-waves would
not be possible. If you want to deny the existence
of the cause of standing-waves, there is nothing
I can to stop you.

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.

The more general analysis technique tells us that
the moon is 1000 miles away from the earth. I don't
know how far away the moon is but I know it is not
1000 miles away.
--
73, Cecil, http://www.qsl.net/w5dxp

Constructive interference in radiowave propagation
 

Jim Kelley wrote:
Hint:
people who write physics books know that power does not interfere.

Please tell that to someone who disagrees with
that statement, Jim, which is not me. Here's what
I said in my years old 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."

You keep making statements like the above in hopes
someone somewhere will believe that I disagree with
it. Old trick - doesn't work.

I say, *EM WAVES DO THE INTERFERING*. Do you want
to argue about that?

I say, *POWERS ARE INCAPABLE OF INTERFERENCE*. Do
you want to argue about that?

Please, if we are going to argue about something,
make it something upon which we disagree.
--
73, Cecil, http://www.qsl.net/w5dxp

Constructive interference in radiowave propagation
 

Cecil Moore wrote in
t:

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
....

Cecil, you have conveniently clipped the context (as you do), the
relevant context being the line-load interface and source-line interface.

Statements in some explanations (by others) like "This clearly proves
that reflected power and forward power in a transmission line are both
real power, and that no fictitious power, or reactive volt-amperes,
exists in either one." seem incompatible with the basic AC circuit theory
explanation of a reactive load which must exchange reactive energy with
the transmission line over a complete cycle (and the same effect at the
source end).

Perhaps it is explained by hopping in an out of the instantaneous and
average context, just like switching between lossless lines and lossy
lines context with declaration, while actually carrying the analytical
simplicity of lossless lines and selectively layering selected aspects of
the loss.

BTW, I am not surprised at your dissertation apparently dismissing the
distributed impedance model of a line, because after all it is the
solution of that model that gives us the classic transmission line
equations that you seem to not want to use.

If the distributed network model you favour is the S paramater model,
properly applied, it is in fact entirely consistent with the distributed
impedance line model because the parameters are derived from the solution
to the distributed impedance line model.

Owen

Constructive interference in radiowave propagation
 

John Smith I wrote in news:evj2m0$jb7$1
@nnrp.linuxfan.it:

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!

John,

With that insight and rigorous development, it must be time for you to
publish a book.

Owen

Constructive interference in radiowave propagation
 

Owen Duffy wrote:

...
John,

With that insight and rigorous development, it must be time for you to
publish a book.

Owen

Owen:

How'd you guess?

Title of book, "Spontaneous Thermal Emission of RF Finals and Feedline
in Amateur Radio Systems With No Apparent Cause(s)!"

Trouble is, the book stores keep putting it with the works on fiction :-(

JS

Constructive interference in radiowave propagation
 

Owen Duffy wrote in
:

lines context with declaration, while actually carrying the analytical

That should have read "without declaration".

Constructive interference in radiowave propagation
 

Roy Lewallen, W7EL wrote:
"A real analysis of energy flow involves calculating the power at
various points and times in the circuit or transmission line of
interest."

Yes. Bird Electronic Corporation has done a good job of this with its
"Thruline" wattmeter for several decades.

Its practice is to measure in a 50-ohm Zo resistive lossless impedance
environment where forward and reflected waves are 180 regrees
out-of-phase. This allows Bird to say:
"Power delivered and dissipated in the load is given by:
Watts into Load = Wforward - Wreflected"

I would not argue with success.

Best regards, Richard Harrison, KB5WZI

Constructive interference in radiowave propagation
 

Richard Harrison wrote:
Roy Lewallen, W7EL wrote:
"A real analysis of energy flow involves calculating the power at
various points and times in the circuit or transmission line of
interest."

Yes. Bird Electronic Corporation has done a good job of this with its
"Thruline" wattmeter for several decades.
. . .

No, the Bird wattmeter measures only the average power and only at one
point. That's vastly different from what I described, which is
instantaneous power as a function of time at many points along the line.
A complete analysis of energy flow would include equations for the power
as a function of time and position. You're sadly mistaken if you think
you're getting this information from your Bird wattmeter.

Roy Lewallen, W7EL

Constructive interference in radiowave propagation
 

John Smith I wrote in news:evji53$kf9$1
@nnrp.linuxfan.it:

Owen Duffy wrote:

...
John,

With that insight and rigorous development, it must be time for you to
publish a book.

Owen

Owen:

How'd you guess?

Title of book, "Spontaneous Thermal Emission of RF Finals and Feedline
in Amateur Radio Systems With No Apparent Cause(s)!"

Trouble is, the book stores keep putting it with the works on fiction
:-(

John, it will never sell to the amateur market... you need a simple,
catchy title. If it is destined for the fiction category, you could offer
an sub title like "How reflections ruined my PA... from a ham who
survived to tell the REAL story", with "Don't let it happen to you"
emblazened in flouro red across the cover.

Seriously, simple explanations are appealing, they provide content for
discussion by experts on-air, whether they are correct or not. Simple
explanations can be good, but incorrect ones are never good.

Owen