Constructive interference in radiowave propagation
 

"Cecil Moore"
Being a little more precise:
With mutually incoherent equal-magnitude sources,
the maximum possible peak intensity is double the
intensity of a single wave. There's no interference.
____________

BUT, the two equal-power signals in my scenario are exactly coherent at the
output port where they combine to produce twice average output power of
either tx.

Please explain, in light of your concepts?

RF

Constructive interference in radiowave propagation
 

Keith Dysart wrote:
Except that Richard's description sure seems to meet the
requirements of coherency. Can you offer a way for use
to know whether two signals are coherent?

If we can cause them to interfere, that is proof that
they are coherent. If their reflected waves superpose
with destructive or constructive interference present,
then they are coherent.

Secondly, I am at a complete loss to understand how you
can be arguing that when two signals of a particular
power interfere, the result is 4 times the power. This
sure seems like you're getting something from nothing.

Maybe it seems that way to you but it's because of
confusion. If the intensity of each of two coherent
waves is one watt/unit-area and total destructive
interference occurs at one point, two watts/unit-area
have seemingly disappeared. Since energy cannot disappear,
those two watts/unit-area must appear as constructive
interference somewhere else. If total constructive
interference appears somewhere else, the total intensity
is one watt/unit-area from the first wave, one watt/unit-area
from the second wave, plus the two watts/unit-area from
the total destructive interference. Adding all those
intensities up gives us four watts/unit-area at the point
of total constructive interference. The intensity at
the total destructive interference point plus the
intensity at the total constructive interference point
still averages out to two watts/unit-area, exactly the
intensities in the original waves and exactly what it
takes to satisfy the conservation of energy principle.

Your "something for nothing" doesn't exist. In the absence
of a local source, any constructive interference must be
offset by an equal magnitude of destructive interference.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Richard Fry wrote:
"Cecil Moore"
Being a little more precise:
With mutually incoherent equal-magnitude sources,
the maximum possible peak intensity is double the
intensity of a single wave. There's no interference.
____________

BUT, the two equal-power signals in my scenario are exactly coherent at
the output port where they combine to produce twice average output power
of either tx.

Please explain, in light of your concepts?

I thought I did. You have combined those outputs
without producing any interference. If there is
no interference, as far as power goes, it doesn't
matter if they are coherent or not.

Assuming P1 is the power output of the first
transmitter and P2 is the power output of the
second transmitter, if Ptotal = P1 + P2 + 0,
the interference (last) term is obviously zero,
i.e. it's prima facie - no interference.

If you double the H-field (current) while keeping
the E-field (voltage) constant, you have not
produced any interference.

If you double the E-field (voltage) while keeping
the H-field (current) constant, you have not
produced any interference.

If you double both the E-field (voltage) and the
H-field (current) at the same time, you have produced
total constructive interference.

If you zero both the E-field (voltage) and the
H-field (current) at the same time, you have produced
total destructive interference.

For interference to exist, both the E-field and
H-field must be changed by the same percentage
thus keeping their Z0 ratio constant.

If both fields decrease, extra energy is available
during that destructive interference event. If both
fields increase, extra energy is required by that
constructive interference event. In the absence
of a local source, |destructive interference| must
always equal |constructive interference|.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Keith Dysart wrote:
The junk science is often presented with very rational sounding
arguments and it can be difficult to detect the flaws. This example
was a case for me and you expose the flaw nicely.

Hint to omniscient gurus: One cannot use ignorance
for exposing flaws. Roy says in his Food for Thought
article:

I personally don't have a compulsion to understand where this power "goes".

Seemingly, that feeling of his is supposed to be enough
incentive to discourage the rest of us to give up on our
quest for tracking the energy through the system.

Roy has ploinked me for disagreeing with him. What
does that say about his inability to technically
defend his concepts?

The S-Parameter equations completely debunk what Roy
posted.

b1 = s11(a1) + s12(a2) = 0

|b1|^2, the reflected power, equals zero because
of wave cancellation involving those components
of a1 (forward normalized voltage) and a2 (reflected
normalized voltage).

If s11, a1, s12, and a2 are all non-zero, then wave
cancellation has occurred between s11(a1) and s12(a2)
proving Roy's statements to be false. The above wave
cancellation happens every time a ham adjusts his
antenna tuner for zero reflected power.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

On 9 Apr 2007 07:08:56 -0700, "Keith Dysart" wrote:

On Apr 9, 9:04 am, Cecil Moore wrote:
Yes, there is obviously no interference between the
two transmitters if the powers simply add together.

is more than slightly disconnected from:

Secondly, I am at a complete loss to understand how you
can be arguing that when two signals of a particular
power interfere, the result is 4 times the power. This
sure seems like you're getting something from nothing.

What happened to the staunch acceptance of 'conservation of
energy'?

Called discarding the baby with the bath water. Such is the fate of
observed reality in the face of novel theories.

This specious argument (posing quadruple powers to confound
expectations) demands the slight of hand rhetoric in that when clear
minds consider the entire field of radiation is summed, then you get
the average of reinforced energy and canceled energy which is:
2

This merely reinforces yet another observed (but rhetorically
dismissed) reality:
Richard Fry wrote:
The total average power available at the hybrid output for both of these
conditions is twice that of a single tx without the hybrid.

73's
Richard Clark, KB7QHC

Constructive interference in radiowave propagation
 

Richard Clark wrote:
This specious argument (posing quadruple powers to confound
expectations) demands the slight of hand rhetoric ...

Do you really think that Born and Wolf engage in
"slight of hand rhetoric"? Quoting them speaking
of the combined intensity of two equal magnitude
waves, I1 and I2.

"... and the intensity varies between a maximum
value Imax = 4*I1, and a minimum value Imin = 0
(Fig. 7.1)."

Fig. 7.1 is a sinusoid with a varying amplitude
from 0 to 4*I1 on the Y axis and relative phase
angle plotted on the X axis.

The average intensity is, of course, 2*I1 in
accordance with the conservation of energy
principle. Such is the nature of constructive
and destructive interference.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Cecil Moore wrote:
Richard Fry wrote:
"Cecil Moore"
Being a little more precise:
With mutually incoherent equal-magnitude sources,
the maximum possible peak intensity is double the
intensity of a single wave. There's no interference.
____________

BUT, the two equal-power signals in my scenario are exactly coherent
at the output port where they combine to produce twice average output
power of either tx.

Please explain, in light of your concepts?

I thought I did. You have combined those outputs
without producing any interference. If there is
no interference, as far as power goes, it doesn't
matter if they are coherent or not.

Assuming P1 is the power output of the first
transmitter and P2 is the power output of the
second transmitter, if Ptotal = P1 + P2 + 0,
the interference (last) term is obviously zero,
i.e. it's prima facie - no interference.

If you double the H-field (current) while keeping
the E-field (voltage) constant, you have not
produced any interference.

If you double the E-field (voltage) while keeping
the H-field (current) constant, you have not
produced any interference.

If you double both the E-field (voltage) and the
H-field (current) at the same time, you have produced
total constructive interference.

If you zero both the E-field (voltage) and the
H-field (current) at the same time, you have produced
total destructive interference.

For interference to exist, both the E-field and
H-field must be changed by the same percentage
thus keeping their Z0 ratio constant.

If both fields decrease, extra energy is available
during that destructive interference event. If both
fields increase, extra energy is required by that
constructive interference event. In the absence
of a local source, |destructive interference| must
always equal |constructive interference|.

Cecil,

You are quite prolific at manufacturing even more crystalline spheres.

8-)


73,
Gene
W4SZ

Constructive interference in radiowave propagation
 

Cecil Moore wrote:
Gene Fuller wrote:
We seem to be switching from RF to optics in order to explain
something or other, ...

Gene, I forgot to ask. At exactly what EM frequency
do the RF waves stop obeying the century old laws of
physics for visible light?

Cecil,

It is interesting that you rarely address the technical points that I
make. It is usually something along the lines of the above throwaway
comments.

What are you trying to hide?

I am still waiting to learn the technical details of "cancellation",
including the proper units and the characteristic equations. There has
been deafening silence in response to my similar query about
"interference".

I have been called lots of things in my life, mostly deserved, but
rarely have I been called ignorant. It is obvious that this thread has
long outlived any chance for a meaningful discussion.

You win! Keep on building more spheres.

73,
Gene
W4SZ

Constructive interference in radiowave propagation
 

Gene Fuller wrote:
You are quite prolific at manufacturing even more crystalline spheres.
8-)

I just love the technical content of your postings. :-)
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

On Mon, 09 Apr 2007 17:17:40 GMT, Cecil Moore
wrote:

The average intensity is, of course, 2*I1

Which satisfies (after a flurry of reference shuffling, oblique
jargon, obscure rhetoric, and ordinary BAFFLEGAB) the simple inquiry:
The total average power available at the hybrid output for both of these
conditions is twice that of a single tx without the hybrid.

Does the quote from Born and Wolf support this?