"Cecil Moore" wrote in message
...
Richard Fry wrote:

TV Ghosting (quotes below)

To elaborate, the visibility of a ghost image in analog TV systems is
related to the magnitude, phase and time displacement of the RF
reflection
that produced it as compared to the original, or non-reflected waveform.

The round-trip transit time from the TV tx output to the mismatch in its
antenna system will determine the time displacement of the ghost, at the
rate of 1 microsecond of displacement per ~490 feet of distance between
the
tx and the reflection plane (vp = 0.997c).

Richard, you know you are going against the conventional wisdom on
this newsgroup. Ghosting cannot exist during steady-state so if
ghosting exists it simply means that you are still in the transient
state and the steady-state doesn't exist (yet).
--
73, Cecil http://www.qsl.net/w5dxp
Looking for the smiley face. It is probably fair to say that in the *general
case* there is no steady reflection in video transmission, unless the round
trip delay is N horizontal lines. BTW, weirdest case I saw came when the dog
chewed through the cable. Now I was seeing the main signal coming from the
cable, plus a ghost that was picked up directly from the transmitter. The
ghost was to the left and above the main signal.

Tam/WB2TT

Tam/WB2TT wrote:

"Cecil Moore" wrote:
Richard, you know you are going against the conventional wisdom on
this newsgroup. Ghosting cannot exist during steady-state so if
ghosting exists it simply means that you are still in the transient
state and the steady-state doesn't exist (yet).

Looking for the smiley face.

Is there a smiley face that means, "sad but true"? Many otherwise
intelligent, knowledgeable, educated engineers have attempted to force
their metaphysical "steady-state" agenda on uninitiated and unsuspecting
victims. One is saddened by such an event and one wonders why. Does
a steady-state religion or creed exist within amateur radio? If so,
what are its purpose and goals?
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Tam/WB2TT wrote:

"Cecil Moore" wrote:
Richard, you know you are going against the conventional wisdom on
this newsgroup. Ghosting cannot exist during steady-state so if
ghosting exists it simply means that you are still in the transient
state and the steady-state doesn't exist (yet).

Looking for the smiley face.

Is there a smiley face that means, "sad but true"? Many otherwise
intelligent, knowledgeable, educated engineers have attempted to force
their metaphysical "steady-state" agenda on uninitiated and unsuspecting
victims. One is saddened by such an event and one wonders why. Does
a steady-state religion or creed exist within amateur radio? If so,
what are its purpose and goals?
--
73, Cecil http://www.qsl.net/w5dxp


From this I infer that Cecil believes that once the transient portion of
the response has concluded you are in the steady state and no more
reflections are occurring. Is this a correct re-statement of your belief,
Cecil?
Steve N.

Steve Nosko wrote:
From this I infer that Cecil believes that once the transient portion of
the response has concluded you are in the steady state and no more
reflections are occurring. Is this a correct re-statement of your belief,

No, no, no. That is a re-statement of the other side of the argument
from mine. I often use devil's-advocate type arguments.

The definition of steady-state by the other side is pure unvarying
sine waves with no noise and no modulation. Then the reflections
sorta disappear into a steady-state mush of standing waves. A
modulated TV signal, according to their argument, is not a steady-
state signal. Within this steady-state mush of standing waves, energy
never makes it from the load back to the match point. Apparently,
because of the uncertainty principle, reflected energy doesn't
actually exist anywhere until it is radiated or dissipated, i.e.
its probability wave collapses.

I have challenged them to produce a standing wave without a rearward-
traveling wave but nobody has been up to that challenge.
--
73, Cecil http://www.qsl.net/w5dxp




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Cecil Moore wrote:

Steve Nosko wrote:
From this I infer that Cecil believes that once the transient portion of
the response has concluded you are in the steady state and no more
reflections are occurring. Is this a correct re-statement of your belief,

No, no, no. That is a re-statement of the other side of the argument
from mine.

Perhaps he thought you believed that because you're the only one who has
said it?

73, Jim AC6XG

Jim Kelley wrote:

Cecil Moore wrote:

Steve Nosko wrote:
From this I infer that Cecil believes that once the transient portion of
the response has concluded you are in the steady state and no more
reflections are occurring. Is this a correct re-statement of your belief,

No, no, no. That is a re-statement of the other side of the argument
from mine.

Perhaps he thought you believed that because you're the only one who has
said it?

It's a very condensed verion of the reams of stuff that some posters have
posted over the past year. In particular, when I tried to introduce noise
and modulation to prove my point, I was told that noise and modulation are
not allowed during steady-state.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
It's a very condensed verion of the reams of stuff that some posters have
posted over the past year. In particular, when I tried to introduce noise
and modulation to prove my point, I was told that noise and modulation are
not allowed during steady-state.

Stands to reason. Intentionally absent from the steady state are noise,
modulation, transients, and any other perturbation. It would be kinda
like opening the lid of an adiabatic chamber in order to see if the
internal temperature stays constant.

73, Jim AC6XG

Cecil Moore wrote:

[snip]

The definition of steady-state by the other side is pure unvarying
sine waves with no noise and no modulation.

[snip]

I have challenged them to produce a standing wave without a rearward-
traveling wave but nobody has been up to that challenge.

73, Cecil http://www.qsl.net/w5dxp

Cecil,

I don't plan to enter this endless argument about transmission lines,
but there are a couple of points you might want to consider.

* Steady state simply means that a phenomenon has no inherent reference
to its time of origin. One cannot observe a steady-state wave and
determine any clue about when it started. It contains no absolute time
markers. A transient, on the other hand, contains direct reference
information about when it was formed. There is no requirement that the
steady state phenomenon is a simple sine wave.

Many problems in math, science, and engineering exhibit both transient
and steady state solutions. It is not clear why there is any confusion
at all in this thread.

* Standing waves don't require the pre-existence of traveling waves. A
straightforward application of Maxwell's equations with appropriate
boundary conditions for the physical environment will lead to standing
waves directly. Check out one of your recently quoted favorite authors,
J. C. Slater, and look at some of the resonant cavity stuff. Most
definitely standing waves, but you will find lots of complex Bessel
functions and darn few traveling waves.

In virtually every transmission line situation proposed on RRAA, whether
tuned antenna feed lines or quarter-wave stubs, the transmission line is
resonant. It is possible to consider the resulting standing waves as the
sum of two traveling waves, but it is equally valid to consider the
transmission line as a simple resonator. The physically measurable
instantaneous voltages and currents are precisely the same whether one
considers oscillation from capacitive to inductive energy storage in the
line or the sum of two counter-traveling waves.

You often refer to wave-particle duality and to the use of S-parameters
instead of lumped circuit analysis. The world of science and engineering
is absolutely filled with this sort of dual description for physical
phenomena. In many cases one approach will be more convenient or more
intuitive, but that does not make the dual approach less valid.

There's more than one way to skin a cat.

73,
Gene
W4SZ

Gene Fuller wrote:
* Standing waves don't require the pre-existence of traveling waves.

Please present an example of a standing wave that exists without
a forward-traveling wave component superposed with a rearward-
traveling wave component.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Gene Fuller wrote:

* Standing waves don't require the pre-existence of traveling waves.


Please present an example of a standing wave that exists without
a forward-traveling wave component superposed with a rearward-
traveling wave component.
--
73, Cecil http://www.qsl.net/w5dxp



Cecil,

Sorry, you are not paying attention.

I gave you a reference that is full of such examples. Another reference
you have quoted on numerous occasions is "Transmission Lines and
Networks" by Walter Johnson. Take a look on page 164. He gives a
description of standing waves and then comments, "One can imagine two
oppositely traveling waves, . . . "

Note that he uses "imagine", not required, essential, or any other
mandatory word.

I do not claim the use of superposed traveling waves is wrong. However,
it is merely a mathematical trick, not unlike describing a square wave
as a summation of Fourier components. This is very commonly done, and it
is often very useful. It does not mean that mathematically derived
sub-components are somehow more valid representations of nature than the
original form.

73,
Gene
W4SZ