Richard Clark wrote:
On Fri, 14 Dec 2007 09:45:04 -0800, Roger wrote:

Hi Richard,

The math seems to work, but if you have no use for it, disregard it. On
the other hand, if another perspective of electro magnetics that
conforms to traditional mathematics can provide additional insight, use it.

Hi Roger,

This does not answer why TWO mathematics (both traditional) are
needed, especially since one is clearly an approximation of the other,
and yet offers no obvious advantage. I've already spoken to the
hazards of approximations being elevated to proof by well-meaning, but
slightly talented amateurs.

The derivation did several things for me. It clearly explains why we do
not have a runaway current when we first connect a voltage to a
transmission line, what transmission line impedance is, that moving
particles can not be the entire explanation for the electromagnetic wave
(because the energy field moves much faster than the electrons), and
puts into place a richer understanding of inductance.

I am surprised at your criticism in using DC. To me, a square wave is
DC for a short time period.

This single statement, alone, is enough to be self-negating. You
could as easily call a car with a standard stick shift an automatic
between the times you use the clutch - but that won't sell cars, will
it?

We could use the concept of a stepped wave, but that would imply the
need for several steps to develop the formula. Only the square wave
front and continued charge maintenance is required, observations that
can be easily verified by experiment.

Is the observation that a square wave can
be described as a series of sine waves troubling to you? Perhaps the
observation that a square wave might include waves of a frequency so
high that they would not be confined in a normal transmission line is
surprising or troubling to you?

DC as sine waves is not a contradiction on the face of it? DC that
consists of waves of a frequency so high that it would not be confined
in a normal transmission line is very surprising, isn't it?


What is your point here? Are implying that the formula is incorrect
because a sine wave was not mentioned in the derivation. I am sure that
all of the sophisticated readers of this news group understand that the
sharp corner of the square wave is composed of ever higher frequency
waves. This leads Cecil to comment that the leading edge of a square
wave could be composed of photons, which is a valid observation. It
also explains your observation that true square waves are not possible
(I am paraphrasing your comments) because of dispersion.

It is interesting to run an FFT on a square wave to see how the
frequencies can be resolved.

Would it surprise you to find your batteries in their packaging direct
from the store are radiating on the shelf? They are DC, are they not?
If the arguments of your sources works for an infinite line, they must
be equally true for an infinitesimal open line. When your headlights
are on, do they set off radar detectors in cars nearby because of the
high frequencies now associated with DC?

They only set off the radar detectors when I turn them on and off. I
have high power lights!! A lightning strike is a much better example of
DC containing high frequencies.


My goal is to better understand electromagnetic phenomena. You have
given some very astute insight many times in the past and thanks for
that. Negative comment is equally valuable, but sometimes a little
harder to swallow.

The pollution of terms such as DC to serve a metaphor that replaces
conventional line mechanics is too shallow glass to attempt to quench
any thirst.

The puzzle here is the insistence on hugging DC, when every element of
all of your links could as easily substitute Stepped Wave and remove
objections. The snake in the wood pile is once having fudged what DC
means, it is only a sideways argument away from rendering the term DC
useless. Is the term Stepped Wave (the convention) anathema for a
leveraging the novel origination (the invention) of DC Wave?

73's
Richard Clark, KB7QHC

We would complicate the concept and thereby begin to confuse people if
we insisted on using the "Stepped Wave" term. It is a simple step to
recognize that if we can make a wave front with one battery, we can use
a lot of batteries and carefully place and switch them to form a sine
wave. The more batteries and switches, the better the representation.

Is there some harm in considering Zo = 1/cC? It should only add to the
tools we have to explain electromagnetic waves.

73, Roger, W7WKB

On Fri, 14 Dec 2007 10:09:59 -0800 (PST), Keith Dysart
wrote:

Do photons also explain how sound can move
at a 1000 ft/s, while the air molecules barely
move at all?

No, because those are called Phonons.

No? Not clear then why they are needed for
electrons.

Phonons and Photons both interact with Electrons as well as with each
other.

Following Cecil's fluff isn't very productive.

73's
Richard Clark, KB7QHC

This general discussion sounds a lot like a description of a traditional
TDR system using a step function. You should be able to find quite a bit
of information about this process on the web.

A number of relationships among delay, Z0, velocity factor, and L and C
per unit length are quite useful, and I've used them for many years. For
example, a transmission line which is short in terms of wavelength at
the highest frequency of interest (related to the rise time when dealing
with step functions) can often be modeled with reasonable accuracy as a
lumped L or pi network. The values of the lumped components can easily
be calculated from the equations relating delay, Z0, L per unit length,
and C per unit length.

Strictly speaking, DC describes only the condition when a steady value
has existed for an infinite length of time. But a frequency spectrum of
finite width also requires a signal which has been unchanging (except
for periodic variation) for an infinite time. In both cases, we can
approximate the condition with adequate accuracy without having to wait
an infinite length of time. In the case of a step response, we wait
until all the aberrations have settled, after which the response is for
practical purposes the DC response. People used to frequency domain
analysis having trouble with the concept of DC characteristics and
responses can often get around the difficulty by looking at DC as a
limiting case of low frequency.

I don't know if it's relevant to the discussion, but the velocity factor
of many transmission lines is a function of frequency. A classic example
is microstrip line, which exhibits this dispersive property because the
fractions of field in the air and dielectric changes with frequency.
Coaxial line, however, isn't dispersive (assuming that the dielectric
constant of the insulator doesn't change with frequency) because the
field is entirely in the dielectric. It will, therefore, exhibit a
constant velocity factor down to an arbitrarily low frequency -- to DC,
you might say. Waveguides, however, are generally dispersive for other
reasons despite the air dielectric. The shape of the step response of a
dispersive line is very distinctive, and is easily recognized by someone
accustomed to doing time domain analysis.

There seems to be a constant search on this newsgroup for amazing new
principles, and "discoveries" are constantly being made by
misinterpretation and partial understanding of very well established
principles. I sense that happening here. Anyone who's really interested
in gaining a deeper understanding of transmission line principles and
operation can benefit from a bit of study of time domain reflectometry
and other time domain applications. All the fundamental rules are
exactly the same, but the practical manifestations are different enough
that it can give you a whole new level of understanding.

Roy Lewallen, W7EL

Is there some harm in considering Zo = 1/cC? It should only add to the
tools we have to explain electromagnetic waves.

73, Roger, W7WKB

yes. because its WRONG. you have made an assumption that is not realistic
for any transmission line. There is no way a transmission line can have a
velocity factor of 1.0, just can't happen... all the equations fall apart
and become meaningless at that point. there is a reason for the velocity
factor, or beta, depending on which you prefer. learn it, and use it
properly, and it will serve you well.

Roy Lewallen wrote:
I don't know if it's relevant to the discussion, but the velocity factor
of many transmission lines is a function of frequency.

Dr. Corum's formulas indicate that the velocity factor
of large coils is also a function of frequency.
--
73, Cecil http://www.w5dxp.com

"Roger" wrote in message
. ..

Is there some harm in considering Zo = 1/cC? It should only add to the
tools we have to explain electromagnetic waves.

73, Roger, W7WKB

yes. because its WRONG. you have made an assumption that is not realistic
for any transmission line. There is no way a transmission line can have a
velocity factor of 1.0, just can't happen... all the equations fall apart
and become meaningless at that point. there is a reason for the velocity
factor, or beta, depending on which you prefer. learn it, and use it
properly, and it will serve you well.

AI4QJ wrote:
. . .
(I sure am learning a lot about antennas and transmission lines here)

I'm glad to hear that. Does the new knowledge include a way to tell the
four black boxes apart at one steady state frequency, or how many
"electrical degrees" each one contains?

Roy Lewallen, W7EL

Cecil Moore wrote:

...
No, mechanical longitudinal waves are well understood.
...

Indeed, I wonder if there is really anything else ...

Although Einstein "debunked" (and, we may even have to revisit this at a
later date) the "luminous ether", he granted the existence of the
"gravitational ether", one way or another, how those em waves-photons
"propagate", they do it in some form of ether ...

Show me an equation which takes that into consideration--I will grant we
are finally close to the right path ...

Regards,
JS

Roy Lewallen wrote:
I'm glad to hear that. Does the new knowledge include a way to tell the
four black boxes apart at one steady state frequency, or how many
"electrical degrees" each one contains?

Print s22 on each box and we won't even need to apply
power to the source.
--
73, Cecil http://www.w5dxp.com

AI4QJ wrote:
"Roger" wrote in message
. ..
AI4QJ wrote:
"Richard Clark" wrote in message
...
In a 231 line posting that contains only original 57 lines:
On Thu, 13 Dec 2007 17:26:17 -0800, Roger wrote:

Hi Roger,

This last round has piqued my interest when we dipped into DC. Those
"formulas" would lead us to a DC wave velocity?
Hi Richard,

Here are two links to pages that cover the derivation of the formula
Zo
= 1/cC and much more.

http://www.speedingedge.com/PDF-File..._Impedance.pdf
http://www.ece.uci.edu/docs/hspice/h...001_2-269.html

Here is the way I proposed to Kevin Schmidt nearly seven years ago
after
seeing him use the formula on a web page:
Hi Roger,

However, none of what you respond with actually gives a DC wave
velocity. At a stretch, it is a transient with the potential of an
infinite number of waves (which could suffer dispersion from the
line's frequency characteristics making for an infinite number of
velocities). The infinite is a trivial observation in the scheme of
things when we return to DC.

Attaching a battery casts it into a role of AC generation (for however
long the transmission line takes to settle to an irresolvable
ringing). Discarding the term DC returns us to conventional
transmission line mechanics.

DC, in and of itself, has no wave velocity.
For the model provided, R= 0, therefore we have a transmission line
consisting of superconductors. The speed at which steady state DC current
is injected into the model will equal the maximum speed of DC current in
the model. Although the electrons themselves will move very slowly, for
each coulomb injected in, one coulomb will be injected out at the same
velocity they were injected in (not to be confused with 'current' which
is the number of coulombs per second). If it were possible for the source
to provide DC current at c, then the DC current moves at c. The
capacitance C can be any value and Zo has no meaning. The only model that
works here is the one with a cardboard tube filled with ping pong balls,
in this case with 0 distance between them.

Ah, but of so little importance because the model is not reality.
While R (ohmic resistance) is specified as zero, impedance is what we are
looking for. Impedance is the ratio of voltage to current.

Roger the impedance is zero because the current is steady state DC. F = 0,

Zo = 0 -j*2*pi*0*C =0

It was already stated that we should ignore the wavefront of the step
function. What we are left with is steady state. So impedance is not what
'we' are looking for.

(I sure am learning a lot about antennas and transmission lines here)


Yes, I am learning a lot also.

Well, I did not say we should ignore the wave front, just the opposite.
The wave front gives us the time marker so that velocity has meaning
in relationship to a length of transmission line.

Roy is giving good advice to study time domain reflectometry. One
reference I looked at used different pulse widths to examine for faults
at different distances. That makes sense to me.

Where did you get the formula for Zo that resulted in a zero impedance?

73, Roger, W7WKB