On May 28, 5:46*pm, lu6etj wrote:
Tonight I said to me: -the worst term
that you could use, Miguel, was "ether"- :), because "ether" is a
hipotetical MATERIAL thing, ...
The first guesses at the nature of the ether were obviously wrong. But
we now know that if you replace the word "ether" with "quantum soup"
in your statements about ether, that you will be technically correct
as far as quantum physics can determine. Take a look at the Casimir
Effect to see if empty space is really empty. In reality, totally
empty space would be outside of the space/time of the known universe.
http://www.answers.com/topic/casimir-effect
I needed know what represent that in a line discontinuity (in a load
seems obvious) to better understand Cecil's examples in web page
(http://www.w5dxp.com/energy.htm).
At the junction of two transmission lines, if the characteristic
impedances (Z01 and Z02) are not the same value, then reflections and
subsequent interference will usually occur. This is similar to saying:
At the junction of two light mediums, if the index of refraction is
not the same value in both mediums, then reflections will occur from a
(laser) light beam normal to the two surfaces. I am specifying
normal=90 deg. and ignoring refraction which is of little importance
in an RF transmission line.
Before continue I want to do a comment to know if we agree (more or
less). We partially think with words or symbols, words and symbols
represent concepts or perceptions, concepts are not "out there", as
Einstein said they a "free creations of human mind".
And Shakespeare said:
"What's in a name? that which we call a rose
By any other name would smell as sweet; ..."
There's not much argument between the definition of "rose" and
"rosal". I call that a 1st level abstraction. Things get a little more
complicated at the Nth level abstraction. If in Texan I said, "Ah
reckon Ah'm gonna amble over yonder directly", you might have trouble
with the meaning (except for "amble". :-)
Cecil I want to ask you if you are using "photon" term to
methaforically refer to "light".
No, EM (light and RF) waves are known to be quantized and therefore
consist of photons. The reason that I refer to the photons is that
photons must obey a certain set of laws of physics. For instance, they
must move at the speed of light in a medium. Photons cannot stand
still in a standing wave. Therefore, any theory of physics that
requires photons to stand still is incorrect. That would include the
particular interpretation of the lumped-impedance model that some
folks are pushing here on this newsgroup. The only time I will refer
to photons is when the presented EM wave theory contradicts the
accepted laws of quantum physics. It is simply an attempt at trying to
keep some folks honest.
Even I agree at
our concept that electromagnetic spectrum includes RF waves and ligh
waves and they are the same phenomenon, I think that is a result of
great insight and efforts of the human mind, it is not so evident. We
see light, we sense infrared radiaton, but we can not perceive well RF
without instruments (unless we introduce ourselves in a micowave oven
or burn with the antenna, of course ).
The point is that what we see at visible light frequencies also
happens at RF frequencies but we cannot see RF. By switching to a
visible light example, I can point out the errors of someone
attempting to pull the wool over the eyes of the unwashed masses.
(I do not forget Roy's article, I'm still trying to sort out all the
puzzle pieces).
Note that Roy seems to be completely ignorant of this fact of physics:
"... the photons are redistributed to regions that permit constructive
interference ..." as described on the Florida State web page at the
bottom of the page:
micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/
waveinteractions/index.html
In an RF transmission line, the only "regions that permit constructive
interference" is the single opposite direction in the transmission
line from the direction of destructive interference. In the absence of
a localized source of energy, any destructive interference in one
direction (at an isolated impedance discontinuity in a transmission
line) must be balanced by an equal magnitude of constructive
interference in the opposite direction. The conservation of energy
theorem will have it no other way.
If you are familiar with the scattering parameter/matrix equations,
much can be learned by analyzing them. Note that the equations are
phasor math, not simple algebra equations.
http://www.sss-mag.com/pdf/hpan95-1.pdf
b1 = s11*a1 + s12*a2
b1, the total reflected voltage toward the load, is equal to the
forward voltage (from the source) reflected from the impedance
discontinuity, phasor added to the transmitted reflected voltage
through the impedance discontinuity (from the load).
b2 = s21*a1 + s22*a2
The total forward voltage toward the load, is equal to the transmitted
forward voltage through the impedance discontinuity (from the source),
phasor added to the reflected voltage (from the load) that is re-
reflected back toward the load by the impedance discontinuity.
The a and b parameters are voltages normalized to the square root of
Z0. Squaring both sides of each equation will yield the interference
terms in watts, that indicate where the energy goes, i.e. which of two
directions in a transmission line.
Note that if b1 = 0, there is (by definition) total destructive
interference between s11*a1 and s12*a2, i.e. the same as a Z0-match in
a transmission line.
Even if no classic reflections (associated with a physical reflection
coefficient) exist, as in Roy's foot-for-thought example, destructive
interference at the source resistor will cause some or all of the
energy in the reflected wave to be *redistributed* (redirected) back
toward the load as constructive interference. Since the wave
cancellation causes a reversal in direction of reflected energy
(somewhat resembling a reflection) Walter Maxwell, in "Reflections"
defines that reversal as a "reflection from a virtual short".
Presumably the virtual short (or open) concept would also apply to a
1/4WL thin-film coating on non-reflective glass.
Miguel, "redistribute" is not in my Spanish/English dictionary but
"redirect" is and might be a reasonable mental substitute for you to
conceptualize. From the FSU web page, ...the photons are redistributed
(i.e. redirected) to regions that permit constructive
interference ... .
--
73, Cecil, w5dxp.com