On May 17, 9:10*am, Wimpie wrote:
On 17 mayo, 14:29, Cecil Moore wrote:









On May 17, 4:49*am, Wimpie wrote:

If you show up with a relevant
quest, maybe I am willing to dive into it.

Wim, here is why my questions for you are more than just relevant. It
is imperative that someone lecturing us on happenings inside that PA
RF volcano be able to understand what is occurring during a passive
event involving forward and reflected EM fields and waves occurring at
an impedance discontinuity outside of a PA.

Two of the physical quantities that must be conserved are energy and
momentum. EM RF fields and waves contain both energy and momentum
which must be conserved. I have asked you to tell us exactly what laws
of physics govern the reversal of the momentum and direction of energy
flow at a Z0-match at a passive impedance discontinuity in a
transmission line. You have refused to do so and asserted that such is
irrelevant. I contend that I could not have asked a more relevant
question - thus the reluctance to provide an answer.

The answer to the question is contained in my energy analysis article
at:http://www.w5dxp.com/energy.htm
A passive Z0-match relies on superposition of waves accompanied by
interference effects to explain the reversal of reflected wave energy
direction and momentum. Walter Maxwell has called the process a
"virtual open-circuit" or a "virtual short". In my article, I explain
how it is a two-step process involving normal reflections and
interference patterns at the impedance discontinuity. It works exactly
like non-reflective glass covering a picture with its 1/4WL thin-film
coating where two sets of reflected light waves undergo destructive
interference toward the viewer and, honoring the conservation of
energy and momentum, reverse their direction and momentum and flow in
the opposite direction toward the picture. This is a well-understood
phenomenon from sophomore physics 201. Why most RF engineers don't
understand this simple physical process involving EM wave interference
is beyond belief. Here's the Florida State University web page again:

micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/
waveinteractions/index.html

Set the java application for opposite phase and when the result is
zero, scroll down to the bottom of the page to find out what happens
to the energy components in the two waves that cancel to zero. Those
energy components "are redistributed to regions that permit
constructive interference" just as they are at a Z0-match in an RF
transmission line where there are only two possible directions for RF
energy flow. For every destructive interference event in one
direction, there will be an equal magnitude constructive interference
event in the opposite direction. At Walt's "virtual short", total
destructive interference energy toward the source is redistributed as
constructive interference energy back toward the load.

I studied this subject in my EE courses at Texas A&M during the
1950's. The textbook was: "Fields and Waves in Modern Radio", by Ramo
and Whinnery, (c) 1944, 1953. The subject is covered under "Quarter-
Wave Coating for Eliminating Reflections" in the chapter titled:
"Propagation and Reflection of Electromagnetic Waves".
--
73, Cecil, w5dxp.com
"Halitosis is better than no breath at all.", Don, KE6AJH/SK

Hello Cecil,

I am familiar with quarter wave (and multi layer) coatings to reduce
reflection. I am not waiting for a lecture on (un)bounded wave
propagation. *If I don't have something present in my mind, I know
where to find it.

As mentioned earlier, you can convert all the wave phenomena in the
coaxial feed line to impedance as seen by the PA. You are unnecessary
complicating things, hence loosing more public that may have interest
in this topic.

Maybe you (and other people) should carry out the experiments I
suggested in this thread (looking to forward power, net power and DC
input power versus small load mismatch [normally referenced to 50
Ohms] ).

With kind regards,

Wim
PA3DJSwww.tetech.nl


Wim, I'm amazed that you don't find the more-detailed explanation of
how impedance matching occurs via wave interference of any value. Many
RF engineers have traditionally believed that a PHYSICAL open or short
circuit is required to produce a reflection. As a professional antenna
engineer with RCA in 1973 I discovered and published the wave
mechanics that produces the VIRTUAL open and short circuits that are
required for achieving an impedance match. I took bashings from those
traditional engineers, who said reflections cannot be engendered by
wave interference, until they studied my data more carefully and
finally agreed I'm right. Remember, James Clerk Maxwell also had his
detractors until they finally saw the light.

Walt