"Richard Harrison" wrote in message
...
Richard Clarks advice is good. Arnold B. Bailey in "TV and Other
Receiving Antennas" does a more extensive job of explaining how antennas
work than most other authors. Wish everybody interested in antennas
could read Bailey.His catalog of antenna types is convenient too.

It's out of print, but I've requested a copy through interlibrary loan. I'm
curious to see what he has to say on the standard V-shaped rabbit ears that
have been in use for decades... although one can readily simulate them and see
exactly how they perform, I've yet to find anyone who had a good idea as to
why rabbit ears haven't traditionally been oriented purely horizontally!

Roy Lewallen wrote:

*Sigh*

Richard Harrison wrote:

Roy Lewallen, W7EL wrote: "A short while ago, I explained why your
Faraday cage doesn`t separate the E and H fields as you claim." n I
am misunderstood. I never used the tem Faraday cage. I understand the
Faraday cage to be a completely shielded enclosure which could be a
metal automobiole body, a steel rebar reinforced concrete structure
or a screened room. These all tend to completely block both the
E-field and the H-field components of an electromagnetic wave.


Sorry, I meant "Faraday screen", which is the term you used, and I used
in my posting explaining its operation.

If you block either the E or H field, you also block the other. You
can't independently block one or the other.

. . .


Why would one pay a lot of extra money for a transformer which
eliminated capacitive coupling if it didn`t work, especially in
Havana, Cuba?


Because in order to "work" it doesn't need to "eliminate capacitive
coupling". All it needs to do is locally reduce the E/H field ratio,
which is what it does.

Roy Lewallen, W7EL

It might be useful to also point out the means by which these electric
and/or magnetic shields do their job. They do it not so much by
blocking as much as by diverting the fields. They serve to conduct the
field around the object that is being shielded.

73 de ac6xg

Cecil,

I do not have a copy of Hecht, but I doubt that he has made any serious
mistakes. Certainly he should have no mistakes in an area that is as
well understand and widely discussed as plane wave interactions with
discontinuities in the medium.

The classic treatment of this problem, found in virtually every
college-level textbook on E&M or optics, is to set up the appropriate
wave equations, add the boundary conditions, and crank out the answer.

Then there is typically some sort of analysis and discussion that says,
"The reflected intensity plus the transmitted intensity is equal to the
incident intensity. Energy is conserved." I suspect Hecht provides
exactly that sort of description. I know that all of the relevant
textbooks I have do so.

I believe you are reading too much into something Hecht is saying,
perhaps in an effort to somehow reconcile conservation of energy.

The beauty of the laws of E&M, as expressed by Maxwell's equations and
other fundamental properties, is that conservation of energy is
automatic, at least in ordinary circumstances. If one correctly solves
for the field equations, the energy conservation will come along for free.

Conversely, it is customary to use energy considerations as the primary
vehicle for addressing many physical problems in advanced mechanics,
quantum mechanics, solid state physics, and other branches of science.

The bottom line is that there are a number of tools available to develop
correct solutions to physical problems. Steve Best chose one path, and
you choose another. You both come up with the same answer in terms of
what can be measured. The mathematical constructs underlying the
solution may be different, but those constructs are not directly measurable.

Don't limit your toolbox. Sometimes a screwdriver is easier to use than
a monkey wrench.

73,
Gene
W4SZ



Cecil Moore wrote:
Gene Fuller wrote:

I thought my intention was obvious, but it seems I failed to communicate.


Others on this newsgroup have admonished me for worrying about
energy and refused to discuss the subject. I thought you were
doing the same. Sorry. But do you actually have any references
that contradict "Optics", by Hecht?

In Dr. Best's article, he superposes V1 with V2 such that constructive
interference energy is needed to complete the superposition. On this
newsgroup, I asked Dr. Best where that necessary constructive interference
energy comes from and he didn't know. That's when I went searching for
references and found them in the field of optics.

Constructive interference energy can be supplied by local sources
as occurs in W7EL's "Food for Thought #1" with its DC example. Or
constructive interference energy can be supplied at a point away
from the source(s) by destructive interference, e.g. wave cancellation
at the non-reflection surface of a layer of thin-film on glass or
at a match point in a transmission line.

Reg Edwards wrote:
What have photons to do with winning a contest? ;o)

Just try winning a contest without them. :-)
--
73, Cecil, http://www.qsl.net/w5dxp

Gene Fuller wrote:
I do not have a copy of Hecht, but I doubt that he has made any serious
mistakes.

It would be worth your while to visit a local university and
check out Hecht's chapters on superposition and interference.

"The reflected intensity plus the transmitted intensity is equal to the
incident intensity. Energy is conserved." I suspect Hecht provides
exactly that sort of description.

Much more than that. As you know, irradiance is power/unit-area
and Hecht spends many pages on irradiance and energy.

I believe you are reading too much into something Hecht is saying,
perhaps in an effort to somehow reconcile conservation of energy.

Spoken by someone who hasn't even read Hecht? I suspect if you
read Hecht, you would perceive the same information as I. Hecht
is big on conservation of energy and spends many pages discussing
such things involving EM waves.

The beauty of the laws of E&M, as expressed by Maxwell's equations and
other fundamental properties, is that conservation of energy is
automatic, at least in ordinary circumstances.

There is still an underlying Q&A about what happens to the energy
in those waves. The energy concept is in addition to what's already
there, not any kind of replacement for it.

The bottom line is that there are a number of tools available to develop
correct solutions to physical problems. Steve Best chose one path, and
you choose another.

Nope, we chose the same path. Steve just fell off the path and
down the cliff about 2/3 of the way through his articles. Steve
gave us a very good picture of what happens to the energy toward
the load but he gave us a distorted view of what happens to the
energy toward the source. Instead of Steve's one-sided approach,
I presented both sides thus merely expanding what Steve had
already done.

Don't limit your toolbox.

Funny, just above you seemed to recommend limiting the toolbox
to Maxwell's equations and tried to discourage me from thinking
about energy.
--
73, Cecil, http://www.qsl.net/w5dxp

Cecil,

The waves you are so worried about are merely convenient, but
fictitious, adjuncts to your mathematical model.

You need worry only about the energy of real, measurable waves, not
those adjuncts that simplify the math.

The use of such adjuncts is done frequently in solving real problems.
Just don't confuse the internals of the model with physical reality.

73,
Gene,
W4SZ

Cecil Moore wrote:
There is still an underlying Q&A about what happens to the energy
in those waves. The energy concept is in addition to what's already
there, not any kind of replacement for it.

Gene Fuller wrote:

Cecil,

The waves you are so worried about are merely convenient, but
fictitious, adjuncts to your mathematical model.

You need worry only about the energy of real, measurable waves, not
those adjuncts that simplify the math.

The use of such adjuncts is done frequently in solving real problems.
Just don't confuse the internals of the model with physical reality.

73,
Gene,
W4SZ

Might this be an example, Gene?

From "An Energy Analysis at an Impedance Discontinuity in an RF
Transmission Line, Part I"

"100% wave cancellation means 100% energy reflection."

73 de ac6xg

Gene Fuller wrote:
The waves you are so worried about are merely convenient, but
fictitious, adjuncts to your mathematical model.

Let's see:
1. Canceled waves are "fictitious adjuncts to my math model".
2. Therefore, they don't need to be canceled, because they
are only "fictitious adjuncts to my math model".
3. Therefore, we can remove whatever is doing the canceling
of those "fictitious adjuncts" without changing anything.
4. Darn, how is it that I can see those "fictitious adjuncts
to my math model" so well that I can't see anything else?

What's wrong with this picture? Could there be a not-so-hidden
contradiction accompanied by confusion of cause and effect?

You need worry only about the energy of real, measurable waves, not
those adjuncts that simplify the math.

You don't even know me, Gene. Where do you get the balls to
decide what I need to worry about and what I don't need to
worry about? I have been worried and needing an energy analysis
model for 40 years. I now have one and can now sleep like a baby
at night, but no thanks to you. :-)
--
73, Cecil, http://www.qsl.net/w5dxp

"Joel Kolstad" bravely wrote to "All" (06 Dec 05 09:28:55)
--- on the heady topic of " Antenna reception theory"

JK From: "Joel Kolstad"
JK Xref: core-easynews rec.radio.amateur.antenna:220898

JK "Richard Harrison" wrote in message
JK ...
Richard Clarks advice is good. Arnold B. Bailey in "TV and Other
Receiving Antennas" [,,,]

JK It's out of print, but I've requested a copy through interlibrary
JK loan. I'm curious to see what he has to say on the standard V-shaped
JK rabbit ears that have been in use for decades... although one can
JK readily simulate them and see exactly how they perform, I've yet to
JK find anyone who had a good idea as to why rabbit ears haven't
JK traditionally been oriented purely horizontally!


I think the reason why you don't see rabbit ears oriented horizontally
is that they don't seem to work well as dipoles. When standing up they
aren't even a V antenna and at first one would think they are
vertically polarized but they are somewhat directive with a bipolar
pattern. Rabbit ears are a *******ized form of a couple antenna types.

Sometimes mainly one element is responsible for most of the signal
while the other behaves as a reference or ground. For example on low
frequency channels like Ch-3, reception is best if one of the elements
is oriented straight up and the other horizontally pointing in the
direction of the transmitter. This won't work well with Ch-12 and the
standing V is best then.

A*s*i*m*o*v

.... Men are men and needs must err. - Euripides

Jim Kelley wrote:
"100% wave cancellation means 100% energy reflection."

That's a no-brainer when quoted in the context of an
RF transmission line. Shame on you for once again quoting
something out of context. If it happened in space, it
would say, "100% wave cancellation means 100% energy
redistribution." as explained on the web pages below.

There are only two directions in a transmission line. If
energy rejected by a mismatched load doesn't make it to
the source, in a lossless system, it must necessarily
be 100% re-reflected. Rho^2 is reflected by the impedance
discontinuity at the match point. That's step one. Step
two is that 100% wave cancellation. Given those two steps,
no reflected energy flows toward the source. Therefore,
it must necessarily have been re-reflected back toward the
load. Since it joins the forward energy wave, we can
measure that is exactly what happens. It's a no-brainer.

Here's the in-context quote.

The destructive interference energy resulting from wave
cancellation at an impedance discontinuity becomes an equal
magnitude of constructive interference in the opposite
direction. Since there are only two directions in a transmission
line, wave cancellation is the equivalent of an energy reflection.
100% wave cancellation means 100% energy reflection. [9]

[9] Quotes from two web pages from the field of optical engineering:

www.mellesgriot.com/products/optics/oc_2_1.htm

"Clearly, if the wavelength of the incident light and the thickness
of the film are such that a phase difference exists between reflections
of p, then reflected wavefronts interfere destructively, and overall
reflected intensity is a minimum. If the two reflections are of equal
amplitude, then this amplitude (and hence intensity) minimum will be
zero."

"In the absence of absorption or scatter, the principle of conservation
of energy indicates all ‘lost’ reflected intensity will appear as
enhanced intensity in the transmitted beam. The sum of the reflected and
transmitted beam intensities is always equal to the incident intensity.
This important fact has been confirmed experimentally."

http://micro.magnet.fsu.edu/primer/j...ons/index.html

"... when two waves of equal amplitude and wavelength that are
180-degrees ... out of phase with each other meet, they are not actually
annihilated, ... All of the photon energy present in these waves must
somehow be recovered or redistributed in a new direction, according to
the law of energy conservation ... Instead, upon meeting, the photons
are redistributed to regions that permit constructive interference, so
the effect should be considered as a redistribution of light waves and
photon energy rather than the spontaneous construction or destruction of
light."

Note from W5DXP: In an RF transmission line, since there are only two
possible directions, the only "regions that permit constructive
interference" at an impedance discontinuity is the opposite direction
from the direction of destructive interference.
--
73, Cecil, http://www.qsl.net/w5dxp