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Dave May 12th 06 10:23 PM

FIGHT! FIGHT! FIGHT!
 
its raining, its going to rain all weekend, i already caught up my qsl card
replies, what can i do for fun this weekend... I know, troll a fight on
r.r.a.a! How about it you guys, you up for a return bout of lumps vs
distributions? how about adding powers, that one hasn't come up recently??
maybe a quick argument over why kirchoff's current equation doesn't work
with distributed systems?? Or could we drum up a good fight about
fractal-quad-yagi efficiency, or how cfa's can't work the way they are
claimed to? Come on, there must be a good one in there somewhere to get you
guys stirred up for a weekend! Who wants to be the first one to tell me i
can't use 75 ohm hardline without some fancy matching system?? Or why my
SWR meter is no good when i do? Come on, just a little fight???



[email protected] May 12th 06 10:35 PM

FIGHT! FIGHT! FIGHT!
 
SWR METERS ONLY INDICATE FORWARD CW POWER AND REVERSE CB JARGON INTO
THE CROSSED-FIELD FRAKTAL YAGI IF THE IMPEDANCE OF THE SLOW-WAVE
LOADING COIL TRANSMISSION LINE IS EXACTLY 49.0003000+j3.50003000 OHMS
PLUS OR MINUS 39%!

73,
Dan
N3OX


Dave May 12th 06 10:40 PM

FIGHT! FIGHT! FIGHT!
 
ALL RIGHT! thats the kind of assertion that should stir things up. I like
the 'slow-wave' part, thats a good one... maybe we should compare it to one
of those faster than light antennas in the patent archives and see if we can
get something going?

wrote in message
oups.com...
SWR METERS ONLY INDICATE FORWARD CW POWER AND REVERSE CB JARGON INTO
THE CROSSED-FIELD FRAKTAL YAGI IF THE IMPEDANCE OF THE SLOW-WAVE
LOADING COIL TRANSMISSION LINE IS EXACTLY 49.0003000+j3.50003000 OHMS
PLUS OR MINUS 39%!

73,
Dan
N3OX




Mike Coslo May 13th 06 02:16 AM

FIGHT! FIGHT! FIGHT!
 
Dave wrote:
ALL RIGHT! thats the kind of assertion that should stir things up. I like
the 'slow-wave' part, thats a good one... maybe we should compare it to one
of those faster than light antennas in the patent archives and see if we can
get something going?



How about a loss of de-Corum...... ;^)

Sorry Cecil, I'm a sucker for a bad pun!


- 73 de Mike KB3EIA -

Sal M. Onella May 13th 06 03:18 AM

FIGHT! FIGHT! FIGHT!
 

"Dave" wrote in message
. ..
its raining, its going to rain all weekend, i already caught up my qsl

card
replies, what can i do for fun this weekend... I know, troll a fight on
r.r.a.a! How about it you guys, you up for a return bout of lumps vs
distributions? how about adding powers, that one hasn't come up

recently??
maybe a quick argument over why kirchoff's current equation doesn't work
with distributed systems?? Or could we drum up a good fight about
fractal-quad-yagi efficiency, or how cfa's can't work the way they are
claimed to? Come on, there must be a good one in there somewhere to get

you
guys stirred up for a weekend! Who wants to be the first one to tell me i
can't use 75 ohm hardline without some fancy matching system?? Or why my
SWR meter is no good when i do? Come on, just a little fight???



Weekend fight promotion follows:

If a chicken-and-a-half can lay and egg-and-a-half in a day-and-a-half, how
long
would it take one regular chicken to lay a dozen eggs?

Most-favorable consideration will be given to answers submitted with a valid
Paypal account number and password. It need not be your own.

Email answers to


(There, that should about do it.)



Cecil Moore May 13th 06 04:17 AM

FIGHT! FIGHT! FIGHT!
 
Mike Coslo wrote:
How about a loss of de-Corum...... ;^)
Sorry Cecil, I'm a sucker for a bad pun!


I'm not sure K1AON and KB1EUD would appreciate
your pun.
--
73, Cecil http://www.qsl.net/w5dxp

[email protected] May 13th 06 12:19 PM

FIGHT! FIGHT! FIGHT!
 
There's a good fight brewing in QEX magazine land. Eric, K8LV, wrote a
pretty good article on directional wattmeters. But he spent a lot of
space asserting that the notion of forward and reflected power in a
transmission line is merely for intuitive convenience, isn't real, and
should be abandoned in favor of unidirectional power flow and lumped
analysis at a single point.

Whoo Hoo. The letters will be fun. Especially if Eric attempts to
extend his assertion to a case not-as-special, such as not-steady-state
or a point in 3D space.

Too bad it wasn't here. Bet we'd get a couple dozen posts before the
weekend's out. Anyone want to take Eric's side?


73,
Glenn AC7ZN


Cecil Moore May 13th 06 03:26 PM

FIGHT! FIGHT! FIGHT!
 
wrote:
There's a good fight brewing in QEX magazine land. Eric, K8LV, wrote a
pretty good article on directional wattmeters. But he spent a lot of
space asserting that the notion of forward and reflected power in a
transmission line is merely for intuitive convenience, isn't real, and
should be abandoned in favor of unidirectional power flow and lumped
analysis at a single point.


K8LV is like the person who is satisfied with the Sun God riding
his chariot across the sky every day as a model of reality. He seems
to believe in a Standing Wave God who wills standing waves into
existence without the necessity for a forward traveling wave and
a rearward traveling wave to exist. It reminds me of what Einstein
said about models of reality needing to be simple, but not too simple.

Over the years, I have challenged anyone on this newsgroup to create
a standing wave in a single source system without having the existence
of a forward wave and a reflected wave. Nobody has furnished any proof
that standing waves are possible in a single source system without the
existence of forward and reflected waves.

Reflected energy is readily apparent using a time domain reflectometer.
Reflected power is easily detected and dissipated using a signal
generator with a circulator and load. A bit of modulation proves that
the reflected wave has made a round trip to the mismatched load and
back to the circulator load.

With the following example, I have shown that, during steady-state,
there are 300 joules of energy in the transmission line that have
not yet reached the load.

100W---one second long 50 ohm lossless feedline---291.5 ohms
Pfor=200W-- --Pref=100W

There are no impedance discontinuities between the source and the
load and EM energy travels at the speed of light. The 300 joules
cannot exist anywhere except in the forward and reflected waves.
Without the existence of forward and reflected waves, there is
nothing to support standing waves. That the energy moving in each
direction is difficult to separate is no reason to assert that it
doesn't exist. According to the IEEE definition of power, the
*potential* for doing work is power. The 300 joules stored in the
above transmission line have the potential for doing work after
the source is powered down. That the work actually performed is
not useful work is irrelevant.

Anyone who doubts the existence of reflected energy should do a
second by second analysis of the above example starting at power
up. The technical facts become undeniable after a few seconds.

Whoo Hoo. The letters will be fun. Especially if Eric attempts to
extend his assertion to a case not-as-special, such as not-steady-state
or a point in 3D space.

Too bad it wasn't here. Bet we'd get a couple dozen posts before the
weekend's out. Anyone want to take Eric's side?


K8LV even contradicts himself in his own article. He says the Z0 of
the line "literally forces all power flow to occur in 50-ohm waves
on the line". In the above example, those 300 joules per second are
necessarily flowing in the one second long line since they cannot
stand still. Where are they if, as K8LV asserts, the Z0 of the line
is forcing a V/I ratio of 50 ohms? They can exist in only one place,
in the 200W forward wave and 100W reflected wave each of which forces
a V/I ratio of 50 ohms, just as K8LV asserts.

Exactly the same thing happens when standing EM waves of light are
formed in free space. Let's see K8LV explain that one without the
existence of forward traveling light waves and rearward traveling
light waves. How do these quotes agree with standing waves of light?

"... the forward and reverse waves do not exist separately ..."

I think I can hear a multitude of physicists laughing at the assertion
that standing waves of light do not require the separate existence of
forward and reverse waves. QEX was interested in publishing an article
of mine with light wave examples until they realized the implications
of those technical facts.

This is just one more example of the dumbing down of amateur radio
accompanying the dumbing down of the US educational system in
general. Unfortunately, it seems to be a trend that cannot be
reversed because it is the biased view being pushed by the ARRL
and its supporters.
--
73, Cecil
http://www.qsl.net/w5dxp

Gene Fuller May 13th 06 05:02 PM

FIGHT! FIGHT! FIGHT!
 
Cecil Moore wrote:

Over the years, I have challenged anyone on this newsgroup to create
a standing wave in a single source system without having the existence
of a forward wave and a reflected wave. Nobody has furnished any proof
that standing waves are possible in a single source system without the
existence of forward and reflected waves.


Cecil,

Why would anyone try to prove that the basic math of adding sinusoidal
functions is incorrect? To the contrary, you are the one who insists
that a standing wave and its constituent traveling wave components are
somehow different and unique. No one denies the simultaneous existence
of standing waves and traveling waves.

Isn't superposition wonderful!

73,
Gene
W4SZ

Cecil Moore May 13th 06 05:29 PM

FIGHT! FIGHT! FIGHT!
 
Gene Fuller wrote:
Why would anyone try to prove that the basic math of adding sinusoidal
functions is incorrect? To the contrary, you are the one who insists
that a standing wave and its constituent traveling wave components are
somehow different and unique.


Actually, it was you who made that assertion and thanks for the
opportunity to quote you once again:

Gene Fuller, W4SZ wrote:
In a standing wave antenna problem, such as the one you describe,
there is no remaining phase information. Any specific phase
characteristics of the traveling waves died out when the startup
transients died out.


So standing waves are "somehow different" from traveling waves
according to your own assertions. The traveling wave possesses
phase characteristics and the standing wave doesn't.

Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be
seen again.


So it was you who asserted that standing wave current is "somehow
different" from traveling wave current and I agree with you. It's
obvious they are "somehow different" because they have different
mathematical equations. Have you changed your mind since your
above quoted posting?

No one denies the simultaneous existence
of standing waves and traveling waves.


Of course they do, Gene, that is the whole point. Here is a quote
from K8LV's article:

"I wish to emphasize the fact that the forward and reverse
waves really do not exist separately ..."

That certainly *denies* the separate existence of the underlying
traveling waves so your above assertion is false. I believe that
W7EL also denies the separate existence of forward and reverse
waves and introduced the technical term, "sloshing", to explain
what happens to the energy in a transmission line with reflections.
--
73, Cecil http://www.qsl.net/w5dxp

[email protected] May 13th 06 06:16 PM

FIGHT! FIGHT! FIGHT!
 
Cecil wrote:
This is just one more example of the dumbing down of amateur radio

accompanying the dumbing down of the US educational system in
general. Unfortunately, it seems to be a trend that cannot be
reversed because it is the biased view being pushed by the ARRL
and its supporters.


Hmmm...not sure I agree that the folks at ARRL are deliberately being
dumb (or maybe I just misunderstood you). Seems more unintentional to
me. After all, the technical editor of QEX let publish that bizarre
article that claimed to prove by math that phasing SSB receivers were
not possible. Can''t imagine a political motivation for that though I
have to wonder bigtime how that one got by. QEX really really needs
for some good peer review.

Ah, to have Ham Radio magazine back again. Loved that thing. Learned
most of my radio from it.

73,
Glenn AC7ZN


[email protected] May 13th 06 06:23 PM

FIGHT! FIGHT! FIGHT!
 
Funny thing is that I'm down with the slow-wave loading coil thing.
Maxwell's equations are your friend... not a very nice friend when
Bessel functions are involved, but...

Faster than light, though? Maybe the phase velocity in some tricky
cryogenic world, but I dunno...

Haven't seen much on superconducting antennas here... I read a paper
once with a superconducting magloop but they forgot to make the
matching network superconducting too.

Let's get the "bizarre but REAL" antenna thread going.

Wouldn't you like to have a QRP CW rig with a 3" magloop for 20m on the
top? The thermos full of liquid nitrogen is kind of a pain to lug
around...

Anyone built a "genetically" designed ham antenna yet? Might be a good
way to go for the "I have 50 feet between two trees to put up an 80m
dipole" crowd.

Maybe we could develop a combined performance+aesthetics genetic
algorithm to design efficient shortened vertical dipoles that look like
nice pieces of modern art and have a nice low voltage section to run
the coax out... you run the electromagnetic algorithm, weed out the
weak designs, then you have your neighbor click the most attractive
five and throw the rest out, and repeat!

-Dan


Yuri Blanarovich May 13th 06 06:49 PM

FIGHT! FIGHT! FIGHT!
 

wrote in message
oups.com...
Cecil wrote:
This is just one more example of the dumbing down of amateur radio

accompanying the dumbing down of the US educational system in
general. Unfortunately, it seems to be a trend that cannot be
reversed because it is the biased view being pushed by the ARRL
and its supporters.


Hmmm...not sure I agree that the folks at ARRL are deliberately being
dumb (or maybe I just misunderstood you). Seems more unintentional to
me. After all, the technical editor of QEX let publish that bizarre
article that claimed to prove by math that phasing SSB receivers were
not possible. Can''t imagine a political motivation for that though I
have to wonder bigtime how that one got by. QEX really really needs
for some good peer review.


I don't think anyone is trying to be "deliberately being dumb", more like
"naturally being dumb" and not knowing it. :-)
Reality is that quality of technical material in ham publications is
slipping, heading for stuck on stupid. Add cheapening of ham ticket exams,
push for mass and no exam recruiting of new hams (a la CB wizards) in effort
to boost numbers and few bad apples with it - you get the picture of
deteriorating standards.

When W8JI had a presentation at Dayton's Antenna Forum and spoke about his
"famous - same current along the antenna loading coil", I came to K3LR
(forum leader) and N6BV (ARRL Antenna Book editor) and pointed out that
perhaps there is an error in W8JI assertions, I got this in private mail
from the "guru":

"When you pull people aside at Dayton to bitch about me or others or make
wild crazy statements it just makes you look worse and worse to the people
you are trying most to impress. At Dayton two years ago several people came
up and told me your tried to start conversations about me with them, or that
you started bitching about me."

Sooo, looks like one has to take some articles in ARRL publications with
biiiig grain of salt. Goofy stuff gets through, real expert material gets
swept under by "know-it-alls" in charge, Goofy is right and Right is not
important anymore. "Gurus" beat their drums into the publications and great
confusion ensues.

As far as SWR, I always tried to avoid it by matching, designing antennas to
have impedance of the feedline, and the TX/Amp output matching the feedline
impedance. Standing Wave Ratio always implied two waves - forward and
reflected and their superposition. Why waste power in "confused" standing
waves, when I can make sure that the waves are marching forward towards the
antenna and be radiated. Let the waves stand in the antenna, where they
belong, doing radiating and not in the lossy feedline.
High SWR is not imaginary, it is real, can create excessive voltages,
dielectric losses and melt the coax.

Happy Mother's Day to all the mothers that did not abort us!
God Bless them and thank you!

Yuri, da BUm



Cecil Moore May 13th 06 07:41 PM

FIGHT! FIGHT! FIGHT!
 
wrote:
Hmmm...not sure I agree that the folks at ARRL are deliberately being
dumb (or maybe I just misunderstood you).


Let me just relate my personal experience. I submitted an article
to QEX which mentioned light wave theory as explained in "Optics",
by Hecht. An (un-named) QEX employee, with whom I was dealing, had
"Optics" as a college textbook and was very interested in the subject.
He suggested that I expand the light wave theory section of my article,
which I did. After about four revisions, he suddenly stopped responding
to my emails. A couple of months later, I received a rejection letter.
That was well over a year ago.

Two QEX articles have recently appeared covering exactly the same
material as my article but with different slants. QEX still will
not answer my emails and will not publish my letters to the editor.
My treatment by QEX is more akin to religious shunning than
anything else.

I am convinced that the QEX employee that I was dealing with is
deliberately publishing dumbed-down material because he previously
indicated that he knows different from his college optics course.
He is most probably being directed to do so by his superiors because
he was, at first, enthusiastic about publishing my article which
is available from my web page below.
--
73, Cecil
http://www.qsl.net/w5dxp/energy.htm

Cecil Moore May 13th 06 07:53 PM

FIGHT! FIGHT! FIGHT!
 
Yuri Blanarovich wrote:
When W8JI had a presentation at Dayton's Antenna Forum and spoke about his
"famous - same current along the antenna loading coil", ...


It is unusual for W8JI to give up on an argument so abruptly. I
wish I had thought of the dual-Z0 shortened stub concept years ago.
--
73, Cecil http://www.qsl.net/w5dxp

Dave May 13th 06 08:17 PM

FIGHT! FIGHT! FIGHT!
 
tell us more, 'dual-z0 shortened stub' sounds like something interesting.

"Cecil Moore" wrote in message
. com...
Yuri Blanarovich wrote:
When W8JI had a presentation at Dayton's Antenna Forum and spoke about
his "famous - same current along the antenna loading coil", ...


It is unusual for W8JI to give up on an argument so abruptly. I
wish I had thought of the dual-Z0 shortened stub concept years ago.
--
73, Cecil http://www.qsl.net/w5dxp




Cecil Moore May 13th 06 09:07 PM

FIGHT! FIGHT! FIGHT!
 
Dave wrote:
tell us more, 'dual-z0 shortened stub' sounds like something interesting.


In my quest to explain the phase shift in a 75m bugcatcher
coil, I thought about a dual-Z0 stub. The shortest 450/50 one
I have come up with that causes the maximum phase shift is:

---19 deg of 450 ohm line---+---18 deg of 50 ohm line---open

Believe it or not, that is an electrical 1/4WL stub with a
whopping 53 degrees of *lossless* phase shift occurring at the
'+' impedance discontinuity point. Are there any applications
for a stub that is physically 0.1 WL long instead of 0.25WL?

It could be shortened even more by using 600 ohm line with
50 ohm line. On top of everything else, the current in the
50 ohm section seems to be much lower than the current in
the 600 ohm section thus reducing the losses in the stub.

From these experiments, I have concluded that the phase shift
in a 75m mobile loading coil may be in the ballpark of 20 degrees
while the phase shift in the stinger is in the ballpark of 20
degrees with the majority of phase shift coming from the
impedance discontinuity between the loading coil and the stinger.
So neither side of the years-long argument was right or wrong.
--
73, Cecil http://www.qsl.net/w5dxp

EA3FYA - Toni May 13th 06 10:07 PM

FIGHT! FIGHT! FIGHT!
 
En/na Dave ha escrit:
... Come on, just a little fight???


Just a question about coax cables:

I know that a coax cable does not radiate (if common mode currents
properly suppressed) because both conductors are apparently "in the same
place" (wouldn't know how to express it in more technical terms).

Now the question is: This is true for big distances from the coax, but
is it also true when you get very close to the coax? Imagine a conductor
taped to the outside of a coax for some meters. The capacitive coupling
to the braid is much higher than the coupling to the inner conductor.
Would it pick some of the current in the coax. If not, why not?

(apart from fun I'm really interested in the answer as I'm not quite
sure if a coax running parallel to unshielded and not twisted computer
cables would pick harmonics from it on RX or create interferences on TX)

--
Toni

Dave May 14th 06 12:27 AM

FIGHT! FIGHT! FIGHT!
 
no... and yes.... there would be some pickup, but only from leakage through
an imperfect braid. because the current is on the inside of the shield it
would not couple to the cable on the outside. the electric and magnetic
fields are contained completely inside the shield.


"EA3FYA - Toni" wrote in message
...
En/na Dave ha escrit:
... Come on, just a little fight???


Just a question about coax cables:

I know that a coax cable does not radiate (if common mode currents
properly suppressed) because both conductors are apparently "in the same
place" (wouldn't know how to express it in more technical terms).

Now the question is: This is true for big distances from the coax, but is
it also true when you get very close to the coax? Imagine a conductor
taped to the outside of a coax for some meters. The capacitive coupling to
the braid is much higher than the coupling to the inner conductor. Would
it pick some of the current in the coax. If not, why not?

(apart from fun I'm really interested in the answer as I'm not quite sure
if a coax running parallel to unshielded and not twisted computer cables
would pick harmonics from it on RX or create interferences on TX)

--
Toni




Roy Lewallen May 14th 06 12:59 AM

FIGHT! FIGHT! FIGHT!
 
EA3FYA - Toni wrote:

Just a question about coax cables:

I know that a coax cable does not radiate (if common mode currents
properly suppressed) because both conductors are apparently "in the same
place" (wouldn't know how to express it in more technical terms).


Here's why it doesn't radiate: In a coaxial cable with a solid shield,
the differential mode current is entirely inside the shield. Current and
fields penetrate only a very small distance from the inner surface of
the shield, and no significant amount ever makes it through to the
outside. This is assuming that the shield is at least several skin
depths thick, which is a good assumption at HF and above.

Common mode current, by contrast, flows on the outside of the shield,
and its field radiates outward from there.

Now the question is: This is true for big distances from the coax, but
is it also true when you get very close to the coax? Imagine a conductor
taped to the outside of a coax for some meters. The capacitive coupling
to the braid is much higher than the coupling to the inner conductor.
Would it pick some of the current in the coax. If not, why not?


Again assuming a solid shield -- the center conductor carries a current
and therefore creates a field. The inner surface of the shield carries
an equal and opposite current and also creates a field. But those fields
are equal and opposite, and cancel at all points beyond a thin layer on
the inner surface of the shield. Since there's no significant field at
any point outside the shield, it doesn't matter where you look, you
won't find any, and there isn't any field to couple to anything else.

In reality, any shield other than a completely solid one (such as the
shield of hard line or semi-rigid coax) will leak some because of gaps
or holes. And the field will couple more strongly to wires which are
close than those which are far away. Whether the amount of leakage is
significant or not depends on the application.

(apart from fun I'm really interested in the answer as I'm not quite
sure if a coax running parallel to unshielded and not twisted computer
cables would pick harmonics from it on RX or create interferences on TX)


You might get enough leakage through the shield of ordinary coax to
cause problems in both cases. It depends on the transmit power level,
the signals in the wires, the length over which they're bundled, the
frequencies involved, the quality of the shield, and so forth.
Separating them even a small distance would reduce the coupling
considerably. But you're likely to have more trouble with common mode
current.

Roy Lewallen, W7EL

Tom Ring May 14th 06 01:16 AM

FIGHT! FIGHT! FIGHT!
 
Gene Fuller wrote:

Isn't superposition wonderful!

73,
Gene
W4SZ


Yup, it's why I find religion so amusing.

tom
K0TAR

Tom Ring May 14th 06 01:19 AM

FIGHT! FIGHT! FIGHT!
 
wrote:

Funny thing is that I'm down with the slow-wave loading coil thing.
Maxwell's equations are your friend... not a very nice friend when
Bessel functions are involved, but...

Faster than light, though? Maybe the phase velocity in some tricky
cryogenic world, but I dunno...


And light has now gone faster than light. Well, sort of. It did get
there before it left in this case.

http://www.scienceblog.com/cms/light...rds-10590.html

tom
K0TAR

Gene Fuller May 14th 06 02:00 AM

FIGHT! FIGHT! FIGHT!
 
Cecil Moore wrote:
Gene Fuller wrote:

Why would anyone try to prove that the basic math of adding sinusoidal
functions is incorrect? To the contrary, you are the one who insists
that a standing wave and its constituent traveling wave components are
somehow different and unique.



Actually, it was you who made that assertion and thanks for the
opportunity to quote you once again:

Gene Fuller, W4SZ wrote:
In a standing wave antenna problem, such as the one you describe,
there is no remaining phase information. Any specific phase
characteristics of the traveling waves died out when the startup
transients died out.


So standing waves are "somehow different" from traveling waves
according to your own assertions. The traveling wave possesses
phase characteristics and the standing wave doesn't.



Cecil,

You keep making the same mistake. Yes, you can analyze traveling waves
instead of standing waves if you so choose. However, there is not one
bit of additional physical information in the traveling waves that is
not in the standing wave. Any "phase characteristic" is simply a
function of the mathematical manipulations you use.

Perhaps someday you will actually understand superposition, but I won't
hold my breath.

73,
Gene
W4SZ

Cecil Moore May 14th 06 04:39 AM

FIGHT! FIGHT! FIGHT!
 
Gene Fuller wrote:
However, there is not one
bit of additional physical information in the traveling waves that is
not in the standing wave.


I agree with you but W8JI and W7EL have rejected the concept that
there is any phase information in the standing wave current magnitude.
They have rejected any use of the arc-cosine function in calculating
that phase. The following graphs show the difference in the standing
wave current and the traveling wave current.

http://www.qsl.net/w5dxp/travstnd.GIF

The standing wave current phase contains zero phase information
as you have stated. As you say, all the standing wave current
phase information is contained in the magnitude but the arc-cosine
function for obtaining that phase information has been rejected by
the experts. For the traveling wave, there is phase information
contained in the phase, none in the magnitude.

Every time you make a technical assertion, you support my argument.
Seems your argument is really with the side that rejects the arc-
cosine function for obtaining phase information.
--
73, Cecil http://www.qsl.net/w5dxp

Toni May 14th 06 11:21 AM

FIGHT! FIGHT! FIGHT!
 
En/na Roy Lewallen ha escrit:
EA3FYA - Toni wrote:

I know that a coax cable does not radiate (if common mode currents
properly suppressed) because both conductors are apparently "in the
same place" (wouldn't know how to express it in more technical terms).


Here's why it doesn't radiate: In a coaxial cable with a solid shield,
the differential mode current is entirely inside the shield. Current and
fields penetrate only a very small distance from the inner surface of
the shield, and no significant amount ever makes it through to the
outside. This is assuming that the shield is at least several skin
depths thick, which is a good assumption at HF and above.


When you say "Current and fields penetrate only a very small
distance...", I agree for the current part, but I'm not so sure for the
fields part:

As I understand it you can not "stop a field" in no way, though you can
certainly nullify it with an identical but opposite field.

Then the question is whether the two fields (the one from the current
flowing in the shield + the one from the current flowing in the inner
conductor) nullify at all points in the immediate vicinity of the
shield. I certainly believe it but would like to understand why this is so.

I guess the mathematical proof would involve assuming the braid is an
infinite number of conductors equally spaced around the center
conductor, each having it's infinitesimal share of the shield current,
and integrating all of their fields at the point of interest (Would
probably be able to do so back when I was at university but now it is
too strong math for me). Would this be a good approximation of the problem?

--
Toni

Toni May 14th 06 11:23 AM

FIGHT! FIGHT! FIGHT!
 
Thanks four your answers.

I was forgetting you normally use coax in a unbalanced configuration
where the braid is supposed to be at 0 voltage so only currents matter.

Would all this still hold if you used the coax as a _balanced_
transmission line? (unusual but -I think- possible). In this case
wouldn't voltages develop on the braid that could capacitively couple to
other conductors?

(assuming perfect solid shield, ...)

--
Toni

Dave May 14th 06 12:38 PM

FIGHT! FIGHT! FIGHT!
 
the voltage on the braid is not zero on the inside, it varies along with the
wave traveling along the inside of the coax. and the currents are exactly
balanced inside the coax also, they have to be or it wouldn't work. this
notion of balanced vs un-balanced transmission lines is totally confusing to
most people, in a proper system, say just with a dummy load on a coax the
currents on the shield exactly balance the current on center conductor. so
why do we go through all this stuff with bal-uns?? and coax chokes?? the
currents are already balanced, so WHY?? come on you gurus out there,
explain this one!


"Toni" wrote in message
...
Thanks four your answers.

I was forgetting you normally use coax in a unbalanced configuration where
the braid is supposed to be at 0 voltage so only currents matter.

Would all this still hold if you used the coax as a _balanced_
transmission line? (unusual but -I think- possible). In this case wouldn't
voltages develop on the braid that could capacitively couple to other
conductors?

(assuming perfect solid shield, ...)

--
Toni




Cecil Moore May 14th 06 03:02 PM

FIGHT! FIGHT! FIGHT!
 
Dave wrote:
so
why do we go through all this stuff with bal-uns?? and coax chokes?? the
currents are already balanced, so WHY?? come on you gurus out there,
explain this one!


Water comes out of a hose whether the hose is leaky or not.
So why ever bother patching or replacing a leaky hose?
--
73, Cecil http://www.qsl.net/w5dxp

Gene Fuller May 14th 06 03:41 PM

FIGHT! FIGHT! FIGHT!
 
Cecil Moore wrote:
Gene Fuller wrote:

However, there is not one bit of additional physical information in
the traveling waves that is not in the standing wave.



I agree with you but W8JI and W7EL have rejected the concept that
there is any phase information in the standing wave current magnitude.
They have rejected any use of the arc-cosine function in calculating
that phase. The following graphs show the difference in the standing
wave current and the traveling wave current.

http://www.qsl.net/w5dxp/travstnd.GIF

The standing wave current phase contains zero phase information
as you have stated. As you say, all the standing wave current
phase information is contained in the magnitude but the arc-cosine
function for obtaining that phase information has been rejected by
the experts. For the traveling wave, there is phase information
contained in the phase, none in the magnitude.

Every time you make a technical assertion, you support my argument.
Seems your argument is really with the side that rejects the arc-
cosine function for obtaining phase information.


Cecil,

You still don't get it.

When I said the phase information was gone, I meant it. Any phase
information you think you find by looking at the constituent traveling
waves is merely an artifact of the math. It has no physical meaning or
reality. If there is anything interesting left in the traveling wave
analysis, then the standing wave is not the complete representation of
the electromagnetic phenomena. This is a different problem.

Yes, you can apply modulation, insert directional couplers, look at
startup transients, or perform other tricks to get "real" phase
information. However, that again becomes a different problem, not the
original simple steady-state combination of traveling waves into a
standing wave.

73,
Gene
W4SZ

Roy Lewallen May 14th 06 06:37 PM

FIGHT! FIGHT! FIGHT!
 


Toni wrote:
En/na Roy Lewallen ha escrit:
EA3FYA - Toni wrote:

I know that a coax cable does not radiate (if common mode currents
properly suppressed) because both conductors are apparently "in the
same place" (wouldn't know how to express it in more technical terms).


Here's why it doesn't radiate: In a coaxial cable with a solid shield,
the differential mode current is entirely inside the shield. Current
and fields penetrate only a very small distance from the inner surface
of the shield, and no significant amount ever makes it through to the
outside. This is assuming that the shield is at least several skin
depths thick, which is a good assumption at HF and above.


When you say "Current and fields penetrate only a very small
distance...", I agree for the current part, but I'm not so sure for the
fields part:

As I understand it you can not "stop a field" in no way, though you can
certainly nullify it with an identical but opposite field.


You bet you can stop a field. It can be stopped either by reflection,
absorption, or a combination of the two. Inside an anechoic chamber,
absorbing materials stop internal fields to prevent reflections. A
screen room or metallic shield reflects external fields.

Then the question is whether the two fields (the one from the current
flowing in the shield + the one from the current flowing in the inner
conductor) nullify at all points in the immediate vicinity of the
shield. I certainly believe it but would like to understand why this is so.


Indeed they do. Look up Ampere's Law. If you draw a boundary through the
middle of the shield or outside the shield, you'll find that the sum of
currents within that boundary is zero. According to the law, that means
that no net field penetrates the boundary. Because of the physical
symmetry, no net field means no field at all.

I guess the mathematical proof would involve assuming the braid is an
infinite number of conductors equally spaced around the center
conductor, each having it's infinitesimal share of the shield current,
and integrating all of their fields at the point of interest (Would
probably be able to do so back when I was at university but now it is
too strong math for me). Would this be a good approximation of the problem?


No, it's not that complicated, but a path or surface integration is
required to use Ampere's law.

Roy Lewallen, W7EL

Roy Lewallen May 14th 06 06:43 PM

FIGHT! FIGHT! FIGHT!
 
Toni wrote:
Thanks four your answers.

I was forgetting you normally use coax in a unbalanced configuration
where the braid is supposed to be at 0 voltage so only currents matter.


How do you define "0 voltage"? Do a groups.google.com search of this
newsgroup and you'll find quite a bit of discussion about the futility
of trying to define a voltage between two distant points in the presence
of a field.

Would all this still hold if you used the coax as a _balanced_
transmission line? (unusual but -I think- possible). In this case
wouldn't voltages develop on the braid that could capacitively couple to
other conductors?

(assuming perfect solid shield, ...)


A coax line is balanced when the common mode current is zero. It's
unbalanced when common mode current exists. See
http://eznec.com/Amateur/Articles/Baluns.pdf for more information.

Voltages don't couple, fields do.

There was also some discussion not too long ago on this group about the
role of current in generating both electric and magnetic fields.

Roy Lewallen, W7EL

Roy Lewallen May 14th 06 06:47 PM

FIGHT! FIGHT! FIGHT!
 
Dave wrote:
the voltage on the braid is not zero on the inside, it varies along with the
wave traveling along the inside of the coax. and the currents are exactly
balanced inside the coax also, they have to be or it wouldn't work. this
notion of balanced vs un-balanced transmission lines is totally confusing to
most people, in a proper system, say just with a dummy load on a coax the
currents on the shield exactly balance the current on center conductor. so
why do we go through all this stuff with bal-uns?? and coax chokes?? the
currents are already balanced, so WHY?? come on you gurus out there,
explain this one!


The currents on the inside are always balanced -- they're purely
differential mode. The purpose of baluns or common mode chokes is to
reduce the common mode current which, on coax, flows entirely on the
outside.

If you're driving a dummy load from your transmitter, the common mode
current will be zero in an ideal system and negligible in a real system.
A balun or common mode choke will do nothing in that situation.

See http://eznec.com/Amateur/Articles/Baluns.pdf for a more complete
explanation.

Roy Lewallen, W7EL

Cecil Moore May 14th 06 06:57 PM

FIGHT! FIGHT! FIGHT!
 
Gene Fuller wrote:
Cecil, You still don't get it.


I get what you said. Here it is again.

Gene Fuller wrote:
The only "phase" remaining is the cos (kz) term, which is really
an amplitude description, not a phase.


So you alluded to phase information in the standing wave
current amplitude.

When I said the phase information was gone, I meant it.


But you also said:

Gene Fuller wrote:
However, there is not one bit of additional physical information
in the traveling waves that is not in the standing wave.


We know that there is phase information in the traveling waves.
So for your statement to be true, there has to be phase information
in the standing wave.

Both of your statements cannot be true. Which one are you
willing to stick with and which one are you going to retract?

If you look at: http://www.qsl.net/w5dxp/travstnd.GIF
you will see that the standing wave amplitude is indeed
a cosine function of the phase. Taking the arc-cosine
of the normalized amplitude yields the phase angle.

I'm sorry, but you have contradicted yourself a couple of times
so I don't know which assertion you want to go with.
--
73, Cecil http://www.qsl.net/w5dxp

Roy Lewallen May 14th 06 07:02 PM

FIGHT! FIGHT! FIGHT!
 
Gene Fuller wrote:
Cecil Moore wrote:
Gene Fuller wrote:

However, there is not one bit of additional physical information in
the traveling waves that is not in the standing wave.



I agree with you but W8JI and W7EL have rejected the concept that
there is any phase information in the standing wave current magnitude.
They have rejected any use of the arc-cosine function in calculating
that phase. The following graphs show the difference in the standing
wave current and the traveling wave current.
. . .


Egad. Of course I reject the notion that there's "phase information in
the standing wave current magnitude". Magnitude and phase are
orthogonal. There's no phase in the magnitude and no magnitude in the
phase. There's no real portion of the imaginary part and no imaginary
portion of the real part. I haven't a clue what you mean by "use of the
arc-cosine,function to calculate that phase", but I certainly reject any
method that assigns a phase value to a magnitude or vice versa. I get
the total voltage or current simply by adding the traveling waves. No
trig functions necessary, just simple vector addition.

Traveling waves have phase information. In a steady state system they
can be expressed as phasors, which consist of a magnitude, a time phase
reference value, and an implicit time varying time rotation. When you
add them to get the total (which Cecil likes to characterize as a
standing wave as though it's something different than just the total
voltage or current), you get the simple vector sum of the constituent
traveling waves. This sum is also a phasor, with magnitude, time phase
reference value, and the same implicit time varying phase rotation.

In summary, both traveling waves and the total voltage or current are
phasors, and both have phase.

What's so complicated about adding a couple of phasors? Cecil, you need
to go back and read, and understand, your freshman circuit analysis text.

What a bunch of irrational smoke and mirrors.

I don't care less what Cecil will make of this. But Gene, do you really
disagree with what I've just said?

Roy Lewallen, W7EL

Cecil Moore May 14th 06 09:59 PM

FIGHT! FIGHT! FIGHT!
 
Roy Lewallen wrote:
Egad. Of course I reject the notion that there's "phase information in
the standing wave current magnitude".


And, of course, you are showing your ignorance. Let's say that
at the current maximum point, the forward current is 0.5 at 0 deg
and the reflected current is 0.5 at 0 deg. The standing wave
current at the current maximum point is 1.0 at 0 deg just like
a cosine function is 1.0 at 0 deg.

Now let's go 45 degrees away from that current maximum point. The
forward current is 0.5 at -45 deg and the reflected current is
0.5 at +45 deg so the standing wave current is 0.707 at 0 deg.

The magnitude of the standing wave current is 0.707. The arc-
cosine of 0.707 is 45 degrees. Do you really and truly believe
that is just a coincidence? Exactly as Gene Fuller said previously,
there is phase information in the standing wave current magnitude.

Here's a quote from Gene:

Gene Fuller wrote:
The only "phase" remaining is the cos (kz) term, which is really
an amplitude description, not a phase.


Your statement above is in direct contradiction to Gene's statement.

What's so complicated about adding a couple of phasors?


I suspect you know how to add phasors. I suspect you don't have
a clue what that answer means in reality. Please try to convince
us that the 0.707 result above for a 45 degree shift is sheer
coincidence.
--
73, Cecil http://www.qsl.net/w5dxp

Gene Fuller May 14th 06 10:15 PM

FIGHT! FIGHT! FIGHT!
 
Roy Lewallen wrote:

I don't care less what Cecil will make of this. But Gene, do you really
disagree with what I've just said?

Roy Lewallen, W7EL


Roy,

I do not disagree with anything you have said. Cecil is up to his
standard trick of selective quoting along with a subtle change of topic
to make it appear that there are conflicts when there are none.

I am sure Cecil will find some other quote to remove from context in
order to prove me wrong.

73,
Gene
W4SZ

Gene Fuller May 14th 06 10:27 PM

FIGHT! FIGHT! FIGHT!
 
Cecil Moore wrote:
Gene Fuller wrote:

Cecil, You still don't get it.



I get what you said. Here it is again.

Gene Fuller wrote:
The only "phase" remaining is the cos (kz) term, which is really
an amplitude description, not a phase.


So you alluded to phase information in the standing wave
current amplitude.

When I said the phase information was gone, I meant it.



But you also said:

Gene Fuller wrote:

However, there is not one bit of additional physical information


in the traveling waves that is not in the standing wave.


We know that there is phase information in the traveling waves.
So for your statement to be true, there has to be phase information
in the standing wave.

Both of your statements cannot be true. Which one are you
willing to stick with and which one are you going to retract?

If you look at: http://www.qsl.net/w5dxp/travstnd.GIF
you will see that the standing wave amplitude is indeed
a cosine function of the phase. Taking the arc-cosine
of the normalized amplitude yields the phase angle.

I'm sorry, but you have contradicted yourself a couple of times
so I don't know which assertion you want to go with.



Cecil,

I have not contradicted myself, and I have nothing to retract. Only in
your imagination is there any useful phase information in the traveling
waves that make up a standing wave. There can be other waves that don't
exactly balance out into a standing wave, but that is another topic.

I am not sure to whom the "we" refers in your statement, "We know that
there is phase information in the traveling waves." Perhaps that is the
Royal We, because it certainly does not include me. The phase
information you might find is of no use, and it is simply an artifact of
the mathematical analysis.

If the standing wave adequately and completely describes the
electromagnetic situation, then there is no additional available from an
arbitrary decomposition in traveling waves. If you try to look at the
traveling waves one at a time, then you are no longer considering a
standing wave.

73,
Gene
W4SZ

Dave May 14th 06 10:50 PM

FIGHT! FIGHT! FIGHT!
 

"Gene Fuller" wrote in message
...
Cecil Moore wrote:
Gene Fuller wrote:

Cecil, You still don't get it.

I get what you said. Here it is again.
So you alluded
I meant it.

But you also said:
there is not one bit of additional physical information

So for your statement to be true, there has to be Both of your statements
cannot be true. Which one are you
willing to stick with and which one are you going to retract?
If you look at
I'm sorry, but you have contradicted yourself a couple of times
so I don't know which assertion you want to go with.

I have not contradicted myself, and I have nothing to retract. but that is
another topic.
I am not sure to whom the "we" refers in your statement,
Perhaps that is the Royal We, because it certainly does not include me.
there is no additional available from


COME ON! KEEP IT GOING!! this rainy wet weekend is almost over and I could
use one more good round of laughter!! Perhaps we cut straight to the
conclusion and have something that is completely a personal attack devoid of
any possible technical statements, that would do nicely! DON'T STOP NOW!



Cecil Moore May 14th 06 11:12 PM

FIGHT! FIGHT! FIGHT!
 
Gene Fuller wrote:
I do not disagree with anything you have said.


Please answer this question. Does the amplitude of the
standing wave current contain any phase information?

You have previously asserted that it does. Roy says
it doesn't. Time to chose between technical fact
and agreeing with your friend (who is technically
incorrect).
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore May 14th 06 11:18 PM

FIGHT! FIGHT! FIGHT!
 
Gene Fuller wrote:
I have not contradicted myself, ...


Either the standing wave current magnitude contains phase
information, as you previously asserted, or it doesn't.
I'll make it easy for you. Just insert an 'X' for the one
you agree with.

_____ Standing wave current magnitude contains some phase
information.

_____ Standing wave current magnitude contains zero phase
information.
--
73, Cecil http://www.qsl.net/w5dxp


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