RadioBanter - Current across the antenna loading coil

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Current across the antenna loading coil - from scratch

Cecil,

You dismissed my honest, straightforward accounting of the
charge transport implied directly by the scenarios you set up.
In no way was it a "logical diversion." It was very much to the
point of explaining just WHY there is in fact a time delay through
your bugcatcher coil.

Then you have the unmitigated gaul to say it's time to stop
the attacks, and then refuse yourself to get into a serious
technical discussion.

Away with you, evil spirit. And be very happy that this is
a polite forum.

Current across the antenna loading coil - from scratch

Richard Fry wrote:

"Cecil Moore" wrote ...
Could it be that the resonant 80 degrees of physical length
is 90 degrees of electrical length?

That a self-resonant, unloaded broadcast radiator length is shorter than
the 90 degree conventional "electrical length" defined by the FCC is a
given. But this reality sometimes is not recognized.

For instance, EZNEC says a 33 ft. vertical made of #30 wire is
resonant on 7.265 MHz while a one foot diameter pipe is resonant
on 6.9 MHz.

Does the FCC define physical lengths or electrical lengths?
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch

"Cecil Moore"
Does the FCC define physical lengths or electrical lengths?
____________

They call it an electrical length, but calculate it as the number of
free-space electrical degrees contained in the physical length of the
radiating structure, at the carrier frequency. So really, FCC "electrical
length" is a measure of a physical length, not of an effective electrical
length.

The effective electrical length of a MW monople radiator determines its
resonant frequencies, and that must include the velocity of propagation
along the structure -- which is a function of the height AND width of the
radiator (mainly), and the operating frequency.

RF

Current across the antenna loading coil - from scratch

On Tue, 04 Apr 2006 16:38:48 GMT, "Tom Donaly"
wrote:

No wonder no one's communicating with him.

Hi Tom,

To him, from him, at him. OK, this is not going to be a grammar
exercise. No, more that complaints should be registered at the box
office where you bought the ticket to this comedy when you expected a
technical presentation.

Myself, on the other hand, I read the program notes and seeing all the
credits and roles played like:
"Occam the magnificent"
or
"Cecileo the ball juggler"
performances of
"My Contacts with the Aliens"
plus dramatic readings
"Sleepless with Kraus"
all that remains is to saunter back for some popcorn during this
between-acts filler routine, or to wait for the strippers when the
real show begins.

-OH- yeah.... I guess now we know what killed vaudeville.

73's
Richard Clark, KB7QHC

PS
So seeing that "from scratch" is beginning to show why, flea bites,
it's time to add some real entertainment value that befits the
gravitas of this opera:

"Pal-yat-chee"

[H&J]

When we was in the city, we was a-wonderin' where to go.
The sign spelled out "Pagliacci" up in lights above the show.
We thought 'twould be a Western, 'til the stage lit up with light,
And ninety-seven people sung, without a horse in sight!
We couldn't unnerstand 'em 'cause they spoke a furrin tongue,
But we can give you some idear of what we think they sung---

[tenor]

Ridi, Pagliaccio,
Sul tuo amore infranto!

[H&J]

All at once, there's a fat guy in a clown suit.
'Tain't Hallerween, that's for shore!
Then this here feller,
This Punchy-neller,
Begins to beller,
Like we all was deef!

[tenor]

Ah, hahahahahahahaha....

[H&J]

That was Pal-yat-chee, and he sung:

Invest in a tuba, and somethin' or other 'bout Cuba,
He sung about a lady, who weighed two-hunnerd-and-eighty.
When she takes a powder, he just starts chirpin' louder,
An' he don't mean a gol-durned thing, 'cept to stand up there and
sing.
When we listen to Pal-yat-chee, we get itchy and scratchy.
This shore is top corn, so we go an' buy some popcorn.
We hate to go back, but we cain't get our dough back;
Ain't no use complainin', 'cause outside it's a-rainin.

[Slicker chorus]

Seven hours later, we're still in the durned thee-aye-ter,
Takin' turns a-nappin, a-waitin' fer somethin' to happen.
Pal-yat-chee, he ain't worryin',
And the folks on stage are flurryin',
And it sounds like Kat-che-turian's "Sabre Dance".

[to the melody of "Sabre Dance"]

Then ole Pal-yat-chee finds the guy he's seekin' cheek-to-cheekin'
With his wife, he grabs a knife
And stabs the louse who stole his spouse
And then he stabs the lady and him self,
'Tain't very sa-ni-ta-ry.
They all collapse,
But then Pal-yat-chee sets up and he gets up singin'
"I am dyin', I am dyin', I am dyin'", we start cryin'
'Cause to tell the truth, we're dyin', too.

[end "Sabre Dance"]

As the footlights fade out, we see Pal-yat-chee laid out,
But the dagger never caused it: Pal-yat-chee was plumb ex-haus-ted!

[tenor]

Ridi, Pagliaccio,
Sul tuo amore in--

[loud belch]

[vaudeville stinger: da-dut dahhhh da-dut DAT! DAAAAAAAHHH! cymbal
crash]

*Rich*

Current across the antenna loading coil - from scratch

Tom Donaly wrote:
Cecil, I won't try to educate you because it's a waste of time, but
for everyone else, consider that in an antenna, there is
energy going into, and being radiated out of, the antenna in the
form of an electromagnetic wave.

That's true, but compared to the standing waves, it is pretty
small. In fact, when Kraus talks about a 1/2WL thin-wire dipole,
he completely ignores the traveling wave and energy "lost" as
radiation and assumes the forward wave and reflected wave have
the same magnitude. If you want to argue that trivial point, take
it up with Kraus.

Here's what he says: "It is generally assumed that the current
distribution of an infinitesimally thin antenna is sinusoidal,
and that the phase is constaant over a 1/2WL interval, changing
abruptly by 180 degrees between intervals.

That would only be true if the reflected wave was equal in
magnitude to the forward wave, i.e. no loss due to radiation
or I^2*R losses. If Kraus gives us permission to ignore the
traveling wave for purposes of discussion, who are you to
argue?

I have calculated that there is only a 10% drop between forward
voltage or current and the reflected voltage or current arriving
back at the feedpoint for a 1/2WL dipole. For the sake of discussion
of standing waves in standing wave antennas, with an accuracy within
10%, the loss due to radiation can be ignored according to Kraus.
It's akin to ignoring the losses in a transmission line for the sake
of discussion.

Since Cecil says standing waves
can't transfer energy from one place to another ...
sthat means that the only way energy can be radiated is
through the traveling wave component of the electromagnetic wave.

Yes, that's true and since I have never said otherwise, this
seems to be just another straw man. With an accuracy of about
10%, Kraus gives us permission to ignore the traveling wave
in standing wave antennas for the purposes of discussion.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch

K7ITM wrote:
You dismissed my honest, straightforward accounting of the
charge transport implied directly by the scenarios you set up.
In no way was it a "logical diversion." It was very much to the
point of explaining just WHY there is in fact a time delay through
your bugcatcher coil.

The biggest clue that you are not arguing in good faith is that
you trimmed out all the technical content and didn't quote
anything I said. This posting of yours is disembodied from
reality so you can demonize me and emote your angry gut feelings.

Responses with no technical content and no quotes are an obvious
attempt to obfuscate - so obfuscate away.

It is possible I misunderstood what you were trying to say but
unless you quote something of technical value, I will have no
idea what my misunderstanding, if any, was all about.

John P. seems to want to discuss instantaneous movement of
energy. Why don't you two keep that discussion going?
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch

Cecil Moore wrote:
John Popelish wrote:

But at any point that is not a node in the standing wave pattern,
there will be an ordinary AC voltage or current at some amplitude
between double the traveling wave amplitude and zero amplitude, and
one of two phases (that switch each time you pass a node).

Please give us the equation for "ordinary AC voltage or current".

The simplest (without a reference phase) would be cos(wt). The
standing wave function contains this term, with a modifier to tell you
how amplitude varies with position. But at any point, cos(wt) times
some amplitude describes the ordinary AC voltage or current swing.

No argument. But a standing wave still represents storage of energy
in the line, as with any resonant structure, and that stored energy
shows up as magnetic fields and electric fields along the line. The big
difference is that the magnetic fields bob up and down at some areas
and the electric fields bob up and down half way in between those
areas. At any given moment, there is a fixed total energy in the
combination of all the magnetic and electric fields.

No argument, and therefore no need for the "But" in your statement.
I agree with you but it doesn't change a thing about the real
argument.

Exactly. How can you write this, but deny the capacitive current that
delivers this electric field energy twice every cycle to all
capacitance feeling this voltage swing?

I don't deny it - never have - never will. Please stop trying
to set up straw men. The discussion has *NEVER* be about what
happens during one cycle. The current measured by W8JI and W7EL
and reported by EZNEC is RMS current. Instantaneous values are
just another straw man diversion.

EZNEC must take those within a cycle currents and voltages into
account to come up with the amplitude values. The RMS value is just
the amplitude value for a cycle.

Profiles do not charge capacitance, ...

I'm glad you agree. Profiles are maximum RMS envelope values
and that is what EZNEC reports.

See? We agree on lots of stuff.

[Standing wave phase] "doesn't rotate at all, and the resultant
wave it represents doesn't progress through space - its a standing
wave."

At a given point the traveling wave phasor doesn't rotate, either.
Phasor rotation only applies to the phase change over length for a
traveling wave. The phase for standing waves has a discontinuous jump
as you pass through a node, instead of a continuous rotation over
length. I guess one might call that a form of jumpy rotation. Who
doesn't recognize these facts?

I suggest you drop talking about phasors, till you understand what
cos(wt).

Hecht and I have been a little lose with words while assuming
the readers have a certain knowledge level. For the uninitiated,
When Hecht (or I) say the phasor doesn't rotate at all, we
mean the phasor doesn't rotate at all with respect to the
source phasor.

....and within a half cycle of propagation length.

Any initiated person would know that. The phase
of the standing waves doesn't change with respect to the phase
of the source signal. Hecht assumed you would know what he meant
by that statement.

Still, it is worth saying well, once in a while.

Speaking of "... net transfer of energy, for the pure standing
wave there is none."

A standing wave does not violate conservation of energy.

Exactly my point!

I missed that point. Sorry.

Nothing violates conservation of energy. If
the RMS forward current in the coil is the same magnitude at
both ends and the RMS reflected current in the coil is the
same at both ends, the conservation of energy principle is
satisfied NO MATTER WHAT THE STANDING WAVE CURRENT TURNS
OUT TO BE. What is it about that statement that you don't
understand?

You don't add superposed RMS values to get the resultant RMS value.
You have to add instantaneous values over a cycle (so that the
relative phases of the two wave cycles are taken into account), and
take the RMS of the resultant cycle. See? We have to get inside an
individual cycle to understand what is going on. You cannot just deal
with RMS (while cycle amplitude values) and get the same answer. This
is why I (and others) keep coming back to what is happening inside a
cycle, instead of discussing RMS values, only. One cannot understand
either traveling wave mechanisms or the super position to a pair of
traveling waves (a standing wave) if you think only in RMS values.
They display the result of the process, but hide the way the process
produces that result.

Storage that must continuously be swapping back and forth from
magnetic field energy to electric field energy. When the energy
storage is all electric, that implies charges capacitance.

Again, nobody has ever been discussing what happens within a
partial cycle.

I have. You may not be, but that is your lack.

Discussion of such is obviously a diversionary
straw man. Feel free to find someone else willing to discuss it.
It is completely irrelevant to this discussion of RMS envelope
values.

There is no discussion of RMS envelope values. There is just you
repeating the same thought, over and over, while the rest of us
discuss the mechanisms that produce that resultant envelope.

You obviously understand how a phase measurement is useless to measure
phase shift within a half cycle of a purely standing wave process.

I am waiting for you to realize that you can measure the phase shift
of each of the traveling waves that superpose in a standing wave
process that includes a coil (or any other network) by using only the
RMS amplitude envelope, with no reference to phase, in an EZNEC
simulation or a real experiment. That was the whole point that began
this discussion, wasn't it?

You keep showing how the current into and out of a particular coil
does not have the same RMS value. We get it.

Now, measure the phase shift of that coil (for each of the equal
amplitude waves traveling through it) without having to change its
environment to put it into a pure traveling wave process. And don't
use a phase measurement to do it (which you know is impossible). Use
the amplitude envelope. You should be able to measure its phase shift
to within a degree or so. And you can then see how that phase shift
changes (or if it does) when you move the coil to different places in
the standing wave system.

Current across the antenna loading coil - from scratch

On Tue, 4 Apr 2006 12:11:20 -0500, "Richard Fry"
wrote:

The effective electrical length of a MW monople radiator determines its
resonant frequencies, and that must include the velocity of propagation
along the structure -- which is a function of the height AND width of the
radiator (mainly), and the operating frequency.

WGOP 80.00° tall 125.2 meters tall 540 kHz
WWCS 63.50° tall 98.8 meters tall 540 kHz
WFTD 79.00° tall 64.0 meters tall 1080 kHz
KYMN 118.60° tall 92.3 meters tall 1080 kHz
WWLV 90.00° tall 47.2 meters tall 1620 kHz
WTAW 204.00° tall 106.7 meters tall 1620 kHz

http://www.fcc.gov/mb/audio/amq.html

The FCC provides BOTH measurements. The correlation is obvious. Any
association between resonance, velocity of propagation, height, width,
etc. and something like our 118.60° tall antenna needs a heap more
explaining than resonance, velocity of propagation, height, width,
etc. - but such explaining is a specialty occupation here in this
group.

73's
Richard Clark, KB7QHC

Current across the antenna loading coil - from scratch

I see that Cecil's latest fetish is that EZNEC reports RMS values of
voltage and current. Because we know that the voltages and currents are
purely sinusoidal, the RMS value and phase angle (also reported by
EZNEC) are adequate to define the time waveform. That is, when we know
the RMS amplitude and the phase angle, we know the value of the waveform
at every instant in time. No additional information is necessary.

Roy Lewallen, W7EL