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Old April 3rd 06, 05:06 AM posted to rec.radio.amateur.antenna
K7ITM
 
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Default Current through coils

Cec wrote, "How does one amp at the top and zero amps at the bottom
grab you?
Please see my other postings."

It grabs me that what you wrote in your other postings about
capacitance to the outside world, " I didn't say there was no
capacitance to the outside world. I said
such is a secondary effect, not a primary effect, and for the sake
of the present argument, can be ignored as secondary effects often
are ignored," is all wet. And I still say that your other postings
before that were saying you believed that there was NO capacitance to
the outside world. It was the message they sent to me, loud and clear.

Given any volume, say a volume containing a Texas Bugcatcher coil and
the air inside and immediately around it, if you push more electrons in
than come out _for_ANY_abritrarily_short_time_period_, you have changed
the net charge in that volume; if you pull out more electrons than go
in, you have changed the net charge in that volume. If the current at
the top and bottom, the only two conductors crossing the boundary of
that volume, is different, that represents flow of charge into (and out
of, in a cyclic fashion) that volume. I don't know what to call that
except capacitance to the outside world. Yes, it's _distributed_
capacitance. But the key point is that it is THE reason--the WHOLE
reason--for the difference in current between the top and the bottom,
NOT a "secondary effect."

In fact, when YOU say that the coil "behaves differently" in different
external environments, you are AFFIRMING it as an important effect, for
surely the presence or absence of some American gas guzzler (or is it
Diesel guzzler?) strongly affects the capacitance to the outside world,
and does not significantly affect internal capacitances (which in any
event, being contained entirely within that volume, do NOTHING for
storing net charge within the volume, because for those internal
capacitances to store charge, what goes in one end comes immediately
out the other end which is still inside the same volume and thus there
is not any net change in charge within the volume). But the "other
end" of capacitance to the gas guzzler or whatever is OUTSIDE the
volume of the coil, thus EXACTLY accounting for the difference in
current at the two leads going to the coil. -- I suppose they covered
all that in a sophomore EE circuits class, but I wouldn't know. I
suppose they also might have covered how a pure lumped model using only
i(t)=C*dv(t)/dt and v(t)=L*di(t)/dt, with no time delay elements, can
mimic lossless transmission line behaviour to any arbitrary degree of
accuracy you want, but perhaps they don't try to hit you with that
concept till later. I wouldn't know that, either...I just know it's
true.

I suppose it's a bit too much to ask all at once, but I do wish you
could see that just because the specific value of the capacitance is
different in different environments, it does not mean that I need a
different model. The coil does not behave in some fundamentally
different way. I only need to adjust the value of that capacitance
within the model--or if you will, the parameters of the
transmission-line-like behaviour, though other models may work as well
in practical antenna analysis. The model stays the same; the
parameters in the model change. When I change the value of a resistor,
my model of a resistor doesn't change. It's still fundamentally
v(t)=R*i(t). Only the value used for R changes. On a grander scale,
when I include the parasitic effects of a real inductOR, I have more
things to account for in the model than just inductANCE. Some of them
are affected significantly by the environment in which I place the
inductor. And even small changes in the values can have a profound
effect on the overall system behaviour. That's especially true in a
system operated near resonance where the Q is extremely high, such as a
system in which there is only a standing wave.

My only wish is that these musings will be useful to the lurkers trying
to actually learn something, if there still happen to be any around.

Cheers,
Tom

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Old April 3rd 06, 07:09 AM posted to rec.radio.amateur.antenna
Richard Harrison
 
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Default Current through coils

Tom, K7ITM wrote:
"Given any volume, say a volume containing a Texas Bugcatcher coil and
the air inside and immediately around it, if you push more electrons in
than come out_for_ANY_arbitrarily_short_time_period_, you have changed
the net charge in that volume;---."

No. This is not charging a capacitor or a battery. Energy stored in an
antenna system is in constant motion. Power delivered by the transmitter
is neadly the same as that used by the load, (the antenna), plus that
consumed by losses.

Power is simply the in-phase volts times amps. It can have any impedance
which is the ratio of in-phase volts to amps. Z in the general case can
include reactance plus resistance and can give the apparent power. It is
the ratio of volts to amps without regard to phase.

The coil which has a great difference between the current at its ends
most likely simply has different impedances at its ends. The power is
nearly the same at both ends of the coil but the voltage to current
ratios are different.

Varying impredance along the RF path is a product of the interference
between the incident and reflected waves. A standing-wave antenna
typically has an open-circuit at its end or ends. The RF has no other
option but to be returned
toward the sender and make standing waves. The large number of possible
incident and reflected wave combinatioms makes it very likely that the
current at opposite ends of a coil inserted in the antenna system will
be unequal.

It`s the power in and out of a coil in an antenna system that`s likely
to be nearly equal at both ends.

Best regards, Richard Harrison, KB5WZI

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Old April 3rd 06, 09:01 AM posted to rec.radio.amateur.antenna
K7ITM
 
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Default Current through coils

Richard H wrote,

"Tom, K7ITM wrote:

"Given any volume, say a volume containing a Texas Bugcatcher coil and
the air inside and immediately around it, if you push more electrons in
than come out_for_ANY_arbitrarily_short_time_period_, you have changed
the net charge in that volume;---."

No. ..."

OK, I'm going to repeat it once mo

If you shove more electrons into ANY volume than you remove, you have
changed the charge within that volume. I do NOT care WHAT is in that
volume. Current is the rate that charge is flowing past a point on a
conductor. If the only way I have of getting charge into and out of a
particular volume is through two wires, then the difference in current
at every instant in time represents the time rate of change of charge
within that volume. That is true INDEPENDENT of whether it is in an
antenna, and it is INDEPENDENT of what's inside that volume.

In fact, energy around an antenna is stored in electric and magnetic
fields. These are inexorably linked to inductance along the conductors
composing the antenna, and capacitance from these conductors to
themselves and to any counterpoise or ground plane which may be part of
the antenna--anything where electric field lines terminate. The charge
per unit length along an antenna wire, be it resonant or not, be it a
"standing wave" or a "travelling wave" antenna, varies with time. If
it did not, then the current would necessarily be identical along the
whole wire all the time.

This all gets back to very basic definitions of charge, and current as
the rate of flow of charge. It's all consistent with Maxwell, Gauss,
Faraday, etc. and with waves both standing and travelling, and with
"impredances" and all the rest.

It's just amazing to me that some of you are fighting so hard against
the very thing which has a chance of unifying your "wave" model with
the realities of the electric and magnetic fields, and the associated
capacitance and inductance along the antenna--indeed, along the wire
itself, and not just along the coil.

Without capacitance, there can be NO difference in current anywhere
along the wire, because there is simply no place to put the charge
implied by differing currents at differing locations. With capacitance
and inductance, everything works just as it's supposed to--just as it
DOES--and a properly developed wave theory will analyze it just fine,
if that's your cup of tea.

Cheers,
Tom

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Old April 3rd 06, 12:00 PM posted to rec.radio.amateur.antenna
Mike Coombes
 
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Default Current through coils

I don't understand what you are all on about, but, I side with K7ITM
"K7ITM" wrote in message

Regards Mike.


ups.com...
Richard H wrote,

"Tom, K7ITM wrote:

"Given any volume, say a volume containing a Texas Bugcatcher coil and
the air inside and immediately around it, if you push more electrons in
than come out_for_ANY_arbitrarily_short_time_period_, you have changed
the net charge in that volume;---."

No. ..."

OK, I'm going to repeat it once mo

If you shove more electrons into ANY volume than you remove, you have
changed the charge within that volume. I do NOT care WHAT is in that
volume. Current is the rate that charge is flowing past a point on a
conductor. If the only way I have of getting charge into and out of a
particular volume is through two wires, then the difference in current
at every instant in time represents the time rate of change of charge
within that volume. That is true INDEPENDENT of whether it is in an
antenna, and it is INDEPENDENT of what's inside that volume.

In fact, energy around an antenna is stored in electric and magnetic
fields. These are inexorably linked to inductance along the conductors
composing the antenna, and capacitance from these conductors to
themselves and to any counterpoise or ground plane which may be part of
the antenna--anything where electric field lines terminate. The charge
per unit length along an antenna wire, be it resonant or not, be it a
"standing wave" or a "travelling wave" antenna, varies with time. If
it did not, then the current would necessarily be identical along the
whole wire all the time.

This all gets back to very basic definitions of charge, and current as
the rate of flow of charge. It's all consistent with Maxwell, Gauss,
Faraday, etc. and with waves both standing and travelling, and with
"impredances" and all the rest.

It's just amazing to me that some of you are fighting so hard against
the very thing which has a chance of unifying your "wave" model with
the realities of the electric and magnetic fields, and the associated
capacitance and inductance along the antenna--indeed, along the wire
itself, and not just along the coil.

Without capacitance, there can be NO difference in current anywhere
along the wire, because there is simply no place to put the charge
implied by differing currents at differing locations. With capacitance
and inductance, everything works just as it's supposed to--just as it
DOES--and a properly developed wave theory will analyze it just fine,
if that's your cup of tea.

Cheers,
Tom

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Old April 3rd 06, 03:59 PM posted to rec.radio.amateur.antenna
Cecil Moore
 
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Default Current through coils

Mike Coombes wrote:
I don't understand what you are all on about, but, I side with K7ITM
"K7ITM" wrote in message
Regards Mike.


1. If the magnitude of the forward current is the same at
both ends of the coil, there is no net storage of charge.

2. If the magnitude of the reflected current is the same at
both ends of the coil, there is no net storage of charge.

These conditions satisfies K7ITM's requirements. But he
is being fooled by the sum of the two above currents
which is meaningless to net charge storage.

Statements 1 and 2, above, already prove there is no net
storage of charge. Looking at the standing wave current
is meaningless after that technical fact.
--
73, Cecil http://www.qsl.net/w5dxp


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Old April 3rd 06, 06:45 PM posted to rec.radio.amateur.antenna
Tom Donaly
 
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Default Current through coils

Cecil Moore wrote:

Mike Coombes wrote:

I don't understand what you are all on about, but, I side with K7ITM
"K7ITM" wrote in message
Regards Mike.



1. If the magnitude of the forward current is the same at
both ends of the coil, there is no net storage of charge.

2. If the magnitude of the reflected current is the same at
both ends of the coil, there is no net storage of charge.

These conditions satisfies K7ITM's requirements. But he
is being fooled by the sum of the two above currents
which is meaningless to net charge storage.

Statements 1 and 2, above, already prove there is no net
storage of charge. Looking at the standing wave current
is meaningless after that technical fact.


There is no "net" charge storage on a capacitor in an AC
environment, either, Cecil, but you can still get current
to go through it. I wouldn't argue with Tom too much if I
were you, Cecil, because without the facts he's pointed out
in regards to charge, your inchoate theorizing wouldn't mean
anything at all.
73,
Tom Donaly, KA6RUH
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Old April 3rd 06, 08:22 PM posted to rec.radio.amateur.antenna
Cecil Moore
 
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Tom Donaly wrote:
There is no "net" charge storage on a capacitor in an AC
environment, either, Cecil, but you can still get current
to go through it.


True, but completely irrelevant to the present discussion
so more than likely another straw man.

Once more, the subject is the RMS standing wave envelope
reported by EZNEC. Brownian motion of individual electrons
is completely irrelevant.
--
73, Cecil http://www.qsl.net/w5dxp
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Old April 3rd 06, 03:55 PM posted to rec.radio.amateur.antenna
Cecil Moore
 
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Default Current through coils

K7ITM wrote:
If you shove more electrons into ANY volume than you remove, you have
changed the charge within that volume.


That is true but having zero standing wave amps at one end
of a coil and one standing wave amp at the other end doesn't
mean the charge is changing.

If the forward current is the same magnitude at both ends
of the coil, there's no change in charge.

If the reflected current is the same magnitude at both
ends of the coil there's no change in charge.

The standing wave current is the sum of those two phasors.
That sum is what is fooling you. Please pay attention to
Hecht, in "Optics".

The standing wave current profile does not move through
the wire just as the standing wave light profile does
not move through space.

Standing wave current doesn't progress through a wire just
as standing wave light doesn't progress through space.
--
73, Cecil http://www.qsl.net/w5dxp
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Old April 3rd 06, 05:26 PM posted to rec.radio.amateur.antenna
K7ITM
 
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Default Current through coils

Hi there, Cec,

You wrote,
"If the forward current is the same magnitude at both ends
of the coil, there's no change in charge.

If the reflected current is the same magnitude at both
ends of the coil there's no change in charge."

Dunno why you keep reverting back to magnitudes, but I'm talking about
current as a function of time, and have been consistently through this
whole thing. Until you get that straight, there's no point in your
even taking part in this. "Cyclical variation in charge (contained
within a volume)" means that on average the charge stays constant, but
it does not mean that it's constant over some arbitratily short but
finite length of time.

Without the capacitance, without the ability to store charge, a
transmission line, an antenna wire, a loading coil, all of them--would
not have the ability to cause delay. Freespace, without a non-zero
permittivity (capacitance), would allow infinite speed of light. But
all these things DO have capacitance, and they DO have
speed-of-propagation at the speed of light or slower.


Cheers,
Tom

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Old April 3rd 06, 07:43 PM posted to rec.radio.amateur.antenna
Cecil Moore
 
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Default Current through coils

K7ITM wrote:
"Cyclical variation in charge (contained
within a volume)" means that on average the charge stays constant, but
it does not mean that it's constant over some arbitratily short but
finite length of time.


The current reported by EZNEC is RMS current, Tom. What happens
within a cycle is irrelevant to this discussion.

We are not and never have been discussing variations within a
cycle. There's just no point. We have been discussing RMS values
of currents. Your attempt to again divert the issue is noted. We
are talking about net charge spread out over many steady-state
cycles. That net charge is always zero no matter what the RMS
value of the standing wave current at the ends of the coil.

Without the capacitance, without the ability to store charge, a
transmission line, an antenna wire, a loading coil, all of them--would
not have the ability to cause delay. Freespace, without a non-zero
permittivity (capacitance), would allow infinite speed of light. But
all these things DO have capacitance, and they DO have
speed-of-propagation at the speed of light or slower.


Please tell us something we don't already know.

It has become apparent that the discussion is not about coils at
all. It is about the nature of standing waves whether existing
in a transmission line, a standing wave antenna wire, or a coil.
--
73, Cecil http://www.qsl.net/w5dxp


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