Current through coils
 

K7ITM wrote:
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.

I may have said that a pure lumped inductance has no capacitance
to the outside world and that is true by definition. Perhaps that
is what you are remembering. Anyone would be crazy to assert that
a real world coil has no capacitance to the outside world. What I
said is that capacitance to the outside world is often a secondary
effect compared to the primary effect of superposing forward and
reflected currents.

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.

But that is not happening. Standing wave current doesn't flow. It just
stands there. How many times do I have to repeat the following.

Assume the forward current is one amp and the reflected current is one
amp. The standing wave current is the phasor sum of those two currents.

One amp of forward current is flowing into the coil and one amp of
forward current is flowing out of the coil. There is ZERO net storage
of charge associated with the forward current.

One amp of reflected current is flowing into the coil and one amp
of reflected current is flowing out of the coil. There is ZERO net
storage of charge associated with the reflected current.

Since these two currents are the only currents, there is ZERO net
storage of charge in the coil. The magnitude of the standing wave
current is irrelevant.

The forward current at the bottom of the coil is one amp at zero deg.
The reflected current at the bottom of the coil is one amp at 180 deg.
Their phasor sum, the standing wave current, is zero.

The forward current at the top of the coil is 0.5 amp at -90 deg.
The reflected current at the top of the coil is 0.5 amp at -90 deg.
Their phasor sum, the standing wave current, is 1.0 amp at -90 deg.

There's no net storage of charge in the coil, zero amps at the
bottom of the coil, and one amp at the top. That proves that standing
wave current doesn't flow, exactly as its equation says it doesn't
flow, exactly as Hecht, in "Optics", says a standing wave "doesn't
move through space".

The rest of your posting is irrelevant since it just repeats
the same old misconception that standing wave current flows.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

"Richard Harrison" wrote

At F1 and F2, current at both ends of the coils are substantially
different. You probably would put them in a box with only 2 terminals.
Pity the fool who argues with Kraus!

Best regards, Richard Harrison, KB5WZI



yea, but, but, but..... (the "equal current choir" :-)

Thanks Richard!
Yuri, K3BU

Current through coils
 

Richard Harrison wrote:
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.

Consider a 1/4WL open-circuit stub. The impedance at the open
is very high and the current is zero.

The impedance at the mouth of the stub is very low and the
current is at a maximum.

Exactly the same thing happens with a coil at the self-resonant
frequency.

The standing wave current at each end of a coil installed in
a standing wave antenna depends upon its position in the
antenna. To paraphrase Hecht, standing wave current "doesn't
progress through a wire - it's a standing wave."
--
73, Cecil http://www.qsl.net/w5dxp

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

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

Current through coils
 

To all and sundry.

You can't locate a loading coil at the top of a short antenna because
it requires infinite inductance.

Before it gets to the top it resonates with its self-capacitance,
becomes a parallel tuned circuit, and isolates itself from the
antenna. The antenna then reverts to an unloaded rod.

The 'mechanism' is modelled in program LOADCOIL, which alows the
loading coil to slide up and down the antenna to find maximum
radiating efficiency.

There is enough information available to further calculate the angles
of the bottom section, the coil. and the top section if you are
prepared to find the time and think about it. But I can assure you
angles take no part in the internal calculations of the program except
perhaps in calculating efficiency. They are just a distraction.

Just enter diameter of bottom section, length and diameter of the
coil, and diameter of the top section and slide the coil up and down
to see what happens with constant overall height at a given frequency.
As a free gift you also get the number of turns on the coil. Its been
some time since I used the program myself. It might even tell you the
wire gauge.

Download program LOADCOIL in a few seconds from website below and run
immediately.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

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

Current through coils
 

Cecil Moore wrote:

Richard Harrison wrote:

Not only does Terman give voltage and current diagrams, he gives a phase
diagram. It shows that whenever the voltage or current crosses the zero
axis (changes sign) the phase angle changes abruptly by 180-degrees.
Phase is unchanging between these inflection points. This agrees with
what Cecil has said all along in this discussion.


Kraus agrees. Yet W7EL used that unchanging phase to measure the
delay through a loading coil. What's wrong with that picture?

Some people, who no doubt have recognized their technical errors,
simply refuse to discuss the technical subjects. Ian, OTOH, seems
open to discussing those topics so please don't be too hard on him.
An honest person deserves respect whether he is right or wrong.

Cecil, since you always leave the phase information out of
your version of the solution of the wave equation, I don't
think Diogenes is going to be knocking on your door anytime soon,
either.
73,
Tom Donaly, KA6RUH

Current through coils
 

Cecil Moore wrote:

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.


It sure would be nice if were as simple as all that. We wouldn't
need NEC to help us if it were. You're missing the point, Cecil,
read Tom's post again, and meditate on this Ch'an buddhist koan
that I just made up in my head: Is the water the wave?
73,
Tom Donaly, KA6RUH

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