Art Unwin wrote:
At the moment I see no mechanism that supports the capacitor field to
expire in the direction of incoming current
prior to the completion of the forward period.

The "capacitive" field is the *electric* field which is
at a *maximum* amplitude at the tip of a dipole. It is
the magnetic (inductive) field that is close to zero
at the tip of a dipole.
--
73, Cecil http://www.w5dxp.com

On Dec 29, 10:26*am, Cecil Moore wrote:
Art Unwin wrote:
At the moment I see no mechanism that supports the capacitor field to
expire in the direction of incoming current
prior to the completion of the forward period.

The "capacitive" field is the *electric* field which is
at a *maximum* amplitude at the tip of a dipole. It is
the magnetic (inductive) field that is close to zero
at the tip of a dipole.
--
73, Cecil *http://www.w5dxp.com
Cecil
I still am looking for an explanation that prevents current flow thru
the center.
I recognise that the common thinking is to accept reflection but I
fail to see
how that can happen so I can follow up with the numbers.
The capacitor is limited with respect to the energy that it can retain
so what happens when that
limit is reached and the forward period has not come to an end? Yes,
the common thinking
is that the current changes direction to oppose the forward moving
current as with a reflection
where the eddy current in the reverse direction cancels the eddy
current moving in the other direction.
It is here that I am looking for a mechanism that justifies this
reasoning of reflection so I can begin to dispel the
closed circuit aproach as seen with a full wave radiator in
equilibrium
Best regards
Art
Art
but I am looking for actual proof

Art wrote:
"The capacitor is limited with respect to energy it can retain so what
happens when that limit is reached and the forward period has not come
to an end?"

There is a sudden flash as energy jumps the gap between the plates.

The energy a capacitor can store expressed in joules is equal to its
capacitance in microfarads times the voltage (squared) across its plates
divided by two million.

For a fixed capacitor, the only vatiable is the voltage. So, the greater
the voltage across the capacitor the greater the energy it stores. The
only limit is the breakdown voltage.

Best regards, Richard Harrison, KB5WZI

On Dec 29, 12:25*pm, (Richard Harrison)
wrote:
Art wrote:

"The capacitor is limited with respect to energy it can retain so what
happens when that limit is reached and the forward period has not come
to an end?"

There is a sudden flash as energy jumps the gap between the plates.

The energy a capacitor can store expressed in joules is equal to its
capacitance in microfarads times the voltage (squared) across its plates
divided by two million.

For a fixed capacitor, the only vatiable is the voltage. So, the greater
the voltage across the capacitor the greater the energy it stores. The
only limit is the breakdown voltage.

Best regards, Richard Harrison, KB5WZI

So one acknowledges the presence of a capacitor at the end of a
radiator
So now we determine the capacitance and the voltage withstand
together
with what comprises as a capacitor at the end of a radiator to relate
to
which way the current flows.
The question with respect to current flow is still present and
unanswered
despite all of the manouvaring the face the question head on.
If the past means anything this subject could go to a 1000 posts with
neither
a modicom of science to bolster the talk
Art

Art Unwin wrote:
So one acknowledges the presence of a capacitor at the end of a
radiator

Let's use IEEE definitions to avoid confusion. A "capacitor"
is a physical component that exhibits capacitance. Capacitance
can be exhibited without the existence of a physical lumped
component. At the end of a radiator, we would have a
distributed capacitance, not *a* lumped capacitor. And
actually, it is not only at the end since it is "distributed".
In fact, an antenna element can be modeled as a distributed
RLC network where the R includes all "losses" including radiation.
--
73, Cecil http://www.w5dxp.com

On Dec 29, 1:14*pm, Cecil Moore wrote:
Art Unwin wrote:
So one acknowledges the presence of a capacitor at the end of a
radiator

Let's use IEEE definitions to avoid confusion. A "capacitor"
is a physical component that exhibits capacitance. Capacitance
can be exhibited without the existence of a physical lumped
component. At the end of a radiator, we would have a
distributed capacitance, not *a* lumped capacitor.

No Cecil. We are at the end of the radiator and there is no eddy
currents in front.
Ther apparently is a gap between the outside of the radiator end which
some see as a capacitor
( tho I see nothing that suggests that as yet) If one accepts a
capacitor as distributed then I will go along with that
but that alone cannot stop the flow of current.
Regards
Art





And
actually, it is not only at the end since it is "distributed".
In fact, an antenna element can be modeled as a distributed
RLC network where the R includes all "losses" including radiation.
--

I would love to see that circuit in its entirety since it will show
the points of collision


73, Cecil *http://www.w5dxp.com

I still am looking for an explanation that prevents current flow thru
the center.

Well, being a logical person, I would ask what mechanism
of physics keeps the forward current from flowing through
the center to start with? Why doesn't the forward current
flow through the center and the reflected current flow
back on the surface?

Whatever that mechanism is, it seems logical to conclude
that it might also prevent reflected current from flowing
back through the center.

If we put a signal generator at each end of a wire,
which current flows on the outside and which flows on
the inside?
--
73, Cecil http://www.w5dxp.com

Art wrote:
"Yes, the common thinking is that current changes direction to oppose
the forward moving current as with a reflection where the eddy current
moving in the reverse direction cancels the eddy current moving in the
other direction."

Transformers are laminated to reduce eddy current core losses.

Reverse currents on a transmission line or on an antenna are usually
called the reflected current.

Reflections are caused by discontinuities in the path of the EM wave.

In the case of an open circuit, the reflection coefficient is infinite
and the incident and reflected waves have the same magnitude and phase.
The voltage at the discontinuity is thus doubled. See Terman`s 1955 opus
page 89. But, the current goes to zero as conduction ends at the open
circuit. No energy is lost in the open circuit. It is just concentrated
in the electric field as the magnetic field loses its energy.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
In the case of an open circuit, the reflection coefficient is infinite

Richard, I'll bet you know that the reflection coefficient
is 1.0 for an open circuit and -1.0 for a short circuit.:-)
--
73, Cecil http://www.w5dxp.com

Cecil, W5DXP wrote:
"Richard , I`ll bet you know that the reflection coefficient is 1.0 for
an open circuit and -1.0 for a short circuit. :-)

Yes, Cecil caught me not paying attention. At an open circuit, the
impedance is infinite but the coefficient of reflection is the ratio of
the voltage of the reflected wave to the voltage of the incident wave.
As both have the same phase and magnitude, value of the reflection
coefficient for an open circuit is 1.0, not infinity.

Best regards, Richard Harrison, KB5WZI