Yuri Blanarovich wrote:

So what is it then you claiming being equal.

In a loading coil with very small distributed capaciatnce to the
outside world compared to termination impedance, current has to be
equal. Phase shift in current at each end has to be nearly zero.

This is true for ANY antenna length or loading coil location.

This is what everyone was saying.

No gang wars intended, just trying to underline that there are two major
supporting "camps" claiming that the current has to be equal, or is
appreciably different.

One group is saying the distributed capacitance of the inductor to the
outside world controls the distribution, another group appears to be
saying it is a function of electrical degrees the coil makes up.

I agree with the majority of people posting in these threads. It is the
capacitance from the coil to the outside world that controls current
distribution in the inductor and produces and phase difference in
CURRENT at each end. If you look at Reg, Ian, Roy, all the Toms, Gene,
Richard Clark, and on and on we are all saying that same thing.

Richard Harrison, Yuri, and Cecil seem to argue against that, but that
is how ANY inductor behaves. It can be proven to behave the way most
people are trying to explain.

The coil does NOT represent the "missing degrees". It does NOT have to
have current taper (as a matter of fact a good indictor and antenna
design won't show any significant current taper).


Right. Although the distributed capacitance can change the shape.

It can change the amplitude, but not the shape of the current distribution
curve, that is the maximum is at the feed point (zero reactance - resonance)
and zero at the tips and follows cosine function.

The current distribution in an antenna is primarily a function of
displacement currents caused by capacitance to the outside world and
series impedance. If I have a short small diameter whip of uniform
cross section, it has triangular distribution.

If I sufficiently end-load the very same antenna with no change in
length, the current distribution becomes close to uniform. The thinner
the elenment and larger the end loading, the more uniform the current.

This is why radiation resistance is someplace around FOUR times greater
in an end-loaded antenna when compared to a base loaded antenna of the
same height. Radiation resistance is tied to ampere-feet, and
ampere-feet is larger with end loading rather than base loading.


What "good book"? It would help to see the context.

Say ARRL Antenna Book, 20th edition, page 16-7, Fig 10
Shows lengths h1 and h2 expressed as 15 deg. eaach.

That does not say 90 degrees. It says 15 degrees.

If you stick the coil at the base in series with radiator and bring it to
resonance (zero reactance at the frequency of interest) what "degree
resonant" will than radiator become, if not 90? ("Measured" from the feed
point, through the coil and then straight radiator.)

It is resonant. It is 15 degrees tall.

It is NOT 90 degree resonant.

Degrees of height is a distance measurement, not an electrical
parameter. If someone is using it to describe resonance thay are
misusing the term.

I can have a 180 degree long resonant dipole.

I can have a 20 degree long resoannt dipole.

I cannot have a 180 degree resonant dipole that is 20 degrees long. I
cannot have a 15 degree tall vertical that is 180 degree resonant, or
90 degree resonant. That argues against itself.


Well, is 180 degrees half wavelength or not?

Yes, 180 degrees is 1/2 wave.

Is the current maximum at the
feedpoint (center) and zero at the end, or not?

Yes.

The current distribution is
not the same, but is exhibiting properties of resonant half wave dipole with
current max at the center and zero at the tips. The shape is not the smooth
continuous cosine curve as in straight dipole, but affected by the loading
coils (drops) in their place (subject of disagreement).

So what? The degrees are a measure of physical length. A 20 degree long
coil loaded dipole is a 20 degree long resonant dipole. It is not a 180
degree resonant antenna.

Can we describe "pieces" or segments of the radiator as having
proportional
amount of degrees corresponding to their physical length, when excited
with
particular frequency?

Yes. It works fine for length. It does NOT work for loading inductors,
it does not work for short antennas which have anything form a uniform
distribution to triangular distribution, or any mix between including
curves of various slopes.

Why not? What happens to cosine current distribution curve when we insert
the loading element (inductance, coil, loading stub, resistance) in the
radiator? What formula applies to get the uniform or triangular
distribution? Can you show some mathematics?

This has all been explained over and over again. You can also see it in
any engineering book. ON4UN's book initially had it wrong, but it is
corrected now.

So we have resonant standing wave element, that has current max at the
feedpoint and zero at the tip, which gives us 90 degree (or 180 with dipole)
or quarter wave distribution from the base to the tip. (reality)

No, it does not. 90 degrees when used with antennas is a measure of
distance as it relates to frequency. You can't have a 15 degree long
antenna that is "180 degree resonant", and the current distribution
depends on distributed capacitance and series impedance.

We can
express the straight pieces of radiator in degrees, but not the coiled up
piece that the wave has to go through?

Right. You cannot build a "60 degree coil to make my 30 degree antenna
90 degrees long".

Think about it. If the coil was 60 degrees long, you could move it
anywhere in the antenna and it would be resonant at the same frequency!

The "uniform" and "triangular" distribution was used for approximation or
simplification of showing the current distribution in short loaded
radiators, while they are in reality segments of the cosine curve belonging
to length of the straight portions of the radiator. EZNEC shows that, when
you magnify the curve you can see there are no uniforms or triangles but a
cosine curve.

Oh, we are picking nits now. In this case we have to get every
engineering book to say "it is such a small portion of a curve it looks
straight" instead of using triangular or uniform.

After all current might be 1.0001 amperes at one point and 1.0000
amperes ten feet away, so I guess that is actually not uniform if we
pick the nits enough.

The cosine shape is not true as a rule, however. That shape depends on
distributed capacitance being uniform.

We are not talking here about base loaded radiator. No detours please.

If your theory does not cover base, center , and top loading it is
incomplete, If it does not treat a coil as a coil no matter how it is
used or set limits, it is incomplete.

Base loaded, center loaded. It doesn't matter.


So how many electrical degrees has the quarter wave resonant radiator that
is loaded with loading coil (or stub) about 2/3 way up and is say 30 deg.
physical "length" to make it resonant?

That's already been explained. If it is 30 degrees tall, it is a
resonant 30-degree tall radiator.

It is not a "90 degree resonant 30 degree tall radiator with a 60
degree coil".

73 Tom

wrote:
In a loading coil with very small distributed capaciatnce to the
outside world compared to termination impedance, current has to be
equal. Phase shift in current at each end has to be nearly zero.

That is a false statement and is at the root of the misconceptions.
Standing wave current does not have to be equal. I have shown how
current at the bottom of the coil can be zero while the current
at the top of the coil is one amp. Do you think the coil is sucking
that one amp sideways from somewhere else through its distributed
capacitance? There's no magic involved, just simple, easy to
understand, distributed network theory. The current at the top
and bottom of a coil depends upon where it is placed in the
standing wave environment. Standing wave current doesn't flow.
It is the underlying forward current and reflected current that
is doing the flowing. Such is obvious from the equations.

Hecht, in "Optics", has the best description of standing waves
that I have ever read. He says: "[Equation (7.30)] is the equation
for a STANDING or STATIONARY WAVE. Its profile does not move
through space. ... [Its phase] doesn't rotate at all, and the
resultant wave it represents doesn't progress through space -
it's a standing wave."

Translating into RF language. Func(kx)*Func(wt) is the equation
for a STANDING or STATIONARY WAVE, i.e. the standing wave is
stationary. Its magnitude does not move through the wire. Its
phase doesn't rotate at all, and the resultant standing wave
it represents doesn't progress through a wire or through a
coil - it's a standing wave.

Until everyone takes time to understand the nature of standing
waves, people will keep making the same tired mistake over and
over.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

wrote:

In a loading coil with very small distributed capaciatnce to the
outside world compared to termination impedance, current has to be
equal. Phase shift in current at each end has to be nearly zero.


That is a false statement and is at the root of the misconceptions.
Standing wave current does not have to be equal. I have shown how
current at the bottom of the coil can be zero while the current
at the top of the coil is one amp. Do you think the coil is sucking
that one amp sideways from somewhere else through its distributed
capacitance? There's no magic involved, just simple, easy to
understand, distributed network theory. The current at the top
and bottom of a coil depends upon where it is placed in the
standing wave environment. Standing wave current doesn't flow.
It is the underlying forward current and reflected current that
is doing the flowing. Such is obvious from the equations.

Hecht, in "Optics", has the best description of standing waves
that I have ever read. He says: "[Equation (7.30)] is the equation
for a STANDING or STATIONARY WAVE. Its profile does not move
through space. ... [Its phase] doesn't rotate at all, and the
resultant wave it represents doesn't progress through space -
it's a standing wave."

Translating into RF language. Func(kx)*Func(wt) is the equation
for a STANDING or STATIONARY WAVE, i.e. the standing wave is
stationary. Its magnitude does not move through the wire. Its
phase doesn't rotate at all, and the resultant standing wave
it represents doesn't progress through a wire or through a
coil - it's a standing wave.

Until everyone takes time to understand the nature of standing
waves, people will keep making the same tired mistake over and
over.

Hecht was talking about two opposing waves of the same phase and
amplitude interfering with each other. You can't guarantee, in a real
antenna,
that the two waves do have the same phase and magnitude.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
Hecht was talking about two opposing waves of the same phase and
amplitude interfering with each other. You can't guarantee, in a real
antenna, that the two waves do have the same phase and magnitude.

:-) Hecht was talking about two coherent EM waves traveling in
opposite directions. We are talking about two coherent EM waves
traveling in opposite directions. There is a small traveling
wave component but it doesn't affect the standing wave. It is
what is left over from the standing wave.

This discussion has not been about coils. We need to discuss
an unterminated lossless transmission line and then move on
to 1/2 wavelength thin-wire standing wave antennas.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

Tom Donaly wrote:

Hecht was talking about two opposing waves of the same phase and
amplitude interfering with each other. You can't guarantee, in a real
antenna, that the two waves do have the same phase and magnitude.


:-) Hecht was talking about two coherent EM waves traveling in
opposite directions. We are talking about two coherent EM waves
traveling in opposite directions. There is a small traveling
wave component but it doesn't affect the standing wave. It is
what is left over from the standing wave.

This discussion has not been about coils. We need to discuss
an unterminated lossless transmission line and then move on
to 1/2 wavelength thin-wire standing wave antennas.

Has it ever occurred to you, Cecil, that a half wave dipole with
equal current and voltage waves traveling in opposite directions
wouldn't accept power?
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
Has it ever occurred to you, Cecil, that a half wave dipole with
equal current and voltage waves traveling in opposite directions
wouldn't accept power?

It is an approximation, Tom, like a lossless line. For real world
dipoles, the voltage and current decay by about 10% between the
forward wave and the arrival of the reflected wave. Kraus and
Terman both use that approximation in their examples.

We aren't saying anything about the traveling wave part of the
waves. The discussion is about the standing wave portion of
the wave which, by definition, requires equal magnitudes.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
wrote:

In a loading coil with very small distributed capaciatnce to the
outside world compared to termination impedance, current has to be
equal. Phase shift in current at each end has to be nearly zero.


That is a false statement and is at the root of the misconceptions.
Standing wave current does not have to be equal.

I assume you are meaning that the RMS current at one physical point
must not equal the RMS current at some other point.

I have shown how
current at the bottom of the coil can be zero while the current
at the top of the coil is one amp. Do you think the coil is sucking
that one amp sideways from somewhere else through its distributed
capacitance?
(snip)

Of course that is what is happening. It is what happens in any
transmission line like device. There is a standing voltage wave,
also, and that produces displacement current through any capacitance,
just as the antenna does.

Aren't you claiming that the coil has transmission line like
properties, in that it takes time for a wave to pass through it?

Any such device needs two mechanisms for storing energy, one magnetic
(inductive) and one electrical (capacitive). Even free space has
both. If you eliminate either mechanism (or make one of them
insignificant, as would happen to the capacitance if the inductor
approaches zero size), you lose the transmission line like properties
as the dominant mechanism.

John Popelish wrote:

Cecil Moore wrote:
That is a false statement and is at the root of the misconceptions.
Standing wave current does not have to be equal.

I assume you are meaning that the RMS current at one physical point must
not equal the RMS current at some other point.

Yes, the RMS value of the standing wave current at the bottom of
the coil doesn't have to bear any relationship to the RMS value
of the standing wave current at the top of the coil.

Aren't you claiming that the coil has transmission line like properties,
in that it takes time for a wave to pass through it?

Yes

Any such device needs two mechanisms for storing energy, one magnetic
(inductive) and one electrical (capacitive). Even free space has both.
If you eliminate either mechanism (or make one of them insignificant, as
would happen to the capacitance if the inductor approaches zero size),
you lose the transmission line like properties as the dominant mechanism.

There is no net charge carried over from cycle to cycle. There is no
net storage of charge even if the steady-state RMS value of the standing
wave current is zero at one end of the coil and 2 amps at the other end.

The problem here is not how a coil works. The problem is how standing
waves work. Forget the coil. Start with a lossless unterminated
transmission line and then step up to a 1/2 wavelength thin wire dipole.

It is obvious that a number of people just don't understand the nature
of a standing wave that doesn't move through a wire along with its
phasor that doesn't rotate relative to the source.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
John Popelish wrote:

Cecil Moore wrote:

That is a false statement and is at the root of the misconceptions.
Standing wave current does not have to be equal.


I assume you are meaning that the RMS current at one physical point
must not equal the RMS current at some other point.


Yes, the RMS value of the standing wave current at the bottom of
the coil doesn't have to bear any relationship to the RMS value
of the standing wave current at the top of the coil.

Aren't you claiming that the coil has transmission line like
properties, in that it takes time for a wave to pass through it?


Yes

Any such device needs two mechanisms for storing energy, one magnetic
(inductive) and one electrical (capacitive). Even free space has
both. If you eliminate either mechanism (or make one of them
insignificant, as would happen to the capacitance if the inductor
approaches zero size), you lose the transmission line like properties
as the dominant mechanism.


There is no net charge carried over from cycle to cycle.

Of course. no one is talking about the red herring of charge stored
over a whole cycle. Everyone (except, possibly you) is talking about
charge stored and recovered twice per cycle.

There is no net storage of charge even if the steady-state RMS value
of the standing wave current is zero at one end of the coil
and 2 amps at the other end.

And no one but you brings up "net storage". We are all talking about
ordinary capacitive charge storage within a cycle. And there are two
equal and opposite half cycles of that. If there is Ac voltage and
capacitance to the universe, there is charge storage, twice within
every cycle, one positive and one negative.

The problem here is not how a coil works. The problem is how standing
waves work.

Standing waves have AC voltage swing. That applied to capacitance
causes real charge storage and retrieval. Just as it does with
traveling waves. How could the standing AC voltage not charge and
discharge, charge the other direction and discharge every cycle, the
capacitance between the conductor and the universe?

Forget the coil. Start with a lossless unterminated
transmission line and then step up to a 1/2 wavelength thin wire dipole.

The capacitance in a lossless transmission line is between the two
conductors. For the 1/2 wavelength thin wire dipole, the capacitance
is to the surroundings. But the charge stored and dumped into that
capacitance twice a cycle is very similar, except that in the case of
the antenna, some energy leaves in the form of radiation.

It is obvious that a number of people just don't understand the nature
of a standing wave that doesn't move through a wire along with its
phasor that doesn't rotate relative to the source.

It is obvious to me that you are one of them. Every point on a line
carrying a standing wave (except the node points) has AC voltage on
it, and AC current through it. The amplitude and phase of those
voltages and currents can be described as a phasor, with respect to
some reference phase of the same frequency. As you move along the
line, the amplitude changes and when you pass through a node the phase
reverses. So the phasor does not rotate with position change, except
for a step change of 180 degrees at nodes, rather than smooth rotation
with respect to position.

For a traveling wave, every point on the line has an AC voltage on it,
and an AC current passing through it. The amplitude is constant along
the line, but the phasor rotates as you move along the line (the phase
is linearly dependent on position). But at any single point on the
line, a non rotating phasor describes the amplitude and phase with
respect to a reference phase of the same frequency.

John Popelish wrote:
Of course. no one is talking about the red herring of charge stored
over a whole cycle.

Of course, *everyone* except you and Tom Donaly are talking about
charge stored over a whole cycle. That's the entire base of their
arguments. The unbalance in the *RMS* current at the bottom of the
coil and the *RMS* current at the top of the coil is what the entire
discussion is all about.

The currents measured by W8JI and W7EL were *RMS* currents. The
currents reported by EZNEC are *RMS* currents.

And no one but you brings up "net storage". We are all talking about
ordinary capacitive charge storage within a cycle.

If so, that is completely irrelevant to the discussion since
W8JI and W7EL are using *RMS* currents for their measurements
and EZNEC is reporting *RMS* currents.

Let me summarize it for you. W8JI and W7EL apparently think
that the RMS current value of zero at the bottom of the coil
Vs the RMS current value of one amp at the top of the coil
means energy is being sucked into the coil from some external
source.

How about assisting in a tutorial on standing waves rather
than diverting and obfuscating the issues?
--
73, Cecil http://www.qsl.net/w5dxp