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

"Richard Clark" wrote Hi Yuri,

This must be a convention that is particular to only a very few Hams.
The FCC database describes AM antennas in both electrical and physical
height as follows.

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

There may be some discrepancy, but it certainly looks like antenna
specification is by the electrical equivalent of the physical height
(and whatever l/d fudging) and with only one happening to be 90°.

Further, given most references (for professionals) is aimed at a
common specification that is largely driven by this agency, it would
seem odd to step out of this expectation to change to calling all
antennas 90° simply because they resonate.


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

73's
Richard Clark, KB7QHC


That's fine, no argument there. But do you agree that there are towers of X
height in meters and when "naked" having Y electrical degrees, loaded with
top hat of size S, not changing the physical height, but adding Z degrees.
So the top hat adds some degrees to the tower.
Is it such ham radio crime to say that coil can do that too, if it is
inserted within the radiator?
We use imaginary lumped inductor to understand coils better, but we can not
use electrical degrees to 'splain the behavior of coiled antenna wire?
I think we are progressing into antenna modeling and design and I see
nothing wrong with using degrees to describe electrical properties
(resonance) of the loaded radiator.

73 Yuri, K3BU

actually
WWLV 90.00° tall 47.2 meters tall 1620 kHz
should show closer to 92 deg. and assuming that they use fatter tower, even
more.

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

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.

On Mon, 3 Apr 2006 10:36:45 -0400, "Yuri Blanarovich"
wrote:

So the top hat adds some degrees to the tower.

Hi Yuri,

This is simply new wine in an old bottle. The same FCC site contains
top loaded antennas too. If you can find an example to support your
thesis, you will still have an obscure usage.

73's
Richard Clark, KB7QHC

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

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.

Richard Clark wrote:
"This must be a convention that is particular to only a very few hams.
The FCC database describes AM antennas in both electrical degrees and
physical height as follows."

It is the convention to describe AM broadcast towers in electrical
degrees. Harold Ennes reprints an RCA resistance chart for heights
between 50 and 200 degrees in "AM-FM Broadcast Maintenance".

Formula given is:
Height in electrical degrees = Height in feet X frequency in kc X 1.016
X 10 to the minus 6 power.

Example Towers:
50-degrees self-supporting: R=7. jx=-j100
50-degrees guyed mast: R=8, jx=-j222
90-degrees self-supporting: R=40, jx=+j35
90-degrees guyed mast: R=36, jx=j0
200-degrees self-supporting: R=23, jx=-j50
200-degrees guyed mast: R=80, jx=-400

There are values of R and X for 16 different heights. If you are
interested, look at the book.

Best regards, Richard Harrison, KB5WZI

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