Current through coils
 

Roy Lewallen wrote:
-- we get
exactly the same result either way because superposition holds.

Thinking that the result is the same and that nothing gets
lost during superpositon is a misconception. Consider the
following.

PSK modem A--------------------------------------PSK modem B

When a single signal flows from A to B, perfect information
transfer occurs. When a single signal flows from B to A,
perfect information transfer occurs. Now superpose the
two information streams. ZERO information transfer occurs.
Superposition is not magic and the result is not the same.

The superposition of forward and reflected currents cause
100% loss of phase information in the standing wave current
phase measurement. It is analogous to the problem above.

A standing wave current cannot be used to determine the
delay through a coil.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

On Sun, 19 Mar 2006 12:41:43 GMT, Cecil Moore
wrote:

Owen Duffy wrote:

Cecil Moore wrote:
Please see http://www.qsl.net/w5dxp/current.htm

I refer to the diagram in the section entitled "What EZNEC Says About
Current Distribution Using Inductive Loading Stubs"

You use the diagram to assert that there is "not a lot of difference
between inductive loading stubs and loading coils" by comparing the
current distribution with another case.

You show graphically the current on each side of the stub. You do not
show the current in each wire of the stub or the sum of the currents
in the stub.

The currents in stubs cannot be displayed very well at full size in
EZNEC just as the currents in coils cannot be displayed very well.
Maybe an enlarged view would show it. I will try to do that.

Or even words that explain that the diagram is incomplete, that there
are currents flowing in the stub wires, and that they don't balance
each other so they participate in the antenna's total current moment.

The currents in the stubs is an explanation for the difference in the
currents in the main radiator at each side of the stub connection.

Is it fair to say that though the diagram may resemble the first
diagram on the page, to some extent, the reason they are similar is
that the second one is incomplete.


EZNEC calculates the currents in each wire of the stub? Aren't those
currents a relevant detail that you have omitted from the diagram.

Remember the present discussion is about the ability to use standing
wave current phase to measure the electrical length of a wire or a
coil. I have run the currents that you mention. The phase of the current
is almost constant through the stubs. The phase of the current is
almost constant through the coils. Would you like to see a list
of the current at points through the stub Vs the current at points
through the coil?

No thanks, I didn't ask the question without creating a model and
inspecting the currents.

The phase of the currents is only one dimension. Though the phase of
the current in adjacent segments in all wires (including the stubs) is
commonly similar (except where a phase reversal occurs), in general,
the magnitude and phase of paired stub segments that effectively form
a transmission line section are not equal in magnitude and phase.

My point is really about whether the subject diagram supports your
argument, especially if it is incomplete and if it misrepresents the
scenario.

Owen
--

Current through coils
 

wrote

This long painful thread (it's been going on years now) started because
K3BU claimed a loading inductor had most of the current in the first
few turns.

I am back after loooong absence here and see more misinformation coming from
Tom, W8JI.

I claimed that current in the antenna coil is NOT CONSTANT (or near) as he
claimed.
The case was of electrical quarter wave vertical radiator (as loaded mobile
antenna) and that the current is distributed, varying across the coil as I
have experienced, W9UCW has measured and Cecil has explained.
The refresher is at
http://www.k3bu.us/loadingcoils.htm

The thread is "painful" because some people try to subvert the reality and
keep clinging to wrong "reality" and some try to set the record straight..
This misinformation keeps being perpetuated in literature and it even crept
into the latest ON4UN 4th edition of Low Band DXing (see page 9-33).

The significance of properly realizing the current distribution in the
loading coil is in how the modeling programs treat the phenomena and major
screw-up will show up in multi element loaded antenna systems, where error
will multiply and give false results.
There are few more statements slightly out of true on W8JI pages, but would
have to be left for later time.

I apologize for being away from this NG, my AOL provider dumped NG and I am
slowly dumping AOL and will migrate to optonline.net and back to NG. Also
business and other QRM keeps me away, but I hope is that "tings" will
improve.

73 to all
Yuri, K3BU
www.K3BU.us
www.TeslaRadio.org

Current through coils
 

Cecil Moore wrote:
Roy Lewallen wrote:

-- we get exactly the same result either way because superposition
holds.


Thinking that the result is the same and that nothing gets
lost during superpositon is a misconception. Consider the
following.

PSK modem A--------------------------------------PSK modem B

When a single signal flows from A to B, perfect information
transfer occurs. When a single signal flows from B to A,
perfect information transfer occurs. Now superpose the
two information streams. ZERO information transfer occurs.
Superposition is not magic and the result is not the same.

The superposition of forward and reflected currents cause
100% loss of phase information in the standing wave current
phase measurement. It is analogous to the problem above.

A standing wave current cannot be used to determine the
delay through a coil.

Cecil, that's the worst analogy I've ever read in my
life.
73,
Tom Donaly, KA6RUH

Current through coils
 

Yuri Blanarovich wrote:
wrote

This long painful thread (it's been going on years now) started because
K3BU claimed a loading inductor had most of the current in the first
few turns.

I am back after loooong absence here and see more misinformation coming from
Tom, W8JI.

I claimed that current in the antenna coil is NOT CONSTANT (or near) as he
claimed.
The case was of electrical quarter wave vertical radiator (as loaded mobile
antenna) and that the current is distributed, varying across the coil as I
have experienced, W9UCW has measured and Cecil has explained.

Yuri,

Why don't you explain in a few words how you think the loading coil
works?

Also, why do you think a mobile antenna is "90 degrees long" when it
has a loading coil?

The loading coil, if well-designed and of compact size, doesn't have to
have any significant current taper. The exception would be if the
antenna above the coil has small capacitance compared to distributed
capacitance from the coil to space or to ground.

Do you still disagree with this?

73 Tom

Current through coils
 

Owen Duffy wrote:
The currents in the stubs is an explanation for the difference in the
currents in the main radiator at each side of the stub connection.

Just as are the currents in the coils.

Is it fair to say that though the diagram may resemble the first
diagram on the page, to some extent, the reason they are similar is
that the second one is incomplete.

I sent you a .gif file giving you the full perspective.

My point is really about whether the subject diagram supports your
argument, especially if it is incomplete and if it misrepresents the
scenario.

The phase shift through the stub is the same as through the coil is
the same as through the wire. It is simply zero according to the
standing wave current phase which is incapable of measuring phase.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Yuri Blanarovich wrote:
I claimed that current in the antenna coil is NOT CONSTANT (or near) as he
claimed.

Only one out of a dozen tests run by W8JI and W7EL showed the
currents to be equal. All the other tests showed the currents to be
*unequal*.

The significance of properly realizing the current distribution in the
loading coil is in how the modeling programs treat the phenomena and major
screw-up will show up in multi element loaded antenna systems, where error
will multiply and give false results.

The helix option in EZNEC supports the notion that the currents
are hardly ever equal. If a coil is installed at a standing wave current
maximum or minimum the currents can be equal. If the coil is installed
at a point where the slope of the current is maximum, the difference
in the currents at each end will be maximum. That's pretty simple physics.
The currents at each end of a coil in a standing wave environment depends
upon where it is installed.

I provided an example where the current "into" the bottom of the coil
was 0.17 amps and the current "out of" the top of the coil was 2.0 amps.
W8JI said the lumped-circuit inductance could explain that so I asked
him to explain it to all of us. So far, no response.

Wonder how a model that assumes faster than light propagation of waves
and absolutely equal current magnitude and phase is going to explain a
1.8 amp difference and a phase shift of 180 degrees?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Tom Donaly wrote:
Cecil, that's the worst analogy I've ever read in my
life.

The PSK signals lose phase when they are superposed. The forward
and reflected currents lose phase when they are superposed. Looks
like a perfect analogy to me. Do you disagree with Gene Fuller?

Gene Fuller, W4SZ wrote:
In a standing wave antenna problem, such as the one you describe, there is no
remaining phase information. Any specific phase characteristics of the traveling
waves died out when the startup transients died out.

Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be seen again.

The only "phase" remaining is the cos (kz) term, which is really an amplitude
description, not a phase.

Do you disagree with Gene? How can Tom and Roy possibly use a signal
whose phase cannot be recovered to measure phase?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

wrote:
The loading coil, if well-designed and of compact size, doesn't have to
have any significant current taper.

The current taper depends upon where the coil is installed in
the standing wave environment. There is no doubt that the coil
distorts the current away from the ideal thin-wire dipole case.
But that coil does have to have a significant delay, in the tens
of degrees according to Dr. Corum. Since you and Roy mistakenly
used standing wave current phase to try to measure the delay
through a coil, the following posting resulted:

Gene Fuller, W4SZ wrote:
In a standing wave antenna problem, such as the one you describe, there is no
remaining phase information. Any specific phase characteristics of the traveling
waves died out when the startup transients died out.

Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be seen again.

The only "phase" remaining is the cos (kz) term, which is really an amplitude
description, not a phase.

Gene is 100% correct and we all should be grateful for that posting.

Neither you nor Roy have ever made a valid measurement of the
delay through a coil. It is admittedly a difficult measurement
to make directly. Ramo and Whinnery say it "is usually of
prohibitive difficulty".
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil Moore wrote:
Owen Duffy wrote:

The currents in the stubs is an explanation for the difference in the
currents in the main radiator at each side of the stub connection.


Just as are the currents in the coils.

Is it fair to say that though the diagram may resemble the first
diagram on the page, to some extent, the reason they are similar is
that the second one is incomplete.


I sent you a .gif file giving you the full perspective.

My point is really about whether the subject diagram supports your
argument, especially if it is incomplete and if it misrepresents the
scenario.


The phase shift through the stub is the same as through the coil is
the same as through the wire. It is simply zero according to the
standing wave current phase which is incapable of measuring phase.

For anyone who is foolish enough to believe Cecil when he says that
all phase information is lost when two oppositely traveling waves create
a standing wave, consider the following, adapted from Georg Joos book
_Theoretical Physics_:
consider two traveling waves going in opposite
directions represented mathematically by Ae^i(wt-kx) + Ae^i(wt+kx+d)
where A is the same amplitude for both waves, i is the square root
of -1, k is 2*pi/wavelength, w is the radian frequency, t is time,
x is distance, and d is the phase difference between the two waves.
This is just another way of writing 2Acos(kx+d/2)(e^i(wt+d/2). Notice
that the part cos(kx+d/2) still contains the phase information?
If Cecil were any kind of experimentalist he could easily tease the
phase information out of any standing wave on his antenna system.
73,
Tom Donaly, KA6RUH