Current across the antenna loading coil - from scratch
 

David G. Nagel wrote:
evidently Cecil doesn't.

It wasn't me who started this thread.

If we have one amp of DC current flowing one direction and
one amp of DC current flowing the other direction, which
direction is the sum of those currents flowing?

If we have one amp of forward RF current and one amp of
reflected RF current, which direction is the sum of those
currents flowing?
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
wrote:

So what exactly is the importance of this current YOU are talking
about?


All the diversionary BS trimmed from your posting. Bottom line,
the equation for standing wave current is:

I(x,t) = Io*cos(kx)*cos(wt)

The equation for traveling wave current is:

I(x,t) = Io*cos(ks+wt)

Since you obviously don't comprehend the difference, please
dust off your old math book and take a look.

In case you need a graphics reference for those two equations,
you can find it at: http://www.qsl.net/w5dxp/travstnd.GIF

You will find the two above currents are virtually opposites
of each other.

In particular, standing wave current phase CANNOT be used to
determine the phase shift through a wire or through a coil
because its phase never changes in a 1/4WL monopole.

I can hardly say it better than Gene Fuller who said:
Regarding the cos(kz)*cos(wt) term in a standing wave:

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.


Please tell us what it is about Gene's posting that you don't
understand.

You know, Cecil, a pulse train also satisfies the wave equation.
Why are you married to sinusoidal waves? Haven't you ever seen
ghosts on a tv picture? What do those Ghosts represent?
73,
Tom Donaly, KA6RUH

Current across the antenna loading coil - from scratch
 

Reg Edwards wrote:

"David G. Nagel" wrote

I have completely lost track of what the object of the exercise is.


=======================================

I gave up trying just after the thread began.

What put me off was "current across the coil" when everybody knows it
should be "current through the coil".

It is VOLTS which appear ACROSS coils.
----
Reg.



They also like to talk about "current drops" when they mean the
difference in current amplitude at two different points.
73,
Tom Donaly, KA6RUH

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
David G. Nagel wrote:

evidently Cecil doesn't.


It wasn't me who started this thread.

If we have one amp of DC current flowing one direction and
one amp of DC current flowing the other direction, which
direction is the sum of those currents flowing?

If we have one amp of forward RF current and one amp of
reflected RF current, which direction is the sum of those
currents flowing?

I was taught that under these circumstances DC and RF work differently.
Yes your DC net current is zero. Your new RF current is one amp in each
direction.

Dave WD9BDZ

Current across the antenna loading coil - from scratch
 

"Cecil Moore" wrote in message
m...
You said essentially the same thing in your earlier posting -
that there is no phase information in the standing wave current
phase and all the phase information is in the amplitude values.

thats the basic problem in this whole discussion. you are all talking about
the same thing, just using different notation and incomplete statements so
that none of you understands exactly what the others are trying to talk
about... when really you are all saying the same thing. its kind of like
after i graduated from college with an ee degree and my sister graduated
from an air force basic electronics course, she tried to ask me something
about currents in a transistor and i saw it all backwards... well of course
she was talking electron flow and i was talking hole flow. we both got the
same result but the notation was all different.

so, now i will raise my voice...

STOP THIS PETTY BICKERING AND GET OUT THERE AND USE AN ANTENNA INSTEAD OF
ARGUING ABOUT WHY THEY DON"T WORK THEY WAY YOU THINK THEY SHOULD!

Current across the antenna loading coil - from scratch
 

Tom Donaly wrote:
You know, Cecil, a pulse train also satisfies the wave equation.
Why are you married to sinusoidal waves? Haven't you ever seen
ghosts on a tv picture? What do those Ghosts represent?

If one doesn't understand sinusoidal waves, one doesn't have
a ghost of a chance of understanding a pulse train. Trying
to introduce a pulse train before understanding sinusoidal
values is just muddying the waters.

In a closed system, such as a source, transmission line, and
receiver, ghosting represents reflected waves.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Tom Donaly wrote:
They also like to talk about "current drops" when they mean the
difference in current amplitude at two different points.

For an EM wave in a lossy environment, the attenuation factor
applies equally to the E-field and H-field, i.e. equally to
voltage and current. Both "drop" at the same rate.

The transmission line voltage equation contains that attenuation
factor and the current equation is simply the voltage equation
divided by the characteristic impedance.

In a lossy transmission line, the H-field and E-field "drop"
at the same rate since their ratio is fixed by the
characteristic impedance.

One more proof that EM waves are NOT lumped circuit voltages
and currents.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

David G. Nagel wrote:

Cecil Moore wrote:
If we have one amp of forward RF current and one amp of
reflected RF current, which direction is the sum of those
currents flowing?

I was taught that under these circumstances DC and RF work differently.
Yes your DC net current is zero. Your new RF current is one amp in each
direction.

Yes, that is true, but EZNEC doesn't report the two separate
currents. EZNEC reports the phasor sum of those two currents
in magnitude and phase. So the question still remains: In
which direction is the total current reported by EZNEC
flowing? What does the unchanging phase really mean?

EZNEC says that, referenced to the source phase, the phase
of the phasor sum of the forward and reflected currents is
UNCHANGING. It makes no sense to pick a direction of flow
for the sum of two equal currents flowing in opposite
directions.

Standing wave current doesn't flow in the commonly accepted
meaning of "flow". Standing wave current just stands there.

I received the following email from a physics professor:

"As for the standing waves, they really aren't independent
creatures. They're an artifact - a construct which happens
to look like the superposition of fields which surround the
antenna. But the fields which superpose look like the traveling
waves. The traveling waves really tell the story."
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Dave wrote:
... when really you are all saying the same thing.

Unfortunately, we are not all saying the same thing.
W7EL and W8JI are saying that using standing wave
current phase to make a phase shift measurement is
a valid approach. They keep reporting their results of
using such an approach as if it were a valid thing to
do. When those useless phase measurements are discarded,
the technical picture becomes a lot clearer.

I, and others, are saying that using a signal with
unchanging phase will not and cannot tell one anything
about any phase shift. There is no phase information
contained in the standing wave phase. All of the phase
information is contained in the standing wave magnitude.

I'm building a web page about this subject. The initial
graphic is at: http://www.qsl.net/w5dxp/travstnd.GIF

Note that for a standing wave current, the only thing
changing with length is magnitude. The flat phase line
of the standing wave current is completely useless for
making phase measurements.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Dave wrote:
thats the basic problem in this whole discussion. you are all talking about
the same thing, just using different notation and incomplete statements so
that none of you understands exactly what the others are trying to talk
about... when really you are all saying the same thing. its kind of like
after i graduated from college with an ee degree and my sister graduated
from an air force basic electronics course, she tried to ask me something
about currents in a transistor and i saw it all backwards... well of course
she was talking electron flow and i was talking hole flow. we both got the
same result but the notation was all different.

That's not true at all Dave. Most of us know that current is current.
It really only flows one direction at any instant of time. We can
indeed consider systems as having current that flows two directions at
one instant of time, but the results of that better agree with the
actual real current that flows only in one direction at any instant of
time or they are wrong.

Also, behavior of basic components cannot change. A two terminal device
like a loading coil cannot have differences in the current flowing
through it at each terminal without a third path. (I assume we all
know current is not an across vector and it does not "drop", the person
who started this thread just used poor wording.)

I think the basic problem is Cecil wants to used some definition of
current that does not allow models to be freely exchanged and does not
produce results that match real world systems. It always has to match.
We can't have different results unless someone has an error.

The only reason I'm skimming the posts here and making the occasional
comment is I hate to see people trying to understand how this stuff
works be confused. The real fuss is a couple people seem to think
standing waves or "missing antenna length" are the root cause of
current being different in the two terminal component called a loading
coil.

It really isn't an argument or debate as much as trying to help lurkers
understand how the system really works, and not let them fall into the
trap that the loading coil behavior is any different than any other
coil, the only possible reason for differences in current at each
terminal is stray capacitance allowing displacement currents to the
outside world, and that any phase differences in current at each coil
terminal are also tied to capacitance from the coil to the world around
the coil.

It's not correct to assume people are talking about the same result
different ways, because both Cecil and Yuri have huge flaws in their
conclusions. They both seem to want the inductor to behave in some very
unique way just because it is an antenna, and the reults they seem to
claim do not match actual measurements. Cecil dismisses real
measurements with frantic arm waving about reflected and forward
current and no one being able to measure current and phase because of
standing waves, and while I think Yuri would accept measurements he
won't accept them when made by others and won't make them himself.

This has gone on for perhaps three years now. It is really up to Cecil
and Yuri to let it go, since they are the ones who seem to disagree
with measurements and accepted theory.

73 Tom