wrote:
If the loading coil is physically large and has a good amount of
displacement current flowing radially to space and objects around the
antenna compared to through current, the coil would have a noticable
difference in current at the bottom terminal and top terminal.

How does one amp at the top and zero amps at the bottom grab you?
Please see my other postings.

It's only when the coil becomes physically large and has appreciable
capacitive reactance to the outside world compared to the load
impedance that it starts to show significant transmission line effects.

Which is certainly the case for a 75m bugcatcher coil.

Every bit of this is not difficult to understand if we really
understand how an antenna behaves and how a coil behaves. The only
source of wonderment and argument seems to come from people who want to
make the inductor behave differently in an antenna than it behaves in
other systems.

The 75m bugcatcher coil certainly behaves differently mounted
one foot above a GMC pickup ground plane than it behaves in
free space. The question is: which is more common? A GMC pickup
or free space?

There is no reason to assign
special properties to an inductor and make it behave differently in an
antenna than it does in other systems.

There is no reason to assume an inductor behaves differently
above a GMC truck ground plane than it behaves in free space???
Tom, would you please describe the free space that exists inside
your head?
--
73, Cecil http://www.qsl.net/w5dxp

Richard Harrison wrote:
Not only does Terman give voltage and current diagrams, he gives a phase
diagram. It shows that whenever the voltage or current crosses the zero
axis (changes sign) the phase angle changes abruptly by 180-degrees.
Phase is unchanging between these inflection points. This agrees with
what Cecil has said all along in this discussion.

Kraus agrees. Yet W7EL used that unchanging phase to measure the
delay through a loading coil. What's wrong with that picture?

Some people, who no doubt have recognized their technical errors,
simply refuse to discuss the technical subjects. Ian, OTOH, seems
open to discussing those topics so please don't be too hard on him.
An honest person deserves respect whether he is right or wrong.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Some people, who no doubt have recognized their technical errors,
simply refuse to discuss the technical subjects. Ian, OTOH, seems
open to discussing those topics so please don't be too hard on him.
An honest person deserves respect whether he is right or wrong.

In accordance with my goal of being honest, here is some ammunition
for the other side of the argument. In Dr. Corum's IEEE paper he
said regarding the Z0 of a loading coil:

"It is worth noting that, for a helical anisotropic wave guide,
the effective characteristic impedance is not merely a function
of the geometrical configuration of the conductors (as it would
be for lossless TEM coaxial cables and twin-lead transmission
lines), but it is ALSO A FUNCTION OF THE EXCITATION FREQUENCY."

I have been assuming that the Z0 of a loading coil didn't change
much with frequency. Both Dr. Corum and EZNEC seem to disagree
with that assumption. So, as is my practice, I am using the
scientific method to adjust my concepts about that subject.

I hope this proves that I am only interested in the technical
facts which have not been proven one way or another as of
this posting.
--
73, Cecil http://www.qsl.net/w5dxp

"Richard Clark" wrote
If it doesn't count for much,
or it has no relevancy, then say so and by all means drop it.

I think it is significant, not as much in "crummy" mobile vertical, as in
antenna systems with loaded, shortened elements.
I saw significant improvement in performance when replacing loading stubs in
say KLM 3 el. 80m Yagi with coils. Performance and pattern improved
significantly.
If you stick wrong values in modeling program, the error will get only
magnified.
That's why this "bothers" me.
I trust what W9UCW measured, and I want to do it myself, just to put the
heated subject to rest with proper conclusions.

Yuri

Cec wrote, "How does one amp at the top and zero amps at the bottom
grab you?
Please see my other postings."

It grabs me that what you wrote in your other postings about
capacitance to the outside world, " I didn't say there was no
capacitance to the outside world. I said
such is a secondary effect, not a primary effect, and for the sake
of the present argument, can be ignored as secondary effects often
are ignored," is all wet. And I still say that your other postings
before that were saying you believed that there was NO capacitance to
the outside world. It was the message they sent to me, loud and clear.

Given any volume, say a volume containing a Texas Bugcatcher coil and
the air inside and immediately around it, if you push more electrons in
than come out _for_ANY_abritrarily_short_time_period_, you have changed
the net charge in that volume; if you pull out more electrons than go
in, you have changed the net charge in that volume. If the current at
the top and bottom, the only two conductors crossing the boundary of
that volume, is different, that represents flow of charge into (and out
of, in a cyclic fashion) that volume. I don't know what to call that
except capacitance to the outside world. Yes, it's _distributed_
capacitance. But the key point is that it is THE reason--the WHOLE
reason--for the difference in current between the top and the bottom,
NOT a "secondary effect."

In fact, when YOU say that the coil "behaves differently" in different
external environments, you are AFFIRMING it as an important effect, for
surely the presence or absence of some American gas guzzler (or is it
Diesel guzzler?) strongly affects the capacitance to the outside world,
and does not significantly affect internal capacitances (which in any
event, being contained entirely within that volume, do NOTHING for
storing net charge within the volume, because for those internal
capacitances to store charge, what goes in one end comes immediately
out the other end which is still inside the same volume and thus there
is not any net change in charge within the volume). But the "other
end" of capacitance to the gas guzzler or whatever is OUTSIDE the
volume of the coil, thus EXACTLY accounting for the difference in
current at the two leads going to the coil. -- I suppose they covered
all that in a sophomore EE circuits class, but I wouldn't know. I
suppose they also might have covered how a pure lumped model using only
i(t)=C*dv(t)/dt and v(t)=L*di(t)/dt, with no time delay elements, can
mimic lossless transmission line behaviour to any arbitrary degree of
accuracy you want, but perhaps they don't try to hit you with that
concept till later. I wouldn't know that, either...I just know it's
true.

I suppose it's a bit too much to ask all at once, but I do wish you
could see that just because the specific value of the capacitance is
different in different environments, it does not mean that I need a
different model. The coil does not behave in some fundamentally
different way. I only need to adjust the value of that capacitance
within the model--or if you will, the parameters of the
transmission-line-like behaviour, though other models may work as well
in practical antenna analysis. The model stays the same; the
parameters in the model change. When I change the value of a resistor,
my model of a resistor doesn't change. It's still fundamentally
v(t)=R*i(t). Only the value used for R changes. On a grander scale,
when I include the parasitic effects of a real inductOR, I have more
things to account for in the model than just inductANCE. Some of them
are affected significantly by the environment in which I place the
inductor. And even small changes in the values can have a profound
effect on the overall system behaviour. That's especially true in a
system operated near resonance where the Q is extremely high, such as a
system in which there is only a standing wave.

My only wish is that these musings will be useful to the lurkers trying
to actually learn something, if there still happen to be any around.

Cheers,
Tom

On Sun, 2 Apr 2006 23:24:05 -0400, "Yuri Blanarovich"
wrote:

If you stick wrong values in modeling program, the error will get only
magnified.
That's why this "bothers" me.

Hi Yuri,

This is a most ambiguous "bothering" in that you haven't put any
quantification to what the "error" leads to. No one can possibly
expect perfection, and ±20% is possibly the best accuracy most hams
can expect in measurement. We have all already identified that the
"error" stemmed from an inappropriate application of lumped inductance
in the place of a helix in modeling.

This begs the question: "What's all the fuss over? What's to be
proven? and How do we know when it has BEEN proven?"

73's
Richard Clark, KB7QHC

Tom, K7ITM wrote:
"Given any volume, say a volume containing a Texas Bugcatcher coil and
the air inside and immediately around it, if you push more electrons in
than come out_for_ANY_arbitrarily_short_time_period_, you have changed
the net charge in that volume;---."

No. This is not charging a capacitor or a battery. Energy stored in an
antenna system is in constant motion. Power delivered by the transmitter
is neadly the same as that used by the load, (the antenna), plus that
consumed by losses.

Power is simply the in-phase volts times amps. It can have any impedance
which is the ratio of in-phase volts to amps. Z in the general case can
include reactance plus resistance and can give the apparent power. It is
the ratio of volts to amps without regard to phase.

The coil which has a great difference between the current at its ends
most likely simply has different impedances at its ends. The power is
nearly the same at both ends of the coil but the voltage to current
ratios are different.

Varying impredance along the RF path is a product of the interference
between the incident and reflected waves. A standing-wave antenna
typically has an open-circuit at its end or ends. The RF has no other
option but to be returned
toward the sender and make standing waves. The large number of possible
incident and reflected wave combinatioms makes it very likely that the
current at opposite ends of a coil inserted in the antenna system will
be unequal.

It`s the power in and out of a coil in an antenna system that`s likely
to be nearly equal at both ends.

Best regards, Richard Harrison, KB5WZI

Richard H wrote,

"Tom, K7ITM wrote:

"Given any volume, say a volume containing a Texas Bugcatcher coil and
the air inside and immediately around it, if you push more electrons in
than come out_for_ANY_arbitrarily_short_time_period_, you have changed
the net charge in that volume;---."

No. ..."

OK, I'm going to repeat it once mo

If you shove more electrons into ANY volume than you remove, you have
changed the charge within that volume. I do NOT care WHAT is in that
volume. Current is the rate that charge is flowing past a point on a
conductor. If the only way I have of getting charge into and out of a
particular volume is through two wires, then the difference in current
at every instant in time represents the time rate of change of charge
within that volume. That is true INDEPENDENT of whether it is in an
antenna, and it is INDEPENDENT of what's inside that volume.

In fact, energy around an antenna is stored in electric and magnetic
fields. These are inexorably linked to inductance along the conductors
composing the antenna, and capacitance from these conductors to
themselves and to any counterpoise or ground plane which may be part of
the antenna--anything where electric field lines terminate. The charge
per unit length along an antenna wire, be it resonant or not, be it a
"standing wave" or a "travelling wave" antenna, varies with time. If
it did not, then the current would necessarily be identical along the
whole wire all the time.

This all gets back to very basic definitions of charge, and current as
the rate of flow of charge. It's all consistent with Maxwell, Gauss,
Faraday, etc. and with waves both standing and travelling, and with
"impredances" and all the rest.

It's just amazing to me that some of you are fighting so hard against
the very thing which has a chance of unifying your "wave" model with
the realities of the electric and magnetic fields, and the associated
capacitance and inductance along the antenna--indeed, along the wire
itself, and not just along the coil.

Without capacitance, there can be NO difference in current anywhere
along the wire, because there is simply no place to put the charge
implied by differing currents at differing locations. With capacitance
and inductance, everything works just as it's supposed to--just as it
DOES--and a properly developed wave theory will analyze it just fine,
if that's your cup of tea.

Cheers,
Tom

I don't understand what you are all on about, but, I side with K7ITM
"K7ITM" wrote in message

Regards Mike.


ups.com...
Richard H wrote,

"Tom, K7ITM wrote:

"Given any volume, say a volume containing a Texas Bugcatcher coil and
the air inside and immediately around it, if you push more electrons in
than come out_for_ANY_arbitrarily_short_time_period_, you have changed
the net charge in that volume;---."

No. ..."

OK, I'm going to repeat it once mo

If you shove more electrons into ANY volume than you remove, you have
changed the charge within that volume. I do NOT care WHAT is in that
volume. Current is the rate that charge is flowing past a point on a
conductor. If the only way I have of getting charge into and out of a
particular volume is through two wires, then the difference in current
at every instant in time represents the time rate of change of charge
within that volume. That is true INDEPENDENT of whether it is in an
antenna, and it is INDEPENDENT of what's inside that volume.

In fact, energy around an antenna is stored in electric and magnetic
fields. These are inexorably linked to inductance along the conductors
composing the antenna, and capacitance from these conductors to
themselves and to any counterpoise or ground plane which may be part of
the antenna--anything where electric field lines terminate. The charge
per unit length along an antenna wire, be it resonant or not, be it a
"standing wave" or a "travelling wave" antenna, varies with time. If
it did not, then the current would necessarily be identical along the
whole wire all the time.

This all gets back to very basic definitions of charge, and current as
the rate of flow of charge. It's all consistent with Maxwell, Gauss,
Faraday, etc. and with waves both standing and travelling, and with
"impredances" and all the rest.

It's just amazing to me that some of you are fighting so hard against
the very thing which has a chance of unifying your "wave" model with
the realities of the electric and magnetic fields, and the associated
capacitance and inductance along the antenna--indeed, along the wire
itself, and not just along the coil.

Without capacitance, there can be NO difference in current anywhere
along the wire, because there is simply no place to put the charge
implied by differing currents at differing locations. With capacitance
and inductance, everything works just as it's supposed to--just as it
DOES--and a properly developed wave theory will analyze it just fine,
if that's your cup of tea.

Cheers,
Tom

"Richard Clark" wrote Hi Yuri,

This is a most ambiguous "bothering" in that you haven't put any
quantification to what the "error" leads to. No one can possibly
expect perfection, and ±20% is possibly the best accuracy most hams
can expect in measurement. We have all already identified that the
"error" stemmed from an inappropriate application of lumped inductance
in the place of a helix in modeling.

This begs the question: "What's all the fuss over? What's to be
proven? and How do we know when it has BEEN proven?"

73's
Richard Clark, KB7QHC

I think we are striving to improve our accuracy and reflection of reality in
modeling antennas.
We know that efficiency is proportional to the area under the current curve
along the radiator. The "fatter" the curve, the better. This has been
confirmed by the experimental measurements by varying position of the
loading coil along the radiator and use of top hats.
If the modeling program starts with wrong assumption (as we have seen using
lumped inductance) and one uses multiple elements, like in vertical arrays
or Yagis, then the results get skewed and we get wrong "recipe" for the
antenna design.
The biggest benefit would be in properly optimizing antenna design for the
best rejection, F/B, cleanest pattern, which is more critical than just
optimizing for max gain. Especially loaded arrays for low bands would
benefit most.
One could get good indication by comparing say 3 el loaded Yagi design with
lumped inductance vs. loading stubs or solenoid model.
Unfortunately, or fortunately, I am not retired, nor making living from the
RF stuff and my time is limited to be working full time on this. My interest
is to maximize the station and antenna design for contesting so I can try to
cream some records.
So far, it looks to me that this exercise is worthwhile if we can improve
the accuracy of modeling and our understanding of the phenomena.
Looks like lots of antennas would be damaged by the Midwest tornados, the
ugly WX is heading our way.

73 Yuri, K3BU