Roy, W7EL wrote:
"Just a couple of hours ago you said the current would have to wind its
way atound each turn, following the wire from one end to the other, and
it would take nearly the wire length divided by the speed of light."

Yes, and I`m still convinced that is the case in an air cored r-f coil
that is long because the coupling between ends of the coil isn`t enough
to bypass the delay of the coil.

I posted speculations on bypassing the delay in the coil. Capacitance
between turns is too small over the length of the coil, said to be about
one loot, and about 100 turns.

Tom, W8JI had said that magnetic coupling between the start and finish
of the coil bypassed the time delay of following the path of the wire.
Well, nothing happens instantly when voltage is applied across a coil.
90-degrees after the voltage has crossed the zero axis on its way up,
the current does the same. It lags the voltage by 90-degrees. It`s the
current which induces a voltage in the coil and this is delayed by the
forces predicted by Lenz`s law. 90-degrees at 4 MHz equates to about the
time required for a radio wave to traverse about 60 feet of thin wire.

100 turns of wire on a 2-inch form requires about 52 feet of wire. The
current travels from start to finish on the coil before the current
reaches its maximum in the coil and before energy could be effectively
induced from one end of the coil to the other. The wave velocity is
about 984 feet per microsecond.

These are just musings aloud and confirm my speculation that signal
progress is through conduction on the surface of the wire of the coil.

Best regards, Richard Harrison, KB5WZI

On Fri, 31 Mar 2006 21:40:46 -0600, (Richard
Harrison) wrote:

Yes. I think turn-to-turn capacitance doesn`t amount to much and won`t
bypass the coil as you have 100 small capacitors in series, so their sum
approaches zero.


Hi Richard,

This "approaches zero" capacitance for a coil has been tossed out so
many times it is approaching infinity.

For the commonplace coils in these applications, we have rather
non-trivial self capacitances. Why, when this evaluates to on the
order of 10-12 pF, that so many feel it incumbent to dismiss mutual
capacitances, then it does not follow.

Yuri's 60 turn coil may have 60 series capacitors, but it also has 60
parallel capacitances too. A back-of-the-napkin calculation for one
turn-to-turn capacitance finds
23.3pF
If we look at the capacitance between the first and last
0.2pF

The capacitance seen at the first loop, then, is a combination of
series/parallel capacitances to all other windings that, on average,
approaches a dozen picofarads.

The apparent capacitance based on reported resonances and modeled
reactance is on the order 12-14pF.

So, across the board and considering that this is RF, and HF at that,
the dismissal of capacitances are unwarranted.

73's
Richard Clark, KB7QHC

Heck, Cecil, I don't see Ian saying that a proper distributed model is
incorrect at all. I see him saying that YOUR model is incorrect! --
For the record, YOU and YOUR below translate to Cecil and Cecil's.

YOUR model doesn't have any capacitance to the outside world, as YOU
have posted and repeated till you are perhaps blue in the face. (No
charge storage translates very directly to no capacitance, in case
anyone could have missed that.)

Because of that YOUR model has, guess what, ZERO time delay along the
coil.

It is ONLY through a combination of both inductance AND capacitance
that you get propagation velocities equal to or less than the speed of
light.

NOTE that in freespace, the speed of light, c, is exactly equal to
1/sqrt(epsilon_naught * mu_naught) -- and the units of epsilon_naught
(freespace permittivity) are FARADS per meter, and mu_naught (freespace
permeability) are HENRIES per meter. A coil increases the henries per
meter, but somehow we seem to have gotten in YOUR model to some space
around the coil in which the permittivity is _zero_ so that we don't
have any capacitance in YOUR model. That would be a good trick, but
it's not one that Ian and I are buying. I suppose that W8JI and Tom D
and Roy and Wes and Reg and Gene and John P and probably the two
Richards and some others are ALSO not buying. Why, even the detailed
Tesla coil calculations I've seen consider the distributed capacitance
to the outside world, in great detail. I'd bet that the authors of
those calculations would ALSO not buy your model.

Putting it another way, propagation of an EM wave requires an
interchange of energy between electric and magnetic fields. With zero
permittivity, there would be no energy stored in the electric field,
and no EM wave. (In a TEM transmission line, it's often said that the
energy is stored in capacitance and inductance along the line, but
that's no different than saying the energy is stored in electric and
magnetic fields.)

It amazes me that you fought so hard for a distributed model in which
that capacitance to the outside world is missing, but insist that the
resulting model allows a non-zero time delay. That's YOUR model; it's
all in the stuff YOU have posted for anyone that wants to go look at
it. By denying the capacitance in the model, YOU are the one who
doesn't accept what's been know since Maxwell and Faraday and Tesla
and...

But YOUR model isn't any use to me, and it seems that it's no use to
Ian. We'd prefer a model that actually accounts for all the currents
correctly, and actually allows for a delay along a transmission-line
structure. Then, knowing it's an ACCURATE model when we can verify
through specific measurements that it agrees to an acceptable level
with those cases we measured, we can look at ways to use that model
as-is, or to use a model which makes life easier for us which matches
the very accurate one closely enough for our purposes.

(Not only does YOUR model with no capacitance to the outside world have
zero propagation delay, but it ALSO leads to a line with infinite
impedance, which I'm ALSO not buying, though with zero delay, the line
impedance really doesn't matter. Also notice that with no capacitance
to the outside world in that area, the model collapses to exactly the
one YOU are arguing AGAINST, except that the straight sections of
antenna are apparently not in the zero-permittivity area, so we need to
keep them separated...it leads to a very strange model, indeed!)

And please note that in the paragraphs above, the only models
specifically mentioned are DISTRIBUTED ones, so don't go giving me any
bull**** about the other kind. And you can save any bull**** about
accepting the fact of capacitance to the outside world, because your
postings repeatedly say otherwise.

wrote:
It seems to me Cecil now agrees the system can be modeled as a lumped
components and loads and we do not need to use standing waves.

A 100% false statement but we are accustomed to such from
W8JI. Since the lumped circuit model is a subset of the
distributed network model, if there is any disagreement
between the two models, the distributed network model wins
every time. They are both right under certain conditions
and the lumped circuit model is wrong under certain
conditions.

Quoting from: http://www.ttr.com/corum/index.htm

"There are no standing waves [allowed] on a lumped element
circuit component. ... for coils whose WIRE LENGTH exceeds
1/6WL", the distributed network model is required.

Quoting from: http://www.ttr.com/TELSIKS2001-MASTER-1.pdf

Concerning the *impedance only* of a loading coil:

"The formula will NOT (and, being lumped, can not) give the
voltage magnification by VSWR dur to physically true
current standing waves on the structure ... If impedance is
the only item of interest, the empirical Medhurst approximation
is acceptable out to about 60 degrees."

But we haven't been arguing about impedance. We have been
arguing about phase. Here's what the above paper says about
phase shift through a loading coil.

"Further, the voltage distribution passes from the loop of a
sinusoid (at 90 degrees) to the linear portion of the sinusoid
(for heights less than 15 degrees)."

It is necessary to use the distributed network model if the
phase shift through the coil is greater than 15 degrees.

Continuing the quote: "Lumped elements 'have no physical
dimensions and no preferred orientation in space; they
can be moved around and rotated at will.' Not so for real
world coils. ... The concept of coil 'self capacitance' is
an attempt to circumvent transmission line effects on small
coils when the current distributions begins to depart from
its DC behavior."
--
73, Cecil http://www.qsl.net/w5dxp

Gene Fuller wrote:
You issued a "challenge" to design and report on a loading coil for 4
MHz, with a whip of 8 feet. I responded with a solution that used a whip
length of 10 feet.

No, you didn't! You responded with a antenna
length of 11.775 feet, 3.775 feet longer than the agreed upon
8 foot antenna. It wasn't the whip that was to be 8 feet, it
was the entire antenna. I made that perfectly clear early on
so it would match the mobile antennas in the ARRL Antenna Handbook.

You did not acknowledge the changes you made until I complained.

Of course I did. Go back and read my postings about such.
It wasn't until you complained that I sent you the corrected
EZNEC files. I made a severe blunder in the traveling wave
model and you copied my blunder.
--
73, Cecil http://www.qsl.net/w5dxp

wrote:
I was complaining about him altering the coil I measured and altering
the context of what I say.

I was doing it from memory, Tom, which may be faulty. As I
remember, you coil was 2" dia and 100 turns at 8 TPI. If
that's not right, what was it?

http://www.w8ji.com/agreeing_measurements.htm
Roy's first. You're way down the list Gene. Get back in line.

Telling Roy about his abortive use of standing wave current
phase to try to measure phase shift when there is zero phase
shift in a wire or in a coil is just stating the technical facts.

As far as measuring phase through a coil goes, neither you
nor W7EL has any clue as to how to make valid measurements.
You guys really need to listen to 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. The so-called "phase reversal" in longer antennas is
not really about phase either. It is merely a representation of the periodic
sign reversal seen in a cosine function.

What is it about Gene's posting that you and W7EL don't understand?
--
73, Cecil http://www.qsl.net/w5dxp

Richard Harrison wrote:
100 turns of wire on a 2-inch form requires about 52 feet of wire.

52 feet of wire on 4 MHz is 0.21 WL. Dr. Corum says anything
over 0.17 WL requires the distributed network model.

The 3 nS delay measured by W8JI through that coil is simply
technically impossible except in his mind.
--
73, Cecil http://www.qsl.net/w5dxp

Richard Clark wrote:
"The apparent capacitance based on reported resonances and modeled
reactance is on the order of 12 -14 pF."

Have you calculated the self-capacitance of a 2in x 12in single-layer
coil for yourself?

The length to diameter ratio is 6.
H = .92
D = 5 cm

HD = 4.6 pF by the formula on page 451 of the "Radiotron Designer`s
Handbook". Course, formulas are a dime a dozen and disputed.

Best regards, Richard Harrison, KB5WZI

Why, yes, in fact it is true that I don't agree in every case with the
unknown guru you've placed on a pedestal above all reproach. So there.
It is also true that I do not agree with your (mis)interpretation of
what your unknown guru has written.

I REGULARLY model transmission lines as "lumped elements" and do NOT
"presuppose that the speed of light" through them is infinite.

I REGULARLY model op amps as "lumped elements" and do NOT presuppose
that the phase shift (and therefore propagation time) through them is
infinite.

I REGULARLY model analog to digital converters as "lumped elements" and
do NOT presuppose that the result comes out at the same time as the
signal that goes in.

I REGULARLY model inductors as "lumped elements", and do not presuppose
that they have no resistances and capacitances parasitic to their
inductANCE.

I find that my models very reliably predict the behaviour I actually
observe in the circuits I build. I am served very well by the models I
use.

By the way, what's EE203? It's very likely that I missed not only that
day but all such days. You yourself may well be presupposing something
that isn't true.

Cheers,
Tom

K7ITM wrote:
YOUR model doesn't have any capacitance to the outside world, as YOU
have posted and repeated till you are perhaps blue in the face. (No
charge storage translates very directly to no capacitance, in case
anyone could have missed that.)

I do wish you guys would argue in good faith.

***STRAWMAN ALERT***
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.

Because of that YOUR model has, guess what, ZERO time delay along the
coil.

No, transmission lines have negligible capacitance to the outside
world and their time delays are NOT zero. You straw man is just
not believable.

It is ONLY through a combination of both inductance AND capacitance
that you get propagation velocities equal to or less than the speed of
light.

Yes, and that capacitance can be either internal or external.
I'm ignoring the rest of your posting because it is based on
the false premises of your straw man. But you get an 'A' in
Obfuscation 101.

It amazes me that you fought so hard for a distributed model in which
that capacitance to the outside world is missing, ...

It is *NOT* missing. That is just your straw man. It is just
secondary to the addition of the forward and reflected current
phasors.

At a point where the the forward and reflected current phasors
add up to zero, it's hard for anything else to contribute much
of an effect.
--
73, Cecil http://www.qsl.net/w5dxp