Current through coils
 

Cecil Moore wrote:
Guess everyone sees the danger in trying to guess what
the results of someone else's measurement will be. Tom
should have measured something around 15.6 degrees. The
fact he didn't sends up a very large red flag.

Translation of what Cecil actually is saying:

"Whenever multiple measurements by independent sources disagree with me
the measurements others made must be wrong."


http://www.w8ji.com/agreeing_measurements.htm

http://www.w8ji.com/mobile_and_loaded_antenna.htm

http://www.w8ji.com/inductor_current_time_delay.htm

Current through coils
 

wrote:

Cecil Moore wrote:
Guess everyone sees the danger in trying to guess what
the results of someone else's measurement will be. Tom
should have measured something around 15.6 degrees. The
fact he didn't sends up a very large red flag.

Tom, I am going to ask you some relatively simple technical
questions. If you continue to refuse to answer those
questions, I and the other readers of r.r.a.a will draw
a logical conclusion about your unwillingness or inability
to answer questions, i.e. a non-technical answer or no
answer at all will cause you to lose credibility.

I was wrong about the radiation resistance equation. See
how readily I admitted my mistake? (When was the last time
you admitted a mistake?)

First question is a short one: Please explain why a century
old method of determining the phase shift through a coil by
measuring its self-resonant frequency is not good enough for
you. Do you really expect us to believe that the phase shift
through a well-designed coil can change by 81% from 16 MHz
to 4 MHz?

Translation of what Cecil actually is saying:

"Whenever multiple measurements by independent sources disagree with me
the measurements others made must be wrong."

I make mistakes but I seem to be on a solid technical
footing here. A number of readers agree. Maybe you can
convince me and them otherwise if you stop refusing to
answer technical questions about your measurements. Your
100 uH coil is the 8+j2500 ohm load in the following
fixed font example. That's at 3.98 MHz with a Q of 313.

Current probes are at X and Y. How is the following
circuit different from your test setup?

+---one wavelength lossless 50 ohm coax-----+
| X
source coil 8+j2500 load
| Y
+-------------------coax braid--------------+

The one wavelength of lossless coax doesn't change any values
in the steady-state situation so the current probes at X and
Y read the same value of currents as yours.

The SWR on the coax is about 16000:1. There is virtually
zero net current flowing through the load because of the
*extreme* mismatch. Virtually all of the current at the coil
is standing-wave current which is known to have unchanging
phase. Roy measured the unchanging phase of standing wave
current and reported close to zero. You measured the
unchanging phase of standing wave current and got close
to zero. It is no wonder you guys get the same value of
current phase delay since you are making exactly the same
error in your measurements spanning a number of years.
I'm surprised that you didn't measure a 0 nS delay.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil Moore wrote:

Jerry Martes wrote:

I feel like Rip Van Winkle. The engineering community has developed a
whole lot of nice things since I left it in 1969. And, its like
I've been sleeping for 37 years.


Ever heard of a "Triactuated Multicomplicator"?

I thought that was three ole farts trying to figger out Ohm's Law :-)

Current through coils
 

On Mon, 13 Mar 2006 13:01:15 GMT, Cecil Moore wrote:
from:
I cannot figure out how to use the VVM to make a valid measurement
it illogically follows that:
It is virtually impossible to eliminate reflections from a 75m mobile bugcatcher
system so the VVM can't measure what we are trying to measure.
aside from the poor grammar - the two statements are consistent to
inability.

Current through coils
 

Cecil Moore wrote:
(snip)
The question is: For a well-designed coil, is the self-
resonance method valid for determining the delay through
a coil at HF frequencies below the self-resonant frequency?

Yes, that is an excellent question.

Since that's been an accepted way of doing it for more
than a century,

This is a conclusion I have not seen you support, except with repeated
assertions. Can you offer something more substantial? Surely a few
references have accumulated in that century. How did you learn about
this as the accepted way?

I don't see how anyone could object.

Man, what I don't see, could almost fill a universe.
But I don't use it to try to win arguments.

Current through coils
 

wrote:

Cecil Moore wrote:

Guess everyone sees the danger in trying to guess what
the results of someone else's measurement will be. Tom
should have measured something around 15.6 degrees. The
fact he didn't sends up a very large red flag.

Translation of what Cecil actually is saying:
"Whenever multiple measurements by independent sources disagree with me
the measurements others made must be wrong."

Other multiple measurements by independent sources agree with
me and disagree with you, Tom. Wonder why you neglected to post
this reference from your own server?

http://lists.contesting.com/archives.../msg00540.html

It is a posting to TowerTalk by Jim Lux, W6RMK. I'll just extract
some excerpts.

"For closewound coils, with length to diameter ratios around 5:1, a
series of fairly careful measurements have been made with the coils
arranged vertically above a ground plane, fed at the base, with a
capacitive load on the other end, and the driving frequency arranged
to be at the resonant frequency of the whole assembly."

Sure sounds like your 100 uH 10"x2" coil installed in a mobile ham
radio antenna environment.

"In most cases, the phase shift in the current at top and bottom [of
the coil] was on the order of 10-20 degrees."

Contrary to the assertions of W8JI. Funny, I predicted 16 degrees for
your coil on 4 MHz based on the self-resonant frequency.

"For inductance the signficant thing is that the magnetic field of
one segment pretty much links to the adjacent segments, and less so
for the rest."

Contrary to the assertions of W8JI.

"At this time, the models are sufficiently well developed that they
predict the actual currents and voltages to substantially better than
one percent ..."

As opposed to W8JI's "accuracy".

"The take home message here, regarding loading coils, is that simple
lumped approximations of a loading coil may do just fine for an
initial design cut, but do not adequately reflect reality."

"I think it's best to leave it at: Loading coils are not isolated
lumped elements and cannot be modeled as such."

To which I add: Since a lumped element model is a subset of the
distributed network model, if the lumped element results disagree
with the distributed network results, the lumped element results
are simply invalid.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil, W5DXP wrote:
"Please explain why a centuries old method of determining phase shift
through a coil by measuring its self-resonant frequency is not good
enough for you?"

A coil is an RLC circuit. At resonance, L offsets C and all that is left
is R. In a resistance, the current is in-phase with the applied voltage.

But, in a physical length of a tuned circuit or in a straight conductor
in its place, in a circuit with reflections, you have energy coming from
both directions creating an interference pattern, which is repeated
every 1/2-wave (180-degrees) in the line Peaks are 1/2-wave apart,
considering the velocity factor of the line. To determine the phase
shift, count the maxima.

The wavelength of a line is the distance a wave must travel for one
complete cycle (360-degrees). If you want the phase shift for a line,
take the length of line required for one degree of phase retardation and
multiply it by the length of line you have.

Best regards, Richard Harrison, KB5WZI

Current through coils
 

John Popelish wrote:

Cecil Moore wrote:
Since that's been an accepted way of doing it for more
than a century,

How did you learn about this as the accepted way?

I'm a part-time teacher and it is described in a physics
history book that is, unfortunately, at work. Interesting
book as it gives a biographical treatment of the major
famous physicists from Galileo to Einstein. The Maxwell
and Heavyside sections are particularly interesting to
me.

For more information, take a look at:

http://lists.contesting.com/archives.../msg00540.html
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

On Mon, 13 Mar 2006 12:20:15 -0500, John Popelish
wrote:

The question is: For a well-designed coil, is the self-
resonance method valid for determining the delay through
a coil at HF frequencies below the self-resonant frequency?

Yes, that is an excellent question.

Since that's been an accepted way of doing it for more
than a century,

This is a conclusion I have not seen you support, except with repeated
assertions. Can you offer something more substantial? Surely a few
references have accumulated in that century. How did you learn about
this as the accepted way?

Hi John,

Well, I for one note that your call for a reference to that one point
(coil self resonance) was met by a "link" to a mailing list on another
point (assembly self resonance).

Be that as it may.

What we do find at that "link" has a rather condemnatory admission:
Amateur antennas vary so much in installation and
design that a rigorous treatment of one case
That case being a Tesla coil SECONDARY which is notably tight wound
would not, in general, be applicable to others.
which quite defines the coils offered here, and are admitted to in the
first words of this sentence.

The thread may now diverge towards Tesla secondary coils and away from
your "well-designed" coil.

SOP

73's
Richard Clark, KB7QHC

Current through coils
 

Cecil Moore wrote:
(snip)
Other multiple measurements by independent sources agree with
me and disagree with you, Tom. Wonder why you neglected to post
this reference from your own server?

http://lists.contesting.com/archives.../msg00540.html

It is a posting to TowerTalk by Jim Lux, W6RMK. I'll just extract
some excerpts.

"For closewound coils, with length to diameter ratios around 5:1, a
series of fairly careful measurements have been made with the coils
arranged vertically above a ground plane, fed at the base, with a
capacitive load on the other end, and the driving frequency arranged
to be at the resonant frequency of the whole assembly."

Sure sounds like your 100 uH 10"x2" coil installed in a mobile ham
radio antenna environment.
(snip)

The tantalizing part from my perspective is this:

"The measurements were made with carefully designed fiberoptic probes
that were specifically designed to avoid perturbing the magnetic and
electric fields."

I would like to read a full description of this instrumentation.