Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
Michael Coslo wrote:

Not that I could fan the flames any more anyhow, but just what was the
original discussion about anyhow?


As I realized what the actual misconception really is, the discussion
shifted from coils to standing waves. Seems to me, W8JI and W7EL do
not understand the difference implied by these two different equations
(assuming |Ifor|=|Iref|).

Ifor = I1*cos(kx+wt) and Iref = I1*cos(kx-wt)

Istnd = I1*cos(kx+wt) + I1*cos(kx-wt) = I2*cos(kx)*cos(wt)

Gene Fuller has kindly explained the difference but W8JI and W7EL
seemed to have ignored his explanation. Gene says there is no
phase information in standing wave current phase and I agree.




I've said it before and I'll say it again, there is no phase variable
in I1*cos(kx+wt) and there is no phase variable in I1*cos(kx-wt) so
there can't possibly be any phase information in 2*I1*cos(kx)*cos(wt).
If you're going to measure a phase difference between two places on
a transmission line and you want to write an equation describing what
you're doing, you have to have the phase variable somewhere in your
equation so you can solve for it. Also, it would help, Cecil, if you
would be a little more careful when you copy these equations from your
favorite Bible. They keep changing form as time passes.
73,
Tom Donaly, KA6RUH

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:

Tom Donaly wrote:

Not everyone is happy with the term "displacement current." Albert
Shadowitz, in his book _The Electromagnetic Field_, has a chapter
entitled "The So-called Displacement Current." The term isn't in
the index to Feynman's _Lectures on Physics_. (At least I couldn't
find it.) All that is academic to the fact that AC current seems to
be able to make its way through a capacitor with no more opposition
than the capacitive reactance. Fortunately, no one on this
newsgroup has any objection to the way the term is commonly used.


Here's an associated quote from "Electromagnetic Engineering"
by R.W.P King: "an adequate representation of the reactance
of a coil with a nonuniformly distributed current is NOT
POSSIBLE in terms of a coil with a uniform current [a lumped-
element inductance] connected in parallel with a lumped
capacitance."

I don't know what that has to do with displacement current, Cecil,
but if you're worried about it you can just use your coil at a frequency
where you get a more satisfactory current distribution. I made a coil
like you talk about (mine was 5.25 inches long,
27 turns, 6 inches in diameter) and it behaved pretty much like
a coil in parallel with a capacitor up to a few megahertz, at least.
Beyond that, it was a different story.
73,
Tom Donaly, KA6RUH

Current across the antenna loading coil - from scratch
 

Gene Fuller wrote:
It is truly unfortunate that none of this is connected to the subject at
hand, displacement current, but it makes for a colorful message.

Please don't tell us that you don't understand how the attenuation
factor in a transmission line current equation causes the current
to drop along the line equaling the percentage drop in the voltage.

One can write a similar equation for a standing wave dipole.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Tom, W8JI wrote:
"Wave theory is just fine, but it has to be understood it is just a
modeling shortcut and the results cannot conflict with the basic laws of
physics,"

The Quantum theory may replace the wave theory some day, but the wave
theory has always satisfied my needs.

Terman writes on page 84 of his 1955 edition:
"The quantity aq. rt. of ZY is called the propagation constant of the
line. It is a complex quantity, having a real part alpha called the
attenuation constant and an imaginary part beta termed the phase
constant."

On the next page 85, Terrman has diagrams showing behavior of the
voltages of the incident and reflected waves on a transmission line. It
is the same as that on antennas. That`s why the antenna section of
Terman`s book tells the reader to refer to the transmission line chapter
for the behavior of antennas. It`s identical.

I`ve erected and operated countless rhombics in the international
broadcasting service. I`ve underloaded them and overloaded them and in
the process melted plenty of dissipation lines. I can attest that Terman
has it right. Sometimes you have to do what you`ve got to do even when
you know better.

When the dissipation line went away we would cover outh America as well
as Central Europe and get lots of fan mail for our troubles. We
shouldn`t have been getting fan mail from South America but lots of
Central Europeans were living there as refugees from the Axis and from
the Allies. When we covered South America, some broadcaster with a valid
claim on the frequency at that hour and place was being clobbered by
us.. We couldn`t help it. Our job was to save the world and we did it
while sometimes stepping on others in the process.

I guarantee we never put anything even close to 100KW into a dissipation
line. Problem was the Signal Corps rhombic kits were maxed out at 5 KW
and it took time to get bigger resistance wire. 100 KW in a dissipation
line would have melted it in days if not sooner. As it was, standard
G.I. lines lasted weeks while glowing a cheerful red and did not erupt
in a blinding flash.

The wave travels along both wires simultaneously. The wires in the
dissipation line melt at the input end not at the far end where the wire
is smaller. Current does not travel through the line like the utility
power frequency through a string of Christmas tree lights.

Tom needs to get with the reality of the program. His idea is seriously
flawed.

Best regards, Richard Harrison, KB5WZI

Current across the antenna loading coil - from scratch
 

Tom Donaly wrote:
I've said it before and I'll say it again, there is no phase variable
in I1*cos(kx+wt) and there is no phase variable in I1*cos(kx-wt) so
there can't possibly be any phase information in 2*I1*cos(kx)*cos(wt).

Sorry, you are wrong about that. EZNEC reports that phase information.
Assuming the EZNEC default convention, the source is 1.0 amp at zero
degrees at t=0. So the RMS value of the traveling wave current is
1.0 amp at -'kx' degrees. -'kx' *IS* the phase angle of the current
up and down the wire referenced to the source. It is negative because
the source naturally leads the traveling wave.

Note 'kx' is how far the point of interest is away from the source
in degrees.

Doesn't anyone understand phasors anymore?
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
John Popelish wrote:

If you have no interest in anything but butting heads with the people
who have disagreed with you, then, please stop responding to my posts.

If you are into playing games, you are responding to the
wrong person. Try W8JI or W7EL instead.

Heck, Cecil, you had years of participation in r.r.a.p. during which you
were a pregnant man, a 300 foot tall alien or you were challenging
others to dunk a basketball. I'd say that game playing is one of your
favorite things.

Dave Heil K8MN

Current across the antenna loading coil - from scratch
 

Dave Heil wrote:
Heck, Cecil, you had years of participation in r.r.a.p. during which you
were a pregnant man, a 300 foot tall alien or you were challenging
others to dunk a basketball. I'd say that game playing is one of your
favorite things.

Wow, what a memory. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Gene Fuller wrote:
The question is what happens to the 75 degrees that was formerly
represented by the now-replaced wire. The coil may offer about 10 degrees.

I believe that Tom is stating that 75 is not equal to 10. Sounds like a
reasonable statement to me.

No argument from me. Obviously you didn't understand my previous
explanation that a resonant mobile antenna doesn't have to be 90
degrees long - something I explained weeks ago. Therefore, the coil
doesn't have to be 75 degrees. Please re-read my postings again below
until you understand what I said.

Think of all the possibilities that make (Vfor+Vref)/(Ifor+Iref)
purely resistive without any one of those terms being in phase with
any other of those terms. Then you will realize why that mobile
antenna is probably not 90 degrees long at all.

In my earlier posting, I gave values of phase that make the feedpoint
purely resistive without any one of those terms being in phase with
any other one of those terms.

BOTTOM LINE: Until you can prove that a mobile antenna is 90
degrees long, your argument is just another straw man. What is it
about my following previous statements that you don't understand?

W5DXP wrote:
You are confused. Some time ago, I explained why a mobile antenna
may not be 90 degrees long at all. Did you understand that posting?
All we can say is that (Vfor+Vref)/(Ifor+Iref) is purely resistive.
We don't know how many degrees the reflected wave has traveled in
its round trip because there are too many variables.

So please stop the diversions. I have always said that the delay
through a coil *IS WHAT IT IS* but it is NOT zero and it is not the
3 nS measured by W8JI for that 100 uH coil. It is also not the near-zero
phase shift measured by W7EL using standing wave current phase as the
reference. You, yourself, implied that is an invalid measurement when
you told us there is no phase information in standing wave phase.

Seems to me you are making my argument for me and that your real
argument is with the other side. Have you told W7EL that standing
wave current phase cannot be used to measure the delay through a
coil?
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

On Mon, 10 Apr 2006 23:05:48 -0400, "Yuri Blanarovich"
wrote:

You don't want to explain W5DXP models and answer his questions.

Yuri,

Even YOU cannot explain his models or answer his questions!

On Tue, 11 Apr 2006 04:08:34 GMT, Cecil Moore
wrote:

BOTTOM LINE: Until you can prove that a mobile antenna is 90
degrees long, your argument is just another straw man.

Are you guys on the same planet?

Now don't get me wrong, I enjoy the comedy all the same and your Punch
and Judy act keeps us all entertained, but don't confuse the applause
as nominations for the Nobel Prize in Physics.

73's
Richard Clark, KB7QHC

Current across the antenna loading coil - from scratch
 

Richard Harrison wrote:

The wave travels along both wires simultaneously. The wires in the
dissipation line melt at the input end not at the far end where the wire
is smaller. Current does not travel through the line like the utility
power frequency through a string of Christmas tree lights.

Tom needs to get with the reality of the program. His idea is seriously
flawed.

I take it you are saying you think current can flow two directions at
the same instant of time in a conductor, can be "lost" from a single
conductor through radiation and resistance without a shunting
impedance, conservation of charge isn't important, and Maxwell's
equations are wrong.

You know that because you installed antennas at one point in your life.
Is that correct or did I misunderstand your post?

73 Tom