Current through coils
 

Cecil Moore wrote:
Gene Fuller wrote:

Emboldened by this apparent success I tried to substitute the
now-famous W8JI coil; 100 turns, 2 inch diameter, 10 inch length. This
time the overall 500 segment count was the limiter (I am cheap), so I
had to make the coil four-sided. The delay through this coil was about
9 degrees at 5.89 MHz and about 6 degrees at 3.9 MHz. Sooooo, the
bottom line for the 17,000 posts in this thread is ...


You wish that was the bottom line. Here's some mud in your eye.

1. I have always been talking about my 75m bugcatcher coil which
is about 6"x6" and designed for actual mobile use. W8JI's coil
is nowhere near what the average ham uses for a 75m bugcatcher
coil. It is much too fragile for long-term mobile use. It can't
even be considered to be a "bugcatcher" because one Texas-
sized bug and it is destroyed.

2. You haven't installed that coil in an 8 foot 75m mobile
antenna so you don't know what the delay is in an 8 foot
4 MHz system. Please feel free to try again - no cigar at
the present time.

You mean your coil has to be attached to an antenna in order
to become a transmission line? This is getting better and
better.
73,
Tom Donaly, KA6RUH

Current through coils
 

Tom Donaly wrote:
You mean your coil has to be attached to an antenna in order
to become a transmission line? This is getting better and
better.

My 75m bugcatcher coil has to be attached to a 75m mobile
antenna installed on my GMC pickup. That's the boundary
conditions and I have been explicit about that. This is
getting stranger and stranger. Next you guys will have
the coil floating in free space between Sol and Alpha
Centauri unconnected from anything in order to remove it
from any resemblance to a real-world environment.

In virtually all my postings, I have specified that I
was talking about a 75m bugcatcher coil installed in
a mobile installation. It really doesn't matter what
happens outside that specified environment.

The gurus are slowly divorcing themselves from reality.
The only way they can be right is to take the mobile
antenna off the vehicle, throw away the antenna, and
keep the coil for testing on a bench. Have you no
shame? How far are you willing to retreat from reality
to make a feeble attempt to be right?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil,

I thought we already agreed that there is no phase shift in the real
environment, namely, a nearly pure standing wave environment. You were
the one who brought up all the special cases in an attempt to prove your
point.

However, your latest message is refreshing. I was afraid for a while
that you were attempting to use a 48 foot tall mobile antenna or drag a
31.5 foot wire terminated in a resistor down the road.

73,
Gene
W4SZ

Cecil Moore wrote:
Tom Donaly wrote:

You mean your coil has to be attached to an antenna in order
to become a transmission line? This is getting better and
better.


My 75m bugcatcher coil has to be attached to a 75m mobile
antenna installed on my GMC pickup. That's the boundary
conditions and I have been explicit about that. This is
getting stranger and stranger. Next you guys will have
the coil floating in free space between Sol and Alpha
Centauri unconnected from anything in order to remove it
from any resemblance to a real-world environment.

In virtually all my postings, I have specified that I
was talking about a 75m bugcatcher coil installed in
a mobile installation. It really doesn't matter what
happens outside that specified environment.

The gurus are slowly divorcing themselves from reality.
The only way they can be right is to take the mobile
antenna off the vehicle, throw away the antenna, and
keep the coil for testing on a bench. Have you no
shame? How far are you willing to retreat from reality
to make a feeble attempt to be right?

Current through coils
 

Gene Fuller wrote:
I thought we already agreed that there is no phase shift in the real
environment, namely, a nearly pure standing wave environment.

You are not arguing in good faith.

We agreed that standing wave current with its unchanging phase
cannot be used to measure the phase shift through a coil. The
fact that there is no phase shift from end to end in a 1/2WL
thin-wire dipole proves that using the standing wave phase
to measure a phase shift is meaningless. You said the same
thing in the following statement. Do you want to retract what
you 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.

You were
the one who brought up all the special cases in an attempt to prove your
point.

No, I'm using your posting to prove that standing wave current phase
is meaningless. There's no special case. Standing wave current phase
is *always* meaningless.

Please install your coils in an 8 foot 75m antenna and get back to
us on the results.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

I know how EZNEC calculates propagation from straight wires. It does
it very well.

But do you know how it calculates the inductance of coils?

How long has it been able to do this?
----
Reg
=========================================



"Cecil Moore" wrote in message
t...
Reg Edwards wrote:
How does EZNEC make its calculations? If you don't know you are
placing your faith in a mirage.

It uses the Moment Method (MM) sometimes called the Method
Of Moments (MOM). It's described in Kraus and Balanis
and credited to Roger Harrington in the 1960's.

Each segment in EZNEC is assumed to have constant current.
In the aforementioned 8-sided coil, there are 200 segments,
each with an assumed constant current. The standing wave
current in each segment depends upon where it is inserted
in the standing wave environment as shown at:

http://www.qsl.net/w5dxp/1WLDIP.EZ
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

"Roy Lewallen" wrote
It's hard to tell from this, but are you still claiming that the
end-to-end C of an inductor is the C of an equivalent transmission
line?
Or even an approximation? Does your program assume this?

Roy Lewallen, W7EL

===================================
Roy,

What do you mean by end-to-end C.

But very recently you did say "Reg is right" when I said "All coils
behave like transmission lines."

You and I agree on most fundamental matters.
----
Reg.

Current through coils
 

Reg Edwards wrote:
I know how EZNEC calculates propagation from straight wires. It does
it very well.

In your last posting, you asked "How does EZNEC make its calculations?"
Wow, you're a quick learner.

But do you know how it calculates the inductance of coils?

Yes. A model of a coil is constructed out of straight wires, making each
turn polygonal. A wire containing a source is connected from one end to
the other and, providing that the coil is short in terms of wavelength,
the reactance seen by the source will be that of the coil at the test
frequency.

How long has it been able to do this?

An automated helix creation feature was introduced in v. 4.0 two years
ago this May. It has always been capable of doing the calculation, but
until v. 4.0 the user would have had to calculate the wire end
coordinates with an external program and import them into EZNEC.

The free demo version has this feature. You can create any size helix
with it to see how the feature works. You won't, however, be able to
calculate its inductance with the demo program due to the segment
limitation.

As I've pointed out before, EZNEC won't account for proximity effect, so
reported loss will be optimistic if the turns are spaced very closely.

Roy Lewallen, W7EL

Current through coils
 

I've a feeling there is some confusion here between phase delay in
degrees, and delay in time (nano-seconds).

The former changes with frequency. The latter does not.

You should all make yourselves perfectly clear.
----
Reg.

Current through coils
 

Reg Edwards wrote:
"Roy Lewallen" wrote
It's hard to tell from this, but are you still claiming that the
end-to-end C of an inductor is the C of an equivalent transmission
line?
Or even an approximation? Does your program assume this?

Roy Lewallen, W7EL

===================================
Roy,

What do you mean by end-to-end C.

What most people would call "self capacitance" -- the equivalent
capacitance from one terminal to the other.

But very recently you did say "Reg is right" when I said "All coils
behave like transmission lines."

More specifically, you said:

EVERYTHING has Inductance, Capacitance and Resistance, and therefore
behaves as a transmission line.

I agreed with that. This doesn't mean that I agree that you can choose
any C you like from any point to any other, plug it into a transmission
line formula, and get a meaningful result. Transmission lines are two
port, four terminal devices, so a completely isolated inductor or other
component, by itself, can't behave as a transmission line, except by
assuming some C to the Earth.

You and I agree on most fundamental matters.

I'll have to take your word for that. It isn't always apparent by what
you say in your postings.

Roy Lewallen, W7EL

Current through coils
 

Reg Edwards wrote:
I know how EZNEC calculates propagation from straight wires. It does
it very well.

But do you know how it calculates the inductance of coils?

I don't think EZNEC cares about the inductance of helical
coils. As I have been advocating, the EZNEC helical option
treats the coil as just another part of the wire antenna
that has been spiraled into a coil.

It is ironic, is it not, that EZNEC treats a helix as just
coiled up wire? Especially after the gurus have asserted
that a coiled up piece of wire is not a piece of wire at
all but is instead transformed into something magical that
violates the theory of relativity with faster than light
propagation?

How long has it been able to do this?

I don't know exactly. I was creating segmented coils long
before EZNEC had the helix option. I even wrote a BASIC
program to generate an ASCII file capable of being imported
into EZNEC.
--
73, Cecil http://www.qsl.net/w5dxp