Cecil Moore wrote in message

I *don't* expect such a coil to simulate reality. That's the whole problem.
The artificial lumped load software doesn't match reality. It only
approaches reality for "physically small" coils. Once again, a 75m Texas
Bugcatcher coil is not physically small.

It's physically small enough that any error should be small. IE: 1 db
or less.
This has been shown a few times. Myself, I don't lose much sleep over
the phasing coil dilemma. I don't think it will be much of an issue
when modeling simple short loaded whips. Being there is a workaround
for phasing antennas, IE: separate sources where you can define the
phase angle, the antenna can still be modeled.
There is something that keeps bothering me and my beady mind though...
You say the current going "one way" will be fairly constant across the
coil. Will the coil position effect this? If not, that creates a new
problem.
If the coil position does not effect the current taper going "one
way", I don't see how it would coming back the other way. Regardless
of coil position. If the current is constant going one way, seems to
me it would also be constant the other way. So in effect, they would
cancel each other out, and would still be fairly constant. I guess
what I want to see is experiments to test your theory of coil position
effecting the current taper. IE: You claim a center load would have
constant current, but off center would not. Seems to me, if this is
true, there should be a position that places maximum current at the
top of the coil, not bottom. If you never see this, I would be
suspect.
Well, back to my 1 db or less rubber room... MK

Mark Keith wrote:

Cecil Moore wrote in message

I *don't* expect such a coil to simulate reality. That's the whole problem.
The artificial lumped load software doesn't match reality. It only
approaches reality for "physically small" coils. Once again, a 75m Texas
Bugcatcher coil is not physically small.

It's physically small enough that any error should be small. IE: 1 db
or less.

A 13% error is small? The error is even larger than that for the current
at the top of the coil.

If the coil position does not effect the current taper going "one
way", I don't see how it would coming back the other way. Regardless
of coil position.

The forward current and reflected current phasors rotate in opposite
directions. Sometimes they are in phase and sometimes they are out
of phase. In a lossless transmission line, the forward current and
reflected current are absolutely constant with zero taper. Yet they
still result in standing waves with minimum and maximum points. This
is explained on my web page.

Seems to me, if this is
true, there should be a position that places maximum current at the
top of the coil, not bottom.

I have already said multiple times, depending upon where the coil is
placed, the net current into the coil can be less than, equal to, or greater
than the net current coming out. It all depends upon the phasor sum of the
forward current and reflected current. It can be zero or maximum or
anything in between depending upon where the coil is placed. For Kraus'
phase-reversing coil, the net current is zero at both ends and maximum
in the middle of the coil.
--
73, Cecil http://www.qsl.net/w5dxp/current.htm



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Sorry about that, missed the period before co

http://web.ukonline.co.uk/g3ldo

Art


"Yuri Blanarovich" wrote in message
...

Yuri, You might want to look at
http://web.ukonlineco.uk/g3ldo
as there is quite a bit of interchange between various hams
on measuring coils.
It may give you some ideas for when the snow melts
Regards
Art


that link don't worky

Cecil Moore wrote in message ...
Mark Keith wrote:

Cecil Moore wrote in message

I *don't* expect such a coil to simulate reality. That's the whole problem.
The artificial lumped load software doesn't match reality. It only
approaches reality for "physically small" coils. Once again, a 75m Texas
Bugcatcher coil is not physically small.

It's physically small enough that any error should be small. IE: 1 db
or less.

A 13% error is small? The error is even larger than that for the current
at the top of the coil.

I don't know where this 13% comes from, but how many db difference
would it make in the modeling results? I bet it's about 1 or less. If
you have an 8 ft antenna, with a 1 ft tall coil, no matter what the
current taper is across the coil, it will not drastically effect the
modeling results. At least 3 or 4 people have shown this. The coil is
not a large enough portion of the overall antenna. And any taper of
the current along that one foot section is not going to make a
difference more than about 1 db. Usually less.



Seems to me, if this is
true, there should be a position that places maximum current at the
top of the coil, not bottom.

I have already said multiple times, depending upon where the coil is
placed, the net current into the coil can be less than, equal to, or greater
than the net current coming out. It all depends upon the phasor sum of the
forward current and reflected current. It can be zero or maximum or
anything in between depending upon where the coil is placed. For Kraus'
phase-reversing coil, the net current is zero at both ends and maximum
in the middle of the coil.

I know you have said it multiple times, but so far I don't recollect
anyone actually measuring a real world coil, and finding max current
at the top of the coil. That is what is bothering me. MK

Cecil Moore wrote:
I have already said multiple times, depending upon where the coil is
placed, the net current into the coil can be less than, equal to, or greater
than the net current coming out.

Which end of the coil is the input and which end is the output?

73, Jim AC6XG

Mark Keith wrote:
Cecil Moore wrote:
A 13% error is small? The error is even larger than that for the current
at the top of the coil.

I don't know where this 13% comes from, but how many db difference
would it make in the modeling results?

Uh Mark,
1 dB error = 13% error 10^(0.1) = 1.26
2 dB error = 29% error 10^(0.2) = 1.58
3 dB error = 50% error 10^(0.3) = 2.00

I know you have said it multiple times, but so far I don't recollect
anyone actually measuring a real world coil, and finding max current
at the top of the coil. That is what is bothering me. MK

Nobody builds an antenna that way but consider the following monopole.
Ground is at the left, top is at the right. Each of the following
1/4WL sections are electrical 1/4WL's.

1/4WL coil
Gnd-FP------1/4WL tubing------//////////------1/4WL stinger------

max--*-------------------------------*-------------------------
* * *
* * *
Current min-------------------*----------------------------------*

The current at the feedpoint will be high. The current at the bottom of
the coil will be low. The current at the top of the coil will be high.
The current at the tip of the antenna will be low.
--
73, Cecil http://www.qsl.net/w5dxp



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Jim Kelley wrote:

Cecil Moore wrote:
I have already said multiple times, depending upon where the coil is
placed, the net current into the coil can be less than, equal to, or greater
than the net current coming out.

Which end of the coil is the input and which end is the output?

The DC model strikes again. For AC, current flows out of the coil
input just as often as it flows in and into the coil output just
as often as it flows out. :-)

But by convention the 'input' of the coil is the end closest to
the antenna feedpoint.
--
73, Cecil http://www.qsl.net/w5dxp



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Mark wrote in reply to Cecil,
(snip)

I have already said multiple times, depending upon where the coil is
placed, the net current into the coil can be less than, equal to, or
greater
than the net current coming out. It all depends upon the phasor sum of the
forward current and reflected current. It can be zero or maximum or
anything in between depending upon where the coil is placed. For Kraus'
phase-reversing coil, the net current is zero at both ends and maximum
in the middle of the coil.

I know you have said it multiple times, but so far I don't recollect
anyone actually measuring a real world coil, and finding max current
at the top of the coil. That is what is bothering me. MK


Hi Mark,
Cecil doesn't actually have to measure anything, since he's already convinced
he's right because his arguments agree with the theory he made up in his head.
Yuri is supposed to measure loading coils using fish tank thermometers and
such. The real test will be when someone tries to make a new, improved
antenna based on the belief that the current taper on the loading coil
of a physically short antenna makes a tinker's damn worth of difference
in the far field radiation of said antenna.
73,
Tom Donaly, KA6RUH

Cecil Moore wrote:

Jim Kelley wrote:

Cecil Moore wrote:
I have already said multiple times, depending upon where the coil is
placed, the net current into the coil can be less than, equal to, or greater
than the net current coming out.

Which end of the coil is the input and which end is the output?

The DC model strikes again.

A poor craftsman always blames his tools.

But by convention the 'input' of the coil is the end closest to
the antenna feedpoint.

And so what you're saying is that by convention RF current flows "in" to
one end, and then "out" of the other?

I must admit I don't like the sound of that one bit. Sounds like you're
describing the direction a "wave" is "traveling", when we know that the
"wave" is really just "standing" there. :-)

73, Jim AC6XG

Tdonaly wrote:
Mark wrote in reply to Cecil,
I know you have said it multiple times, but so far I don't recollect
anyone actually measuring a real world coil, and finding max current
at the top of the coil. That is what is bothering me. MK

Cecil doesn't actually have to measure anything, since he's already convinced
he's right because his arguments agree with the theory he made up in his head.

Well, just so you guys can understand what I am talking about, here is
an EZNEC file that clearly demonstrates low current at the bottom of
the coil and high current at the top of the coil.

http://www.qsl.net/w5dxp/sqcoil.ez

The real test will be when someone tries to make a new, improved
antenna based on the belief that the current taper on the loading coil
of a physically short antenna makes a tinker's damn worth of difference
in the far field radiation of said antenna.

Nice try, but that's just a copout diversion because the far field
radiation is irrelevant to the argument over current through a
loading coil.
--
73, Cecil http://www.qsl.net/w5dxp



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