Ah,

So now you're saying that any coil at the base of a short vertical
antenna, regardless of its value, will have equal currents at the input
and output?

Ok, suppose I make the measurement at, say, 10 MHz, where the coil is no
longer at the current maximum. Tell you what. I'll set up a 33 foot wire
vertical, to eliminate the difficulty of the mounting arrangement. I'll
furnish you the base impedance at 10 MHz, and even let you choose the
inductor value. Be sure and choose a value that will clearly illustrate
your point. Using the fine education you received from Balanis et al,
calculate the current into and out of the inductor (phase and
magnitude), and I'll set it up and measure it. Since it is a fair amount
of work on my part, though, I'd like to do a dry run first, using, say,
the base impedance predicted by EZNEC. Then, after you've shown us how
you make the calculations, I'll build the antenna and do the
measurement. I'd hate to go to the considerable trouble of setting it up
and find that you somehow aren't able to do the calculation.

Other predictions would be welcome, too, such as Yuri's, based on the
"missing antenna length" theory of inductor currents.

Better yet, you can do the measurement yourself. As you can see from the
picture I just posted to my web site, the measurement ain't exactly
rocket science. I don't have much time to burn, but still shook loose
enough to set it up. Anybody with a two channel scope, a soldering iron,
and a signal generator or transmitter can do just what I've done. You
can too.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

Can I conclude from this that if I were to make a coil with more or
less inductance, then I would see a current difference between the
ends of the coil?

So tell you what. If you'll pull out your equations and calculate the
expected current difference, I'll replace the coil with one of 100
ohms reactance and remeasure. How much current difference (magnitude
andd phase, of course) between the ends of a 100 ohm inductor at the
base of that same antenna?


I know you are not that naive, Roy. I have said many times over the past
few days that if you locate a coil at a current maximum point, the current
will be approximately equal at each end. So what did you do? You locate
your coil at a current maximum point and I assume your measurements proved
me to be correct. As long as you install the coil at the base of the
antenna, the currents are guaranteed to be close to equal as I have
said any number of times.

If you place the coil at a location where the slope of the current is
maximum and positive, the current through the coil will *INCREASE*.

If you place the coil at a location where the slope of the current is
maximum and negative, the current through the coil will decrease. This
is typical of center-loaded mobile HF antennas.

Incidentally, Kraus engages in some of your alleged "pseudo-analysis"
in his book. He clearly shows the current drop through loading coils.
He even says a coil can be used to shift the current by 180 degrees.
Come to think of it, my 440 MHz mobile antenna has a coil in the center
that shifts the current by 180 degrees yielding considerable gain
from those two phased elements.

Roy Lewallen wrote:
So now you're saying that any coil at the base of a short vertical
antenna, regardless of its value, will have equal currents at the input
and output?

No, I didn't say that. I wish you would read what I say. If the coil is
a low reactance (not many degrees) and the current maximum point is inside
the coil, the two currents will tend to be equal.

Ok, suppose I make the measurement at, say, 10 MHz, where the coil is no
longer at the current maximum. Tell you what. I'll set up a 33 foot wire
vertical, to eliminate the difficulty of the mounting arrangement. I'll
furnish you the base impedance at 10 MHz, and even let you choose the
inductor value. Be sure and choose a value that will clearly illustrate
your point. Using the fine education you received from Balanis et al,
calculate the current into and out of the inductor (phase and
magnitude), and I'll set it up and measure it. Since it is a fair amount
of work on my part, though, I'd like to do a dry run first, using, say,
the base impedance predicted by EZNEC. Then, after you've shown us how
you make the calculations, I'll build the antenna and do the
measurement. I'd hate to go to the considerable trouble of setting it up
and find that you somehow aren't able to do the calculation.

I can't do the calculation because I don't know the attenuation factor.
Do you think my inability to do the calculation proves anything about
what's happening in reality at the antenna? You guys need to turn loose
of the concept that what happens or doesn't happen on a piece of paper
dictates reality.

I can describe a base-loaded configuration that will demonstrate the
principle. Take a 75m bugcatcher coil, one of the 6"x6" models, and
choose a stinger that resonants the antenna in the 75m-80m band. Then
measure the in and out currents at a frequency a little below resonance.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:
Roy Lewallen wrote:

So now you're saying that any coil at the base of a short vertical
antenna, regardless of its value, will have equal currents at the
input and output?


No, I didn't say that. I wish you would read what I say. If the coil is
a low reactance (not many degrees) and the current maximum point is inside
the coil, the two currents will tend to be equal.

I did read what you said. You said that it wouldn't exhibit a phase
shift if placed at a current maximum. The current at the base of a short
vertical antenna is at its maximum there. So now if you're saying that
it *won't* exhibit a phase shift if placed at the base of a short
antenna, let's try this. Suppose I remount my antenna to eliminate the
shunting effect of the mounting, and do my measurements at 3.8 MHz as
before. Suppose the base input Z is, say, 35 -j380. You choose any
inductor value you'd like, that will best illustrate your method, and
tell me what output to input current ratio to expect.

Ok, suppose I make the measurement at, say, 10 MHz, where the coil is
no longer at the current maximum. Tell you what. I'll set up a 33 foot
wire vertical, to eliminate the difficulty of the mounting
arrangement. I'll furnish you the base impedance at 10 MHz, and even
let you choose the inductor value. Be sure and choose a value that
will clearly illustrate your point. Using the fine education you
received from Balanis et al, calculate the current into and out of the
inductor (phase and magnitude), and I'll set it up and measure it.
Since it is a fair amount of work on my part, though, I'd like to do a
dry run first, using, say, the base impedance predicted by EZNEC.
Then, after you've shown us how you make the calculations, I'll build
the antenna and do the measurement. I'd hate to go to the considerable
trouble of setting it up and find that you somehow aren't able to do
the calculation.


I can't do the calculation because I don't know the attenuation factor.

What "attenuation factor" is it you need? Is it something that can be
measured? If not, how about an equation or prediction with the
"attenuation factor" as a variable? We can estimate a probable range of
values, then see if the measurement results are within them.

Do you think my inability to do the calculation proves anything about
what's happening in reality at the antenna? You guys need to turn loose
of the concept that what happens or doesn't happen on a piece of paper
dictates reality.

I hope to demonstrate what constitutes reality by theoretical analysis
and by measurement. Where I come from, that counts much more than
arm-waving, insulting, and vague explanations. Ultimately, each of the
readers of these exchanges will decide what to believe, and I'm sure you
will have convinced some.

I can describe a base-loaded configuration that will demonstrate the
principle. Take a 75m bugcatcher coil, one of the 6"x6" models, and
choose a stinger that resonants the antenna in the 75m-80m band. Then
measure the in and out currents at a frequency a little below resonance.

I have no disagreement that a "bugcatcher" coil, or any coil of
physically significant size, will exhibit a phase shift and magnitude
change of current from one end to the other. Where we disagree is that
you believe that a physically very small inductor will also exhibit
this. I don't. I'm proposing a test which will show, with reasonable
certainty, which viewpoint is correct. I fully expect every test I make
to bring forth a flurry of objections. So I'm giving you the opportunity
to choose the inductor which will best illustrate your point of view. I
want to limit the parameters of the test to conditions I think I can
measure with reasonable accuracy. With the equipment I've got, that
pretty much limits me to doing measurements at the antenna base. But I
think (although I'm still not sure) that you're now saying that there
should be a substantial current difference between the input and output
of a small inductor at the base of an antenna, if the antenna and
inductor are properly chosen. So, you choose. And if you won't make the
measurement, I will.

Roy Lewallen, W7EL

Roy Lewallen wrote:
I did read what you said. You said that it wouldn't exhibit a phase
shift if placed at a current maximum.

I'm sorry, there is a misunderstanding that is my fault. When I say
"current is the same.", I'm implying magnitude only. That's a
convention left over from my college days and may not be a
convention any longer. If I said anything at all about phase, I
used the word, "phase", in my posting. So I will stop omitting
the word, "magnitude", when I am talking about magnitude.

So do a system reset on what you think I said. There is always a
phase shift through a real-world inductor. Whether it can be
measured accurately is another matter. When I said: "If the
current maximum point is located in the middle of a coil, the
current (implied magnitude) in and out of a coil will be equal.",
I was implying current magnitude only. I didn't imply or say anything
about phase unless I used the word, "phase" in the sentence.

I also have not said anything about the phase of the currents into
and out of your toroidal inductance except to say it replaces
approximately 18 degrees of antenna.

The current at the base of a short
vertical antenna is at its maximum there. So now if you're saying that
it *won't* exhibit a phase shift if placed at the base of a short
antenna, let's try this.

As you can see above, I never said anything like that.

Suppose I remount my antenna to eliminate the
shunting effect of the mounting, and do my measurements at 3.8 MHz as
before. Suppose the base input Z is, say, 35 -j380. You choose any
inductor value you'd like, that will best illustrate your method, and
tell me what output to input current ratio to expect.

I am still leery about your ability to separate small phase shifts
from noise. We need to make the inductor large enough to ensure
the phase shift measurements are above the noise level.

I have no disagreement that a "bugcatcher" coil, or any coil of
physically significant size, will exhibit a phase shift and magnitude
change of current from one end to the other.

Huh?????? I thought that was what the argument was all about. What
triggered this whole discussion was W8JI's alleged assertion that
a loading coil like a bugcatcher doesn't affect the current at all.

Where we disagree is that
you believe that a physically very small inductor will also exhibit
this. I don't.

The effect of a very small inductor may be too small to measure in
the presence of strong fields and noise. Ask yourself, at exactly
what value of inductor does the phase shift completely disappear?
+j1? +j10? +j100? +j1000? What is the crossover point from some
phase shift to zero phase shift? Can you measure a phase shift of
0.1 degree at HF? Zero phase implies faster than light propagation
through the coil.
--
73, Cecil, W5DXP

So, you've retracted your prediction. What's your new one, then?

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

I did read what you said. You said that it wouldn't exhibit a phase
shift if placed at a current maximum.


I'm sorry, there is a misunderstanding that is my fault. When I say
"current is the same.", I'm implying magnitude only. That's a
convention left over from my college days and may not be a
convention any longer. If I said anything at all about phase, I
used the word, "phase", in my posting. So I will stop omitting
the word, "magnitude", when I am talking about magnitude.

So do a system reset on what you think I said. There is always a
phase shift through a real-world inductor. Whether it can be
measured accurately is another matter. When I said: "If the
current maximum point is located in the middle of a coil, the
current (implied magnitude) in and out of a coil will be equal.",
I was implying current magnitude only. I didn't imply or say anything
about phase unless I used the word, "phase" in the sentence.

I also have not said anything about the phase of the currents into
and out of your toroidal inductance except to say it replaces
approximately 18 degrees of antenna.

The current at the base of a short vertical antenna is at its maximum
there. So now if you're saying that it *won't* exhibit a phase shift
if placed at the base of a short antenna, let's try this.


As you can see above, I never said anything like that.

Suppose I remount my antenna to eliminate the shunting effect of the
mounting, and do my measurements at 3.8 MHz as before. Suppose the
base input Z is, say, 35 -j380. You choose any inductor value you'd
like, that will best illustrate your method, and tell me what output
to input current ratio to expect.


I am still leery about your ability to separate small phase shifts
from noise. We need to make the inductor large enough to ensure
the phase shift measurements are above the noise level.

I have no disagreement that a "bugcatcher" coil, or any coil of
physically significant size, will exhibit a phase shift and magnitude
change of current from one end to the other.


Huh?????? I thought that was what the argument was all about. What
triggered this whole discussion was W8JI's alleged assertion that
a loading coil like a bugcatcher doesn't affect the current at all.

Where we disagree is that you believe that a physically very small
inductor will also exhibit this. I don't.


The effect of a very small inductor may be too small to measure in
the presence of strong fields and noise. Ask yourself, at exactly
what value of inductor does the phase shift completely disappear?
+j1? +j10? +j100? +j1000? What is the crossover point from some
phase shift to zero phase shift? Can you measure a phase shift of
0.1 degree at HF? Zero phase implies faster than light propagation
through the coil.
--
73, Cecil, W5DXP

Roy Lewallen wrote:
So, you've retracted your prediction. What's your new one, then?

No, you misunderstood my prediction. I cannot make an accurate
prediction until you tell us the feedpoint impedance of the
antenna including the coil. Is it 34.6+j8 or what? You have
told us the feedpoint impedance of the antenna without the
coil and the impedance of the coil but we still don't have
an accurate measurement for the feedpoint impedance of the
antenna including the coil. Did you measure it? If not, any
estimate is not going to be very accurate.
--
73, Cecil, W5DXP

Yes, I did measure it. But how much difference in your prediction would,
say, +/- 10 ohms of reactance make -- I can't guarantee my measurements
any closer than that in any case. So why not make your predictions for
35 - j2 and 35 + j18, and let's see just how much difference it makes.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

So, you've retracted your prediction. What's your new one, then?


No, you misunderstood my prediction. I cannot make an accurate
prediction until you tell us the feedpoint impedance of the
antenna including the coil. Is it 34.6+j8 or what? You have
told us the feedpoint impedance of the antenna without the
coil and the impedance of the coil but we still don't have
an accurate measurement for the feedpoint impedance of the
antenna including the coil. Did you measure it? If not, any
estimate is not going to be very accurate.
--
73, Cecil, W5DXP

Cecil Moore wrote in message ...
Roy Lewallen wrote:
I did read what you said. You said that it wouldn't exhibit a phase
shift if placed at a current maximum.

I'm sorry, there is a misunderstanding that is my fault. When I say
"current is the same.", I'm implying magnitude only. That's a
convention left over from my college days and may not be a
convention any longer. If I said anything at all about phase, I
used the word, "phase", in my posting. So I will stop omitting
the word, "magnitude", when I am talking about magnitude.

So do a system reset on what you think I said. There is always a
phase shift through a real-world inductor. Whether it can be
measured accurately is another matter. When I said: "If the
current maximum point is located in the middle of a coil, the
current (implied magnitude) in and out of a coil will be equal.",
I was implying current magnitude only. I didn't imply or say anything
about phase unless I used the word, "phase" in the sentence.

I also have not said anything about the phase of the currents into
and out of your toroidal inductance except to say it replaces
approximately 18 degrees of antenna.

The current at the base of a short
vertical antenna is at its maximum there. So now if you're saying that
it *won't* exhibit a phase shift if placed at the base of a short
antenna, let's try this.

As you can see above, I never said anything like that.

Suppose I remount my antenna to eliminate the
shunting effect of the mounting, and do my measurements at 3.8 MHz as
before. Suppose the base input Z is, say, 35 -j380. You choose any
inductor value you'd like, that will best illustrate your method, and
tell me what output to input current ratio to expect.

I am still leery about your ability to separate small phase shifts
from noise. We need to make the inductor large enough to ensure
the phase shift measurements are above the noise level.

I have no disagreement that a "bugcatcher" coil, or any coil of
physically significant size, will exhibit a phase shift and magnitude
change of current from one end to the other.

Huh?????? I thought that was what the argument was all about. What
triggered this whole discussion was W8JI's alleged assertion that
a loading coil like a bugcatcher doesn't affect the current at all.

Where we disagree is that
you believe that a physically very small inductor will also exhibit
this. I don't.

The effect of a very small inductor may be too small to measure in
the presence of strong fields and noise. Ask yourself, at exactly
what value of inductor does the phase shift completely disappear?
+j1? +j10? +j100? +j1000? What is the crossover point from some
phase shift to zero phase shift? Can you measure a phase shift of
0.1 degree at HF? Zero phase implies faster than light propagation
through the coil.

Cecil
Is not the group straying somewhat from the initial discussion
on E ham? That discussion that started all this was with regard to a
whip antenna and the coil on it. Why has the discussion been pulled
away from the original coil to a torroid of all things ? The basic
discussion was on a inductor of length which can be considered a major
part of the antennas length. It is this situation that Yuri stated
that he measured a current difference at the inductors end, to which
Tom replied that it was probably capacitive coupling to ground, so
even Tom did not dispute the possibility of a current drop per Yuri's
measurements !
Maneuvering to to a toroid style of inductance is placing darkness
over the original statement, probably to prevent the application of
light by others. Now the playing on words is intruding again ( phase )
so I suggest that in that atmosphere one should relate to a inductive
network to prevent
the accusation of a 'pure' inductance which is a whole different ball
game as conditions imposed in the solution of such a network is
certainly not the same.
Best regards and have fun.
Please do not pull into the discussion the root of minus one or all
the answers given by the application of a quadratic equation since
many will go crazy by taking them to the lab and measuring them. Grin
Art

Art Unwin KB9MZ wrote:
Is not the group straying somewhat from the initial discussion
on E ham? That discussion that started all this was with regard to a
whip antenna and the coil on it. Why has the discussion been pulled
away from the original coil to a torroid of all things ?

Because someone can't stand to be wrong?
--
73, Cecil, W5DXP

Chuckle.

I'm continually amazed at how different our backgrounds are. Whenever
I've encountered a complex system I don't understand, I try to begin
with a simple system, to make sure I understand it first. Only after I
know how a simple one will behave do I have a chance of understanding
the more complex one. This is the method adopted by virtually all the
capable engineers I've had the pleasure to work with over the years.

In contrast, complexity is embraced by people who have a need to conceal
a lack of understanding. By resisting simplification and constantly
pleading that the system is too complex to analyze, fundamental
understanding isn't required, and one can never be shown to be wrong. If
the best you can do in any case is to give vague answers and wave hands,
it doesn't really make any difference whether you understand it or not
-- it's impossible to tell. On the other hand, if it's necessary to
actually calculate values (as I've had to do for years as a design
engineer) and truly understand what's happening, there's no way I'll be
able to do it for a complex system if I can't even do it for a simple one.

As for standing to be wrong, I'm willing to post my measurements and my
predictions, and be wrong. So far, only Yuri has joined me.

And, Art, I'm surprised at your objecting to my bringing up the dreaded
complexity of -- gasp -- phase. You should rejoice, because it gives me
twice the opportunity to show just how wrong I am. If the small inductor
shows a measureable phase shift from input to output, I'll be just as
wrong as I'll be if it shows a magnitude change. So I've doubled the
odds I'll fall on my face. At the same time, it puts Cecil at no extra
risk at all, since he won't venture a prediction of either magnitude or
phase, and I feel confident in my assumption that you won't, either. I'm
the only one (except Yuri, who has bravely given a range of magnitude
values at least) who *can* be wrong, and including phase makes it all
the more likely. Surely, that should cheer you up a bit.

Roy Lewallen, W7EL

Cecil Moore wrote:
Art Unwin KB9MZ wrote:

Is not the group straying somewhat from the initial discussion
on E ham? That discussion that started all this was with regard to a
whip antenna and the coil on it. Why has the discussion been pulled
away from the original coil to a torroid of all things ?


Because someone can't stand to be wrong?
--
73, Cecil, W5DXP