Current across the antenna loading coil - from scratch
 

Yuri Blanarovich wrote:
Check my article that describes the controversy, shows some proof of
reality and then efforts of the "gurus" to deny it and "reason" why
it can't be so. http://www.k3bu.us/loadingcoils.htm The problem is
that back in 1953 in QST article there was erroneous
conclusion/statement made, which propagated through the books, until
W9UCW measured the current across the loading coils and found that
there is significant drop from one end to the other, and the rest is
(ongoing) history

Hmm, certainly it would seem to make sense that:

The current in a typical loading coil in the shortened antennas drops
across the coil roughly corresponding to the segment of the radiator
it replaces.

Quote from your page.

I would not expect anything else. If the loading coil is making the
antenna act like a physically longer antenna, other "qualities" of that
simulation are likely to be similar.

Is there a reason why the coil would *not* do this?

- 73 de Mike KB3EIA -

Current across the antenna loading coil - from scratch
 

Mike Coslo wrote:
Yuri Blanarovich wrote:
Check my article that describes the controversy, shows some proof of
reality and then efforts of the "gurus" to deny it and "reason" why
it can't be so. http://www.k3bu.us/loadingcoils.htm The problem is
that back in 1953 in QST article there was erroneous
conclusion/statement made, which propagated through the books, until
W9UCW measured the current across the loading coils and found that
there is significant drop from one end to the other, and the rest is
(ongoing) history

Hmm, certainly it would seem to make sense that:

The current in a typical loading coil in the shortened antennas drops
across the coil roughly corresponding to the segment of the radiator
it replaces.

Quote from your page.

I would not expect anything else. If the loading coil is making the
antenna act like a physically longer antenna, other "qualities" of that
simulation are likely to be similar.

Is there a reason why the coil would *not* do this?

Yes, many, and they've been discussed here at length. That this concept
is wrong can and has been shown by theory, modeling, and measurement. I
made and posted measurements on this newsgroup in November 2003 which
demonstrated clearly that the presumption is false.

The loading coil isn't making the antenna act like a physically longer
antenna. In the extreme case of a physically short inductor at the
feedpoint, it's simply modifying the feedpoint impedance and has no
effect whatever on the antenna's radiation. As the inductor gets longer,
it does become some part of the antenna, but adding an inductor which
resonates, say, a 45 degree physical radiator doesn't make the antenna
act like a 90 degree physical radiator.

Roy Lewallen, W7EL

Current across the antenna loading coil - from scratch
 

Wes Stewart wrote:

Responding to no one in particular.

This is starting to make me miss the shorter Fractenna threads.

Phil, comeonback good buddy.


They certainly made more sense.

Dave N

Current across the antenna loading coil - from scratch
 

Richard Harrison wrote:
Tom, W8JI wrote:
"The directional coupler in a Bird meter samples the across vector
(voltage) from a capacitive divider and adds it to a sample voltage of
the through vector (current) from a current transformer in a
predetermined ratio.

That`s close. In the cartridges is a loop terminated in a diode.
Capacitive coupling of the loop to the center conductor of the precision
ccoax supplies the voltage sample. Inductive coupling of the loop
supplies the current sample.

I`ve described operation several times here and once in this thread, so
I won`t repeat it.


We're all agreed on what happens with the Bird's sampling lines and
detector. The only differences arise from each person's attempt to
condense it all into a couple of sentences, and aren't worth arguing
about.

But Richard cuts it too short when he claims that:
A Bird Thruline wattmeter uses a directional coupler to separate
forward direction power from reverse direction power.

That claim confuses two different things: what the line-loop-detector
hardware physically *does*; and what the indicated results *mean*. The
first of these is agreed; the second is not.

The disagreement is entirely about the interpretation - in other words,
it's about the theory about standing and travelling waves. Richard
habitually misses out this step, which makes it look as if the Bird
wattmeter "proves" the physical existence of forward and reverse
travelling waves of power.

It doesn't. Everything that you see printed on the Bird's meter scale,
and in the Bird literature, represents that company's particular
interpretation of theory about waves on transmission lines. The details
of that theory are *not* agreed within this newsgroup, which means that
- to some people - the two halves of Richard's claim do not join up.



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Current across the antenna loading coil - from scratch
 

Mike Coslo wrote:

Yuri Blanarovich wrote:
The current in a typical loading coil in the shortened antennas drops
across the coil roughly corresponding to the segment of the radiator
it replaces.

Quote from your page.

I would not expect anything else. If the loading coil is making the
antenna act like a physically longer antenna, other "qualities" of that
simulation are likely to be similar.

Is there a reason why the coil would *not* do this?
- 73 de Mike KB3EIA -

Every reason in the world. This misconception is EXACTLY what started
this whole thing years ago.

The loading coil doesn't "replace" missing electrical degrees, it
primarily corrects power factor by compensating reactance. Anything
else is generally secondary, and is related to flaws in the system
rather than something necessary.

That idea repeats one of the worse myths about loading coils.

The truth is the loading inductor almost never has the same phase shift
in current as the missing antenna area it replaces, and it almost never
has the same "current drop". "Current drop" isn't even a good English
description of what happens in any circuit.

I can have an antenna of given dimensions with a loading coil at one
fixed spot. The difference in current flowing into one end and out the
other can go all over the place, depending only on the coil's physical
design wity the antenna resonant on the same frequency. This happens
ONLY by changing the coil.

If I had a coil that was compact and not against the groundplane with
low stray capacitance compared to the antenna area above the coil,
current difference between each terminal or through the coil could be
immeasurable with reasonably good instrumentation. Phase shift in
current could also be nearly zero. None of this would be anywhere near
the area the coil replaces.

Without any change in anything except the coil, I could change all
that. If I replaced the coil with a long stub or very large single
turn, it would indeed act more like the antenna area it "replaces". The
reason for this is the coil's capacitance to ground and capacitance to
space around the antenna, NOT the electrical degrees it replaces and
certainly not the standing waves. This all can and has been proven over
and over again. The very few people offering the long drawn out
arguments against this really are violating basic electrical laws of
how systems really work, and enforcing the myth that a loading coil is
so many electrical degrees long or that displacement currents are not
at work and current magically vanishes, or magically flows two
directions at the same time at one point in a conductor.

A few people have taken the model of standing waves, not understood the
limits or boundary conditions of that model, and thought it to be an
actual literal description of what really is happening. They appear to
actually think current can flow two directions at the same time at the
same point. They somehow thing we can have charge drift velocity in two
directions at the same instant of time at one point in a conductor, or
that current can just vanish into thin air without actually being
diverted through a second path.

A few people have violated the rules of charge conservation, charge
movement, and misapplied the concept of standing waves, but the single
largest error is standing behind the myth or misconception that that
loading coil somehow acts like the "missing area of antenna".

73 Tom

Current across the antenna loading coil - from scratch
 

Roy Lewallen wrote:
Yes, many, and they've been discussed here at length. That this concept
is wrong can and has been shown by theory, modeling, and measurement. I
made and posted measurements on this newsgroup in November 2003 which
demonstrated clearly that the presumption is false.

By now, even you know that standing wave current phase is
fixed and unchanging and that those delay measurements of yours
are invalid whether made on a wire or on a coil.

The loading coil isn't making the antenna act like a physically longer
antenna.

Of course not! The loading coil is making the antenna act
like an electrically longer antenna by adding a phase
shift through the coil. The electrical lengthening is
what resonates the antenna feedpoint to a pure resistance.

In the extreme case of a physically short inductor at the
feedpoint, it's simply modifying the feedpoint impedance and has no
effect whatever on the antenna's radiation.

Nobody has ever said it affected the antenna's radiation so
that has been and is still just a straw man.

As the inductor gets longer,
it does become some part of the antenna, but adding an inductor which
resonates, say, a 45 degree physical radiator doesn't make the antenna
act like a 90 degree physical radiator.

Of course not and nobody has ever said it does. It increases
the electrical length and brings the forward and reflected
waves into phase with each other. That's why the the feedpoint
impedance is resistive.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Ian White GM3SEK wrote:
The disagreement is entirely about the interpretation - in other words,
it's about the theory about standing and travelling waves. Richard
habitually misses out this step, which makes it look as if the Bird
wattmeter "proves" the physical existence of forward and reverse
travelling waves of power.

Those are traveling waves of *EM energy* where the power is indicated
at a point as the energy flows through that point. Assuming Z0=50 ohms,
the Bird indicates the number of joules per second flowing toward the
load when the slug is in the forward position. Turning the slug around
causes the Bird to indicate the number of joules per second flowing
toward the source.

The only way to have standing waves of EM energy in a transmission
line is to have two EM waves flowing in opposite directions. I have
asked you before to explain how standing waves develop without the
existence of a forward traveling wave and a rearward traveling wave.
Your silence on that subject has been conspicuous by its absence.
Do standing waves appear by magic?

It doesn't. Everything that you see printed on the Bird's meter scale,
and in the Bird literature, represents that company's particular
interpretation of theory about waves on transmission lines. The details
of that theory are *not* agreed within this newsgroup, which means that
- to some people - the two halves of Richard's claim do not join up.

Are you asserting that Bird is engaging in false advertising?
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Ian White GM3SEK wrote:
[SNIP]

The disagreement is entirely about the interpretation - in other words,
it's about the theory about standing and travelling waves. Richard
habitually misses out this step, which makes it look as if the Bird
wattmeter "proves" the physical existence of forward and reverse
travelling waves of power.

It doesn't. Everything that you see printed on the Bird's meter scale,
and in the Bird literature, represents that company's particular
interpretation of theory about waves on transmission lines. The details
of that theory are *not* agreed within this newsgroup, which means that
- to some people - the two halves of Richard's claim do not join up.


Ian, I've not detected this particular disagreement about waves on
transmission lines in the group. I would be most grateful to see a brief
statement of where and how Bird's interpretation of theory is found infirm.

73,

Chuck NT3G

Current across the antenna loading coil - from scratch
 

wrote:
The loading coil doesn't "replace" missing electrical degrees, it
primarily corrects power factor by compensating reactance.

If correcting the power factor didn't cause a phase shift, the
power factor wouldn't change but we know it does. That phase
shift is exactly what we are talking about. The coil shifts
the phase of both the forward wave and reflected wave thus
furnishing some much needed electrical degrees in order to
resonate the antenna by bringing the phasor sum of the forward
and reflected voltages into phase with the phasor sum of the
forward and reflected currents.

Any power engineering textbook will tell you what happens to the
phase when the power factor is corrected. Hint: If the phase
stayed the same, as you assert, nothing would change. But we
know that correcting the power factor changes the phase. That's
exactly what correcting the power factor is all about.

The truth is the loading inductor almost never has the same phase shift
in current as the missing antenna area it replaces, and it almost never
has the same "current drop".

The inductor does indeed
contribute a phase shift that is not zero. In a one wavelength
system, the coil can just as easily contribute a current RISE
as a current DROP. That fact alone is reason to drop the flawed
model. Current cannot be created in a coil by sucking it out of
earth ground which is what your theory have us believe. But of
course, you have refused to discuss the subject.

I can have an antenna of given dimensions with a loading coil at one
fixed spot. The difference in current flowing into one end and out the
other can go all over the place, depending only on the coil's physical
design wity the antenna resonant on the same frequency. This happens
ONLY by changing the coil.

Of course, but that is beside the point. Every real world inductor does
contribute its own unique phase shift and its own unique current change,
rise, fall, or equal at current nodes and antinodes. You have absolutely
refused to discuss that current rise. One wonders why.

If I had a coil that was compact and not against the groundplane with
low stray capacitance compared to the antenna area above the coil,
current difference between each terminal or through the coil could be
immeasurable with reasonably good instrumentation. Phase shift in
current could also be nearly zero. None of this would be anywhere near
the area the coil replaces.

Resorting to a specially designed coil completely different from
anything used in the real world has been your specialty. If your
theory only works for only one special case and is not valid for
the general case, it's time to junk that theory.

After failing a dozen times to achieve equal current at both ends
of numerous coils, you finally declared victory using a small
toroidal coil. Uhhhh Tom, one out of twelve doesn't prove much.
I have shown you how to achieve equal current with any coil. It
just depends upon where the coil is placed in the standing wave
environment.

A few people have violated the rules of charge conservation, charge
movement, and misapplied the concept of standing waves, but the single
largest error is standing behind the myth or misconception that that
loading coil somehow acts like the "missing area of antenna".

The coil's function is to bring the forward and reflected waves
into phase so the feedpoint impedance will be purely resistive.
It cannot do that if it has no effect on phase. Your theory
is full of holes.

The coil affects the electrical length of the antenna, not the
physical length. Nobody has ever said it replaces the missing
physical length of the antenna. Your implication is that same
tired old straw man riding that same old dead horse.

Please stop trying to twist what we are saying and fix the
twist in your own misconceptions. For instance, how does your
theory handle a current rise through a coil as illustrated at:

http://www.qsl.net/w5dxp/test316.GIF

in the right hand part of the graphic. Why do you refuse to
discuss this current RISE?
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

K7ITM wrote:
In your two messages included above by reference, you complained that I
had in the other two included messages put things you had written, but
that I did not properly attribute them to you. I don't know whether to
be offended, feel sorry for you, or laugh. In each of my two messages,
immediately following my signature, is a line that begins, "Cecil
wrote..." I trust it's not too difficult for most folk to understand,
but I'll explain it for you. That line means that YOU wrote the stuff
that follows that line, not me. In general, I would absolutely NOT
want anyone to think I'd written anything you wrote! Guess I'm
inclined to feel a bit of the second, and do some of the third.

You are doing the "Cecil wrote" in the wrong way and falsifying
attributions in the process. If you want to be known as the
netnews guy who falsifies attributions, that is your business.

What I am officially asking you to do is to cease and desist
falsifying the attributions associated with my postings.
--
73, Cecil http://www.qsl.net/w5dxp