Current across the antenna loading coil - from scratch
 

"Roy Lewallen" wrote in message
...
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

Oooops, carefull here.
As far as I know, nobody has claimed that inserted loading coil replaces the
"missing" degrees of the radiator in terms of providing magical properties
that would look like that "replaced" portion of the antenna, or make the
antenna act like 90 degree full size physical radiator.
What we are saying that the loading coil appears to replace "missing"
electrical degrees of the radiator in order to make it resonant, that is
back to 90 electrical degrees (has to be in order to resonant), which rest
of the existing "straight" radiator forces it to do (+/-). Radiation
properties and efficiency of the loaded antenna is proportional to the area
under the current curve. It is obvious to anyone comparing the area under
the current curve of full size quarter wave radiator vs. loaded radiator
that there is huge difference in area under the curve and performance,
efficiency, which is known and been verified by numerous measurements.
HOW the current curve is modified by different loadings and position along
the radiator is important in knowing how the current distribution curve
along the radiator is modified.
The whole controversy is that "gurus" claim current doesn't drop across the
coil, while we say that it does, therefore making the area under current
curve above the coil smaller and effciency of loaded antenna worse than they
believe and insist on.
Again, when applied in modeling programs, wrong assumption will produce
erroneous results, which will be magnified in multielement antenna designs.
So the "gurus" basically ignore behavior of coil in the standing wave
environment along the loaded radiator, where the current drops from max at
base to zero at the tip, but coil would magicaly resist that, because, bla,
bla, bla.... (see their "reasons")
So while everyone knows (?) that standing wave current drops acros (along)
the wire (all the antenna books show that), but it is "impossible" to drop
along the coiled wire (real inductance - coil, loading stub). Reality and
measurments prove that, but according to them "it can't be so".

I am already gathering necessary hardware to do more experiments,
measurements to show what is really happening, and will prepare articles how
to model and apply it to antenna design.
I would challenge the "unbelievers" to join me and repeat the tests, to see
wasaaaap.

73 Yuri, K3BU

Current across the antenna loading coil - from scratch
 

Yuri Blanarovich wrote:
What we are saying that the loading coil appears to replace "missing"
electrical degrees of the radiator in order to make it resonant, ...

W8JI says we are correcting the power factor. Every EE knows that
correcting the power factor involves shifting the phase, i.e.
the coil cannot correct the power factor without providing a phase
shift.

The whole controversy is that "gurus" claim current doesn't drop across the
coil, while we say that it does, ...

That context is specifically inductively loaded mobile antennas
where the current decreases from source to tip of the antenna,
true for all electrical 1/4WL monopoles.

For other antennas, the current may DROP, the current may RISE,
or the current may STAY THE SAME magnitude depending upon where
the coil is installed in the standing wave system. In particular,
none of the "gurus" has even attempted to explain the RISE IN
CURRENT through the coil in the right hand system at:

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

There have been about 10 examples proving the "gurus" wrong and
they simply chose to ignore those examples. They complain that
those examples are biased toward technical correctness. I say,
YES, THEY ARE. AREN'T THEY SUPPOSED TO BE TECHNICALLY CORRECT?
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

chuck wrote:
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.
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.

The Bird 43 has only one scale calibration: power. Readings on that
scale represent the power delivered to a 50-ohm load when the sensor is
turned to the forward direction. However, the instrument internally
senses only the voltage and current on the line. The "power" reading is
only a calibration, and is only completely meaningful when you use the
instrument in the same circumstances as when it was calibrated.

Now what happens if the load is not exactly 50 ohms? What happens when
you turn the sensor around? You then get some new and different readings
which have to be called "forward power" and "reflected power" - because
"power" is the only thing the Bird's meter scale is calibrated to
indicate.

The Bird Corporation's Application Note "Straight Talk About
Directivity" discusses the meaning of "forward and reflected power"
indications with a mismatched load. That document does not directly
address your question, Chuck, but takes the subject to a further level
of detail about the accuracy of the real-life instrument, and its
limited ability to discriminate between forward and reflected waves.
http://www.bird-electronic.com/app_n...irectivity.pdf

One notable thing about "Straight Talk" is how all the calculations
begin by taking the square root of the power indications. In other
words, all the relative RF power indications from the meter scale are
converted into relative RF voltages, and all the real calculations are
done on the voltages.

Another interesting observation is that if you have a mismatched load,
such that the meter indicates say 93W with the arrow on the sensor
pointing forward and say 23W with the sensor rotated 180deg, then you
would find that 70W is being delivered into the resistive part of the
mismatched load impedance (assuming perfect directivity and no errors of
any other kind).

There are two schools of thought about the physical meaning of all this.

One is that if the meter scale says "power", then there genuinely are
forward and reflected traveling waves of power on the line. In the "93 -
23 = 70W" example, the belief is that there genuinely is a power flow of
93W towards the load, only 70W of which is accepted and 23W is returned.

The other school of thought is that that's not true. The meter may
*read* more "forward power" than is actually being delivered to the
load, but that is a false indication because the instrument is not being
used in the situation for which the power scale was calibrated.
Therefore it is not to be taken at face value - and above all, the
letter "W" on the meter scale does not prove the physical existence of
forward and reflected waves of power.

Every detail about a Bird 43 or similar "directional wattmeter" can be
explained quite simply in terms of travelling waves of voltage and
current. And I do mean every detail - including why a meter that happens
to have been calibrated in "power" will read as it does.

The classic explanation was by Warren Bruene, W5OLY, of the Collins
company. He invented the familiar "Bruene bridge" directional coupler
which samples current through a toroidal transformer, and voltage by a
voltage divider. The principle of the Bird 43 is the same, but the two
separate sampling functions are easier to see in the Bruene bridge.

After a previous incarnation of this debate in 2002, I wrote a 2-page
article which summarised Bruene's original article (from QST, April
1959) and explained the crossover to the Bird sampling technique:
http://www.ifwtech.co.uk/g3sek/in-pr...-of.htm#bruene

An equally good explanation of those same meter readings can be
constructed by regarding the Bruene "bridge" literally as an impedance
bridge. There is no inconsistency between the two approaches - they are
just two different viewpoints looking at the same reality.

On the other hand, we have yet to see an explanation in equivalent
physical detail that is based entirely and exclusively on the viewpoint
of travelling waves of power (with no borrowing from explanations based
on voltage and current).

I am not blaming the Bird Corporation for any of these
misunderstandings. They are simply telling users how to work with the
available "power" markings on the meter scale. The problem is when some
users take them too literally.



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

Current across the antenna loading coil - from scratch
 

Thank you, Ian, for the quick and thorough reply! I look forward to
reading both papers.

73,

Chuck NT3G

Current across the antenna loading coil - from scratch
 

On Wed, 12 Apr 2006 16:32:22 +0100, Ian White GM3SEK
wrote:

On the other hand, we have yet to see an explanation in equivalent
physical detail that is based entirely and exclusively on the viewpoint
of travelling waves of power (with no borrowing from explanations based
on voltage and current).

Now Ian,

That is like asking us to explain a speedometer without recourse to
the units for distance and time.

73's
Richard Clark, KB7QHC

Current across the antenna loading coil - from scratch
 

On Wed, 12 Apr 2006 16:32:22 +0100, Ian White GM3SEK
wrote:

One is that if the meter scale says "power", then there genuinely are
forward and reflected traveling waves of power on the line. In the "93 -
23 = 70W" example, the belief is that there genuinely is a power flow of
93W towards the load, only 70W of which is accepted and 23W is returned.

The other school of thought is that that's not true. The meter may
*read* more "forward power" than is actually being delivered to the
load, but that is a false indication because the instrument is not being
used in the situation for which the power scale was calibrated.
Therefore it is not to be taken at face value - and above all, the
letter "W" on the meter scale does not prove the physical existence of
forward and reflected waves of power.

Hi Ian,

This argument sets up the first school for failure that is already
admitted to. Your statement from the second school that:
*read* more "forward power" than is actually being delivered to the
load, but that is a false indication
is already admitted to explicitly from the first school:
93W towards the load, only 70W of which is accepted and 23W is returned.
in that the 70W NOT 93W is the correct indication.

The "second" school has nothing to offer on the subject. The
"because" that attends their "discovery" of this error is specious
logic.

The fact remains that when you subtract 23W from the 93W you do find
70W in the load. The second school would have us believe none of the
numbers correlate to power, and yet the results bear out just the
opposite every day.

The second school needs to stay after class.

73's
Richard Clark, KB7QHC

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
(snip)
W8JI says we are correcting the power factor. Every EE knows that
correcting the power factor involves shifting the phase, i.e.
the coil cannot correct the power factor without providing a phase
shift.

Power factor correction shifts the relative phase of current with
respect to voltage. When talking about a phase shift, you have to be
careful to say what is being shifted relative to what else. There are
lots of possibilities.

A series inductor (a non real, ideal one) with absolutely no phase
shift or magnitude change in the current from one end to the other,
still produces a phase shift of input voltage to output voltage, so
the relative phase of voltage to current at the input is different
compared to the relative phase of voltage to current at the output. I
think this is the power factor correction effect W8JI is referring to.

Any real inductor does this, and also does some other things.

Current across the antenna loading coil - from scratch
 

Ian White GM3SEK wrote:
Now what happens if the load is not exactly 50 ohms?

If the feedline is 50 ohms, what happens is reflected
energy that is easily visible using a TDR, time domain
reflectometer.

One is that if the meter scale says "power", then there genuinely are
forward and reflected traveling waves of power on the line. In the "93 -
23 = 70W" example, the belief is that there genuinely is a power flow of
93W towards the load, only 70W of which is accepted and 23W is returned.

One correction. The Bird wattmeter is installed at a point
on the transmission line and it measures the power at that
point. What is traveling is the energy. Power is the number
of joules per second passing a fixed point. "Power flow" is
somewhat of a misnomer.

The other school of thought is that that's not true. The meter may
*read* more "forward power" than is actually being delivered to the
load, but that is a false indication because the instrument is not being
used in the situation for which the power scale was calibrated.

It certainly is being used in the situation for which it was
calibrated if the Z0 of the transmission line is 50 ohms.

On the other hand, we have yet to see an explanation in equivalent
physical detail that is based entirely and exclusively on the viewpoint
of travelling waves of power ...

Please give up on your misconception. Those are traveling waves
of *ENERGY*. Power is what is measured when traveling energy passes
a fixed point. Perhaps that is your whole point of confusion.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Cecil, W5DXP wrote:
"Any power engineering handbook will tell you what happens to the phase
when the power factor is corrected."

Most industrial loads have a lagging power factor. They represent an
inductive reactance in addition to their resistive loads. Extra energy
must be generated and transmitted just to charge this inductance which
does no work but demands current. Extra loss comes from this reactive
load. This is eliminated by tuning the inductance out with a capacitive
reactance at the load. This is often an overexcited synchronous motor.
When the motor has no mechanical load it is often called a "synchronous
capacitor".

An antenna needs zero reactance too if it is to accept maximum energy
and not make standing waves. Reactance impedes energy to the antenna.
Reactive current also increases loss in the transmission line as it does
in the case of the power utility frequency. So j0 is a goal in many
instances.

Best regards, Richard Harrison, KB5WZI

Current across the antenna loading coil - from scratch
 

Richard Harrison wrote:

Cecil, W5DXP wrote:
"Any power engineering handbook will tell you what happens to the phase
when the power factor is corrected."

Most industrial loads have a lagging power factor. They represent an
inductive reactance in addition to their resistive loads. Extra energy
must be generated and transmitted just to charge this inductance which
does no work but demands current. Extra loss comes from this reactive
load. This is eliminated by tuning the inductance out with a capacitive
reactance at the load.

Yet W8JI would have us believe that power factor correcting capacitor
functions faster than the speed of light, making an instantaneous
phase correction. Sorry, the real world doesn't work that way.

The bottom line is that we cannot shift phase without delaying
something, either voltage or current. Contrary to the presuppositions
of the lumped-circuit model, neither voltage nor current can travel
faster than the speed of light. That means that any phase shifting
of the relative phase angle difference down to zero results in a
delay.

I have seen it explained as "apparently" traveling faster than
light. That's just one more patch on an already flawed mode.
--
73, Cecil http://www.qsl.net/w5dxp