Yuri Blanarovich wrote:

"Ian White GM3SEK" wrote in message
...

From the beginning, then:
snippydidudaa

As we have seen, if the whip is loaded by pure inductance only, there is
no change in current between the two terminals of the inductance - but
there's a big step increase in voltage. At the upper terminal, the current
is the same but the voltage is very high, so we're into a much
higher-impedance environment.


Reality check here. I need explanation how the above could happen. "Current
stays the same ... and the big step increase in voltage." As far as "idiot"
professors taught me, (current x voltage) = power. So, am I to discover
that the pure inductance is better than perpetual motion amplifier of power?
More power coming out of the coil than going in? Eureka!!! How could I
overlook that? :-)


Your professor would have told you that you "overlooked" the phase shift
in the voltage.

The rest is just more of the same kind of name-calling. You didn't
really read what I wrote, and you don't really want to hear any answers.
All you really want is a shouting match. Well, tough, you don't get one.



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

Ian White GM3SEK wrote:

SNIPPED

Your professor would have told you that you "overlooked" the phase shift
in the voltage.

SNIPPED

Does this mean: "HERE WE GO AGAIN"?

I was taught that there is a 90 degree phase shift in an inductor. But,
in a loading coil there must be less than 90 degree phase shift because
the top portion of the antenna still has a small, ~3 to 5 degree, phase
shift required to achieve resonance. So, does the inductance have a 90
degree phase shift or an approximate 85+ degree phase shift.

Voltage and current are in phase at the base and 90 degrees out of phase
at the tip, at resonance, conclusion: less than 90 degree phase shift in
the inductor. PLEASE EXPLAIN this physics anomaly!

:-)

Cecil Moore wrote:
Ian White GM3SEK wrote:
Evidently I was in too much of a hurry to leave for the GMDX
convention, because what I mean to write next was:
"Cecil's theory does not work for this test case, "
[ I definitely did type the word "not", but it accidentally
disappeared from the version that was posted. ]

Well there you have it, folks. Gurus don't even make typo mistakes.
Some evil server removed that "not" on purpose from Ian's posting.


In trying to respond to your points as clearly as possible, some parts
of my previous posting went through several versions. I simply made a
mistake in editing that particular sentence. I have already apologised
for any confusion that might have caused.


Cecil's theory does not work for this test case,
because it requires that basic electrical properties like current
and inductance switch into a different kind of behaviour in what he
calls a "standing wave environment".

RF current switches from a different kind of behavior than DC current.

True, but irrelevant. You are asking for RF current to switch its
behaviour while still being RF current.

Phase, capacitance, inductance, and wavelength all have to be taken
into account in the steady-state analysis. That is a technical fact
that I'm sure you appreciate.

Yes...

Why is it such a stretch to recognize that standing wave current behaves
differently from traveling wave current? That standing wave current is
different from traveling wave current is readily apparent from the
equations. In the following equations, 'K' is used for a constant,
'z' is the linear distance up and down the line, and 'w' is omega.

Forward traveling wave current = K1*cos(kz+wt)
Reflected traveling wave current = K2*cos(kz-wt)
Standing wave current =
K1*cos(kz+wt) + K2*cos(kz-wt) = K3*cos(kz)*cos(wt)

If tK1 = K2, then the standing wave doesn't move. Please dust off
your old math books and realize what the above equations imply at
a physical level.

Let's try it a different way. At any point located a distance z along
the antenna, there is the normal cyclical variation in current I with
TIME, so:

I(t, z) = Ipk(z) cos(wt)

where Ipk(z) is the peak value of the current at point z. The cos(wt)
term represents the cyclical time dependence of the back-and-forth
movement of electrons; it has no dependence on z.

Ipk(z) is simply a scaling factor whose value depends only on the
LOCATION of point z within the antenna. It has NO time dependence.

The next issue to describe how Ipk varies with the location z along the
wire. The aim of antenna analysis is to find out what the current
distribution along the wire(s) actually is. All the rest of the
antenna's properties can be calculated from this.

Ipk(z) does not have to be a simple cosine function as you seem to
assume above. A cosine function may be a good approximation for very
simple (or simplified) cases; but when the antenna includes a physical
discontinuity such as a loading coil, Ipk(z) will definitely NOT be a
simple cosine function of distance z. So in general it will not be
correct to bundle the z dependence into the same cosine function as
(wt).

There are several methods of finding the current distribution. If you
choose a method based on forward, reflected and standing waves (which
can be done), the "standing wave" is simply a plot of Ipk as a function
of location z. Ipk(z) is a scalar quantity representing the peak
magnitude of the current, and its only dependence is on LOCATION. It is
not an alternating RF current because it has no time dependence.

"Current" remains what it always was: simply the movement of charge
(electrons). If it's an alternating RF current, the cos(wt) term
describes how the charge moves cyclically forward and back past the
observation point. A loading coil, the RF ammeter or the
current-transformer measuring probe all respond to exactly the same
cyclical back-and-forth movement of charge.

In the standing wave analysis, the current is still the net movement of
charge, ie the instantaneous difference between the forward and
reflected currents. These vary together in time according to cos(wt). It
is not possible to measure the "wrong kind" of current by mistake,
because there is only one kind.



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

Richard Clark challenged me:

Didn't you start a new thread to clear out the cobwebs? That seems to
have gone the way of the dodo.


Hi Yuri,

Instead of chewing old gum over and over again, why not simply fulfill
a promise offered two years ago?


Yea, the dodo was the contest I was trying to beat another record and then
the fricken taxes came.

I will dust off my whips and coils and do some 'sperimenting.
But where are all the gurus? Nobody got mobile antenna and can do crude
"feel the turns" 'speriment?
Must be too busy with charger 'lectrons, Eh?!

Yuri, K3BU

"Ian White GM3SEK" wrote in message
...
Yuri Blanarovich wrote:

"Ian White GM3SEK" wrote in message
...

From the beginning, then:
snippydidudaa

As we have seen, if the whip is loaded by pure inductance only, there is
no change in current between the two terminals of the inductance - but
there's a big step increase in voltage. At the upper terminal, the
current
is the same but the voltage is very high, so we're into a much
higher-impedance environment.


Reality check here. I need explanation how the above could happen.
"Current
stays the same ... and the big step increase in voltage." As far as
"idiot"
professors taught me, (current x voltage) = power. So, am I to discover
that the pure inductance is better than perpetual motion amplifier of
power?
More power coming out of the coil than going in? Eureka!!! How could I
overlook that? :-)


Your professor would have told you that you "overlooked" the phase shift
in the voltage.

The rest is just more of the same kind of name-calling. You didn't really
read what I wrote, and you don't really want to hear any answers. All you
really want is a shouting match. Well, tough, you don't get one.
--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek


Yep, when we try to argue the case, it ends up like this. So you know what I
read, but you would not want to explain, enlighten this "dummy" what is
going on, eh?
Uhm, the phase shift is different for current and different for voltage, or
you claim that current distribution curve would be way different from the
voltage distribution curve?
Can you draw the picture of current and voltage distribution in the case in
question or provide the file for EZNEC or whateverNEC?

Got it!

Yuri, K3BU

Yuri Blanarovich wrote:

"Ian White GM3SEK" wrote in message
The rest is just more of the same kind of name-calling. You didn't really
read what I wrote, and you don't really want to hear any answers. All you
really want is a shouting match. Well, tough, you don't get one.
--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek


Yep, when we try to argue the case, it ends up like this. So you know what I
read, but you would not want to explain, enlighten this "dummy" what is
going on, eh?

I already told you what is going on, the best and most accurate way I
know. It isn't easy, and it took some time to make it concise and
clear.

Your questions are based on a totally different way of looking at it,
much of which I don't even accept as valid. Unfortunately that means I
cannot answer them in any way that would make sense to me.


Uhm, the phase shift is different for current and different for voltage,

If you mean the phase differences across the coil, then this is one I
can answer: yes, that is exactly what I mean. The phase difference
across the coil is quite small for the current but much larger for the
voltage. This is normal behaviour for inductance. When current is being
pushed through an inductance into a small capacitance, it generates a
high voltage across the inductance, and also a large phase shift in that
voltage. That is the dominant feature when the inductance of your
real-life loading coil drives current into the relatively short top
section of the whip.


Can you draw the picture of current and voltage distribution in the case in
question or provide the file for EZNEC or whateverNEC?

I did some drawings in a RadCom article - and we could certainly use a
few diagrams here. It's late now and I have a tower to take down
tomorrow... get back to you later.



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

Ian White GM3SEK wrote:

Cecil Moore wrote:
RF current switches from a different kind of behavior than DC current.

True, but irrelevant. You are asking for RF current to switch its
behaviour while still being RF current.

Standing wave RF current does not exhibit the same behavior as traveling
wave RF current. If you understood the formulas, you would understand
my statement.

where Ipk(z) is the peak value of the current at point z. The cos(wt)
term represents the cyclical time dependence of the back-and-forth
movement of electrons; it has no dependence on z.

Therefore, the phase of the standing wave current has no dependence
on z. In fact, for a 1/2WL thin-wire dipole the phase is fixed
at zero degrees no matter what is the value of z.

Moral: Standing wave current phase cannot be used to measure the
delay through a piece of wire, much less the delay through a coil.
But that's exactly what W7EL measured. Now do you see why those
measurements were meaningless?

THE PHASE OF THE CURRENT IN AND AROUND A LOADING COIL HAS NO DEPENDENCE
ON Z. Think about the implications of your statement.

Ipk(z) is simply a scaling factor whose value depends only on the
LOCATION of point z within the antenna. It has NO time dependence.

There is an Ipk1(z) at the bottom of the coil. There is an Ipk2(z)
at the top of the coil. Both of them have NO time dependence.
Therefore, the phase shift between them CANNOT be used to determine
the delay through a coil.

The next issue to describe how Ipk varies with the location z along the
wire. The aim of antenna analysis is to find out what the current
distribution along the wire(s) actually is. All the rest of the
antenna's properties can be calculated from this.

Ipk(z) does not have to be a simple cosine function as you seem to
assume above.

I do NOT assume a simple cosine function. I have said many times that
the fields of the loading coil warps the current waveform away from
the simple cosine function. It puts a bump in the cosine curve but
the fact remains that the current envelope magnitude contains the only
phase information in the standing wave current. Above, you have
essentially agreed with Gene Fuller that zero phase information exists
in the standing wave current except in the magnitude.

A cosine function may be a good approximation for very
simple (or simplified) cases; but when the antenna includes a physical
discontinuity such as a loading coil, Ipk(z) will definitely NOT be a
simple cosine function of distance z. So in general it will not be
correct to bundle the z dependence into the same cosine function as (wt).

I suggest that the standing wave current for each segment of the antenna
can be plotted as has been done at:
http://www.k6mhe.com/n7ws/Loaded%20antennas.htm in figure 3
and that a cosine function can be plotted underneath that curve.
Associating the bottom of the coil with one point on the cosine
curve and the top of the coil with another point on the cosine
curve will allow us to make a *rough* estimate of the delay through
the coil. The cosine curve doesn't disappear - it is just warped
by the current distribution through the coil.

There are several methods of finding the current distribution. If you
choose a method based on forward, reflected and standing waves (which
can be done), the "standing wave" is simply a plot of Ipk as a function
of location z. Ipk(z) is a scalar quantity representing the peak
magnitude of the current, and its only dependence is on LOCATION. It is
not an alternating RF current because it has no time dependence.

Yet W7EL used that current with no time dependence to try to measure
the delay through a coil. I don't recall you objecting.

"Current" remains what it always was: simply the movement of charge
(electrons). If it's an alternating RF current, the cos(wt) term
describes how the charge moves cyclically forward and back past the
observation point. A loading coil, the RF ammeter or the
current-transformer measuring probe all respond to exactly the same
cyclical back-and-forth movement of charge.

Yes, but two RF ammeters gives us a different and more complete view
of reality. In a traveling wave antenna, the two RF ammeters would
read the same value. In a standing wave antenna, the values read
by the two RF ammeters depend upon where they are located. In the
1WL standing wave antenna at: http://www.qsl.net/w5dxp/1WLDIP.GIF,
an RF ammeter located at point B might read one amp. An identical
RF ammeter located at point D will read zero amps.

In the standing wave analysis, the current is still the net movement of
charge, ie the instantaneous difference between the forward and
reflected currents.

There is no net transfer of energy in a pure standing wave. As
Hecht says: "Its profile does not move through space." Nor does
it move through a wire. Here's the above 1WLDIP.GIF wire replaced
by a loading coil.

|----1/4WL---|-1/4WL-|----------1/2WL------------|

------A------B-/////-D-------------fp-------------

An RF ammeter placed at B may read one amp. An identical RF
ammeter placed at D will read zero amps. How can one amp
be "flowing" out of the top of the coil while zero amps
is "flowing" into the bottom of the coil. That is standing
wave current and it is NOT flowing. It is just standing still
as explained by Hecht.

These vary together in time according to cos(wt). It
is not possible to measure the "wrong kind" of current by mistake,
because there is only one kind.

Sorry, you are wrong about that. A look at the equations while
varying 'x' proves your statement is wrong. Please reference what
Hecht said about those equations in another one of my postings.

You have already admitted that there is more than one kind of
current, e.g. DC Vs RF. It's time to admit that standing wave
current and traveling wave current have different equations and
therefore are different "kinds" of current.
--
73, Cecil http://www.qsl.net/w5dxp

Ian, GM3SEK wrote:
'There are several methods of finding current distribution."

"I may be a fool, but I`n not the fool to be pitied because I disagreed
with Terman. On page 893 of the 1955 edition of "Electronic and Radio
Engineering" Terman writes:
"An antenna can therefore be regarded as a resonant system with
distributed constants. As a result, the impedance of an antenna behaves
in much the same manner as does the impedance of a transmission line
(see Sec. 4-7)."

This is not news to many thread participants. Fig. 4-7 on page 96 shows
an open-circuited transmission line. At the open circuit there is
maximum voltage and zero current. Except for radiation and loss to heat,
the typical standing-wave antenna would behave much the same as this
ideal transmission line.

Not only does Terman give voltage and current diagrams, he gives a phase
diagram. It shows that whenever the voltage or current crosses the zero
axis (changes sign) the phase angle changes abruptly by 180-degrees.
Phase is unchanging between these inflection points. This agrees with
what Cecil has said all along in this discussion.

Best regards, Richard Harrison, KB5WZI

Dave wrote:

I was taught that there is a 90 degree phase shift in an inductor.

Dave, there is a phase shift between applied voltage and maximum
current. That should not be confused with phase shift or phase
difference in current at both ends of the inductor.
,
in a loading coil there must be less than 90 degree phase shift because
the top portion of the antenna still has a small, ~3 to 5 degree, phase
shift required to achieve resonance. So, does the inductance have a 90
degree phase shift or an approximate 85+ degree phase shift.

No.

What happens in an antenna is voltage and current are out-of-phase by
some amount. This by definition means the antenna is reactive.

The loading coil's primary function is to shift voltage in relationship
to current, and compensate the relationship between voltage and current
so they are back in phase.

If the loading coil is physically large and has a good amount of
displacement current flowing radially to space and objects around the
antenna compared to through current, the coil would have a noticable
difference in current at the bottom terminal and top terminal. The
current also would also not be in phase when compared at each end.

Voltage and current are in phase at the base and 90 degrees out of phase
at the tip, at resonance, conclusion: less than 90 degree phase shift in
the inductor. PLEASE EXPLAIN this physics anomaly!

Again, you are comparing electrical degrees of the antenna with degrees
phase shift between voltage and current in a circuit containing only a
pure inductor.

Degrees of antenna only deals with the length. It is a way of
expressing length in terms of wavelength, with 360 degrees being a full
wavelength.

Degrees of phase angle in an antenna or any load is really just a
comparison between voltage and current. It is not related to electrical
degrees.

Mixing those two very different things up is a source of great
confusion. If we have a 10 degree tall antenna we really don't need an
inductor that behaves like it is a 80 degree long antenna section to
resonate the system, and the system is not "90-degree resonant". It is
simply resonant. The antenna is 10 degrees long, and the coil is
whatever it needs to be to bring voltage back in phase with current.


Consider this. If I have a coil in series with a resistor and measure
the input voltage as a reference point, the current at BOTH ends of the
coil will lag voltage by a certain amount. If the coil has low
capacitive reactance to the outside world compared to the load
resistance, current at each end of the coil will be essentially equal.
Phase shift in current at each end will be very low.

It's only when the coil becomes physically large and has appreciable
capacitive reactance to the outside world compared to the load
impedance that it starts to show significant transmission line effects.

Every bit of this is not difficult to understand if we really
understand how an antenna behaves and how a coil behaves. The only
source of wonderment and argument seems to come from people who want to
make the inductor behave differently in an antenna than it behaves in
other systems.

It really isn't complicated at all. The very first post in this 900
plus post long thread explained it quite well, and it's been explained
dozens of more times along the way. There is no reason to assign
special properties to an inductor and make it behave differently in an
antenna than it does in other systems.

73 Tom

On Sun, 2 Apr 2006 18:34:11 -0400, "Yuri Blanarovich"
wrote:
I will dust off my whips and coils and do some 'sperimenting.
But where are all the gurus? Nobody got mobile antenna and can do crude
"feel the turns" 'speriment?
Must be too busy with charger 'lectrons, Eh?!

Hi Yuri,

This was YOUR self-appointed mission. If it doesn't count for much,
or it has no relevancy, then say so and by all means drop it. This
revisiting of old battleground cemeteries is stodgy tourism and I
prefer Buenos Aires. Seeing Evita's tomb in the Recolleta is far more
interesting than watching the grave robbing here.

73's
Richard Clark, KB7QHC