Tom Donaly wrote:
What is a "sinusoidal magnitude function," Cecil?

Y = sin(X)

The magnitude 'Y' is equal to the sine of an angle,
'X', in degrees.

Wouldn't you agree with me that it is ridiculously
ignorant to assert that the magnitude 'Y' has nothing
to do with the phase angle 'X', i.e. that there's no
"phase information in the ... magnitude".
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Tom Donaly wrote:

What is a "sinusoidal magnitude function," Cecil?


Y = sin(X)

The magnitude 'Y' is equal to the sine of an angle,
'X', in degrees.

Wouldn't you agree with me that it is ridiculously
ignorant to assert that the magnitude 'Y' has nothing
to do with the phase angle 'X', i.e. that there's no
"phase information in the ... magnitude".

Actually, I don't think it's "ridiculously ignorant" at
all. If all you have is the value of current at one point,
you can't possibly tell anything about the phase. You need
to compare it to something - itself even - somewhere or sometime else in
order to have an idea of phase. Here's what I mean: suppose I have a
piece of wire of unknown length, excited by an unknown frequency, and
picking a random point on the wire I measure 1.73 amps. What is the
phase? You're trying to square the circle and hear the sound of one
hand clapping at one and the same time, Cecil. Of course, in your
case, you know the length of the wire, the frequency of the wave and
its wavelength, and you think you know the current distribution
on the wire (a half wavelength dipole) so you don't need anything
but a ruler to find what you're looking for. Of course, you have to
decide what you mean by the term "phase." Try not to get a permanent
headache thinking about it.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
If all you have is the value of current at one point,
you can't possibly tell anything about the phase.

But the value of current at one point is *NOT* all we have
so your supposition is irrelevant. After a century of theory
by some of the most brilliant human minds, we know virtually
everything there is to know about a 1/2WL thin-wire dipole.
We know there *IS* indeed phase information in the standing
wave current magnitude just Kraus graphed it in his book.

You need
to compare it to something - itself even - somewhere or sometime else in
order to have an idea of phase.

The standard thing to compare it to is the feedpoint current,
e.g. provided by EZNEC, usually 1.0 amps at 0 degrees.

Here's what I mean: suppose I have a
piece of wire of unknown length, excited by an unknown frequency, and
picking a random point on the wire I measure 1.73 amps. What is the
phase? You're trying to square the circle and hear the sound of one
hand clapping at one and the same time, Cecil.

First, you insult me with irrelevant ad hominem attacks ...

Of course, in your
case, you know the length of the wire, the frequency of the wave and
its wavelength, and you think you know the current distribution
on the wire (a half wavelength dipole) so you don't need anything
but a ruler to find what you're looking for.

And second, you agree with Kraus and me ...

Here is a chart regarding Kraus' 1/2WL thin-wire dipole copied from
my other posting. Please tell us what is wrong with it and exactly
why the standing wave current magnitude doesn't tell us how many
degrees away the feedpoint is for the formula I = Io*cos(X).

X degrees away standing wave arc-cosine of the
from feedpoint current magnitude current magnitude
0 1.000 amps 0 deg
30 0.866 amps 30 deg
45 0.707 amps 45 deg
60 0.500 amps 60 deg
90 0.000 amps 90 deg

Do you really think it is a mere coincidence that column 1 and
column 3 are identical???
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Tom Donaly wrote:

If all you have is the value of current at one point,
you can't possibly tell anything about the phase.


But the value of current at one point is *NOT* all we have
so your supposition is irrelevant. After a century of theory
by some of the most brilliant human minds, we know virtually
everything there is to know about a 1/2WL thin-wire dipole.
We know there *IS* indeed phase information in the standing
wave current magnitude just Kraus graphed it in his book.

You need
to compare it to something - itself even - somewhere or sometime else
in order to have an idea of phase.


The standard thing to compare it to is the feedpoint current,
e.g. provided by EZNEC, usually 1.0 amps at 0 degrees.

Here's what I mean: suppose I have a
piece of wire of unknown length, excited by an unknown frequency, and
picking a random point on the wire I measure 1.73 amps. What is the
phase? You're trying to square the circle and hear the sound of one
hand clapping at one and the same time, Cecil.


First, you insult me with irrelevant ad hominem attacks ...

Of course, in your
case, you know the length of the wire, the frequency of the wave and
its wavelength, and you think you know the current distribution
on the wire (a half wavelength dipole) so you don't need anything
but a ruler to find what you're looking for.


And second, you agree with Kraus and me ...

Here is a chart regarding Kraus' 1/2WL thin-wire dipole copied from
my other posting. Please tell us what is wrong with it and exactly
why the standing wave current magnitude doesn't tell us how many
degrees away the feedpoint is for the formula I = Io*cos(X).

X degrees away standing wave arc-cosine of the
from feedpoint current magnitude current magnitude
0 1.000 amps 0 deg
30 0.866 amps 30 deg
45 0.707 amps 45 deg
60 0.500 amps 60 deg
90 0.000 amps 90 deg

Do you really think it is a mere coincidence that column 1 and
column 3 are identical???

Cecil, you can always know something you already know. Knowing that your
antenna is 1/2 wavelength long gives you all the information you need
for your definition of phase. By the way, where did you get that table,
from EZNEC?
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
Cecil, you can always know something you already know. Knowing that your
antenna is 1/2 wavelength long gives you all the information you need
for your definition of phase.

Apparently that knowledge is not enough for W7EL who said
regarding the current distribution in a 1/2WL thin-wire
dipole:

W7EL wrote:
Of course I reject the notion that there's "phase information
in the standing wave current magnitude".

This in the face of technical evidence that the standing
wave current magnitude is a cosine function of the number
of degrees the referenced point is away from the feedpoint.

Also contradicting Gene Fuller who said:
The only "phase" remaining is the cos (kz) term, which is really
an amplitude description, not a phase.

By the way, where did you get that table, from EZNEC?

From page 464 of "Antennas for all Applications", 3rd Edition,
by Kraus and Marhefka. Where Kraus presents the independent
variable in fractions of a wavelength, I simply converted it
to degrees. Most knowledgeable people comprehend that there
are 360 degrees per sinusoidal cycle, i.e. per one wavelength.
--
73, Cecil http://www.qsl.net/w5dxp