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Roy Lewallen wrote:
It looks like Cecil is trying to use "phase" as a function of position,

Referenced to the source current, the phase of the forward traveling
wave current *IS* directly proportional to position along the dipole.
Any competent engineer knows that. So is the phase of the rearward
traveling wave current. That is obvious from the equations for those
two currents. Those are simply facts of physics that you probably
should try to comprehend instead of dismissing them.

Inet = Io*cos(X)*cos(wt) = Ifor*cos(-X+wt) + Iref*cos(X-wt)

Inet is the standing wave current. X is the distance in degrees from
the feedpoint. If the source current is 1.0 amps at 0 degrees, e.g.
from EZNEC, at t=0 Inet = Io*cos(X) = Ifor*cos(-X) + Iref*cos(X)

As I pointed out some time ago, the envelope of a standing wave isn't in
general sinusoidally shaped.

Balanis says: "If the diameter of each wire is very small (d lamda)
the ideal standing wave pattern of the current along the arms of
the dipole is sinusoidal with a null at the end."

Kraus says: "It is generally assumed that the current distribution
of an infinitesimally thin antenna is sinusoidal,..."

d lamda for an 80m dipole made out of #18 wire. I'm sorry to hear
that you disagree with both Balanis and Kraus.
--
73, Cecil http://www.qsl.net/w5dxp

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Dave wrote:
you guys are just fighting over your own statements since there was no
initial technical question or statement that started this thread...

Doesn't have to be. This is a continuation of earlier threads.
And I'm not fighting - I'm simply stating the laws of physics
as asserted by Balanis, Kraus, and Hecht.
--
73, Cecil http://www.qsl.net/w5dxp

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Cecil Moore wrote:
Gene Fuller wrote:

Cecil is so good at quoting that he should have no problem with
providing the exact unedited words from Kraus that support the
arc-cosine analysis.


"It is generally assumed that the current distribution of an
infinitesimally thin antenna is sinusoidal, ..."

Simply look at Kraus' graph in Figure 14-2. A sinusoid with
current amplitude equal to 1.0 at the center and current
amplitude equal to zero at the end is obviously a cosine
wave. Since the magnitude varies from 1.0 at the center to
zero at the end, taking the arc-cosine of the magnitude
yields the distance from the center in degrees.

The key words are "infinitesimally thin," and "generally assumed."
With you, Cecil those words become just "thin," and "dead certain."
I'm glad you clarified that for us. I was beginning to wonder about
Kraus. Now I know it's just Kraus' message suffering from Cecil distortion.
73,
Tom Donaly, KA6RUH

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Cecil Moore wrote:
Gene Fuller wrote:

Cecil is so good at quoting that he should have no problem with
providing the exact unedited words from Kraus that support the
arc-cosine analysis.


"It is generally assumed that the current distribution of an
infinitesimally thin antenna is sinusoidal, ..."

Simply look at Kraus' graph in Figure 14-2. A sinusoid with
current amplitude equal to 1.0 at the center and current
amplitude equal to zero at the end is obviously a cosine
wave. Since the magnitude varies from 1.0 at the center to
zero at the end, taking the arc-cosine of the magnitude
yields the distance from the center in degrees.

Cecil,

Sorry, I missed the comments that Kraus made about the phase of a
standing wave. Is that the concept that is represented by the " ..." in
your quote above?

73,
Gene
W4SZ

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Tom Donaly wrote:
The key words are "infinitesimally thin," and "generally assumed."
With you, Cecil those words become just "thin," and "dead certain."

Kraus is using author-speak as most technical authors do to
avoid nit-picking from people like you. Balanis uses the words,
"very small" for the wire diameter.

I'm glad you clarified that for us. I was beginning to wonder about
Kraus. Now I know it's just Kraus' message suffering from Cecil distortion.

It is true for infinitesimally thin wire *AND* anything close
to that condition, i.e. also true for d lamda, according
to Balanis who says: "If the diameter of each wire is very
small (d lamda), the ideal standing wave pattern of the
current along the arms of the dipole is sinusoidal with a null
at the end."

The diameter of #18 wire is certainly very small compared to
a wavelength at 80m (0.003' 246') ensuring that the standing
wave current distribution on the real world dipole is sinusoidal
within a certain degree of real world accuracy.

If you want to see the sinusoidal current waveform for yourself,
observe the current distribution reported by EZNEC for a G5RV
used on 20m. Anyone with EZNEC, presumably including W7EL,
can observe that sinusoidal standing wave current pattern.
--
73, Cecil http://www.qsl.net/w5dxp

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Gene Fuller wrote:
Sorry, I missed the comments that Kraus made about the phase of a
standing wave.

Quoting: "Figure 14-2 Relative current amplitude AND
PHASE along a center-fed 1/2WL cylindrical antenna."
Emphasis mine so you can't miss it this time.

I thought you were knowledgable enough to convert
Kraus's independent variable of wavelength to degrees in
his graph on page 464 of the 3rd edition of "Antennas For
All Applications". Allow me to assist you in that task.

The 'X' axis is "Distance from center of antenna in WL"

X in X in
wavelength degrees
0.00 0
0.05 18
0.10 36
0.15 54
0.20 72
0.25 90

Hope that helps you to understand Kraus's graph better.
Using the degree column, the standing wave current,
Itot, on that graph equals cos(X). The standing wave
current also equals Ifor*cos(-X) + Iref*cos(X) where
'X' is the phase angle of the forward traveling current
wave and the rearward traveling current wave. A phasor
diagram at 0.02WL = 72 degrees would look something
like this:

/ Iref
/
/
+----- Itot = Ifor*cos(-X) + Iref*cos(X)
\
\
\ Ifor

Incidentally, from the above phasor diagram, it is easy
to see why the phase angle of the standing wave current
is always zero (or 180 deg) since Ifor and Iref are
rotating in opposite directions at the same phase
velocity.
--
73, Cecil http://www.qsl.net/w5dxp

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On Tue, 16 May 2006 05:54:59 GMT, Cecil Moore
wrote:

Roy Lewallen wrote:
It looks like Cecil is trying to use "phase" as a function of position,

Referenced to the source current, the phase of the forward traveling
wave current *IS* directly proportional to position along the dipole.
Any competent engineer knows that. So is the phase of the rearward
traveling wave current. That is obvious from the equations for those
two currents. Those are simply facts of physics that you probably
should try to comprehend instead of dismissing them.

Inet = Io*cos(X)*cos(wt) = Ifor*cos(-X+wt) + Iref*cos(X-wt)

Inet is the standing wave current. X is the distance in degrees from
the feedpoint. If the source current is 1.0 amps at 0 degrees, e.g.
from EZNEC, at t=0 Inet = Io*cos(X) = Ifor*cos(-X) + Iref*cos(X)

As I pointed out some time ago, the envelope of a standing wave isn't in
general sinusoidally shaped.

Balanis says: "If the diameter of each wire is very small (d lamda)
the ideal standing wave pattern of the current along the arms of
the dipole is sinusoidal with a null at the end."

Kraus says: "It is generally assumed that the current distribution
of an infinitesimally thin antenna is sinusoidal,..."

d lamda for an 80m dipole made out of #18 wire. I'm sorry to hear
that you disagree with both Balanis and Kraus.

Could you explain how to build one of those antennas that has infinite
impedance at its ends?

73
Gary K4FMX

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Cecil Moore wrote:
Tom Donaly wrote:

The key words are "infinitesimally thin," and "generally assumed."
With you, Cecil those words become just "thin," and "dead certain."


Kraus is using author-speak as most technical authors do to
avoid nit-picking from people like you. Balanis uses the words,
"very small" for the wire diameter.

I'm glad you clarified that for us. I was beginning to wonder about
Kraus. Now I know it's just Kraus' message suffering from Cecil
distortion.


It is true for infinitesimally thin wire *AND* anything close
to that condition, i.e. also true for d lamda, according
to Balanis who says: "If the diameter of each wire is very
small (d lamda), the ideal standing wave pattern of the
current along the arms of the dipole is sinusoidal with a null
at the end."

The diameter of #18 wire is certainly very small compared to
a wavelength at 80m (0.003' 246') ensuring that the standing
wave current distribution on the real world dipole is sinusoidal
within a certain degree of real world accuracy.

If you want to see the sinusoidal current waveform for yourself,
observe the current distribution reported by EZNEC for a G5RV
used on 20m. Anyone with EZNEC, presumably including W7EL,
can observe that sinusoidal standing wave current pattern.

Give it up, Cecil. You don't even have a coherent notion of the
meaning of the term "phase." Selectively quoting, and re-interpreting
Bibles in order to make it seem as if the Gods agree with you won't cut
it, either. All the simple-minded rural sophistry in the world won't
make you right, or the rest of us wrong.

73,
Tom Donaly, KA6RUH

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Gary Schafer wrote:
Could you explain how to build one of those antennas that has infinite
impedance at its ends?

An open circuit is close enough to infinite to satisfy
almost anyone. In virtually every technical textbook,
ideal conditions are assumed until one understands the
concepts involved. Then the real world conditions are
introduced. That's all I am doing - presenting the
concepts involved in an ideal dipole as described by
Kraus and Balanis. Do secondary real world conditions
exist in reality. Of course they do and nobody is
saying that they don't. The difference between infinity
and ten megohms is often negligible for analysis purposes.
--
73, Cecil http://www.qsl.net/w5dxp

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Tom Donaly wrote:
Give it up, Cecil. You don't even have a coherent notion of the
meaning of the term "phase." Selectively quoting, and re-interpreting
Bibles in order to make it seem as if the Gods agree with you won't cut
it, either. All the simple-minded rural sophistry in the world won't
make you right, or the rest of us wrong.

When you lose the technical argument, Tom, you always respond
with ad hominem attacks devoid of any technical content.

Fact is, the phase of the forward traveling current referenced
to the source current is equal to the distance from the source
expressed in degrees. The laws of physics will not stand for
anything else. That same number of degrees *IS* the phase
angle of the traveling wave(s). Every competent engineer knows
that as it is obvious from the equations in any good textbook.
--
73, Cecil http://www.qsl.net/w5dxp