On 19 May 2006 03:26:29 -0700, wrote:

I do not agree with you on antenna linearity, but that is another
subject for another rainy weekend, and I'm not the right person to be
discussing that anyway.

Hi Glenn,

By this very post you are discussing it.

Who, in your estimation, does qualify to discuss it? Despite all
outward appearances (and certainly the troll inspired name of the
topic), this is NOT about one-upmanship competition.

73's
Richard Clark, KB7QHC

Richard,

Who, in your estimation, does qualify to discuss it?

I would like to hear from someone who has actually measured the
linearity of a simple antenna. I have not done this, so would only be
one guy with an opinion. Plenty of us around.

By 'simple antenna' I mean an antenna such as a wire dipole without
traps, baluns or other things that could degrade linearity. Since the
linearity of antenna systems in general is in question, the simplest
setup that answers the question would be best.

In the absence of measurement, can anyone comment on the modelling
software? Does it assume and model a linear system? If so, do we know
of any substantial nonlinear departures from the modelling software?

Anyone?

73,
Glenn AC7ZN

wrote:
By 'simple antenna' I mean an antenna such as a wire dipole without
traps, baluns or other things that could degrade linearity.

Seems the easiest measurement of nonlinearity would be the
harmonics (if any) generated by the antenna that do not
appear in the source signal.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

wrote:

By 'simple antenna' I mean an antenna such as a wire dipole without
traps, baluns or other things that could degrade linearity.


Seems the easiest measurement of nonlinearity would be the
harmonics (if any) generated by the antenna that do not
appear in the source signal.

Which wouldn't tell you a single thing about the current
distribution along the length of the dipole.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:

Cecil Moore wrote:
Seems the easiest measurement of nonlinearity would be the
harmonics (if any) generated by the antenna that do not
appear in the source signal.

Which wouldn't tell you a single thing about the current
distribution along the length of the dipole.

Yes it would. It would be proof that the current distribution
along the length of the dipole is sinusoidal no matter what
your illusionary perceptions are telling you.

For standing wave antennas, if the source is a pure single
frequency sine wave and if no harmonics are generated
by the antenna system:

1. The forward wave is sinusoidal.

2. The reflected wave is sinusoidal and coherent with the
forward wave.

3. Their superposition results in a sinusoidal standing wave
with the same angular velocity.

Any non-linearity would introduce harmonics.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Tom Donaly wrote:

Cecil Moore wrote:

Seems the easiest measurement of nonlinearity would be the
harmonics (if any) generated by the antenna that do not
appear in the source signal.


Which wouldn't tell you a single thing about the current
distribution along the length of the dipole.


Yes it would. It would be proof that the current distribution
along the length of the dipole is sinusoidal no matter what
your illusionary perceptions are telling you.

For standing wave antennas, if the source is a pure single
frequency sine wave and if no harmonics are generated
by the antenna system:

1. The forward wave is sinusoidal.

2. The reflected wave is sinusoidal and coherent with the
forward wave.

3. Their superposition results in a sinusoidal standing wave
with the same angular velocity.

Any non-linearity would introduce harmonics.

The purpose of most antennas is to radiate electromagnetic waves.
That means there is loss. It also means that the current envelope is
affected. That's one of the reasons we use EZNEC. I suppose, Cecil,
that if you keep repeating the same old tired line, over and over
again, you might find someone who will agree with you. Certainly,
no antenna measurement would.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
The purpose of most antennas is to radiate electromagnetic waves.
That means there is loss. It also means that the current envelope is
affected. That's one of the reasons we use EZNEC.

The current envelope is affected but remains a linear
system function since it is the result of superposition
which itself is a linear system function.

I suppose, Cecil,
that if you keep repeating the same old tired line, over and over
again, you might find someone who will agree with you. Certainly,
no antenna measurement would.

The current envelope is a linear system function. I am
repeating the rules and laws of mathematics. Sounds
like you need to review the definition of linear systems.
You can do that at:

http://www.cns.nyu.edu/~david/linear...r-systems.html

In particular, quoting: "Systems that satisfy both homogeneity
and additivity are considered to be linear systems. These two rules,
taken together, are often referred to as the principle of superposition."

In general, antennas are linear systems that satisfy the principle
of superposition. If they were non-linear, they would not satisfy
the principle of superposition. Two linear system functions, like
forward waves and reflected waves, cannot superpose to a non-linear
function. Therefore, standing waves are linear, not non-linear,
functions. To argue otherwise exhibits a certain degree of ignorance.

Until the obvious mathematical misconception is corrected, no
rational discussion is possible. To the best of my knowledge,
Maxwell's equations are also linear system functions so claims
of non-linearity also contradict Maxwell's equations.
--
73, Cecil http://www.qsl.net/w5dxp

I suppose, Cecil,
that if you keep repeating the same old tired line, over and over
again, you might find someone who will agree with you.
=========================================

I agreed with Cecil the first time he said it.
But I'm only a foreigner.
So whatever I say doesn't carry any weight.
Or does it?
----
Reg.

On 19 May 2006 10:14:30 -0700, wrote:
I would like to hear from someone who has actually measured the
linearity of a simple antenna. I have not done this, so would only be
one guy with an opinion. Plenty of us around.

Hi Glenn,

Then you have a point in that regard. Bench work is rarely offered
here and when it is, we are lucky if it is accompanied with the
particulars of measurement so that it could be assessed or
re-performed. It took very many years between cfa antenna claims, and
legitimate field work by cfa proponents to show that their claims were
unsupported.

By 'simple antenna' I mean an antenna such as a wire dipole without
traps, baluns or other things that could degrade linearity. Since the
linearity of antenna systems in general is in question, the simplest
setup that answers the question would be best.

Well, a BalUn is one of those elements that would be welcome so as to
enforce the simplicity you demand, and so as to not disturb what is
being measured. The BalUn (more properly, a choke) for this purpose
would be for isolating the antenna from the transmission line.

In the absence of measurement, can anyone comment on the modelling
software? Does it assume and model a linear system? If so, do we know
of any substantial nonlinear departures from the modelling software?

The modelers using NEC generally obtain results that conform to
observable phenomenon. The modelers are supposed to be neutral
observers. In other words, the non-linearity shown by the lack of
congruence to the Cosine curve is not a presumption of non-linearity
by the modeler; it is merely reporting an analysis. It may be noted
that this analysis has been supported by a combination of bench work
and theory.

All of this is the long way of saying non-linearity has been
demonstrated, that is has been measured, and that it has been long
explained. There are no surprises here.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
In other words, the non-linearity shown by the lack of
congruence to the Cosine curve is not a presumption of non-linearity
by the modeler; it is merely reporting an analysis.

You are being fooled by an illusion. Any deviation from
single frequency sinusoidal signals would generate harmonics
which we know doesn't happen. Your "non-linearity" is not
really there. For instance, a decrease in VF may compress
the waveform but that is not non-linearity.
--
73, Cecil http://www.qsl.net/w5dxp