FIGHT! FIGHT! FIGHT!
 

I would amend Cecil's statement to:
'We hope antennas are linear systems.'

A nonlinear antenna is a terrible beast indeed. It will mix every
signal it receives with every other signal, creating a nasty mush of
signals. On transmit it is not so bad, maybe generating harmonics and
a wider signal than we'd like.

We've all heard stories of a poor antenna connection causing problems,
or a nearby raingutter joint causing TV inteference. These are
nonlinear antennas.

73,
Glenn AC7ZN

FIGHT! FIGHT! FIGHT!
 

On 18 May 2006 08:42:06 -0700, wrote:

I would amend Cecil's statement to:
'We hope antennas are linear systems.'

A nonlinear antenna is a terrible beast indeed. It will mix every
signal it receives with every other signal, creating a nasty mush of
signals. On transmit it is not so bad, maybe generating harmonics and
a wider signal than we'd like.

We've all heard stories of a poor antenna connection causing problems,
or a nearby raingutter joint causing TV inteference. These are
nonlinear antennas.

Hi Glenn,

Cecil is being deliberately obtuse to the matter of linearity. In the
game of describing an antenna as a transmission line, the
non-linearity is compellingly obvious.

If you start with standard twin line, its characteristic Z is
dominated by geometry and a ratio of wire diameter to wire separation.
Pull that twin line apart to construct a V or a dipole, and the
geometry necessarily forces a non-linearity into the picture.

Reggie also has considerable difficulty with this concept too as he
prefers to switch to earth as the main arbiter of transmission line
dynamics. Both seem to abandon the generator's view of a 50 to 70 Ohm
load to replace it with their 600 Ohm concepts so as to artificially
impose their need to see a linear load.

These 600 Ohm concepts are achieved only if the operator strains to
fail most spectacularly. Few debates are won this way, but arguments
successfully persist for hundreds of postings. Even then, these
concepts do not answer the initial non-linearity that inhabits the
system. Both the 50 to 70 to 600 Ohm prognostications are artifacts
of a measurement at the terminal of the non-linear device.

The proof lies along the line, and this returns us to the underlying
concept and argument about the distribution of current along the
length of the quarter wave dipole's arms. This is stated in terms of
the Cosine function. However, as with a deliberate failure forcing an
erroneous general solution, the Cosine distribution is only found in
the extreme (or the fevered dream). A 1mm wire strung 36 meters in
outer space is certainly thin by engineering conventions, but it
doesn't qualify as the current distribution misses the mark of
Cosinality by 5 or 6% (the distribution of a poor fit demonstrates the
non-linearity).

Given Cecil's penchant for abstracting considerable error to general
proofs of his crystalline logic, this may not seem much. However, the
precision above is not outside of achievement, and it does demonstrate
with simplicity that linearity does not reside in the
transmission-line-as-antenna. Pulling this antenna down to earth to
allow the boys their investment in the 600 Ohm concepts does nothing
to recover linearity - if anything, it worsens it (albeit, by very
slim margins). Clearly, the dominant factor in the linearity of the
dipole's characteristic Z is with its own wire. This has been long
reported in the literature (Schelkunoff).

Further, to anticipate this does not demonstrate any spurious
emissions - this is only due to your (not yours, Glenn, your in the
sense of the general reader, and our boys with their loss of
investment) inability to resolve them.

This class of non-linearity falls under the heading of "scattering"
and in these most mundane of applications would barely present
spurious products higher than 70dB below excitation, and only several
parts-per-million from the center frequency (called Stokes shift).
When Cecil comes to the table armed with slop on the order of ±59%
allowable error, such products are swamped in stupidity.

73's
Richard Clark, KB7QHC

FIGHT! FIGHT! FIGHT!
 

"Richard Clark" wrote:
In the
game of describing an antenna as a transmission line, the
non-linearity is compellingly obvious.

A non-linear system would generate harmonics so where are
those harmonics?

A 1mm wire strung 36 meters in
outer space is certainly thin by engineering conventions, but it
doesn't qualify as the current distribution misses the mark of
Cosinality by 5 or 6% (the distribution of a poor fit demonstrates the
non-linearity).

Nobody said it was a perfectly ideal cosine curve. You seem to have
a strange definition of non-linearity as anything that differs from the
ideal. By that definition, everything is non-linear (including your
definition).
The definition of non-linearity being used here is "discontinuous".
Exactly where does the current in an antenna become discontinuous?

Heaven forbid the cosine curve exhibit the same accuracy as a resistor.
Would you also assert that a 52 ohm resistor that is marked 50 ohms is
exhibiting non-linearity?
--
73, Cecil, W5DXP

FIGHT! FIGHT! FIGHT!
 

"Cecil Moore" wrote:
The definition of non-linearity being used here is "discontinuous".
Exactly where does the current in an antenna become discontinuous?

For readers who don't understanding the meaning of "linear systems",
here is a tutorial:

http://doctord.dyndns.org:8000/cours...ar_Systems.htm
--
73, Cecil, W5DXP

FIGHT! FIGHT! FIGHT!
 

On Thu, 18 May 2006 20:04:12 GMT, "Cecil Moore"
wrote:
A non-linear system would generate harmonics so where are
those harmonics?

There's no need to repeat one post removed coverage so early.

FIGHT! FIGHT! FIGHT!
 

Richard,

Wow. You spent a lot of time on this. Thanks.

Let's abandon antennas and postulate a twin-lead vacuum-dielectric 100
ohm transmission line that is ideal in the respects we consider
important (except loss). There may be (resistive) loss, but no
coupling to outside sources or objects, no hysteresis, no
electromagnetic radiation. The characteristic impedance is exactly 100
ohms real over our frequency of interest. The velocity factor, for
convenience, is 0.5.

We feed it on one end with a sinewave generator whose impedance is
matched to the line. On the other end we terminate the line with a
floating load of arbitrary impedance. The only requirement of the load
is that it be perfectly linear and can be described completely as a
real and imaginary impedance at any given frequency of interest.

Would you consider this system linear? We are not talking antennas
now...nothing is radiating.

I'm not sure I'm going to go anywhere with this, and I'm not setting a
trap. I'm just curious what conditions would have to be set before you
would consider a transmission line system linear (you are welcome to
add any conditions I might have forgotten). By the way, if you want to
discuss any really subtle effects such a Stokes shifting, I define
linearity as obeying the law of superposition within a reasonable
dynamic range, say 140 dB, which is about 20 dB better than the input
dynamic range of our best HF receivers.

I understand you are in an argumentative mood with others in the group,
but I am taking no sides (I do happen to like Cecil's motorbike...) and
will try to keep things civil. If I go anywhere with this, I hope to
explain it clearly enough and with enough supporting material that
there will be no arguments. I am not a guru so don't expect anyone to
believe anything on my word alone.

So what say you Richard? Do we have linearity?

73,
Glenn AC7ZN

FIGHT! FIGHT! FIGHT!
 

On 18 May 2006 13:52:52 -0700, wrote:

Wow. You spent a lot of time on this. Thanks.

Hi Glenn,

Most of this time has long preceded these posts (by as many years as
Reggie has been posting here).

Would you consider this system linear?

Yes.

I'm not sure I'm going to go anywhere with this, and I'm not setting a
trap. I'm just curious what conditions would have to be set before you
would consider a transmission line system linear (you are welcome to
add any conditions I might have forgotten).

I see no reason to constrain an open-ended topic; your definition is
fairly self referential after all:
I define X as a linear system;
Is X linear?

What correspondence that follows may upset the apple-cart, but aside
from the velocity factor gaff (which bears no relation, yet, on
linearity), I have no dispute.

What could upset the apple cart? Power.

Power has the capacity to distort systems and introduce
non-linearities even in your simple example. If I were to expand upon
what you call the subtle effects (they were in my earlier discussion);
this would give rise to back-scattering which could power limit the
line (in other words, it could never deliver more than a baseline
value). The onset of this condition is, again, nothing anyone here
has ever experienced, and to even approach this limit in the lines you
have constructed would tax most sources.

Such topics that may appear to be new here, have been exhibited in
fiber optic transmission lines for quite a while now.

73's
Richard Clark, KB7QHC

FIGHT! FIGHT! FIGHT!
 

Glenn, can you understand whatever it is poor, demented Richard is
waffling about?

FIGHT! FIGHT! FIGHT!
 

Richard Clark wrote:

On 18 May 2006 08:42:06 -0700, wrote:


I would amend Cecil's statement to:
'We hope antennas are linear systems.'

A nonlinear antenna is a terrible beast indeed. It will mix every
signal it receives with every other signal, creating a nasty mush of
signals. On transmit it is not so bad, maybe generating harmonics and
a wider signal than we'd like.

We've all heard stories of a poor antenna connection causing problems,
or a nearby raingutter joint causing TV inteference. These are
nonlinear antennas.


Hi Glenn,

Cecil is being deliberately obtuse to the matter of linearity. In the
game of describing an antenna as a transmission line, the
non-linearity is compellingly obvious.

If you start with standard twin line, its characteristic Z is
dominated by geometry and a ratio of wire diameter to wire separation.
Pull that twin line apart to construct a V or a dipole, and the
geometry necessarily forces a non-linearity into the picture.

Reggie also has considerable difficulty with this concept too as he
prefers to switch to earth as the main arbiter of transmission line
dynamics. Both seem to abandon the generator's view of a 50 to 70 Ohm
load to replace it with their 600 Ohm concepts so as to artificially
impose their need to see a linear load.

These 600 Ohm concepts are achieved only if the operator strains to
fail most spectacularly. Few debates are won this way, but arguments
successfully persist for hundreds of postings. Even then, these
concepts do not answer the initial non-linearity that inhabits the
system. Both the 50 to 70 to 600 Ohm prognostications are artifacts
of a measurement at the terminal of the non-linear device.

The proof lies along the line, and this returns us to the underlying
concept and argument about the distribution of current along the
length of the quarter wave dipole's arms. This is stated in terms of
the Cosine function. However, as with a deliberate failure forcing an
erroneous general solution, the Cosine distribution is only found in
the extreme (or the fevered dream). A 1mm wire strung 36 meters in
outer space is certainly thin by engineering conventions, but it
doesn't qualify as the current distribution misses the mark of
Cosinality by 5 or 6% (the distribution of a poor fit demonstrates the
non-linearity).

Given Cecil's penchant for abstracting considerable error to general
proofs of his crystalline logic, this may not seem much. However, the
precision above is not outside of achievement, and it does demonstrate
with simplicity that linearity does not reside in the
transmission-line-as-antenna. Pulling this antenna down to earth to
allow the boys their investment in the 600 Ohm concepts does nothing
to recover linearity - if anything, it worsens it (albeit, by very
slim margins). Clearly, the dominant factor in the linearity of the
dipole's characteristic Z is with its own wire. This has been long
reported in the literature (Schelkunoff).

Further, to anticipate this does not demonstrate any spurious
emissions - this is only due to your (not yours, Glenn, your in the
sense of the general reader, and our boys with their loss of
investment) inability to resolve them.

This class of non-linearity falls under the heading of "scattering"
and in these most mundane of applications would barely present
spurious products higher than 70dB below excitation, and only several
parts-per-million from the center frequency (called Stokes shift).
When Cecil comes to the table armed with slop on the order of ±59%
allowable error, such products are swamped in stupidity.

73's
Richard Clark, KB7QHC

Thanks a lot for this one, Richard.

And of course, Cecil has already ignored the important bits and state4d
that 6% is no big deal. Typical.

As I said earlier, the responses to Cecil are where the gold resides.

I had not heard of the Stokes shift, nor the scattering you mentioned.
I have some looking up and reading to do. Which, of course, Cecil does
not, since it's not a Xerox moment.

tom
K0TAR

FIGHT! FIGHT! FIGHT!
 

On Thu, 18 May 2006 19:01:58 -0500, Tom Ring
wrote:

I had not heard of the Stokes shift, nor the scattering you mentioned.
I have some looking up and reading to do. Which, of course, Cecil does
not, since it's not a Xerox moment.

Hi Tom,

It is pretty exotic, it only relates to radiation, reflection,
refraction, heat, and conduction, topics that are alien to discussion
here in more than TV Guide English it appears. Other difficult
concepts include linearity, coherence, mixing, and gain.

Stokes shift is the change in frequency due to the non-linear response
of a media to excitation. Typically the excitation is a photon
interacting with a phonon with radiation scattering following.
Injecting an electron (current) can achieve the same end. The effect
of power clamping in fiber optic transmission lines is due to SBS
(Stimulated Brillouin Scattering) threshold. I've been working with
this (Stokes and Anti-Stokes Shift) for some 20 years, and it fails
easy access through a copier.

The mention came only response to questions of linear response to what
at first glance would be a rather pedestrian transmission line
definition, but Glenn appears to have followed the clown instead of
pursuing his own question - he warned me it may have been pointless.

SBS and SRS (Stimulated Raman Scattering) would be suitable search
engine terms (esp. SBS threshold), but I warn you, they lead to
remarkably dense work where only one link in 20 will be accessible.

73's
Richard Clark, KB7QHC

FIGHT! FIGHT! FIGHT!
 

Richard,

Since we agree the transmission line setup is substantially linear, I'm
not sure we have much to discuss.

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.

73,
Glenn

FIGHT! FIGHT! FIGHT!
 

Hi. How's about you guys going to Dayton.
I'm sure a Tag Fight could be arranged for you all.
Two Pin Falls, Two Submissions,or a KO to decide the winner.

Maybe if you all meet face to face, you will come to some common agreement,
or this thread wii continue ad nausium.

Regards Mike.

FIGHT! FIGHT! FIGHT!
 

Richard Clark wrote:

snip

SBS and SRS (Stimulated Raman Scattering) would be suitable search
engine terms (esp. SBS threshold), but I warn you, they lead to
remarkably dense work where only one link in 20 will be accessible.

73's
Richard Clark, KB7QHC

Thanks.

tom
K0TAR

FIGHT! FIGHT! FIGHT!
 

Richard Clark wrote:
Injecting an electron (current) can achieve the same end.

How accurate are your electron position and velocity
measurements?
--
73, Cecil http://www.qsl.net/w5dxp

FIGHT! FIGHT! FIGHT!
 

Richard Clark wrote:
On Thu, 18 May 2006 19:01:58 -0500, Tom Ring
wrote:


I had not heard of the Stokes shift, nor the scattering you mentioned.
I have some looking up and reading to do. Which, of course, Cecil does
not, since it's not a Xerox moment.


Hi Tom,

It is pretty exotic, it only relates to radiation, reflection,
refraction, heat, and conduction, topics that are alien to discussion
here in more than TV Guide English it appears. Other difficult
concepts include linearity, coherence, mixing, and gain.

Stokes shift is the change in frequency due to the non-linear response
of a media to excitation. Typically the excitation is a photon
interacting with a phonon with radiation scattering following.
Injecting an electron (current) can achieve the same end. The effect
of power clamping in fiber optic transmission lines is due to SBS
(Stimulated Brillouin Scattering) threshold. I've been working with
this (Stokes and Anti-Stokes Shift) for some 20 years, and it fails
easy access through a copier.

The mention came only response to questions of linear response to what
at first glance would be a rather pedestrian transmission line
definition, but Glenn appears to have followed the clown instead of
pursuing his own question - he warned me it may have been pointless.

SBS and SRS (Stimulated Raman Scattering) would be suitable search
engine terms (esp. SBS threshold), but I warn you, they lead to
remarkably dense work where only one link in 20 will be accessible.

73's
Richard Clark, KB7QHC

Hi Richard,
Stokes' law and the Raman effect can be found in
physics texts dealing with quantum mechanics. Georg Joos, in
his book _Theoretical Physics_ deals with such things. The reading
is dense but the underlying concepts aren't too difficult. The
difficulty might lie in understanding how they apply to this
discussion.
73,
Tom Donaly, KA6RUH

FIGHT! FIGHT! FIGHT!
 

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

FIGHT! FIGHT! FIGHT!
 

On Fri, 19 May 2006 15:08:11 GMT, "Tom Donaly"
wrote:

Stokes' law and the Raman effect can be found in
physics texts dealing with quantum mechanics. Georg Joos, in
his book _Theoretical Physics_ deals with such things. The reading
is dense but the underlying concepts aren't too difficult. The
difficulty might lie in understanding how they apply to this
discussion.

Hi Tom,

Certainly Joos would give some entry into the field, but finding work
as accessible outside of a bookstore or library (in other words,
through a search engine) makes for drinking out of a fire hose to
quench a sip's worth of thirst.

Insofar as HOW this applies, I've spoken to that and Tom shows
interest. That alone goes beyond the typical churning that passes for
discussion. The point is that these underlying concepts are fairly
simple as you imply and they are certainly not remote from the usual
topics of consideration here. What they lack is specifics that relate
to our common applications, and there too I've offered discussion.
However, few seem inspired to travel those paths and that fault can
hardly be laid at my doorstep.

73's
Richard Clark, KB7QHC

FIGHT! FIGHT! FIGHT!
 

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

FIGHT! FIGHT! FIGHT!
 

Richard Clark, KB7QHC wrote:
"Who. in your estimation, does qualify to discuss it?"

If it`s about antennas, I nominate Kraus. If it`s about mathematics,
many marhematicians qualify.

In algebra, y = mx + b, (the point slope formula), is called linear
because it is the graph of a straight line.

In the discussion of transmission lines and antennas, you must admit
that a uniform transmission line enforces a unique characteristic
impedance (a resistance) on energy traveling in either direction. A
resistance is linear because Ohm`s law prevails. In free-space, everyone
agrees the characteristic impedance is about 377 ohms (a resistance).

Kraus says on page 2 of his 1950 edition of "Antennas":
"Let the transmission line now be connected to a dipole antenna as in
Fig.1-2. The dipole acts as an antenna because it launches a free-space
wave. However, it may also be regarded as a section of transmission line
(see Sec. 1-2). In addition, it exhibits many of the characteristics of
a resonator, since energy reflected from the ends of the dipole gives
rise to a standing wave on the antenna. Thus a single device, in this
case the dipole, exhibits simutaneously properties characteristic of an
antenna, transmission line, and a resonator.

Best regards, Richard Harrison, KB5WZI

FIGHT! FIGHT! FIGHT!
 

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

FIGHT! FIGHT! FIGHT!
 

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

FIGHT! FIGHT! FIGHT!
 

"Richard Clark" wrote in message
...
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

don't you call me a troll... i just set the stage with an aptly named thread
to get things started for my own amusement... wait a minute, maybe that
does make me a troll! but at least i was open about my motives, and boy am
i enjoying it.... especially since its still raining! maybe you guys can
keep going through this weekend???

FIGHT! FIGHT! FIGHT!
 

FIGHT! FIGHT! FIGHT!
 

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

FIGHT! FIGHT! FIGHT!
 

Richard Clark wrote:

On Fri, 19 May 2006 15:08:11 GMT, "Tom Donaly"
wrote:


Stokes' law and the Raman effect can be found in
physics texts dealing with quantum mechanics. Georg Joos, in
his book _Theoretical Physics_ deals with such things. The reading
is dense but the underlying concepts aren't too difficult. The
difficulty might lie in understanding how they apply to this
discussion.


Hi Tom,

Certainly Joos would give some entry into the field, but finding work
as accessible outside of a bookstore or library (in other words,
through a search engine) makes for drinking out of a fire hose to
quench a sip's worth of thirst.

Insofar as HOW this applies, I've spoken to that and Tom shows
interest. That alone goes beyond the typical churning that passes for
discussion. The point is that these underlying concepts are fairly
simple as you imply and they are certainly not remote from the usual
topics of consideration here. What they lack is specifics that relate
to our common applications, and there too I've offered discussion.
However, few seem inspired to travel those paths and that fault can
hardly be laid at my doorstep.

73's
Richard Clark, KB7QHC

Hi Richard,
I didn't intend any criticism. People like Cecil, with
home-grown theories, don't ever seem to want things considered in
depth. That's understandable from a psychological standpoint, but
it isn't any help to the rest of us when some of the things the theory
ignores become significant. In the case of antennas, practically
everything is significant.
73,
Tom Donaly, KA6RUH

FIGHT! FIGHT! FIGHT!
 

Reg,

Thank heavens there is someone here who knows the Queen's English.

Glenn

========================================
The trouble with Richard is that he wraps everything up in
Shakespearian prose, verse and poetry. The sonnets. Queen Elizabeth
the First's language.
----
Reg.

FIGHT! FIGHT! FIGHT!
 

On Fri, 19 May 2006 19:01:23 GMT, "Tom Donaly"
wrote:

In the case of antennas, practically everything is significant.

Les Mots Juste ;-)

FIGHT! FIGHT! FIGHT!
 

Richard Clark wrote:

On Fri, 19 May 2006 15:08:11 GMT, "Tom Donaly"
wrote:


Stokes' law and the Raman effect can be found in
physics texts dealing with quantum mechanics. Georg Joos, in
his book _Theoretical Physics_ deals with such things. The reading
is dense but the underlying concepts aren't too difficult. The
difficulty might lie in understanding how they apply to this
discussion.


Hi Tom,

Certainly Joos would give some entry into the field, but finding work
as accessible outside of a bookstore or library (in other words,
through a search engine) makes for drinking out of a fire hose to
quench a sip's worth of thirst.

Insofar as HOW this applies, I've spoken to that and Tom shows
interest. That alone goes beyond the typical churning that passes for
discussion. The point is that these underlying concepts are fairly
simple as you imply and they are certainly not remote from the usual
topics of consideration here. What they lack is specifics that relate
to our common applications, and there too I've offered discussion.
However, few seem inspired to travel those paths and that fault can
hardly be laid at my doorstep.

73's
Richard Clark, KB7QHC

And a web search produced a couple very good links out of the first 20.
One was a great discussion of problems in long optical fibers, and
some relatively simple ways to work around some of them, or at least to
mitigate them.

tom
K0TAR

FIGHT! FIGHT! FIGHT!
 

On Fri, 19 May 2006 14:24:07 -0500, Tom Ring
wrote:
And a web search produced a couple very good links out of the first 20.
One was a great discussion of problems in long optical fibers, and
some relatively simple ways to work around some of them, or at least to
mitigate them.

Hi Tom,

In my early days in this game (late 80s), I sought to turn lemons into
quantum-aide. That is, I sought erbium doped fiber optics to amplify
nanowatt fluorescence signals with 10 to 50 µS decay times. Not one
of those off-the-shelf commodities, however; so I had to amplify in
the conventional way with an PMT.

For those interested, long haul communications fiber optics
(transoceanic grade) met with the same requirements for amplifiers
placed along the length to maintain S+N/N. Erbium doped fibers were
projected as a solution. You could pulse UV into the fiber to charge
it, and a IR data pulse would be amplified, continuously along its
length. The IR data pulse would be boosted by the previous charge of
energy. This is an example of forward Raman scattering and is called
Raman Amplification (which at the time would have been about 30dB and
10% efficient).

73's
Richard Clark, KB7QHC

FIGHT! FIGHT! FIGHT!
 

Tom Donaly, KA6RUH wrote:
"Actually, it`s supposed to be impossible to represent the current
distribution along a dipole using simple mathematical formulas because
integral equations have to be solved that are impervious to any solution
other than numerical approximation."

How many places do you attach to pi?

First, what is linearity? It is the absence of nonlinearity.

Millman and Seely wrote on page 525 of the 1951 edition of "Electronics"
(one of my old textbooks):
"Because of this nonlinear characteristic of the dynamic curve over the
operating range, the wave form of the output wave differs slightly from
that of the grid-exciting-voltage waveshape. Distortion of this type is
called "nonlinear" or "amplitude" distortion.."

All of the antennas I`ve worked with had no noticeable amplitude
distortion. They caused no harmonics or mixing products.

On page 235 of Kraus` 1950 edition of "Antennas" he sets out to solve
Hallen`s equation for current distribution. On page 239, Kraus writes:
"It is generally assumed that the current distribution of an
infinitesimally thin antenna is sinusoidal, and that the phase is
constant over a 1/2-wavelength interval, changing abruptly by
180-degrees between intervals."

You can take what Kraus says to the bank.

Best regards, Richard Harrison, KB5WZI

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On Fri, 19 May 2006 16:01:53 -0500, (Richard
Harrison) wrote:

"Because of this nonlinear characteristic of the dynamic curve over the
operating range, the wave form of the output wave differs slightly from
that of the grid-exciting-voltage waveshape. Distortion of this type is
called "nonlinear" or "amplitude" distortion.."

Hi Richard,

This harkens back to your observation about how many places in Pi.

How much distortion has to exist before you hear it? As this directly
relates to your quoted selection, are we to believe that distortion
does not exist if you cannot perceive it?

This gives a great range of flexibility to the word linear through the
careful selection for tone-deaf judges.

Back in the late 40s, Bell labs experimented with human subjects'
ability to discern distortion. Turns out that they could take quite a
bit (10 to 15%) before they could faithfully call it noticeable. So,
by these stricter standards (Cecil would allow 59% before ringing the
alarm) no distortion exists below 10%.

All of the antennas I`ve worked with had no noticeable amplitude
distortion. They caused no harmonics or mixing products.

No noticeable "amplitude" distortion? In a world of possible
distortions, does linearity boil down to just one metric? Are you
asking us to believe you anticipated any antenna would be non-linear
and purposely tested them all? Nah, this is wholly unreasonable.

Richard, I frankly doubt you looked for spurs that would have been
70dB down in the worst of circumstances. More overwhelming would be
corroded joints swamping that pursuit.

On page 235 of Kraus` 1950 edition of "Antennas" he sets out to solve
Hallen`s equation for current distribution. On page 239, Kraus writes:
"It is generally assumed that the current distribution of an
infinitesimally thin antenna is sinusoidal, and that the phase is
constant over a 1/2-wavelength interval, changing abruptly by
180-degrees between intervals."

You can take what Kraus says to the bank.

So is Kraus bankrupt by contrary evidence that presumes he meant his
quote to be taken strictly? Even Kraus hedges with "assumed" and he
does not otherwise force the conclusion, does he? Why indeed would he
for such a trivial topic is the more astute observation.

This entire line of argument (distortion) is wholly specious. This
violates most analysis by demanding that a wavelength sizeable element
conform to lumped expectations. The non-linearity is found along the
entire length of the element, not at a point. The characteristic Z
varies by simple geometrical observation - it doesn't take quantum
mechanics to arrive at this obvious conclusion. The ONLY linear
quarterwave antenna is a biconical dipole - that has been established
since the 40s. Even the Cosine distribution is blatant evidence of
non-linearity (try listening to Mozart with an amp that has a cosine
gain curve). An antenna has to be huge (wavelengths) and close (far
less than a wavelength) to the earth before any linearity begins to
arise - this too is historic.

73's
Richard Clark, KB7QHC

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Richard,

Maybe someone can help us here. Linearity is well-defined in
electronics by the law of superposition, and is characterized by
well-known measurements such as harmonic generation, compression point,
and third-order intercept point. I'm assuming antennas must follow the
same law of superposition while transmitting and receiving to be
linear.

It is not clear to me that a nonlinear or even unpredictable current
distribution along a wire antenna produces signals that violate the law
of superposition. Under a strange current distribution the antenna
radiation pattern will certainly distort, but how does that violate the
law of superposition? That is, how can a strong received signal
influence a weak one on an antenna with nonlinear current distribution?

Maybe, like so many other threads in this group, we are discussing
orthogonal concepts.

73,
Glenn AC7ZN

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In article .com,
wrote:

Maybe, like so many other threads in this group, we are discussing
orthogonal concepts.

I believe you're correct.

As I see it, in the *general* sense, linearity refers to a
relationship between two variables, where the relationship is one of

OUT = IN * F + C

where F and C are constants (plus a dimensional factor in many cases).
In other words, it's a straight-line relationship (hence, the name)
between two variables of the same or different dimension.

The sort of "linearity" that people usually refer to in electronics,
involves voltages and currents (vs. one another). A theoretically
perfect resistor, capacitor, or inductor is linear, because (e.g.) the
peak current through it has a strictly linear relationship to the peak
voltage across it.

A semiconductor junction is described as nonlinear, because the
current through it is not related to the voltage across it in a
strictly linear relationship.

The sort of "linearity" which Cecil seems to be referring to (if I
understand what he's written correctly) involves a completely
different sort of relationship. It's not current-vs-voltage, or
voltage-vs-current - it's current-vs-distance.

If I recall correctly, an infinitesimally-short "monopole" has a
current-vs-distance relationship which is close to linear. A
half-wave monopole does not.

Nonlinearities of this sort would have entirely different effects on
an antenna system than nonlinearities of the voltage-vs-current sort.

They're two different beasts entirely.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

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Richard Harrison wrote:
Tom Donaly, KA6RUH wrote:
"Actually, it`s supposed to be impossible to represent the current
distribution along a dipole using simple mathematical formulas because
integral equations have to be solved that are impervious to any solution
other than numerical approximation."

How many places do you attach to pi?

First, what is linearity? It is the absence of nonlinearity.

Millman and Seely wrote on page 525 of the 1951 edition of "Electronics"
(one of my old textbooks):
"Because of this nonlinear characteristic of the dynamic curve over the
operating range, the wave form of the output wave differs slightly from
that of the grid-exciting-voltage waveshape. Distortion of this type is
called "nonlinear" or "amplitude" distortion.."

All of the antennas I`ve worked with had no noticeable amplitude
distortion. They caused no harmonics or mixing products.

On page 235 of Kraus` 1950 edition of "Antennas" he sets out to solve
Hallen`s equation for current distribution. On page 239, Kraus writes:
"It is generally assumed that the current distribution of an
infinitesimally thin antenna is sinusoidal, and that the phase is
constant over a 1/2-wavelength interval, changing abruptly by
180-degrees between intervals."

You can take what Kraus says to the bank.

Best regards, Richard Harrison, KB5WZI


It certainly is interesting how many supposedly knowledgeable people
can't tell the difference between length and time. Millman and Seely
were writing about cycles per _second_. Kraus was talking about
distribution over _length_. Moreover, read Richard Clark's post
on this subject. Brother!
73,
Tom Donaly, KA6RUH

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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

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Tom Donaly wrote:
What he believes is that
since he can't detect any harmonics emanating from a sinusoidally
fed dipole, the current along its length must be a sinusoid.

The non-existence of harmonics is prima facie evidence
that only single frequency sinusoids exist. A properly
functioning antenna system is linear. Any perceived
non-linearity is an illusion.
--
73, Cecil http://www.qsl.net/w5dxp

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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

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Tom Donaly wrote:
People like Cecil, with
home-grown theories, don't ever seem to want things considered in
depth. That's understandable from a psychological standpoint, but
it isn't any help to the rest of us when some of the things the theory
ignores become significant. In the case of antennas, practically
everything is significant.

All of the theories I am quoting were developed long before I was
born. Almost every technical explanation starts out with simple
concepts and proceeds to more complex concepts. For the sake of
teaching and understanding simple concepts, the secondary variables
are often ignored for the time being. Thus, every textbook on
transmission lines starts off with an explanation of lossless lines
with perfectly resistive characteristic impedances even though such
lines don't exist in reality.
--
73, Cecil http://www.qsl.net/w5dxp

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Richard Clark wrote:
How much distortion has to exist before you hear it? As this directly
relates to your quoted selection, are we to believe that distortion
does not exist if you cannot perceive it?

How about: Distortion can be measured.
--
73, Cecil http://www.qsl.net/w5dxp

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Dave Platt wrote:
The sort of "linearity" which Cecil seems to be referring to (if I
understand what he's written correctly) involves a completely
different sort of relationship. It's not current-vs-voltage, or
voltage-vs-current - it's current-vs-distance.

Assuming thin constant diameter wires with a constant Z0 and VF.

If the diameter of the wire changes, or Z0 changes, or VF changes,
the 'K' term in the cos(KX) expression changes. A change in a
constant does NOT produce non-linearity in a linear system. Just
because a wave slows down in a medium with a low VF doesn't mean
that the system has gone non-linear.
--
73, Cecil http://www.qsl.net/w5dxp