Ed Cregger wrote:

You are the acknowledged expert here (we're not worthy!!!).

What is the flaw in the proposed thinking? You have to admit that lots
of the commercial antenna companies and ham publications either do, or
used to, emphasize the point that "most of the radiation of a 1/4 wave
ground plane antenna (half of a half wave) occurs near the feed point".

Instead of just saying, no, this thinking is incorrect, how about
teaching your students (includes me) precisely what is wrong with this
line of thinking. Not at the engineering level necessarily (oodles of
formulas), but in the analog/real world level.

Please?

Be merciful, oh great one. I'm on enough prescription drugs to put half
a football team to sleep, so, occasionally, I get quite tangential to
the topic at hand. I hope this isn't one of those times. G

Thank you, oh merciful one.

C'mon, now, I'm not the Great Guru. I'm just somebody who's interested
in antennas and has spent a lot of time thinking and learning about
them. As I said when I was in the service (as an enlisted man), "Don't
call me 'sir'! My parents were married."

The question of where radiation "comes from" is really a complicated
one. Not long ago I came across a recent paper in the IEEE Transactions
on Antennas and Propagation which addresses the issue, and it's one of
many. One of the conclusions of the paper is that it's really not
possible to assign any part or parts of an antenna as being responsible
for a particular share of the radiation.

A lot of people confuse the field generated by a current-carrying
conductor with far field radiation. It's very well known and established
that a field is created which is proportional to the current flowing on
a conductor -- antenna analysis programs use this principle to produce
very accurate results. This is certainly the source of claims that the
middle of a half wave dipole or the bottom of a quarter wave monopole
does most of the "radiating", because those points are where the current
is highest and therefore the field most intense.

However, the fields all parts of the antenna add together to become the
radiation which "escapes" beyond the region close to the antenna. You
can, for example, have two different parts of an antenna which each
produce intense fields, but out of phase in some directions so they
cancel completely or partially out of phase in such a way that they
nearly cancel in all directions. If you could somehow make the field
from one of those parts disappear without affecting the other, the
contribution to the overall radiation from the other would increase.
(However, the law of conservation of energy requires that radiation from
somewhere else would have to decrease to keep the total the same.) So
the radiation is the result of contributions from all parts of the
antenna, but in a way that's not easy to apportion to individual parts.
In the example, the two parts of the antenna, in combination, contribute
little to the radiated field. But each one, by itself, would contribute
quite a bit if it weren't for the other. An antenna has an infinite
number of radiating parts which all sum together to produce the radiated
field, so you can hopefully see the problem here.

That being said, some professional papers do establish some sort of
criteria for apportioning it. In ones I've seen, the radiation from half
a dipole as a function of position looks sort of tub-shaped, with
considerable radiation arising from all parts of the antenna, but having
a somewhat larger amount coming from the center and ends. As far as I
can tell, though, this depends on exactly how you define in what way a
particular part of the antenna is responsible for each fraction of the
total radiated power.

The bottom line is that any simplified assignment of radiation as coming
from one part of the antenna or another is too much of a simplification
and will lead to erroneous conclusions.

All I can say about what antenna publications and commercial antenna
manufacturers say is that a very large fraction of it is just plain
wrong. Consequently, they're very poor sources of information. Good
information can be found in textbooks and professional publications, and
very few other places. One exception (that is, one good source not in
these categories) is the _ARRL Antenna Book_, since when Jerry Hall
overhauled it (15th Edition if I recall correctly). The current editor,
Dean Straw, is knowledgeable about antennas and very conscientious about
correcting errors and misinformation. So it's become the only reference
I know of which is fundamentally accurate while keeping explanations at
a level which is easily understood by non-professionals.

Hope this helped.

Roy Lewallen, W7EL

Roy Lewallen wrote:
Ed Cregger wrote:

You are the acknowledged expert here (we're not worthy!!!).

What is the flaw in the proposed thinking? You have to admit that lots
of the commercial antenna companies and ham publications either do, or
used to, emphasize the point that "most of the radiation of a 1/4 wave
ground plane antenna (half of a half wave) occurs near the feed point".

Instead of just saying, no, this thinking is incorrect, how about
teaching your students (includes me) precisely what is wrong with this
line of thinking. Not at the engineering level necessarily (oodles of
formulas), but in the analog/real world level.

Please?

Be merciful, oh great one. I'm on enough prescription drugs to put
half a football team to sleep, so, occasionally, I get quite
tangential to the topic at hand. I hope this isn't one of those times.
G

Thank you, oh merciful one.

C'mon, now, I'm not the Great Guru. I'm just somebody who's interested
in antennas and has spent a lot of time thinking and learning about
them. As I said when I was in the service (as an enlisted man), "Don't
call me 'sir'! My parents were married."

The question of where radiation "comes from" is really a complicated
one. Not long ago I came across a recent paper in the IEEE Transactions
on Antennas and Propagation which addresses the issue, and it's one of
many. One of the conclusions of the paper is that it's really not
possible to assign any part or parts of an antenna as being responsible
for a particular share of the radiation.

A lot of people confuse the field generated by a current-carrying
conductor with far field radiation. It's very well known and established
that a field is created which is proportional to the current flowing on
a conductor -- antenna analysis programs use this principle to produce
very accurate results. This is certainly the source of claims that the
middle of a half wave dipole or the bottom of a quarter wave monopole
does most of the "radiating", because those points are where the current
is highest and therefore the field most intense.

However, the fields all parts of the antenna add together to become the
radiation which "escapes" beyond the region close to the antenna. You
can, for example, have two different parts of an antenna which each
produce intense fields, but out of phase in some directions so they
cancel completely or partially out of phase in such a way that they
nearly cancel in all directions. If you could somehow make the field
from one of those parts disappear without affecting the other, the
contribution to the overall radiation from the other would increase.
(However, the law of conservation of energy requires that radiation from
somewhere else would have to decrease to keep the total the same.) So
the radiation is the result of contributions from all parts of the
antenna, but in a way that's not easy to apportion to individual parts.
In the example, the two parts of the antenna, in combination, contribute
little to the radiated field. But each one, by itself, would contribute
quite a bit if it weren't for the other. An antenna has an infinite
number of radiating parts which all sum together to produce the radiated
field, so you can hopefully see the problem here.

That being said, some professional papers do establish some sort of
criteria for apportioning it. In ones I've seen, the radiation from half
a dipole as a function of position looks sort of tub-shaped, with
considerable radiation arising from all parts of the antenna, but having
a somewhat larger amount coming from the center and ends. As far as I
can tell, though, this depends on exactly how you define in what way a
particular part of the antenna is responsible for each fraction of the
total radiated power.

The bottom line is that any simplified assignment of radiation as coming
from one part of the antenna or another is too much of a simplification
and will lead to erroneous conclusions.

All I can say about what antenna publications and commercial antenna
manufacturers say is that a very large fraction of it is just plain
wrong. Consequently, they're very poor sources of information. Good
information can be found in textbooks and professional publications, and
very few other places. One exception (that is, one good source not in
these categories) is the _ARRL Antenna Book_, since when Jerry Hall
overhauled it (15th Edition if I recall correctly). The current editor,
Dean Straw, is knowledgeable about antennas and very conscientious about
correcting errors and misinformation. So it's become the only reference
I know of which is fundamentally accurate while keeping explanations at
a level which is easily understood by non-professionals.

Hope this helped.

Roy Lewallen, W7EL


------------


Thanks, Roy. Much appreciated.

Ed, NM2K

In article , Roy Lewallen
wrote:

All I can say about what antenna publications and commercial antenna
manufacturers say is that a very large fraction of it is just plain
wrong. Consequently, they're very poor sources of information. Good
information can be found in textbooks and professional publications, and
very few other places. One exception (that is, one good source not in
these categories) is the _ARRL Antenna Book_, since when Jerry Hall
overhauled it (15th Edition if I recall correctly). The current editor,
Dean Straw, is knowledgeable about antennas and very conscientious about
correcting errors and misinformation. So it's become the only reference
I know of which is fundamentally accurate while keeping explanations at
a level which is easily understood by non-professionals.

Hope this helped.

Roy Lewallen, W7EL

You got that right, Roy. Do marketing departments ever talk to the
engineers? At least I haven't seen a dial 1-800 TV commercial such as
"Call right now and we'll include the matching network and balun free of
charge. But call right now and we'll also include a CFA free!"

Adding to what you said above how about a little gray box that can save
you up to 25% on your electric bill (you can Google this one). Sincerely,
and 73s from N4GGO,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

J. B. Wood wrote:
In article , Roy Lewallen
wrote:

All I can say about what antenna publications and commercial antenna
manufacturers say is that a very large fraction of it is just plain
wrong. Consequently, they're very poor sources of information. Good
information can be found in textbooks and professional publications, and
very few other places. One exception (that is, one good source not in
these categories) is the _ARRL Antenna Book_, since when Jerry Hall
overhauled it (15th Edition if I recall correctly). The current editor,
Dean Straw, is knowledgeable about antennas and very conscientious about
correcting errors and misinformation. So it's become the only reference
I know of which is fundamentally accurate while keeping explanations at
a level which is easily understood by non-professionals.

Hope this helped.

Roy Lewallen, W7EL

You got that right, Roy. Do marketing departments ever talk to the
engineers? At least I haven't seen a dial 1-800 TV commercial such as
"Call right now and we'll include the matching network and balun free of
charge. But call right now and we'll also include a CFA free!"

Adding to what you said above how about a little gray box that can save
you up to 25% on your electric bill (you can Google this one). Sincerely,
and 73s from N4GGO,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337


------------


I have quite a few engineering books on antennas (that I use G), so I
can appreciate the value of good, solid engineering text/sources.

However, the point that the OP was trying to make was that it is likely
that superconductive radiating elements could establish the need for a
serious rethinking of antenna theory. After all, superconductive
radiating elements did not exist before and the math has not been done.
Perhaps, their inclusion, will demand something more than a simple
extrapolation of existing antenna theory. I believe this to be the point
of the OP.

I added the other type of radiating element, plasma radiators, as a part
of the same discussion with the same reasoning behind it. Can you
imagine an antenna ray that only manifests itself physically when
needed? Wow!


Ed, NM2K

On Wed, 05 Dec 2007 10:36:59 -0500, Ed Cregger
wrote:

However, the point that the OP was trying to make was that it is likely
that superconductive radiating elements could establish the need for a
serious rethinking of antenna theory.

Hi Ed,

This is uni-dimensional thinking.

"A new breakfast cereal could establish the need for a serious
rethinking of sewing machine theory."

There are probably more things possible ("could establish") than time
to consider them - and probably on file pending patent. In that
sense, patent publishing could establish the need for a serious
rethinking of replacing burning oil for heat.

"Could establish" ...this could establish a new form of gaming
entertainment in this group. [and conforms to the usage of
self-referential claims]

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Wed, 05 Dec 2007 10:36:59 -0500, Ed Cregger
wrote:

However, the point that the OP was trying to make was that it is likely
that superconductive radiating elements could establish the need for a
serious rethinking of antenna theory.

Hi Ed,

This is uni-dimensional thinking.

"A new breakfast cereal could establish the need for a serious
rethinking of sewing machine theory."

There are probably more things possible ("could establish") than time
to consider them - and probably on file pending patent. In that
sense, patent publishing could establish the need for a serious
rethinking of replacing burning oil for heat.

"Could establish" ...this could establish a new form of gaming
entertainment in this group. [and conforms to the usage of
self-referential claims]

73's
Richard Clark, KB7QHC


--------------


So, rather than talk about the subject at hand, you would rather argue
about the technically poor writing style I employed. No thanks. G


Ed, NM2K

On Wed, 05 Dec 2007 16:34:50 -0500, Ed Cregger
wrote:

So, rather than talk about the subject at hand, you would rather argue
about the technically poor writing style I employed. No thanks. G

Hi Ed,

Talking already sputtered to the usual banal offerings so common with
the glazed-eye "what if we could only reach that golden city on the
hill," when I turned to commenting on the only thing left: the quality
of entertainment.

And going further with plasma antennas indeed! I remember plasma
speakers. We've had reports of burning water that would rescue us
from our dependence on Oil, -sigh- if only it didn't take more power
lighting up a bottle of Evian than you got out of it. But even
struggling through this doomed topic finds the cliff crumbling from
beneath its heels and its only hope is that the inventors are making a
living as scabs writing for daytime TV.

73's
Richard Clark, KB7QHC

Ed Cregger wrote:

I have quite a few engineering books on antennas (that I use G), so I
can appreciate the value of good, solid engineering text/sources.

However, the point that the OP was trying to make was that it is likely
that superconductive radiating elements could establish the need for a
serious rethinking of antenna theory. After all, superconductive
radiating elements did not exist before and the math has not been done.
Perhaps, their inclusion, will demand something more than a simple
extrapolation of existing antenna theory. I believe this to be the point
of the OP.
. . .

And I disagree. The assumption of zero loss is implicit or explicit in
nearly all the analyses in your antenna texts and mine. So no new math
or "rethinking of antenna theory" is required to deal with lossless
conductors. It is, in fact, the simplest case and so underlies virtually
all the current theory. What it would do is cause a change in tradeoffs
which would be made by engineers in the design of real antennas.

However, superconductors (at least all known conventional and
high-temperature superconductors) are lossless only at DC.
Superconductor loss increases with frequency and, except at DC, with
temperature. The resistivity of copper decreases quite dramatically with
temperature, so it's not uncommon to find situations at very high
frequencies and very cold temperatures where copper does better than a
superconductor. Even high temperature superconductors have to be cooled
to cryogenic temperatures to do reasonably well at very high
frequencies. But again no new math or "rethinking of antenna theory" is
necessary to deal with them -- the same electromagnetic principles apply
and they can be treated like any other conductors with finite resistivity.

Roy Lewallen, W7EL

Roy Lewallen wrote:
Ed Cregger wrote:

I have quite a few engineering books on antennas (that I use G), so
I can appreciate the value of good, solid engineering text/sources.

However, the point that the OP was trying to make was that it is
likely that superconductive radiating elements could establish the
need for a serious rethinking of antenna theory. After all,
superconductive radiating elements did not exist before and the math
has not been done. Perhaps, their inclusion, will demand something
more than a simple extrapolation of existing antenna theory. I believe
this to be the point of the OP.
. . .

And I disagree. The assumption of zero loss is implicit or explicit in
nearly all the analyses in your antenna texts and mine. So no new math
or "rethinking of antenna theory" is required to deal with lossless
conductors. It is, in fact, the simplest case and so underlies virtually
all the current theory. What it would do is cause a change in tradeoffs
which would be made by engineers in the design of real antennas.

However, superconductors (at least all known conventional and
high-temperature superconductors) are lossless only at DC.
Superconductor loss increases with frequency and, except at DC, with
temperature. The resistivity of copper decreases quite dramatically with
temperature, so it's not uncommon to find situations at very high
frequencies and very cold temperatures where copper does better than a
superconductor. Even high temperature superconductors have to be cooled
to cryogenic temperatures to do reasonably well at very high
frequencies. But again no new math or "rethinking of antenna theory" is
necessary to deal with them -- the same electromagnetic principles apply
and they can be treated like any other conductors with finite resistivity.

Roy Lewallen, W7EL


-------------


All excellent points.

I'm thinking - I'm thinking...G


Ed Cregger

Roy Lewallen wrote:
Ed Cregger wrote:

I have quite a few engineering books on antennas (that I use G), so
I can appreciate the value of good, solid engineering text/sources.

However, the point that the OP was trying to make was that it is
likely that superconductive radiating elements could establish the
need for a serious rethinking of antenna theory. After all,
superconductive radiating elements did not exist before and the math
has not been done. Perhaps, their inclusion, will demand something
more than a simple extrapolation of existing antenna theory. I believe
this to be the point of the OP.
. . .

And I disagree. The assumption of zero loss is implicit or explicit in
nearly all the analyses in your antenna texts and mine. So no new math
or "rethinking of antenna theory" is required to deal with lossless
conductors. It is, in fact, the simplest case and so underlies virtually
all the current theory. What it would do is cause a change in tradeoffs
which would be made by engineers in the design of real antennas.

However, superconductors (at least all known conventional and
high-temperature superconductors) are lossless only at DC.
Superconductor loss increases with frequency and, except at DC, with
temperature. The resistivity of copper decreases quite dramatically with
temperature, so it's not uncommon to find situations at very high
frequencies and very cold temperatures where copper does better than a
superconductor. Even high temperature superconductors have to be cooled
to cryogenic temperatures to do reasonably well at very high
frequencies. But again no new math or "rethinking of antenna theory" is
necessary to deal with them -- the same electromagnetic principles apply
and they can be treated like any other conductors with finite resistivity.

Roy Lewallen, W7EL


-------------


All excellent points.

I'm thinking - I'm thinking...G


Ed Cregger