Dr. Slick wrote:
Roy Lewallen wrote in message ...

.. . .


I see your point, that the primary could be considered one
antenna, and the core material like free space, and the secondary
would be the receive antenna. But i suspect even a single
transducer/antenna can be optimized for maximum lines of flux through
a core at a particular frequency, or max ERP in the case of the
antenna. Otherwise we wouldn't have to tune these things.


Yep, and an automobile can be optimized for maximum acceleration. Good
argument for considering an antenna a type of automobile, no?

Y'see, if you really, really want an antenna to be a kind of automobile,
you can cook up a bunch of reasons to convince yourself that it is. The
same method works for astrology and fortune telling, too.



Shall i call this a Straw man argument? Or putting words in
someone's mouth?

Feel free to call it what you want. I believe I've made as valid an
argument for an antenna being an automobile as you did for it being a
transformer, and based on the same criteria.

Ok, an antenna is a transducer. But you can still optimize it for
ERP, and that will depend on the impedance of free space or water or
whatever. Why not throw out the whole concept of free space impedance
if it doesn't matter?

The optimization of an antenna depends on many factors, only one of
which is the nature of the medium in which it's immersed. And among the
medium's important properties are its permeability, permittivity, and
the velocity of a wave propagating in it. The phase velocity and
characteristic impedance can both be calculated from the permeability
and permittivity, so you can't really say any one of these is more
important than the other.

It doesn't make any sense to throw out the concept of free space
impedance just because it confuses people who don't know what it means.
It's an extremely useful and well-understood concept. For example,
reflection of a wave from a plane conductor or the ground can easily be
found by calculating a reflection coefficient based on the impedance of
the reflecting surface and the impedance of the impinging wave. (The
impedance of a wave can be quite different close to an antenna than it
is after it's traveled some distance.) If you look in some of those
texts I recommended, you'll find the impedance of free space cropping up
all over the place.

What needs to be thrown away is the belief that all impedances are the
ratio of a voltage to a current, along with the notion that only
resistors can have resistance.

Roy Lewallen, W7EL

Roy Lewallen wrote:
What needs to be thrown away is the belief that all impedances are the
ratio of a voltage to a current, along with the notion that only
resistors can have resistance.

I agree, Roy, but what can we do about it? I had been using "virtual
impedance" to differentiate a voltage to current ratio from an intrinsic
physical impedance. How would you differentiate an intrinsic physical
impedance from a voltage to current ratio?
--
73, Cecil, W5DXP

You can do about it what you like. What I've chosen to do about it is to
try and educate the people who will listen, and ignore those who won't.
I find the concepts perfectly understandable without the need for
additional adjectives.

Roy Lewallen, W7EL

W5DXP wrote:
Roy Lewallen wrote:

What needs to be thrown away is the belief that all impedances are the
ratio of a voltage to a current, along with the notion that only
resistors can have resistance.


I agree, Roy, but what can we do about it? I had been using "virtual
impedance" to differentiate a voltage to current ratio from an intrinsic
physical impedance. How would you differentiate an intrinsic physical
impedance from a voltage to current ratio?
--
73, Cecil, W5DXP

Roy Lewallen wrote in message ...

Y'see, if you really, really want an antenna to be a kind of automobile,
you can cook up a bunch of reasons to convince yourself that it is. The
same method works for astrology and fortune telling, too.



Shall i call this a Straw man argument? Or putting words in
someone's mouth?

Feel free to call it what you want. I believe I've made as valid an
argument for an antenna being an automobile as you did for it being a
transformer, and based on the same criteria.



Well, if you agree that two antennas/transducers in close
proximity will make a transformer (albeit a somewhat inefficient
one!), then i don't think i was that far off base.




The optimization of an antenna depends on many factors, only one of
which is the nature of the medium in which it's immersed. And among the
medium's important properties are its permeability, permittivity, and
the velocity of a wave propagating in it. The phase velocity and
characteristic impedance can both be calculated from the permeability
and permittivity, so you can't really say any one of these is more
important than the other.

It doesn't make any sense to throw out the concept of free space
impedance just because it confuses people who don't know what it means.
It's an extremely useful and well-understood concept. For example,
reflection of a wave from a plane conductor or the ground can easily be
found by calculating a reflection coefficient based on the impedance of
the reflecting surface and the impedance of the impinging wave. (The
impedance of a wave can be quite different close to an antenna than it
is after it's traveled some distance.) If you look in some of those
texts I recommended, you'll find the impedance of free space cropping up
all over the place.

What needs to be thrown away is the belief that all impedances are the
ratio of a voltage to a current, along with the notion that only
resistors can have resistance.

Roy Lewallen, W7EL


You have convinced me that you are correct about both of these
points.

But i don't think that an antennas impedance will not be affected
by the permeability of the medium that surrounds it. An antennas
input impedance will be different in free space as opposed to being
immersed in water, for example.

This indicates to me that the antenna is indeed "matching" 50
Ohms to the impedance of free space, even if it is a different type of
impedance.

Do you think that the characteristics of a transformer of a
specific turns ratio, gauge wire, and core geometry, will NOT depend
on the core material? I would say definitely it WILL depend on the
material.


Slick

Dr. Slick wrote:
Roy Lewallen wrote in message ...

Y'see, if you really, really want an antenna to be a kind of automobile,
you can cook up a bunch of reasons to convince yourself that it is. The
same method works for astrology and fortune telling, too.



Shall i call this a Straw man argument? Or putting words in
someone's mouth?

Feel free to call it what you want. I believe I've made as valid an
argument for an antenna being an automobile as you did for it being a
transformer, and based on the same criteria.




Well, if you agree that two antennas/transducers in close
proximity will make a transformer (albeit a somewhat inefficient
one!), then i don't think i was that far off base.

I agree.




The optimization of an antenna depends on many factors, only one of
which is the nature of the medium in which it's immersed. And among the
medium's important properties are its permeability, permittivity, and
the velocity of a wave propagating in it. The phase velocity and
characteristic impedance can both be calculated from the permeability
and permittivity, so you can't really say any one of these is more
important than the other.

It doesn't make any sense to throw out the concept of free space
impedance just because it confuses people who don't know what it means.
It's an extremely useful and well-understood concept. For example,
reflection of a wave from a plane conductor or the ground can easily be
found by calculating a reflection coefficient based on the impedance of
the reflecting surface and the impedance of the impinging wave. (The
impedance of a wave can be quite different close to an antenna than it
is after it's traveled some distance.) If you look in some of those
texts I recommended, you'll find the impedance of free space cropping up
all over the place.

What needs to be thrown away is the belief that all impedances are the
ratio of a voltage to a current, along with the notion that only
resistors can have resistance.

Roy Lewallen, W7EL



You have convinced me that you are correct about both of these
points.

Good. Then the effort was worthwhile.


But i don't think that an antennas impedance will not be affected
by the permeability of the medium that surrounds it. An antennas
input impedance will be different in free space as opposed to being
immersed in water, for example.

Indeed it will.


This indicates to me that the antenna is indeed "matching" 50
Ohms to the impedance of free space, even if it is a different type of
impedance.

That's a leap I'm unable to make or to follow.

Do you think that the characteristics of a transformer of a
specific turns ratio, gauge wire, and core geometry, will NOT depend
on the core material? I would say definitely it WILL depend on the
material.

Actually, an adequate core shouldn't appear as a significant factor in
transformer performance. Naturally, an inadequate core will adversely
affect it. But I just don't accept that as evidence, let alone "proof"
that an antenna is fundamentally an impedance matching device.

I see that you won't be swayed from your visualization. But hopefully
some of the other readers can see the fallacy of the concept. I think
I've done all I can, so I'll leave this topic now.

*Chuckle* I was just reminded of something that happened years ago, when
my son was a small boy. He learned that I was an engineer, so he
couldn't wait to see the train I drove. After a great deal of repeated,
patient, explanation, I finally got across (I thought) a description of
what I did, and that it had nothing to do with trains. Well, he had
occasion to visit me at work quite a long time later. He kept wandering
off. When I asked why, he explained that he was trying to find where the
train was kept. Yeah, I might not drive trains, but I must have
*something* to do with trains.

Slick, you've got the right concepts now, but you're still looking for
that train.

Roy Lewallen, W7EL

Roy Lewallen wrote in message ...

What needs to be thrown away is the belief that all impedances are the
ratio of a voltage to a current, along with the notion that only
resistors can have resistance.

Roy Lewallen, W7EL



You have convinced me that you are correct about both of these
points.

Good. Then the effort was worthwhile.


Absolutely.



But i don't think that an antennas impedance will not be affected
by the permeability of the medium that surrounds it. An antennas
input impedance will be different in free space as opposed to being
immersed in water, for example.

Indeed it will.


This indicates to me that the antenna is indeed "matching" 50
Ohms to the impedance of free space, even if it is a different type of
impedance.

That's a leap I'm unable to make or to follow.



Clearly, neither of us are PhDs in EM wave propagation, but water
certainly has a different E versus H impedance than the 377 Ohms of
free-space, which is why the input impedance of the antenna will
change. This is not the same, but similar to how the load on the
secondary will affect the primary impedance of a transformer.



Do you think that the characteristics of a transformer of a
specific turns ratio, gauge wire, and core geometry, will NOT depend
on the core material? I would say definitely it WILL depend on the
material.

Actually, an adequate core shouldn't appear as a significant factor in
transformer performance. Naturally, an inadequate core will adversely
affect it. But I just don't accept that as evidence, let alone "proof"
that an antenna is fundamentally an impedance matching device.



Well, you've already agreed that an antenna/transducer can be
considered one half of a transformer, but what i'm saying is that the
permeability of the core or medium will certainly affect the impedance
of the transducer.

What do you mean by "adequate core"? One that suits your purpose
i suppose. But a material of the wrong permeability will definitely
affect your transformer performance. So the impedance of the core
definitely affects the transformer characteristics, as does the
impedance of the air (or water) between two antennas.



I see that you won't be swayed from your visualization. But hopefully
some of the other readers can see the fallacy of the concept. I think
I've done all I can, so I'll leave this topic now.



You've convinced me that antennas are transducers, which are one
half of a transformer, by giving me logical statements.

But you have not come up with anything to convince me otherwise
on this point, which i don't believe is a fallacy at this time.



*Chuckle* I was just reminded of something that happened years ago, when
my son was a small boy. He learned that I was an engineer, so he
couldn't wait to see the train I drove. After a great deal of repeated,
patient, explanation, I finally got across (I thought) a description of
what I did, and that it had nothing to do with trains. Well, he had
occasion to visit me at work quite a long time later. He kept wandering
off. When I asked why, he explained that he was trying to find where the
train was kept. Yeah, I might not drive trains, but I must have
*something* to do with trains.


I'm not a small boy Roy, and I'm an engineer too. Your NG
inspired sarcasm doesn't change my opinion at all, and cannot even be
compared to logical reasoning.

Roy, thanks for your insight, and you have definitely helped me
out with your strict semantics (sometimes needed, especially in the
engineering world!).

But your need to be always right closes your mind to new ideas
and new learning. This is the sign of someone who claims to know
everything about a subject, which i personally believe to be
impossible, even for such a specialized topic as antennas (actually,
it's quite broad, isn't it?), and even for someone as bright and
knowledgable as you are.


Again, much thanks for your input.


Dr. Slick