I hardly know where to start with this topic. If one picks up some of the
fairly popular (available?) books on the matter, the authors invariably
start throwing different types of antennas at the reader, yagi, helical,
dipole, folded dipole, parabolic, loop, dish, microwave, quads, etc. For
example, I'm looking at an older book on the topic I bought some 20 years
ago, The Radio Amateur Handbook by Orr and Cowan. The book is basically for
builders. Many such books are. What about the underlying methodology behind
this? More generally, here's my question.

I would guess that in the beginning (late 1800s) the simple dipole was it.
As years passed, the complexity of antennas has increased. What was the
driving force for these changes? For example, how did the inventor of the
Yagi (Yagi-Uda) ever dream up the idea for the antenna? Was it the
application of theory or did he just get lucky? In fact, is there some
underlying theory that drives the design of antennas? For example, the
computation of radiation patterns. I'm sure these days the computer would be
an aid, but what theory and application drove the development of varied
designs before 1960? When did Maxwell's equations seriously get used for
this? What suggested a tin can could become an antenna? How did anyone think
up the idea of a microwave antenna?

I would think that in the case of antennas that are used for different parts
of the EM spectrum a driving force would be the consideration of the wave
itself. For example, it would seem unlikely an x-ray antenna (I believe
there is such a thing on one of the space satellites used in astronomy)
would be anything like one used to receive TV. Certainly the 'antenna' to
collect visible light is different than that for AM radio.

--
Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet

Traveling in remote places in the winter. What's the best
tool to carry with you? An axe.
-- Survivorman, Discovery (SCI) Channel

Web Page: home.earthlink.net/~mtnviews

Wayne Watson wrote:
For example, it would seem unlikely an x-ray antenna (I believe
there is such a thing on one of the space satellites used in astronomy)
would be anything like one used to receive TV. Certainly the 'antenna' to
collect visible light is different than that for AM radio.

Is it easier to pick up a twig than to pick up a tree?
Methinks you need a better understanding of wavelength.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

Wayne Watson wrote:

For example, it would seem unlikely an x-ray antenna (I believe
there is such a thing on one of the space satellites used in astronomy)
would be anything like one used to receive TV. Certainly the 'antenna' to
collect visible light is different than that for AM radio.


Is it easier to pick up a twig than to pick up a tree?
Methinks you need a better understanding of wavelength.
Why not provide it then?

--
Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet

Traveling in remote places in the winter. What's the best
tool to carry with you? An axe.
-- Survivorman, Discovery (SCI) Channel

Web Page: home.earthlink.net/~mtnviews

W. Watson wrote:

Cecil Moore wrote:

Wayne Watson wrote:

For example, it would seem unlikely an x-ray antenna (I believe
there is such a thing on one of the space satellites used in astronomy)
would be anything like one used to receive TV. Certainly the
'antenna' to
collect visible light is different than that for AM radio.



Is it easier to pick up a twig than to pick up a tree?
Methinks you need a better understanding of wavelength.

Why not provide it then?

Let me try to make it easier on you. Why do I have to resort to using an
optical telescope to see a star rather than using a radio receiver that
might work in the same part of EM spectrum, visual light? After all an EM
wave is an EM wave, isn't it? Shouldn't we be able to use the same equipment
to observe the entire spectrum? Before I suggest an answer in this case,
I'll let you have a go at it.

--
Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet

Traveling in remote places in the winter. What's the best
tool to carry with you? An axe.
-- Survivorman, Discovery (SCI) Channel

Web Page: home.earthlink.net/~mtnviews

Wayne Watson wrote:
I hardly know where to start with this topic. If one picks up some of
the fairly popular (available?) books on the matter, the authors
invariably start throwing different types of antennas at the reader,
yagi, helical, dipole, folded dipole, parabolic, loop, dish,
microwave, quads, etc. For example, I'm looking at an older book on
the topic I bought some 20 years ago, The Radio Amateur Handbook by
Orr and Cowan. The book is basically for builders. Many such books
are. What about the underlying methodology behind this? More
generally, here's my question.

I would guess that in the beginning (late 1800s) the simple dipole
was it. As years passed, the complexity of antennas has increased.
What was the driving force for these changes?


Since the beginning of radio, antenna design has been driven mostly by
specific needs, to name just a very few examples:

-- By broadcasters to increase their coverage areas
-- By military users:
to increase portability and range
to decrease detectable emissions in some directions
to allow broadband performance for frequency hopping
-- By satellite system designers to concentrate limited energy in
particular regions.
-- By cell phone companies to provide coverage to well-defined regions

The list is endless.

Take a trip to your local library and get an index to the I.R.E. (now
the IEEE) Transactions on Antennas and Propagation. You'll see that many
advances were made in the '20s and '30s in AM broadcast antennas, in the
'40s and '50s in aircraft antennas, in the '60s and '70s in satellite
antennas. Much of today's development work involves compact antennas for
the wireless networks now proliferating.

Antennas provide a limitless pool of tradeoffs involving size, cost,
ruggedness, and a large handful of performance characteristics such as
directionality, gain, and bandwidth. This pretty much guarantees that
new designs will continue to be created.

For example, how did the inventor of the Yagi (Yagi-Uda) ever dream
up the idea for the antenna? Was it the application of theory or did
he just get lucky?

How is any creative design accomplished? How did Armstrong come up with
the idea for FM, Watt for the steam engine? I've spent most of my career
doing circuit design, and it requires a deep knowledge of theory, but
also involves a creative synthesis not unlike what an artist has in
deciding what to paint or an architect in deciding what form a building
will take.

In fact, is there some underlying theory that drives the design of
antennas? For example, the computation of radiation patterns.

You're confusing design and analysis. Design is driven primarily by a
need for a particular set of performance parameters. Analysis is done by
computation. Analysis is an important part of the design process, in
that a design, once created, is analyzed to see if and how well it meets
design goals. The design is then often modified and re-analyzed many
times until the goal is reached, the design abandoned, or the goal
redefined. And yes, indeed, there's solid theory underlying antenna
operation.

I'm sure these days the computer would be an aid, but what theory and
application drove the development of varied designs before 1960?

Hopefully what I've said above has answered this. A lot more physical
modeling and experimentation were required before computers were
available, but design was still driven by need, and theory hasn't
changed significantly for many decades.

There's no magic computer program that you can put some numbers into and
out comes the optimum aircraft design, or bridge, or car, or house.
Antennas are no different. Computers can be used to optimize a
particular class of antenna (e.g., Yagi or patch) for a particular set
of performance criteria, just as they can be used to fine-tune an
aircraft or bridge once the basic structure is designed. But not to
design an antenna from nothing.

When did Maxwell's equations seriously get used for this?

They were used long ago as the basis of equations more directly
applicable to antenna analysis, and those equations are still used by
modern computer programs. In that sense, Maxwell's equations are still
being used, although not directly.

What suggested a tin can could become an antenna?

It's obvious to anyone who understands the most basic of principles. Any
conductor can act as an antenna. A tin can is a conductor.

How did anyone think up the idea of a microwave antenna?

Actually, some of the first experiments with radio waves by Heinrich
Hertz were done in the microwave region, so some of the very first
antennas were microwave antennas. As for modern microwave antennas, once
you have microwave energy (which first became available at high power
levels with the invention of the cavity magnetron in 1940), the
need for an antenna becomes obvious.

I would think that in the case of antennas that are used for
different parts of the EM spectrum a driving force would be the
consideration of the wave itself. For example, it would seem unlikely
an x-ray antenna (I believe there is such a thing on one of the
space satellites used in astronomy) would be anything like one used
to receive TV. Certainly the 'antenna' to collect visible light is
different than that for AM radio.

All antennas obey the same fundamental physical laws. But you're correct
that the wavelength of the signal to be transmitted or
received plays a big role in determining which antenna designs are
practical and optimum. That's just one of the many factors that have to
be considered when designing an antenna. All bridges obey the same
physical laws, but the optimum design for a bridge crossing a creek is
quite different from one crossing the Golden Gate.

In fact, if you change "antenna" to "bridge" in your questions, you'll
probably find most of the answers to be pretty obvious.

Roy Lewallen, W7EL

W. Watson wrote:
W. Watson wrote:
Wayne Watson wrote:
Let me try to make it easier on you.

Are you bipolar? :-)
--
73, Cecil http://www.qsl.net/w5dxp

Roy Lewallen wrote:

Wayne Watson wrote:

I hardly know where to start with this topic. If one picks up some of
the fairly popular (available?) books on the matter, the authors
invariably start throwing different types of antennas at the reader,
yagi, helical, dipole, folded dipole, parabolic, loop, dish,
microwave, quads, etc. For example, I'm looking at an older book on
the topic I bought some 20 years ago, The Radio Amateur Handbook by
Orr and Cowan. The book is basically for builders. Many such books
are. What about the underlying methodology behind this? More
generally, here's my question.

I would guess that in the beginning (late 1800s) the simple dipole was
it. As years passed, the complexity of antennas has increased. What
was the driving force for these changes?



Since the beginning of radio, antenna design has been driven mostly by
specific needs, to name just a very few examples:

-- By broadcasters to increase their coverage areas
-- By military users:
to increase portability and range
to decrease detectable emissions in some directions
to allow broadband performance for frequency hopping
-- By satellite system designers to concentrate limited energy in
particular regions.
-- By cell phone companies to provide coverage to well-defined regions

The list is endless.

Take a trip to your local library and get an index to the I.R.E. (now
the IEEE) Transactions on Antennas and Propagation. You'll see that many
advances were made in the '20s and '30s in AM broadcast antennas, in the
'40s and '50s in aircraft antennas, in the '60s and '70s in satellite
antennas. Much of today's development work involves compact antennas for
the wireless networks now proliferating.

Antennas provide a limitless pool of tradeoffs involving size, cost,
ruggedness, and a large handful of performance characteristics such as
directionality, gain, and bandwidth. This pretty much guarantees that
new designs will continue to be created.

For example, how did the inventor of the Yagi (Yagi-Uda) ever dream up
the idea for the antenna? Was it the application of theory or did he
just get lucky?


How is any creative design accomplished? How did Armstrong come up with
the idea for FM, Watt for the steam engine? I've spent most of my career
doing circuit design, and it requires a deep knowledge of theory, but
also involves a creative synthesis not unlike what an artist has in
deciding what to paint or an architect in deciding what form a building
will take.

In fact, is there some underlying theory that drives the design of
antennas? For example, the computation of radiation patterns.


You're confusing design and analysis. Design is driven primarily by a
need for a particular set of performance parameters. Analysis is done by
computation. Analysis is an important part of the design process, in
that a design, once created, is analyzed to see if and how well it meets
design goals. The design is then often modified and re-analyzed many
times until the goal is reached, the design abandoned, or the goal
redefined. And yes, indeed, there's solid theory underlying antenna
operation.

I'm sure these days the computer would be an aid, but what theory and
application drove the development of varied designs before 1960?


Hopefully what I've said above has answered this. A lot more physical
modeling and experimentation were required before computers were
available, but design was still driven by need, and theory hasn't
changed significantly for many decades.

There's no magic computer program that you can put some numbers into and
out comes the optimum aircraft design, or bridge, or car, or house.
Antennas are no different. Computers can be used to optimize a
particular class of antenna (e.g., Yagi or patch) for a particular set
of performance criteria, just as they can be used to fine-tune an
aircraft or bridge once the basic structure is designed. But not to
design an antenna from nothing.

When did Maxwell's equations seriously get used for this?


They were used long ago as the basis of equations more directly
applicable to antenna analysis, and those equations are still used by
modern computer programs. In that sense, Maxwell's equations are still
being used, although not directly.

What suggested a tin can could become an antenna?


It's obvious to anyone who understands the most basic of principles. Any
conductor can act as an antenna. A tin can is a conductor.

How did anyone think up the idea of a microwave antenna?


Actually, some of the first experiments with radio waves by Heinrich
Hertz were done in the microwave region, so some of the very first
antennas were microwave antennas. As for modern microwave antennas, once
you have microwave energy (which first became available at high power
levels with the invention of the cavity magnetron in 1940), the
need for an antenna becomes obvious.

I would think that in the case of antennas that are used for different
parts of the EM spectrum a driving force would be the consideration of
the wave itself. For example, it would seem unlikely
an x-ray antenna (I believe there is such a thing on one of the space
satellites used in astronomy) would be anything like one used to
receive TV. Certainly the 'antenna' to collect visible light is
different than that for AM radio.


All antennas obey the same fundamental physical laws. But you're correct
that the wavelength of the signal to be transmitted or
received plays a big role in determining which antenna designs are
practical and optimum. That's just one of the many factors that have to
be considered when designing an antenna. All bridges obey the same
physical laws, but the optimum design for a bridge crossing a creek is
quite different from one crossing the Golden Gate.

In fact, if you change "antenna" to "bridge" in your questions, you'll
probably find most of the answers to be pretty obvious.

Roy Lewallen, W7EL
Thanks. Well said. Makes sense to me.
I have a very modest understanding of how antennas work, but from my
simplistic view I just find it a bit odd that if one thinks of an EM wave
shape and content (electric and magnetic) to all sorts of radiation that to
observe much of this radiation different devices are required. From my
underdeveloped perspective, I'd probably trying to design everything with
some wild combinations of dipoles. Maybe I'm thinking of (hoping for) some
grand unified radio or telescope (and methodology) that sucks up any EM wave
one can throw at it. One size fits all. Apparently, we've got a long way to
go on that. :-)

--
Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet

Traveling in remote places in the winter. What's the best
tool to carry with you? An axe.
-- Survivorman, Discovery (SCI) Channel

Web Page: home.earthlink.net/~mtnviews

On Mon, 28 Nov 2005 12:05:15 GMT, "W. Watson"
wrote:

...Maybe I'm thinking of (hoping for) some grand
unified radio or telescope (and methodology) that
sucks up any EM wave one can throw at it. One size
fits all. Apparently, we've got a long way to go
on that. :-)

The methodology (and perhaps the viewpoint) you are
looking for is... Optics.

From an Optics viewpoint, you're born with two antennas
in your head (that you are using to read this).

From an Optics viewpoint, a hole in a piece of cardboard
is an antenna (an aperture).

From an Optics viewpoint, radio antennas (monopoles,
dipoles, yagis, Sterba curtains) are just minor
peculiarities one encounters when wavelength becomes
"human-sized".

From an Optics viewpoint, we've been at this for an
awfully long time. Maxwell's equations and quantum
mechanics are just frosting on a very large cake. A
great deal of Physics has been devoted to studying
electromagnetic radiation over the centuries.

Unfortunately, the study of Optics is not for the
faint of heart. It leads directly into the heart of
the Physical Universe and things tend to get very
messy, and very mathematical. However, even from
the periphery, the insights are rewarding. Every
time you pick up a camera, you think "antenna".
Every time you see an incandescent lamp, you think
"antennas" (jillions of them). Every time you see
a satellite dish, you think "telescope". And so on...

Jim, K7JEB

K7JEB wrote:
From an Optics viewpoint, we've been at this for an
awfully long time. Maxwell's equations and quantum
mechanics are just frosting on a very large cake. A
great deal of Physics has been devoted to studying
electromagnetic radiation over the centuries.

In particular:
An understanding of how RF reflections can be eliminated
by a 1/4WL series matching section can be had from
understanding how a 1/4WL layer of thin-film on glass can
eliminate coherent light reflections from the surface of
the thin-film. The irradiance equations which predict the
power distribution of light waves undergoing interference
can be used to understand RF energy flow in a transmission
line with reflections. Staring at oneself in a mirror
should convince any skeptical RF engineer that reflected
energy actually makes a round trip to the reflection point
and back and doesn't flow directly from the image-source
to the eye (or to the circulator load resistor). :-)
--
73, Cecil http://www.qsl.net/w5dxp

Wayne Watson wrote:
"What about the underlying methodology behind this?"

Please refer to the 3rd. edition of "Antennas for All Applications", by
John D. Kraus with a host of other professors, for answers to nearly all
your questions. Kraus organizes antennas by types.

The dipole is the simplest complete antenna. But, the first practical
antenna was patented by Marconi. He was interested in communications
over the ocean, so only 1/2 of a dipole is needed. The return circuit is
provided by the ocean. Sea water is nearly lossless.

Marconi imagined the antenna as a capacitor plate.. Then he discovered
the antenna worked about as well with just the connectng wires inplace,
without the plate. As the 19th century turned into the 20th century,
Marconi spanned the Atlantic with signals from his antennas.

Best regards, Richard Harrison, KB5WZI