On Sat, 21 Oct 2006 13:11:52 -0400, jawod wrote:

consider
the applications to amateur radio.

http://www.breitbart.com/news/2006/1....em0doxnf.html

First application that comes to mind is hiding that 40M SteppIR on your
roof.

Or, more fun, how about having your entire house disappear along with
your CW transmissions? Not exactly RFI but ...

Hi John,

The link above is rather facile in its reporting, but so are most of
the pages provided by Dr. Smith (there's something of "Lost in Space"
about them).

Anyway, the science behind this news is found at:
http://www.ee.duke.edu/~drsmith/neg_ref_home.htm
which relates to topics I've offered in this group in the past 3 or 4
years. It comes from the photonics of negative refraction abstracted
to RF.

Boeing Phantom Works, here, has already done the bulk of the work and
their devices are displayed at the pages above (without citation), are
better documented at:
http://www.boeing.com/news/frontiers...gust/i_tt.html
and
http://ceta-p5.mit.edu/metamaterials...r_apl_2003.pdf

The last is a real paper, not the fluff going around in the popular
press.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Sat, 21 Oct 2006 13:11:52 -0400, jawod wrote:


consider

the applications to amateur radio.

http://www.breitbart.com/news/2006/1....em0doxnf.html

First application that comes to mind is hiding that 40M SteppIR on your
roof.

Or, more fun, how about having your entire house disappear along with
your CW transmissions? Not exactly RFI but ...


Hi John,

The link above is rather facile in its reporting, but so are most of
the pages provided by Dr. Smith (there's something of "Lost in Space"
about them).

Anyway, the science behind this news is found at:
http://www.ee.duke.edu/~drsmith/neg_ref_home.htm
which relates to topics I've offered in this group in the past 3 or 4
years. It comes from the photonics of negative refraction abstracted
to RF.

Boeing Phantom Works, here, has already done the bulk of the work and
their devices are displayed at the pages above (without citation), are
better documented at:
http://www.boeing.com/news/frontiers...gust/i_tt.html
and
http://ceta-p5.mit.edu/metamaterials...r_apl_2003.pdf

The last is a real paper, not the fluff going around in the popular
press.

73's
Richard Clark, KB7QHC
Richard,

Thanks so much for the links.

John
AB8O

Richard Clark wrote:
On Sat, 21 Oct 2006 13:11:52 -0400, jawod wrote:


consider

the applications to amateur radio.

http://www.breitbart.com/news/2006/1....em0doxnf.html

First application that comes to mind is hiding that 40M SteppIR on your
roof.

Or, more fun, how about having your entire house disappear along with
your CW transmissions? Not exactly RFI but ...


Hi John,

The link above is rather facile in its reporting, but so are most of
the pages provided by Dr. Smith (there's something of "Lost in Space"
about them).

Anyway, the science behind this news is found at:
http://www.ee.duke.edu/~drsmith/neg_ref_home.htm
which relates to topics I've offered in this group in the past 3 or 4
years. It comes from the photonics of negative refraction abstracted
to RF.

Boeing Phantom Works, here, has already done the bulk of the work and
their devices are displayed at the pages above (without citation), are
better documented at:
http://www.boeing.com/news/frontiers...gust/i_tt.html
and
http://ceta-p5.mit.edu/metamaterials...r_apl_2003.pdf

The last is a real paper, not the fluff going around in the popular
press.

73's
Richard Clark, KB7QHC

You know, I've always been puzzled by negative refraction. The basis of
positive refraction is that the speed of EMR (say light) decreases
within a given material. In negative refraction, the speed of light
INCREASES?

I guess as long as it is less than the speed of light in a vacuum, no
laws have been broken?

On Sat, 21 Oct 2006 18:20:40 -0400, jawod wrote:

You know, I've always been puzzled by negative refraction. The basis of
positive refraction is that the speed of EMR (say light) decreases
within a given material. In negative refraction, the speed of light
INCREASES?

I guess as long as it is less than the speed of light in a vacuum, no
laws have been broken?

Hi John,

My first reaction too.

However, when you look at the math, negative refraction is, well,
negative. What you describe (and I initially anticipated) is the
ratio of speed of light and the phase velocity being less than one.
Not the same thing being discussed here.

Another expression for negative refraction is "left-handed."

Anyway, more grist for you to review at:
http://physicsweb.org/articles/world/17/5/3

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Sat, 21 Oct 2006 18:20:40 -0400, jawod wrote:

You know, I've always been puzzled by negative refraction. The basis of
positive refraction is that the speed of EMR (say light) decreases
within a given material. In negative refraction, the speed of light
INCREASES?

I guess as long as it is less than the speed of light in a vacuum, no
laws have been broken?

Hi John,

My first reaction too.

However, when you look at the math, negative refraction is, well,
negative. What you describe (and I initially anticipated) is the
ratio of speed of light and the phase velocity being less than one.
Not the same thing being discussed here.

Another expression for negative refraction is "left-handed."

Anyway, more grist for you to review at:
http://physicsweb.org/articles/world/17/5/3

Following Richard's informative links, there is a page on the Duke site
which answers the "velocity of light" question:
http://www.ee.duke.edu/~drsmith/nega...ndex_about.htm

Near the end, it points out the difference between the phase velocity -
which is what we usually mean by "the velocity" of light - and the group
(or energy) velocity. It's only the latter that is made negative, but
the transport of energy is still in the forward direction.



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

jawod wrote:

You know, I've always been puzzled by negative refraction. The basis of
positive refraction is that the speed of EMR (say light) decreases
within a given material. In negative refraction, the speed of light
INCREASES?

I guess as long as it is less than the speed of light in a vacuum, no
laws have been broken?

I know very little about optics, but the velocity factor of EM waves in
hollow waveguide is always greater than one, that is, the phase velocity
is always greater than the speed of light. In fact, it increases as the
frequency lowers, approaching infinity at the cutoff frequency.

What prevents it from breaking any laws is that the group velocity,
which is the speed at which any change or information can be sent, is
always less than the speed of light.

I suspect that negative refraction is related to this, but will leave it
to the optics experts to say for sure.

Roy Lewallen, W7EL

Roy,
I haven't reviewed the physics of relativity lately, but I 'believe'
that value of C is specified as the velocity of energy propagation in a
vacuum... SInce that limit is not violated when the wave front is
propagating in a medium with a refractive index greater than vacuum,
i.e. C is slower than in a vacuum, then by O'Connor's Law of
Reciprocity the limit will not be broken if the the wave front is
propagating a medium with a refractive index less than a vacuum, i.e. C
is greater than in a vacuum...

denny / k8do

Denny wrote:
Roy,
I haven't reviewed the physics of relativity lately, but I 'believe'
that value of C is specified as the velocity of energy propagation in a
vacuum... SInce that limit is not violated when the wave front is
propagating in a medium with a refractive index greater than vacuum,
i.e. C is slower than in a vacuum, then by O'Connor's Law of
Reciprocity the limit will not be broken if the the wave front is
propagating a medium with a refractive index less than a vacuum, i.e. C
is greater than in a vacuum...

denny / k8do

Denny

I'm afraid I don't understand your post at all. Perhaps you are kidding
and I am fished in. So be it.

I do not understand how EMR can travel in any medium "faster" than in a
vacuum. Regarding Ray's post, I don't have a precise definition of
velocity factor but I suspect it is not describing wave propagation
directly. (And I am speaking as a total mathematical pedestrian

Negative refraction is damned puzzling ... and fascinating. Richard
seems to have the best links on the subject.

John
AB8O

jawod wrote:
. . .
I do not understand how EMR can travel in any medium "faster" than in a
vacuum. Regarding Ray's post, I don't have a precise definition of
velocity factor but I suspect it is not describing wave propagation
directly. (And I am speaking as a total mathematical pedestrian
. . .

Suppose you put a 1 GHz signal into a waveguide and stopped time so you
could look at it. Measure the distance taken up by one complete cycle,
and you'll find that it's greater than c/f. (In a vacuum, the distance
is c/f, and in a medium with velocity factor less than 1 it's less.) Now
start time up again, and look at just one spot along the waveguide. Sure
enough, a whole cycle goes by every ns. Sure looks like it's going
faster than c. This is the phase velocity.

But if you turn the signal off at one end of the waveguide and measure
how long it takes for it to disappear at the other, dang. The change
travels at the group velocity, which is never faster than the speed of
light.

Roy Lewallen, W7EL

John, it's all relative...

You need to do some basic reading...
First for antenna knowledge:
Walter Maxwell's book, Reflections II - most highly recommended by me -
and will clear up why you can't just 'fold' half of the dipole EM
around the arc of a circle to get more gain...

The ARRL antenna Handbook - pay particular attention to the Smith Chart
instructional..
John Krause, W8JK's, college text on antennas called, 'Antennas'

For basic physics of EM waves
'Dummy' series on physics
Start with Richard Feynman's public lecture series of popular books,
especially his QED...
Any college level text on physics and optics..

For that special moment with a loved one:
Any popular level book on the Special Theory of Relativity...

Unfortunately for non speakers, like the language of Spanish is
spanish, the language of all science is mathematics... Get the 'Dummy"
series book on algebra and do enough of the problems so that basic
equations don't panic you... This alone will make most of the
university level science books accessible...

I'll leave the Calculus to your discretion

I use the 'Dummy' series of books for skimming any topic that I lack
the basics in... Well done for the most part - or maybe I just don't
'get' the ones I thought weren't well done, eh?..

cheers ... denny / k8do


Roy Lewallen wrote:
jawod wrote:
. . .
I do not understand how EMR can travel in any medium "faster" than in a
vacuum.