Weird stuff: tiny resonant antennas
Science Hobbyist
Here's some weird ramblings I've posted on my site:
ENERGY-SUCKING ANTENNAS (electrically small resonators)
http://www.amasci.com/tesla/tesceive.html
MORE MUSINGS ABOUT ENERGY-SUCKING ANTENNAS
http://www.amasci.com/tesla/tescv2.html
Briefly: if an atom is 0.1 nanometer across, how can it
intercept light waves which have 500 nanometer wavelengths?
As an "antenna", an atom is far too small!
Answer: the atom resonates electrically, which creates a
strong synchronous AC field in its nearfield region. The local
e-field and b-field of the atom superposes with the fields of
the incoming EM waves, which causes the waves to bend towards
the atom. If we plot the Poynting vector field, we find that
the atom "sucks in" the energy like a miniature black hole.
As the waves march along, the phase of the atom's fields stay in
step, and the Poynting vector keeps pointing in towards the
atom. This works even though the atom is extremely small compared
to the wavelength, since the fields of the nearfield region *ARE*
the antenna.
The same thing occurs with conventional radio waves and
electrically small dipole antennas if a large AC voltage is
impressed upon the antenna. The same thing occurs with small
loop antennas if they are given a large current. Actively
resonating antennas draw in far more energy than passive
pickup coils. In theory, a tiny loop antenna can behave as if it
were electrically enormous, and can reach out and intercept
huge amounts of energy. At VLF frequencies, this effect
is significant. Nikola Tesla could have used this effect as part
of his "wireless power" scheme. It explains how even a tiny
antenna could intercept significant VLF wattage.
And you thought "crossed-field antennas" were weird! What about
the loopstick inside an AM receiver?
--
((((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
William Beaty bbe...@microscan.com
Software Engineer http://www.microscan.com
Microscan Inc., Renton, WA 425-226-5700 x1135
Sent via Deja.com http://www.deja.com/
Before you buy.
Ed Price
Bill:
So what limits the energy "sucked up" by the ferrite rod antenna in that
AM radio? I don't think I ever heard of a loopstick melting right out of
one of those cheap plastic radios.
Also, specifically which "theory" are you referring to when stating that
a small loop antenna can be "electrically enormous"?
Ed
russell shaw
If the losses in a ferrite rod antenna are made very low,
the currents will become much higher, limited only by the
radiation resistance which is very low for around 1MHz.
The selectivity will also become sharper.
Science Hobbyist wrote:
>
> And you thought "crossed-field antennas" were weird! What about
> the loopstick inside an AM receiver?
--
*******************************************
* Russell Shaw, B.Eng, M.Eng(Research) *
* Electronics Consultant *
* email: rus...@webaxs.net *
* Australia *
*******************************************
Scott Stephens
Science Hobbyist wrote in message <88uusc$irk$1...@nnrp1.deja.com>...
> Briefly: if an atom is 0.1 nanometer across, how can it
> intercept light waves which have 500 nanometer wavelengths?
> As an "antenna", an atom is far too small!
>
> Answer: the atom resonates electrically, which creates a
> strong synchronous AC field in its nearfield region. The local
> e-field and b-field of the atom superposes with the fields of
> the incoming EM waves,
It can't be a 'normal' radio wave, or it would disperse. Must be some type
of soliton?
> The same thing occurs with conventional radio waves and
> electrically small dipole antennas if a large AC voltage is
> impressed upon the antenna.
Is a large voltage/current necessary? Consider a high permitivity
peizoceramic will suck electric flux in, and a high mu ferromagnet will suck
magnetic flux in. A shorted multi-turn solenoid, having a greater reluctance
than free space will suck in magnetic flux too?
This is part of the mystery of field-theory, wheather you prefer aether or
virtual photons. If you place a relatively lower-resistance metal on a
carbon sheet that has a voltage gradient, and plot the voltage on the sheet,
you will notice a reduced voltage gradient around the low resistance metal
object. How does the current know to bend towards the metal discontinuity?
Same with current flowing in bent metal. How does current know to bend
smoothly rather than sharply? Electrodynamics has some answers. But the same
gradient, or pit, occurs around lower permitivity and permiability
materials. Regardless of the energy they contain.
> The same thing occurs with small
> loop antennas if they are given a large current. Actively
> resonating antennas draw in far more energy than passive
> pickup coils.
That is news to me.
> In theory, a tiny loop antenna can behave as if it
> were electrically enormous, and can reach out and intercept
> huge amounts of energy. At VLF frequencies, this effect
> is significant. Nikola Tesla could have used this effect as part
> of his "wireless power" scheme. It explains how even a tiny
> antenna could intercept significant VLF wattage.
I realy doubt it. I believe a highly charged small resonant circuit could
cancel out a complementary field.
It seems you have the picture in mind of what powdered iron does around a
magnet. I have heard stories about a steel chain around a superconducting
magnet, that when energized, became so rigid it could be sat on, unsupported
on end. I don't think that is true of space, at least at typical energies. I
realy doubt passing more current in a solenoid will reduce its reluctance,
or increase permiability.
Science Hobbyist
edp...@pacbell.net wrote:
> Bill:
>
> So what limits the energy "sucked up" by the ferrite rod antenna in
that
> AM radio? I don't think I ever heard of a loopstick melting right out
of
> one of those cheap plastic radios.
I imagine that the resistance of the wire, and maybe the losses in
the core would be the biggest limiting factor. If the current in
the loop antenna determines the "effective area" of the antenna,
but also the effective area of the antenna determines the
energy received (and so determines the current) ...then it sounds
to me like feedback, and if so, then there'd be exponential
growth initially when the circuit is first assembled. If the Q
is low, the current would never get to the steep part of
the exponential growth, so wouldn't rise to unexpected high
levels. We might never see any sort of "meltdown", because the
slight heating of the wire nips the growth process in the bud.
That doesn't mean the current wouldn't grow disproportionally huge
if the Q was made much higher.
Also, this phenomenon would be expected to occur at lower
frequencies. If the frequency is high, the effective area would
never become really huge. If the nearfield is assumed to be about
1/3 wavelength wide, then at 500KHz a "superconductor loopstick"
would act like an absorber-disk 200 meters across. That sounds
large, but for a 10KW station at 10KM distance, the ideal
antenna could only grab about a quarter of a watt. Even so, it
would be pretty neat to run a solar-cell motor using a little
bitty antenna.
> Also, specifically which "theory" are you referring to when stating
that
> a small loop antenna can be "electrically enormous"?
The ones discussed in these two papers mentioned in the references:
C. F. Bohren, "How can a particle absorb more than the light incident
on it?", Am J Phys, 51 #4, pp323 Apr 1983
H. Paul and R. Fischer "Light Absorbtion by a dipole", SOV. PHYS.
USP.,
26(10) Oct. 1983 pp 923-926
The above authors analyze the effect in terms of atoms and light
waves, but the phenomenon is classical physics, so it works for
any electrically short antenna connected to a high-Q resonator.
These guys below used the effect as part of a NASA project to
study ELF radio. They added active feedback to a loop antenna
in order to increase the received energy while allowing the system
to remain broadband. If the point is to create a local field in
synch with the incoming waves, then it doesn't matter how you do
it. You can build a resonator and let the received energy build up
a large field. Or you can drive the antenna with a op-amp in a
feedback loop that nulls out the wire resistance.
J. F. Sutton and C. C. Spaniol, "An Active Antenna for ELF Magnetic
Fields", PROCEEDINGS OF THE INTERNATIONAL TESLA SYMPOSIUM, 1990,
International Tesla Society, 1990
I've yet to draw any pictures, but here's one way to convince
yourself that this stuff is real. Plot the field lines of one
cycle of an EM wave (basically some parallel lines), then
superpose the field of a small dipole placed at the spot where
the transverse field lines of the EM wave go to zero. The EM
wave distorts the field of the dipole, so erase the dipole's field
and re-draw it with the appropriate distortion. Now draw some
flux lines perpendicular to the lines you've already drawn.
These transverse lines show the Poynting-vector energy flow. It
comes in from the side, following the EM wave as you'd expect.
Then it plunges into the dipole from all sides. (The above
papers contain proper diagrams.)
Apparantly ALL antennas do this (they "attract" the Poynting
vector lines so the lines dive into the metal surface of the
antenna elements.) That's how thin wires can intercept those
big broad EM wavefronts. The weirder things only start happening
when we make the wavelength enormous, then use a tiny resonator as
an antenna rather than a long thin wire. Also, I think it pays to
use voltage-mode antennas (dipoles with lots of volts on them)
rather than loop antennas, because the loop antennas rely on
high currents and consequent heat losses. Build a resonator
with small C and large L, and hook it to a dipole. (As opposed
to using large C and small L, and hooking it to a loop antenna.)
Science Hobbyist
russell shaw <rus...@webaxs.net> wrote:
> At last, someone has stated what i figured 10 years ago!
>
> If the losses in a ferrite rod antenna are made very low,
> the currents will become much higher, limited only by the
> radiation resistance which is very low for around 1MHz.
> The selectivity will also become sharper.
When I first started jabbering about this last September,
somebody mentioned that a massive loop antenna made from copper
pipe can pick up significant energy. There's a guy in Chicago
who runs little motors using high-Q resonant antennas (makes for
a good perpetual motion hoax!) But if he had an AM tower within
a few thousand meters, then that's not so impressive.
What would be impressive is if a resonator could be persuaded to
build up a high voltage rather than a high current. Maybe it
would take the shape of a tesla coil secondary, but super-
conductive. Even if it can intercept a fraction of a watt, a
corona discharge at that wattage would be amazing.
Robert Strand
> At last, someone has stated what i figured 10 years ago!
>
> If the losses in a ferrite rod antenna are made very low,
> the currents will become much higher, limited only by the
> radiation resistance which is very low for around 1MHz.
> The selectivity will also become sharper.
Not such a good thing, if the resonant circuit Q is greater about 200
the bandwidth gets so small that it cuts off the sidebands, which, after
demodulation, attenuates the high freqencies of the base-band signal.
Regards
Rob
Science Hobbyist
"Scott Stephens" <Sco...@Mediaone.net> wrote:
>
> > Answer: the atom resonates electrically, which creates a
> > strong synchronous AC field in its nearfield region. The local
> > e-field and b-field of the atom superposes with the fields of
> > the incoming EM waves,
>
> It can't be a 'normal' radio wave, or it would disperse. Must be some
type
> of soliton?
Nope, it's just the usual e-fields and b-fields that appear
around capacitors and coils. If the coil or capacitor is way
smaller than a wavelength, then you are able to create very strong
AC fields without having much radiation loss. The weird part is
that these fields can themselves act like an "invisible antenna."
They don't radiate, but they do interact with incoming waves if
the waves and the oscillating fields are in synch.
But after thinking about this for weeks, I see that it's not
so weird after all. Ever it was thus. Your normal half-
wave receiving dipole does exactly the same thing. It generates
a local field which, when superposed on the incoming waves, bends
them so that their energy "flows" into the extremely narrow
antenna wire.
We never think about it, but these relatively narrow wires always
have a relatively huge effective area. How can a LINE act as
a good absorber, when the waves look like a PLANE? The line
causes the planes to collapse inwards. If the same is true of
a "pointlike" antenna, and if small antennas can easily
absorb plane waves much larger than themselves, everyone gets
weirded out. But we should also get weirded out about the thinness
of conventional antenna wires.
> > The same thing occurs with conventional radio waves and
> > electrically small dipole antennas if a large AC voltage is
> > impressed upon the antenna.
>
> Is a large voltage/current necessary? Consider a high permitivity
> peizoceramic will suck electric flux in, and a high mu ferromagnet
will suck
> magnetic flux in. A shorted multi-turn solenoid, having a greater
reluctance
> than free space will suck in magnetic flux too?
I think this is the same effect. The EM waves can induce a current
in a loop antenna, but they can also align a bunch of electron
spins in a ferrite rod. In both cases there is energy stored
as fields around the antenna, and the enhanced fields cause a
greater energy flow to be diverted into the antenna from
surrounding space. I guess an LC resonator is like a "giant
iron atom" (or an iron atom is like a tuned loop antenna.)
However, a PZT or ferrite rod is broadband. The effect should be
much larger during resonance because the stored energy in
the resonator can build up to a high level and create a much
larger field. I think.
> This is part of the mystery of field-theory, wheather you prefer
aether or
> virtual photons. If you place a relatively lower-resistance metal on a
> carbon sheet that has a voltage gradient, and plot the voltage on the
sheet,
> you will notice a reduced voltage gradient around the low resistance
metal
> object. How does the current know to bend towards the metal
discontinuity?
This resonant-antenna idea would be equivalent to replacing your
metal object with two electrodes connected to a tiny battery.
It bends the fields at a much greater distance than a passive
object. Or better yet, make it passive but let it power
itself: connect a large-value capacitor to the electrodes. As
the drive voltage on the carbon sheet pumps current through
the capacitor, its voltage rises, but its incoming wattage does
not remain constant. The capacitor intercepts energy at a
greater rate when it is partially charged than when it is
totally discharged. By DRIVING those electrodes, our receiver
can absorb more energy. It's not a perfect analogy, but I think
it illustrates the basic idea behind a driven (oscillating) antenna.
> > The same thing occurs with small
> > loop antennas if they are given a large current. Actively
> > resonating antennas draw in far more energy than passive
> > pickup coils.
>
> That is news to me.
It's the weirdest part! Suppose I set up two big metal plates a
few feet apart, and connect a high-freq AC power supply to them.
Any small pair of "pickup plates" with a load resistor could
intercept some of this energy via capacitive coupling. We
could improve things by chosing the right load resistor to
draw maximum power from the pickup plates. However, what happens
if we connect a coil across the pickup plates and tune it
for resonance? A big oscillation builds up. The voltage across
the plates grows much higher, but the induced current going
through them does not drop in proportion, and this means that
the received power is higher. It resembles impedance matching,
but it's really something different. It involves the e-field and
b-field in the region around the plates rather than the impedance
of circuit components. Rather than "impedance match", it
more resembles an increase in the AREA of the pickup plates.
Yes it's just a "coupling" effect. But where EM waves are
concerned, whenever we "couple" to a larger region of space,
the effective area of the antenna becomes larger, and it
essentially sucks energy in from a greater distance around itself.
As a friend pointed out, AM radio really "sucks."
I like the concept of the jar of sodium gas which blocks sodium
light but passes everything else. Those atoms are way smaller
than the light waves, right? At most frequencies they act small,
and the gas is transparent. At the sodium line frequency, how
is it that they can block the light? Simple: each atom grows
a fuzzy black cloud around itself, and the cloud is made
of oscillating EM fields at the resonant frequency. The "cloud" is
in synch with the sodium light, so it only looks big and black to
the waves at that frequency. When you tune your light to the
right frequency, the little atoms seem to swell into big
black puffballs. So does the loopstick in a portable AM radio.
Or so this "resonant antenna" concept says.
> It seems you have the picture in mind of what powdered iron does
around a
> magnet. I have heard stories about a steel chain around a
superconducting
> magnet, that when energized, became so rigid it could be sat on,
unsupported
> on end. I don't think that is true of space, at least at typical
energies. I
> realy doubt passing more current in a solenoid will reduce its
reluctance,
> or increase permiability.
Hey, that's it! That's what's happening. It doesn't have anything
to do with the DC permiability of course. Because the
oscillating fields of the tuned circuit are locked in synch with
the incoming EM waves, they present a constant "back EMF" which
lets the antenna interact more strongly with the waves. It only
works at a particular frequency, but at that frequency, the
loop antenna would seem to attain a huge permiability, and it
would distort the fields across a much greater volume of space,
as if it had grown a big ferrite rod down its middle.
Alan Boswell
> Here's some weird ramblings I've posted on my site:
>
> ENERGY-SUCKING ANTENNAS (electrically small resonators)
> http://www.amasci.com/tesla/tesceive.html
>
> MORE MUSINGS ABOUT ENERGY-SUCKING ANTENNAS
> http://www.amasci.com/tesla/tescv2.html
>
> Briefly: if an atom is 0.1 nanometer across, how can it
> intercept light waves which have 500 nanometer wavelengths?
> As an "antenna", an atom is far too small!
>
> Answer: the atom resonates electrically, which creates a
> strong synchronous AC field in its nearfield region. The local
> e-field and b-field of the atom superposes with the fields of
> the incoming EM waves, which causes the waves to bend towards
> the atom. If we plot the Poynting vector field, we find that
> the atom "sucks in" the energy like a miniature black hole.
> As the waves march along, the phase of the atom's fields stay in
> step, and the Poynting vector keeps pointing in towards the
> atom. This works even though the atom is extremely small compared
> to the wavelength, since the fields of the nearfield region *ARE*
> the antenna.
>
> The same thing occurs with conventional radio waves and
> electrically small dipole antennas if a large AC voltage is
> impressed upon the antenna. The same thing occurs with small
> loop antennas if they are given a large current. Actively
> resonating antennas draw in far more energy than passive
> pickup coils. In theory, a tiny loop antenna can behave as if it
> were electrically enormous, and can reach out and intercept
> huge amounts of energy. At VLF frequencies, this effect
> is significant. Nikola Tesla could have used this effect as part
> of his "wireless power" scheme. It explains how even a tiny
> antenna could intercept significant VLF wattage.
>
> And you thought "crossed-field antennas" were weird! What about
> the loopstick inside an AM receiver?
>
> --
> ((((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
> William Beaty bbe...@microscan.com
> Software Engineer http://www.microscan.com
> Microscan Inc., Renton, WA 425-226-5700 x1135
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Small resonant antennas can be very effective. If you have a lossless
small
antenna its receiving area is wavelength^2/4pi, no matter how small it is.
So at 1MHz even a tiny antenna has a capture area of about 700 square
metres.
BUT there's a catch - it has to be a lossless antenna and the impedance of
the
load (i.e. the input impedance of the receiver) has to be the complex
conjugate
of the antenna impedance. If the antenna impedance is (say) 10^-3 - j1000
there is a problem in matching that without introducing losses. There's
another
catch - the Q factor of my example is 10^6, which means that its
bandwidth
is only 1Hz for a 1MHz carrier frequency. That is useless for just about
any purpose.
Loopstick antennas as used in radios are effective for their purpose but
they
are very lossy. It doesn't matter because enough power is transmitted to
allow the programme to get through. With one transmitter serving 1 million
cheap receivers the economics of this system is right. For communications,
when there is 1 transmitter and 1 receiver, it is better to transmit less
power
and use a more efficient receive antenna.
Alan
Peter Lawton
>
> Small resonant antennas can be very effective. If you have a lossless
> small
> antenna its receiving area is wavelength^2/4pi, no matter how small it is.
> So at 1MHz even a tiny antenna has a capture area of about 700 square
> metres.
So does that mean that it has bigger shadow than one might expect?
If you had two such antennas fairly close to each other, the one would
decrease the signal available for the other?
Peter Lawton
Scott Stephens
metaphors will get very confusing and deceptive. There are three ball parks
to play in:
1. The vacuum or aether, and its fields and/or virtual particles
2. Electrons and nuclei that have their own fields and modes
3. Antenni or transducers, inductors, capacitors, ferrites and ceramics.
Electrons and particles seem to be forms of the vacuum energy has twisted
into stable shapes (according to E=MC^2), particles can condense out of the
vacuum with appropriate energy and conditions. And antenni, inductors and
capacitors are made out of particles. In effect the unpaired spins of
ferrites make them big (magnetic) atoms.
Atoms are dynamic systems. A photon, with an impulse-like field, causes
orbital momentum change in the electron-atom system, that changes its field
to cancel the photon field as it is absorbed. The fields of photons and
atoms are matched, because atoms make photons (unless the atoms have a
velocity spread, such as in a high-temperature/pressure laser). The atom is
not like a normal tuned circuit, it dyamicaly changes tuning as it absorbs
and radiates.
If the atom doesn't absorb the photon, the electron probably has some type
of temporary orbit change, and re-radiates the photon. There is a time delay
as energy leaves the photon field and shakes the electron-atom system.
Therefore the refractive index (time delay) effects we see with glass, water
and transparent materials?
Rather than orbiting particles, I like the concept of resonant ring
particles joined by fields, and separated by trapped photons (stored
resonant modes), such as the models at http://www.oophda.com/ and
http://www.commonsensescience.org/ Nothing orbits, but strings of flux
vibrate a geodesic dome of electrons around the nucleus.
Why don't atoms and photons radiate their fields away? What confines the
fields? Some form of nonlinearity or extra dimensions are needed, which I
was able to gather from some papers at http://xxx.lanl.gov/find :
"9902008 The energy conservation law in classical electrodynamics" (which
highlights problems with the Poynting vector) and "9802039 Historical Note
on Relativistic Theories of Electromagnetism".
I'm partial to considering a 4th longitudinal wave mass-time dimension, that
can compress (the magnetic force), and increase density (electric force)
which Paul Stowe explained here back in 7/1/99 in his "Re: what *is*
magnetic permeability ?" post, which you can retrieve at Deja. The other
three dimension (normal space) only support transverse, not longitudinal
waves. Charge, coulombs, equates to kilogram-seconds with a magnetic
tension, and electric density. This may explain why displacement currents in
space do not produce magnetic fields.
Oscillating fields trap themselves into solitons-photon waves or loop in on
themselves to form soliton standing wave particles, that have increased
density, which shows up as electric charge. The increased density,
permitivity, trapped by the soliton particles is what sucks flux in, warps
the fields around the particles.
But to make your own radio frequency particle, or electromagnetic soliton
wave (and wouldn't those be usefull!!!) it would probably require quite a
bit of power. Maybe some differential-geometery expert would care to help me
calculate the cutoff frequency and power densities for such things?
The field around your tank might cancel an incident wave, but it better not
radiate away its energy. If it is an active system, it may have a large
static field that changes to cancel an incident wave, like a feedback
control system. But then it can't extend over 1/2 wavelength deep without an
extended structure. And what does it buy you? Probably not a better noise
figure or power efficiency.
One application I thought of was a miniture phased array radar. A small, say
8 x 10" panel has ferro-ceramic spheres arranged in a grid, like a photonic
crystal. In the high permitivity-permiability substrate I could shrink the
size of the array. But to impedance match the array to space so it will
transduce energy, I would have to have a large matching device, that would
defeat the purpose of the small array.
>Your normal half-
> wave receiving dipole does exactly the same thing. It generates
> a local field which, when superposed on the incoming waves, bends
> them so that their energy "flows" into the extremely narrow
> antenna wire.
The antenna wire is a conductor which is a virual dead short for the
electric field of space (x-rays above the metal plasma-freq
notwithstanding). But it doesn't do much good over 1/2 wavelength
>How can a LINE act as
> a good absorber, when the waves look like a PLANE?
It can only suck in as much flux as space will permit it, by setting up
opposing currents and fields, according to electrodynamics. You can model
space as an LC network in this case. Its not a black hole.
> I guess an LC resonator is like a "giant iron atom" (or an iron atom is
like a tuned loop antenna.)
The LC resonator will not warp space (electricaly) around it, like an atom
will. It will radiate away its field.
Once again, I don't see how (atomic particles notwithstanding) the current
and voltages in inductors and capacitors will cause more flux to be bent
into them, although they will cancel out or transmit as well as larger
elements.
>> If you place a relatively lower-resistance metal on a
>> carbon sheet that has a voltage gradient, and plot the voltage on the
>sheet,
>> you will notice a reduced voltage gradient around the low resistance
>metal
>> object. How does the current know to bend towards the metal
>discontinuity?
>
> This resonant-antenna idea would be equivalent to replacing your
> metal object with two electrodes connected to a tiny battery.
> It bends the fields at a much greater distance than a passive
> object.
Yes, the gradient has changed, no energy is not otherwise sucked in. A plot
of the impedance of the sheet will reveal it is linear, a battery will just
superpostion itself. If the sheet was a nonlinear semiconductor, that's
different. If space is longitudinal and/or hyperdimensional, thats like a
nonlinear sheet.
> I like the concept of the jar of sodium gas which blocks sodium
> light but passes everything else. Those atoms are way smaller
> than the light waves, right?
Both the light and atoms are probably smaller physicaly than electricaly
>At the sodium line frequency, how
> is it that they can block the light?
The absorb it, but don't re-radiate it? Convert it too heat via atomic
vibration?
Scott
Tom Bruhns
Science Hobbyist (William Beaty) wrote:
> The same thing occurs with conventional radio waves and
> electrically small dipole antennas if a large AC voltage is
> impressed upon the antenna. The same thing occurs with small
> loop antennas if they are given a large current. Actively
> resonating antennas draw in far more energy than passive
> pickup coils.
Are you suggesting that such antennas are not linear systems?
> In theory, a tiny loop antenna can behave as if it
> were electrically enormous, and can reach out and intercept
> huge amounts of energy.
Do you have pointers to such theory?
> At VLF frequencies, this effect
> is significant. Nikola Tesla could have used this effect as part
> of his "wireless power" scheme. It explains how even a tiny
> antenna could intercept significant VLF wattage.
I live a couple wavelengths from a VLF transmitting station that
radiates about 500kW. Do you have an estimate of the useful energy I
could expect to intercept ... with how tiny an antenna, and with what
sort of practical configuration?
>
> And you thought "crossed-field antennas" were weird! What about
> the loopstick inside an AM receiver?
Are you proposing that they (loopsticks) might be any different than
explained in the standard antenna reference books? It seems to me that
those explanations predict the performance actually measured for such
antennas.
Cheers,
Tom
Science Hobbyist
"Scott Stephens" <Sco...@Mediaone.net> wrote:
> Were talking apples, oranges and tomatoes here.
True. There are the static fields associated with charges and
with the spin of charges. There are the dynamic fields of the
nearfield region. And there are the EM fields of propagating
waves. All of these are part of antenna physics, and also part
of coil/capacitor physics. If you want get into other
things besides Maxwell's equations and conventional Quantum
Physics, then that's frontier science. I'm talking
conventional science here.
> Atoms are dynamic systems. A photon, with an impulse-like field,
A photon does not have an impulse-like field, at least according
to conventional Quantum Mechanics. It has an impulse-like
interaction with atoms, but that's entirely different. For example,
a single photon can carry an entire 1MHz radio wave, yet the photon
is still pointlike (and the Fourier spectrum of such a tiny
pointlike field would be broadband rather than single-frequency.)
For photons to be pointlike, yet without ending up with a
broadband frequency spectrum, we assume that the fields
associated with photons are spread out over a huge volume of
space, yet the photons themselves are not. A photon is not like
an electron, it does not have flux lines diving into the
photon. Instead, the flux-lines of a big broad EM wave ARE
the photon, and the photon *IS* the big broad EM wave. This
involves wave/particle duality, wavefunction collapse,
and Schrodinger's Cat stuff of course.
> The atom is
> not like a normal tuned circuit, it dyamicaly changes tuning as it
absorbs
> and radiates.
That's what I'm wondering about. If I visualize an atom to be
a normal tuned circuit which also has nonlinear characteristics
AFTER it absorbs energy, then I can better understand how tiny
atoms can absorb relatively huge wavelengths of light. DURING
the absorbtion of an EM wave, I can visualize the atom as being
a coil/capacitor which surrounds itself with fields and behaves
like a conventional EM antenna.
One incorrect explanation I've heard is this: atoms can absorb
long lightwaves because atoms absorb tiny photons rather than
absorbing the waves themselves.
This is not true. It violates wave/particle duality. The
correct explanation is in the Bohren paper. Light does NOT
change into tiny photons in order to be absorbed, any more than
antenna wires absorb tiny photons rather than big broad EM
plane waves. In both cases we can think entirely in terms
of fields and forces applied to charges. As with antennas, we MUST
be able to explain light absorbtion in terms of either waves
OR particles, otherwise we've discovered a hole in Quantum
Mechanics. If you discover a situation where EM waves MUST be
made of photons rather than fields, then you've discovered
something important which is not part of normal science. The
Bohren paper shows how to explain atomic absorbtion in terms of
antennas and wave mechanics rather than particle interactions.
It's conventional science. True, it is very non-traditional.
That's why I like it! :)
> Rather than orbiting particles, I like the concept of resonant ring
> particles joined by fields, and separated by trapped photons (stored
> resonant modes), such as the models at http://www.oophda.com/ and
> http://www.commonsensescience.org/ Nothing orbits, but strings of flux
> vibrate a geodesic dome of electrons around the nucleus.
Good analogy. Sounds analogous to LC resonators to, eh?
> >How can a LINE act as
> > a good absorber, when the waves look like a PLANE?
>
> It can only suck in as much flux as space will permit it, by setting
up
> opposing currents and fields, according to electrodynamics. You can
model
> space as an LC network in this case. Its not a black hole.
Exactly. That's my point. The fields of the antenna act to suck
EM waves into the wire. In the example of the half-wave dipole
two things get missed:
If we could make the fields very strong, even a much
smaller receiving antenna could "suck in" EM waves.
This explains how a 0.1 nanometer atom can absorb waves
of 600 nanometers wavelength, but without needing to
include the "photon" concept in our explanations.
> > I guess an LC resonator is like a "giant iron atom" (or an iron
atom is
> like a tuned loop antenna.)
>
> The LC resonator will not warp space (electricaly) around it, like an
atom
> will. It will radiate away its field.
>
> Once again, I don't see how (atomic particles notwithstanding) the
current
> and voltages in inductors and capacitors will cause more flux to be
bent
> into them, although they will cancel out or transmit as well as larger
> elements.
The inductors and capacitors do the same thing that a thin
antenna wire does. A thin antenna wire acts like a broad sheet
of absorbtive material. It does so because the fields created
by the current and voltage of the wire cause EM energy to divert
from space and flow into the wire. A one-dimensional antenna wire
can absorb a two-dimensional plane wave, but a zero-dimensional
dipole (a tiny coil or capacitor) can do the same thing for the
same reasons. If an antenna wire can erect a large "absorber
sheet" thats made of fields, then a tiny coil or capacitor can do
the same. The explanation is contained in totally conventional
field dynamics. The only unusual part is that people don't think
in these terms already!
> >> If you place a relatively lower-resistance metal on a
> >> carbon sheet that has a voltage gradient, and plot the voltage on
the
> >sheet,
> >> you will notice a reduced voltage gradient around the low
resistance
> >metal
> >> object. How does the current know to bend towards the metal
> >discontinuity?
> >
> > This resonant-antenna idea would be equivalent to replacing your
> > metal object with two electrodes connected to a tiny battery.
> > It bends the fields at a much greater distance than a passive
> > object.
>
> Yes, the gradient has changed, no energy is not otherwise sucked in.
A plot
> of the impedance of the sheet will reveal it is linear, a battery
will just
> superpostion itself. If the sheet was a nonlinear semiconductor,
that's
> different. If space is longitudinal and/or hyperdimensional, thats
like a
> nonlinear sheet.
I'm not being entirely clear. The "nonlinearity" involves changes
in the shape of the linear fields, not nonlinearities in the
medium. In the carbon-sheet example, it boils down to this:
a charged capacitor absorbs energy at a greater rate than an
uncharged capacitor if the charging current is the same for
both, since energy absorbtion is just V x I. If I is
relatively constant, then a capacitor with larger V is absorbing
more energy per second. This is obvious in terms of
circuit concepts. I terms of EM field concepts, we end up
realizing that the distorted voltage fields created by the
charged capacitor will end up attracting more energy from the
carbon sheet. This is a non-traditional way to view the
situation, but it is just as correct. The "nonlinearity"
is a natural part of P = V x I.
Science Hobbyist
peter_jo...@virgin.net wrote:
> Alan Boswell wrote:
> >
>
> So does that mean that it has bigger shadow than one might expect?
> If you had two such antennas fairly close to each other, the one would
> decrease the signal available for the other?
AM loopstick antennas supposedly do just this.
I don't have two AM portable radios here, but I've heard that if
you receive a weak station with one radio, then you tune
a nearby *unpowered* radio to the same frequency, the unpowered
radio can steal some of the signal. That's the shadow effect.
Even when the power is off, there's still a tuning capacitor
connected across the loopstick. (The AGC in the radios will
probably hide this effect if strong stations are used.)
Cortland Richmond
changes in the energy levels of the associated electrons. Since these energy
levels are quantized, such interactions may only occur at specific energy
levels, which explanation got Einstein the Nobel prize. However, we are
talking about photons of _light_ here, not radio. As far as I know, the
lowest frequencies at which atoms may absorb or emit energy in this manner
are in the microwave range, where the effect lets masers operate. Or used
to, until transistors got so good.
Cortland
(ka...@saber.net)
Cortland
(ka...@saber.ent)
Scott Stephens
Science Hobbyist wrote in message <8948v1$d2i$1...@nnrp1.deja.com>...
>In article <k4gt4.10143$84.332786@elnws01>,
> "Scott Stephens" <Sco...@Mediaone.net> wrote:
>> Atoms are dynamic systems. A photon, with an impulse-like field,
I mean a photon is not a sinusoid wave train...
>For example a single photon can carry an entire 1MHz radio wave
...
>and the Fourier spectrum of such a tiny pointlike field would be broadband
rather than single-frequency.)
Of course, it doesn't oscillate long certainly, isn't the bandwidth
inversely proportional to the pulse width?
> For photons to be pointlike, yet without ending up with a
> broadband frequency spectrum, we assume that the fields
> associated with photons are spread out over a huge volume of
> space, yet the photons themselves are not.
Yea, and an advance wave has to be emitted by the recieving atom to travel
backwards in time to the photon emitting atom, so it can emit the photon,
right? I hate that about QED. Just because the theory is so irritatingly
accurate, doesn't mean reality is realy that way. The fourier transform is
not the only one. If you can stomach extra dimensions, or longitudinal waves
and nonlinear equations, you can have solitons and Wavelets and no spooky
QED non-sense that is so well-refuted at http://www.commonsensescience.org/
> A photon is not like
> an electron, it does not have flux lines diving into the
> photon. Instead, the flux-lines of a big broad EM wave ARE
> the photon, and the photon *IS* the big broad EM wave. This
> involves wave/particle duality, wavefunction collapse,
> and Schrodinger's Cat stuff of course.
Solitons are wave-particles that are compact and non-dispersive like
particles, and scatter and interfere like waves.
>> It can only suck in as much flux as space will permit it, by setting
>up
>> opposing currents and fields, according to electrodynamics.
> Exactly. That's my point. The fields of the antenna act to suck
> EM waves into the wire. In the example of the half-wave dipole
> two things get missed:
>
> If we could make the fields very strong, even a much
> smaller receiving antenna could "suck in" EM waves.
No, you missed my point! Its not the field of the antenna, its the
displacement currents, the reaction fields in space that prevents more flux
from flowing into the antenna. Poisson's equation.
> The inductors and capacitors do the same thing that a thin
> antenna wire does. A thin antenna wire acts like a broad sheet
> of absorbtive material. It does so because the fields created
> by the current and voltage of the wire cause EM energy to divert
> from space and flow into the wire.
I don't buy it. It is like your saying the voltage across or current through
a resistor determines its resistance. Of course the resistance of a resistor
can be defined by V/I, but when we talk about a given resistor it is
typicaly the cause and the current the effect of the voltage across it.
Similarly, the gain, radiation resistance, of a given metal dipole, or
inductor/capacitor combination in space will not be determined by the
voltage across or current through it.
True the fields surrounding it may cancel out the field in a large field
around it. So you could contrive a scenario where a tiny LC resonator with
lots of power cancels out (absorbs, if you will) the same incident wave a
much larger dipole can. But this is not the same as an atom sucking in the
field-space around it.
When the energy density, rates of change and field configurations are
favorable for solitons, the Poynting vector of the soliton's field bends the
Poynting vector of incident energy into the soliton, very similar to
relativistic distortions. Now you might think I am agreeing with you (I
guess I am) at this point, but the power density is such for particles and
photons that I don't think you will be doing it short of microwave and
kilojoule regimes. The fringe conspiracy stuff I read on Keely-net says the
Russians need power plants to fire up their scalar toys ;-)
Scott
Science Hobbyist
Cortland Richmond <Cortland...@usa.alcatel.com> wrote:
> I understand that atom/photon interaction is a result of (or causes)
> changes in the energy levels of the associated electrons. Since these
energy
> levels are quantized, such interactions may only occur at specific
energy
> levels, which explanation got Einstein the Nobel prize. However, we
are
> talking about photons of _light_ here, not radio.
Does this mean you believe that light is fundamentally different
than radio? :)
The big question is this: when atoms absorb light, is the process
at all similar to the way an electrically small resonant loop
antenna absorbs radio waves? Well, electron shells of the atoms
have big quanta, while the quantized states of a macroscopic
metal antenna are incredibly small. That doesn't mean that atoms
only use photons, while radio antennas only use waves. Wave/
particle duality applies to both, and no matter how few photons
are on the fly, they still form an extended electromagnetic
waves. For this reason we can can talk about light absorbtion
in terms of fields and resonance, rather than in terms of photons
and electron states. The uniform size of an atom's energy
states corresponds to the narrow bandwith of a resonant antenna.
And the enhanced "effective area" of a loop antenna at
resonance corresponds to the enhanced "photon collision
cross-section" area of an atom when the photons have the same
energy as the atom's internal electron transistions.
> As far as I know, the
> lowest frequencies at which atoms may absorb or emit energy in this
manner
> are in the microwave range, where the effect lets masers operate. Or
used
> to, until transistors got so good.
Right. But look how small an ammonia molecule is when compared
to the microwave wavelength. How can small atoms absorb more
than the radiation incident upon them? The Bohren paper points
out that the same question also applies to electrically-small
resonant antennas. Because strong AC fields occur at
resonance, small antennas can swell up in "size" until
they resemble quarter-wave dipoles. If atoms behave in the same
way, then at resonance an atom will cast a shadow which resembles
the shadow of a quarter wave dipole, even though the atom is far,
far smaller.
I wonder how big a wavelength a molecule can absorb? Is the
cutoff really up in the microwave band? If for some reason a
molecule had a low-energy electron transition, then that
molecule will be resonant at that low frequency, and will absorb
waves having that wavelength, even if the wavelength
is immensely larger than the diameter of the molecule. Since
the resonant molecule can be physically much smaller than
a quarter wavelength, in principle a single molecule could
absorb AM radio or 60Hz radiation.
Separate topic: I hear that head shields for cellphone users
are selling for $50 a pop. On the one hand, maybe there's a
physical mechanism whereby 900MHz radiation can affect
chemical reactions. On the other hand, I bet somebody
eventually starts selling "ferrite ointment" which you can
slather on the side of your head to keep the nasty EMFs out of
your brain!
:)
(((((((((((((((((( ( ( ( ( (O) ) ) ) ) ))))))))))))))))))
William J. Beaty SCIENCE HOBBYIST website
bi...@eskimo.com http://www.amasci.com
EE/programmer/sci-exhibits science projects, tesla, weird science
Seattle, WA 206-781-3320 freenrg-L taoshum-L vortex-L webhead-L
Alan Boswell
> Alan Boswell wrote:
> >
>
> > Small resonant antennas can be very effective. If you have a lossless
> > small
> > antenna its receiving area is wavelength^2/4pi, no matter how small it is.
> > So at 1MHz even a tiny antenna has a capture area of about 700 square
> > metres.
>
> So does that mean that it has bigger shadow than one might expect?
> If you had two such antennas fairly close to each other, the one would
> decrease the signal available for the other?
>
> Peter Lawton
The shadowing effect is only noticed when they are very close. Their actual
capture area is always much smaller than the theoretical figure because it is
impossible to extract the available power since the optimum load impedance
is impossible to achieve. Shadowing occurs when the mutual impedance between
two antennas is of comparable magnitude to the self-impedance of either. For
loopstick antennas the self-impedance is dominated by the large reactance, and
the mutual impedance is small unless they are very close. There can be an
effect when you put two radios close together.
Alan
Alan Boswell
Tom - assuming the station is on 17kHz you are 35km away, and with 500kW
radiated you can expect the field intensity to be 190 millivolts per metre.
With a 10m-high monopole receiving antenna in your garden the open-circuit
voltage will be about 0.9 volts. But - the source impedance for this
voltage
will be about (0.0001 - j200000) ohms, which is determined by the radiation
resistance and the capacitance of the antenna. If you can match perfectly
to this
impedance the available power is 2kW. The catch is, it's impossible to
provide
the right load impedance, so, practically, the extracted power is
negligible.
Similar arguments apply to a loop antenna.
Alan
Cortland Richmond
of photons by atoms is limited to energy levels corresponding to states
their orbital electrons can occupy (the photoelectric effect).
Consequently, radio signals, unless of sufficiently high frequency specific
to the elements concerned, won't be absorbed in this way.
Actually, the above is incomplete. There IS an effect, in which atoms
subjected to a magnetic field will absorb radio waves of specific
frequencies at lower ranges, but this involves (I think) resonating with
the spin of protons in the nucleus. This is used in NMR imaging. I don't
know what frequency a "normal" earth magnetic field would resonate, but I
understand 70 MHz is typical for an NMR machine, with its much stronger
magnetic field.
Cortland
(ka...@saber.net)
Science Hobbyist wrote:
> In article <38B5AE7C...@usa.alcatel.com>,
> Cortland Richmond <Cortland...@usa.alcatel.com> wrote:
> > I understand that atom/photon interaction is a result of (or causes)
> > changes in the energy levels of the associated electrons. Since these
> energy
> > levels are quantized, such interactions may only occur at specific
> energy
> > levels, which explanation got Einstein the Nobel prize. However, we
> are
> > talking about photons of _light_ here, not radio.
>
> Does this mean you believe that light is fundamentally different
> than radio? :)
>
> The big question is this: when atoms absorb light, is the process
> at all similar to the way an electrically small resonant loop
> antenna absorbs radio waves? Well, electron shells of the atoms
> have big quanta, while the quantized states of a macroscopic
> metal antenna are incredibly small. That doesn't mean that atoms
> only use photons, while radio antennas only use waves. Wave/
> particle duality applies to both, and no matter how few photons
> are on the fly, they still form an extended electromagnetic
> waves. For this reason we can can talk about light absorbtion
> in terms of fields and resonance, rather than in terms of photons
> and electron states. The uniform size of an atom's energy
> states corresponds to the narrow bandwith of a resonant antenna.
> And the enhanced "effective area" of a loop antenna at
> resonance corresponds to the enhanced "photon collision
> cross-section" area of an atom when the photons have the same
> energy as the atom's internal electron transistions.
>
> > As far as I know, the
> > lowest frequencies at which atoms may absorb or emit energy in this
> manner
> > are in the microwave range, where the effect lets masers operate. Or
> used
> > to, until transistors got so good.
>
Cortland Richmond
your own hgh-quality vacuums. Started with refrigerator compressors and went
through mercury pumps for a hard vacuum.
Interesting Web Page. Thanks!
Cortland
(ka...@saber.net)
Science Hobbyist wrote:
> In article <38B6FAF9...@usa.alcatel.com>,
> Cortland Richmond <Cortland...@usa.alcatel.com> wrote:
> > No, I'm not saying radio and light are different. Only that the
> absorption
> > of photons by atoms is limited to energy levels corresponding to
> states
> > their orbital electrons can occupy (the photoelectric effect).
> > Consequently, radio signals, unless of sufficiently high frequency
> specific
> > to the elements concerned, won't be absorbed in this way.
>
> We're in agreement. If a molecule for some reason had a low-
> energy state transition, it could receive radio waves, even
> though the "antenna" is the size of a molecule. The energy
> per photon would be extremely low. Maybe that's why we
> never hear about such things: if the energy per photon is
> far less than the energy stored in a chemical bond, then
> longwave EM wouldn't be able to break bonds directly, and
> radio waves wouldn't affect chemistry. This would only be
> true if there were no effects involving the absorbtion of
> multiple photons, or effects where a tiny nudge could have
> a big effect on a chemical reaction already under way.
>
> > Actually, the above is incomplete. There IS an effect, in which atoms
> > subjected to a magnetic field will absorb radio waves of specific
> > frequencies at lower ranges, but this involves (I think) resonating
> with
> > the spin of protons in the nucleus. This is used in NMR imaging. I
> don't
> > know what frequency a "normal" earth magnetic field would resonate,
>
> Proton precession magnetometers use the proton spin of the H
> in water molecules, and the frequency is around 2100Hz. This
> was in an old THE AMATEUR SCIENTIST project in SciAm, where a
> bottle of water with a coil around it produced a "ding" sound
> after amplification. This is a case where you can directly
> hear the resonant frequency of atoms, but it doesn't really
> correspond to photon absorbtion by electron shells.
>
> home-grown proton precession magnetometers
> http://www.portup.com/~dfount/proton.htm
>
> ((((((((((((((((( ( ( ( ( (O) ) ) ) ) ))))))))))))))))))
> William J. Beaty SCIENCE HOBBYIST website
> bi...@eskimo.com http://www.amasci.com
> EE/programmer/sci-exhibits science projects, tesla, weird science
> Seattle, WA 206-781-3320 freenrg-L taoshum-L vortex-L webhead-L
>
russell shaw
a nearby am transmitter.
If you have a big resonant loop, and the voltage builds up, then
this also implies the *current* builds up.
Science Hobbyist wrote:
>
> In article <38B3BFE3...@webaxs.net>,
> russell shaw <rus...@webaxs.net> wrote:
> > At last, someone has stated what i figured 10 years ago!
> >
> > If the losses in a ferrite rod antenna are made very low,
> > the currents will become much higher, limited only by the
> > radiation resistance which is very low for around 1MHz.
> > The selectivity will also become sharper.
>
> When I first started jabbering about this last September,
> somebody mentioned that a massive loop antenna made from copper
> pipe can pick up significant energy. There's a guy in Chicago
> who runs little motors using high-Q resonant antennas (makes for
> a good perpetual motion hoax!) But if he had an AM tower within
> a few thousand meters, then that's not so impressive.
>
> What would be impressive is if a resonator could be persuaded to
> build up a high voltage rather than a high current. Maybe it
> would take the shape of a tesla coil secondary, but super-
> conductive. Even if it can intercept a fraction of a watt, a
> corona discharge at that wattage would be amazing.
>
> --
> ((((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
> William Beaty bbe...@microscan.com
> Software Engineer http://www.microscan.com
> Microscan Inc., Renton, WA 425-226-5700 x1135
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
--
Science Hobbyist
"Scott Stephens" <Sco...@Mediaone.net> wrote:
>
> Science Hobbyist wrote in message <8948v1$d2i$1...@nnrp1.deja.com>...
> > "Scott Stephens" <Sco...@Mediaone.net> wrote:
>
> >> Atoms are dynamic systems. A photon, with an impulse-like field,
>
>
> ...
> >and the Fourier spectrum of such a tiny pointlike field would be
broadband
> rather than single-frequency.)
>
> inversely proportional to the pulse width?
Right, so if you have narrowband light such as laser light, it
means that each photon must be very long compared to the
wavelength. And each photon must be extremely wide if it's to
hit both telescopes of a small-baseline stellar interferometer.
(I hear that the photons from Beteleguse act like they're about
10 ft across!) I don't think you can stretch the "photon"
concept until the photons resemble electromagnetic waves, since
an EM wave really can be huge in extent, even for optical
frequencies.
> Yea, and an advance wave has to be emitted by the recieving atom to
travel
> backwards in time to the photon emitting atom, so it can emit the
photon,
> right? I hate that about QED.
I've heard these issues mentioned, but never heard about
the details. My math is fairly weak (being into digital,
rather than analog electronics!) :)
> >> It can only suck in as much flux as space will permit it, by
setting
> >up
> >> opposing currents and fields, according to electrodynamics.
>
> > Exactly. That's my point. The fields of the antenna act to suck
> > EM waves into the wire. In the example of the half-wave dipole
> > two things get missed:
> >
> > If we could make the fields very strong, even a much
> > smaller receiving antenna could "suck in" EM waves.
>
> No, you missed my point! Its not the field of the antenna, its the
> displacement currents, the reaction fields in space that prevents
more flux
> from flowing into the antenna. Poisson's equation.
Ah, I think I'm saying "flux" meaning energy flux, and you're
talking about e-field and b-field flux. You're right, the
resonant antenna doesn't suck in flux lines of e-fields or
b-fields. Instead it does some weird things to those fields
which end up sucking in Poynting-vector flux into the
antenna. A small, resonant antenna acts ANALOGOUS to iron or
ferroelectric, but it doesn't concentrate the field lines.
Instead it ends up concentrating the Poynting vector flux. It
does so by "sculpting" the e-fields and b-fields of the
incoming EM waves in order to direct the flow of energy
inwards towards the antenna.
> > The inductors and capacitors do the same thing that a thin
> > antenna wire does. A thin antenna wire acts like a broad sheet
> > of absorbtive material. It does so because the fields created
> > by the current and voltage of the wire cause EM energy to divert
> > from space and flow into the wire.
>
> I don't buy it. It is like your saying the voltage across or current
through
> a resistor determines its resistance. Of course the resistance of a
resistor
> can be defined by V/I, but when we talk about a given resistor it is
> typicaly the cause and the current the effect of the voltage across
it.
Yep, it's weird and counterintuitive. But it's not nonlinear.
It's like the example I gave with the capacitor: if you
charge a capacitor at a 1mA rate, with 1 volt across the
capacitor, then you're pumping in a millijoule of energy per
second into the capacitor. But if you let the voltage across
the capacitor rise to 2 volts, then you're pumping in 2mJ
per second. Suppose the capacitor is being charged by a 100
volt power supply with a 100k resistor in series. The higher
you let the capacitor voltage rise, the higher grows the energy
flow into the capacitor. In the case of small resonant
antennas, if we let the AC fields around the antenna build
up to a high level, then the antenna gathers energy at a higher
and higher rate, but only until the surrounding fields start
to affect the "power supply" and prevent further gains in
power reception. This occurs when the fields generated by
the antenna become significant at 1/4 wavelength, and the
antenna starts radiating as much as it absorbs.
> Similarly, the gain, radiation resistance, of a given metal dipole, or
> inductor/capacitor combination in space will not be determined by the
> voltage across or current through it.
> True the fields surrounding it may cancel out the field in a large
field
> around it. So you could contrive a scenario where a tiny LC resonator
with
> lots of power cancels out (absorbs, if you will) the same incident
wave a
> much larger dipole can.
Right. Electrically small antennas can "act large" if they're
tuned to resonance, and the effect occurs only if the AC
fields generated by the antenna are synchronized to the fields
of the incoming waves. But the antenna's fields are created by
the voltage and current in the coil/capacitor, so it forces me to
say that the voltage and current causes the effective size of
the antenna to be much larger than the physical size, but ONLY if
the voltage and current waveforms are locked in phase to those of
the incoming waves. This occurs naturally in a resonant
circuit, so we don't have to artifically drive a coil with a
power supply in order to see the "energy sucking" effect (but
we could do so if we wanted to.)
> But this is not the same as an atom sucking in the
> field-space around it.
Why not? That C. Bohren paper points out that a tiny metal
particle does "suck energy" from the surrounding space because
the surface plasmons are resonant with the incoming waves.
If the same applies to individual atoms, then when an EM wave
hits an atom, and one of the electron clouds is resonant at
that frequency, then the electron cloud starts sloshing more
and more, which creates a larger and larger AC field around the
atom, which diverts more and more wave-energy towards the
atom... until the electron suddenly changes state. This
doesn't explain most of QM, but it does explain how a 0.1nM atom
can strongly interact with 600nM radiation, as if the diameter
of the atom was a quarter wavelength across instead of hundreds
of times smaller.
>
> When the energy density, rates of change and field configurations are
> favorable for solitons, the Poynting vector of the soliton's field
bends the
> Poynting vector of incident energy into the soliton, very similar to
> relativistic distortions. Now you might think I am agreeing with you
(I
> guess I am) at this point, but the power density is such for
particles and
> photons that I don't think you will be doing it short of microwave and
> kilojoule regimes. The fringe conspiracy stuff I read on Keely-net
says the
> Russians need power plants to fire up their scalar toys ;-)
If this happens, it means that the fields must be intense enough
to make space go nonlinear. (Don't solitons only travel in
a nonlinear medium?) If the vacuum is nonlinear at high
field strengths, then you can probably make atoms out of
collapsing hunks of EM radiation.
Small resonant antennas are "nonlinear" only in the sense that
an incoming EM wave sees all matter as a nonlinearity in space.
If the hunk of matter happens to be a resonant circuit, it acts
even more "nonlinear" than the surrounding matter.
Science Hobbyist
russell shaw
and connected to a 415pF tuning cap, so it resonated 600-1600kHz.
Now put a ferrite rod tranny in the box, tuned to a weak station.
Now adjust the box tuning cap to resonate the big coil. Your station
will increase by 20-40dB ! (Hint: orient the box coil in the right
direction, and use thickish automotive wire for the coil).
By connecting an OA91 diode, resistor, and crystal earphone, i could
get 5 sharply tuned stations without needing an external antenna or
earth.
Science Hobbyist wrote:
>
> In article <38B566...@virgin.net>,
> peter_jo...@virgin.net wrote:
> > Alan Boswell wrote:
> > >
> >
> > So does that mean that it has bigger shadow than one might expect?
> > If you had two such antennas fairly close to each other, the one would
> > decrease the signal available for the other?
>
> AM loopstick antennas supposedly do just this.
>
> I don't have two AM portable radios here, but I've heard that if
> you receive a weak station with one radio, then you tune
> a nearby *unpowered* radio to the same frequency, the unpowered
> radio can steal some of the signal. That's the shadow effect.
> Even when the power is off, there's still a tuning capacitor
> connected across the loopstick. (The AGC in the radios will
> probably hide this effect if strong stations are used.)
>
> --
> ((((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
> William Beaty bbe...@microscan.com
> Software Engineer http://www.microscan.com
> Microscan Inc., Renton, WA 425-226-5700 x1135
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
--
Scott Stephens
Science Hobbyist wrote in message <897h2d$ogr$1...@nnrp1.deja.com>...
>In article <9Mjt4.10475$84.334756@elnws01>,
> "Scott Stephens" <Sco...@Mediaone.net> wrote:
>>
>> Science Hobbyist wrote in message <8948v1$d2i$1...@nnrp1.deja.com>...
>> >In article <k4gt4.10143$84.332786@elnws01>,
>> > "Scott Stephens" <Sco...@Mediaone.net> wrote:
> Right, so if you have narrowband light such as laser light, it
> means that each photon must be very long compared to the
> wavelength.
Frequency is statistical, an average of many events over time. A photon is a
particle, an individual instance. Better to specify its energy. Solitons
have a width, roughly equivalent to frequency.
> And each photon must be extremely wide if it's to
> hit both telescopes of a small-baseline stellar interferometer.
I don't buy it. I think there are lots of soliton-photons being emitted by
atoms in the distant star that scatter, interfere with each other. Next you
will protest that the double-slit experiment proves that a single photon
must travel through both slits. But consider the vacuum or aether as a
transmission line or multi-mode waveguide supporting solitons. If you affect
one of the paths, you actualy detune the transmission line, and affect the
source and paths for coherent soliton or wave emissions. So you can account
for spooky QED stuff like tunneling, entanglement and Hiesenburg exclusion
with solitons, or more properly a vacuum or aether.
>> Yea, and an advance wave has to be emitted by the recieving atom to
>travel
>> backwards in time to the photon emitting atom, so it can emit the
>photon,
>> right? I hate that about QED.
>
> I've heard these issues mentioned, but never heard about
> the details. My math is fairly weak (being into digital,
> rather than analog electronics!) :)
An interesting explanation is at
http://chaos.fullerton.edu/~jimw/general/inertia/index.html 3/4 of the page
down. Not that I'm a true believer of transient mass fluctuations, but the
LANL paper "9902008 The energy conservation law in classical
electrodynamics" and CSS point out some problems with the Standard Model. It
is also mentioned in (IIRC) in the Relativity FAQ. It has to do with the
finite propagation speed of the Lorentz force, and gravity has a similar
problem. Gravity and EM force points at where the attractor was, not is, so
orbits can decay, and EM solutions blow up. By adding dynamic reaction
forces, the systems stabilize and don't decay. But at relativistic energies,
particle self-energies change making for some very difficult, chaotic and
questionable predictions by the Standard Model.
>> > If we could make the fields very strong, even a much
>> > smaller receiving antenna could "suck in" EM waves.
> A small, resonant antenna acts ANALOGOUS to iron or
> ferroelectric, but it doesn't concentrate the field lines.
> Instead it ends up concentrating the Poynting vector flux. It
> does so by "sculpting" the e-fields and b-fields of the
> incoming EM waves in order to direct the flow of energy
> inwards towards the antenna.
> Yep, it's weird and counterintuitive. But it's not nonlinear.
> It's like the example I gave with the capacitor: if you
> charge a capacitor at a 1mA rate, with 1 volt across the
> capacitor,
That would require a current source composed of a dynamic, nonlinear,
resistance.
> then you're pumping in a millijoule of energy per
> second into the capacitor.
The current source to charge that capacitor might have used 1 volt, but you
failed to spec the capacitor which I must assume was constant, as E=1/2
CV^2. Now if C is constant, and the voltage is constant, the energy is
constant too.
> But if you let the voltage across
> the capacitor rise to 2 volts, then you're pumping in 2mJ
> per second.
You must be talking about a capacitor that is dynamicaly changing
capacitance, that is nonlinear, because you keep a constant voltage across a
capacitor as you increase the stored energy at a linear rate.
> In the case of small resonant
> antennas, if we let the AC fields around the antenna build
> up to a high level, then the antenna gathers energy at a higher
> and higher rate, but only until the surrounding fields start
> to affect the "power supply" and prevent further gains in
> power reception.
Now we're talking about a different situation, with an LC and sinusoid. The
LC will 'ring up', initialy presenting a greater load to a source delivering
a constant voltage. Now I see what you mean, I think. You mean that the
power extracted from the incident field is dependant on the energy in the LC
tank. Considering a sinusoidal field potential, and a sinusoidal tank
voltage of equal value, there be no energy or complete energy extracted
depending on relative phases, of 0 or 180 degrees respectively. OK.
This has nothing to do with "concentrating the Poynting vector
flux..."sculpting" the e-fields and b-fields of the
incoming EM waves in order to direct the flow of energy inwards towards the
antenna." Or, IMHO what goes on with atoms and photons. Your arguement
involve changing the potential difference across circuit elements. I think
what happens with atoms and photons is a changing of the properties of the
vacuum, a warping of space-time for the EM poynting vector and dynamic E and
B fields.
> But the antenna's fields are created by
> the voltage and current in the coil/capacitor, so it forces me to
> say that the voltage and current causes the effective size of
> the antenna to be much larger than the physical size, but ONLY if
> the voltage and current waveforms are locked in phase to those of
> the incoming waves.
Right, ok.
> This occurs naturally in a resonant
> circuit, so we don't have to artifically drive a coil with a
> power supply in order to see the "energy sucking" effect (but
> we could do so if we wanted to.)
I don't think so. If you don't criticaly damp, that is conjugate match,
absorb all the energy from the LC antenna, it
will not cancel the field as you think. If you let it ring up to the
incident field potential and cease to absorb power. How do you get a 180
degree phase shift field without constantly supplying the energy to do it,
and then radiating away that energy? It sounds like your talking about
active signal cancellation. What wonderfull stealth that trick would make!
>> But this is not the same as an atom sucking in the
>> field-space around it.
>
> Why not?
...
> If the same applies to individual atoms, then when an EM wave
> hits an atom, and one of the electron clouds is resonant at
> that frequency, then the electron cloud starts sloshing more
> and more,
A photon field has that many cycles?
> which creates a larger and larger AC field around the
> atom, which diverts more and more wave-energy towards the
> atom... until the electron suddenly changes state.
Consider an electron with its relatively powerfull magnetic and electric
potential, and its wavefunction. An incident photon impulse causes it to
ride the wave, and if the (DeBroglie?) wavelength is in phase, it gets stuck
in a new orbit, otherwise it falls. As the electron moves, it actively
cancels the incident field with its powerfull potential, and stores it in
the potential energy of its orbit (or resonance). Or consider a Lucas ring
electron vibrating lines of flux around between the nucleous and its
neighbor electrons. Not quite as simple as the classical case, but I think
more realistic.
>> When the energy density, rates of change and field configurations are
>> favorable for solitons, the Poynting vector of the soliton's field
>bends the
>> Poynting vector of incident energy into the soliton, very similar to
>> relativistic distortions. Now you might think I am agreeing with you
>(I
>> guess I am) at this point, but the power density is such for
>particles and
>> photons that I don't think you will be doing it short of microwave and
>> kilojoule regimes. The fringe conspiracy stuff I read on Keely-net
>says the
>> Russians need power plants to fire up their scalar toys ;-)
> If this happens, it means that the fields must be intense enough
> to make space go nonlinear. (Don't solitons only travel in
> a nonlinear medium?)
Yes, sort of. Nonlinear as in changing Mu0 or E0, as ferromagnetic and
ferroelectric ceramics do near saturation, no. You would see lasers
intermodulating and frequency dispersion and stuff. The nonlinearity I'm
talking about is like the nonlinearity of the Lorentz transform in Special
Relativity, where fields are bent and distorted, as energy (Poynting vector)
changes from dispersing as transverse waves in 3d space to higher
dimensional longitudinal waves, which in turn can warp the transverse waves.
Energy knots can form. Fast rates of change are required, as we don't see EM
solitons short of Maser emissions (that I'm aware of).
> If the vacuum is nonlinear at high
> field strengths, then you can probably make atoms out of
> collapsing hunks of EM radiation.
Yep. Ever year of Beamstraalung (not bremstraalung, breaking radiation)?
Intense particle beams can shear the vacuum, spawing particles like the
turbulence in fluid wake.
> Small resonant antennas are "nonlinear" only in the sense that
> an incoming EM wave sees all matter as a nonlinearity in space.
> If the hunk of matter happens to be a resonant circuit, it acts
> even more "nonlinear" than the surrounding matter.
I think you are confusing the transient (or forced) response of a linear, LC
circuit with different phenomena with atoms.
Scott
DrMilankov
Science Hobbyist <bbe...@microscan.com> wrote in message
news:88uusc$irk$1...@nnrp1.deja.com...
>
>
> Here's some weird ramblings I've posted on my site:
>
> ENERGY-SUCKING ANTENNAS (electrically small resonators)
> http://www.amasci.com/tesla/tesceive.html
>
>
> MORE MUSINGS ABOUT ENERGY-SUCKING ANTENNAS
> http://www.amasci.com/tesla/tescv2.html
>
>
> Briefly: if an atom is 0.1 nanometer across, how can it
> intercept light waves which have 500 nanometer wavelengths?
> As an "antenna", an atom is far too small!
>
> Answer: the atom resonates electrically, which creates a
> strong synchronous AC field in its nearfield region. The local
> e-field and b-field of the atom superposes with the fields of
> the incoming EM waves, which causes the waves to bend towards
> the atom. If we plot the Poynting vector field, we find that
> the atom "sucks in" the energy like a miniature black hole.
> As the waves march along, the phase of the atom's fields stay in
> step, and the Poynting vector keeps pointing in towards the
> atom. This works even though the atom is extremely small compared
> to the wavelength, since the fields of the nearfield region *ARE*
> the antenna.
>
> The same thing occurs with conventional radio waves and
> electrically small dipole antennas if a large AC voltage is
> impressed upon the antenna. The same thing occurs with small
> loop antennas if they are given a large current. Actively
> resonating antennas draw in far more energy than passive
> pickup coils. In theory, a tiny loop antenna can behave as if it
> were electrically enormous, and can reach out and intercept
> huge amounts of energy. At VLF frequencies, this effect
> is significant. Nikola Tesla could have used this effect as part
> of his "wireless power" scheme. It explains how even a tiny
> antenna could intercept significant VLF wattage.
>
>
> And you thought "crossed-field antennas" were weird! What about
> the loopstick inside an AM receiver?
>
>
>
Scott Stephens
tank initialy acts as a short to the field, absorbing power as it rings up,
until it is oscillating with the same potential as the incident field and
absorbing no more energy (its losses not withstanding).
Now if it could be switched, inverted 180 degrees in phase, it would indeed
cancel the field around it. That is called active noise cancelation. The
trick is to generate the conjugate field, quickly without becoming an
oscillator.
Consider a small spiral patch antenna that covers an octave. It is placed on
a very dissipative ferrite-graphite composite, 1/2 wavelength (mid-band)
thick. Underneath is another spiral patch. The spiral patch on top is the
input port, the patch on bottom the output port, with an amplifier MMIC in
between. The system is now a feedback amplifier, designed to cancel the
incident field.
An aircraft would be covered with this oscillator skin. Each oscillator is a
sandwich of a top and bottom conical spiral with graphite in between. There
are multiple layers of these spirals, in a 3 dimensional fractal pattern, to
cover decades of radar illumination.
Sound workable?
Scott
Science Hobbyist
> > electrically small dipole antennas if a large AC voltage is
> > impressed upon the antenna. The same thing occurs with small
> > loop antennas if they are given a large current. Actively
> > resonating antennas draw in far more energy than passive
> > pickup coils.
>
Not at all. As far as I know, their behavior is totally
covered by Maxwell's equations. It's part of the dynamics
of the nearfield region. The only "nonlinearity" is that the
EM fields do not behave the same in the nearfield region as
they do in empty space far from an antenna.
> > In theory, a tiny loop antenna can behave as if it
> > were electrically enormous, and can reach out and intercept
> > huge amounts of energy.
>
> Do you have pointers to such theory?
Not on WWW. Of the papers mentioned at the end of
http://www.amasci.com/tesla/tesceive.html, the C. Bohren
paper and the Paul/Fischer paper go into the details of
the mathematics. (Me, I understand the overall concepts
and the implications, but don't have the math needed to
see any errors they might make.)
> > At VLF frequencies, this effect
> > is significant. Nikola Tesla could have used this effect as part
> > of his "wireless power" scheme. It explains how even a tiny
> > antenna could intercept significant VLF wattage.
>
> I live a couple wavelengths from a VLF transmitting station that
> radiates about 500kW. Do you have an estimate of the useful energy I
> could expect to intercept ... with how tiny an antenna, and with what
> sort of practical configuration?
I haven't seen equations for making practical predictions. For
a lossless resonator antenna, supposedly you can assume that
the capture area of your antenna is a disk of radius 1/6
wavelength or so. For waves moving parallel to the ground, it
would act like a 1/2-disk (I think). The max received power
at 2 wavelenghts distance would be roughly:
500KW*(PI*1/6^2)/2/(4*PI*2^2) = 400 watts
For an antenna with finite Q, it certainly would be lots
lower that 400W. I bet you can light some LEDs or maybe run
a solar cell motor. Also, I think the physical size of the
antenna interacts with the Q required, so a tall tower or a
very wide metal loop would not require as high a Q in order
to "suck in" power. A big square loop made from copper
water pipe would be much better than a tiny ferrite loopstick.
If the e-field is vertical, maybe a tower with a tank circuit
at its base would be best. Expect some RF voltage to appear
on the tower!
I heard a story that a poor farmer who lived downrange from
a big VLF station in Europe discovered that he could run a
heater off of a long wire fence. The station owners tracked
him down because of the changes in the antenna pattern.
They couldn't do anything legally, so they paid to heat his
home in exchange for his removing the offending "receiver."
> Are you proposing that they (loopsticks) might be any different than
> explained in the standard antenna reference books? It seems to me
that
> those explanations predict the performance actually measured for such
> antennas.
Not as far as I know. I have no such books. Do they
calculate the gain for loopsticks with and without a
tuning capacitor? According to the resonant-antenna
explanations, a 6" loopstick acts "small" for a straight
resistive load, but acts "larger" and pulls in more signal
energy if the loopstick is part of a high-Q resonator. This
is not just a matter of impedance matching, since you can
pick the best resistor for both situations, yet the received
power is different.
Roy Lewallen
> . . .
> > Are you suggesting that such antennas are not linear systems?
>
> Not at all. As far as I know, their behavior is totally
> covered by Maxwell's equations. It's part of the dynamics
> of the nearfield region. The only "nonlinearity" is that the
> EM fields do not behave the same in the nearfield region as
> they do in empty space far from an antenna.
> . . .
This statement could be interpreted in a couple of ways, and lead to a
misunderstanding if the wrong interpretation is chosen.
The equations governing EM fields are the same at any distance from the
antenna, including all of the near and far field. In this sense, then,
EM fields behave exactly the same in all regions. There's no magic area
or distance at which the equations and behavior change.
However, some components of the EM wave change and fade very rapidly
with distance from the antenna, so components and characteristics which
are significant or even dominant when close to the antenna are for all
practical purposes nonexistent at greater distances. This allows
simplification of the equations governing EM waves in the far field. The
factors important in the near field still apply, but in the far field
they're so small they can be ignored with no practical loss in accuracy.
So in this sense the behavior of the EM wave is different in the near
and far fields as Beaty said.
Roy Lewallen, W7EL
A. Scott Chesnick
Cortland Richmond wrote:
>
>
> Actually, the above is incomplete. There IS an effect, in which atoms
> subjected to a magnetic field will absorb radio waves of specific
> frequencies at lower ranges, but this involves (I think) resonating with
> the spin of protons in the nucleus. This is used in NMR imaging. I don't
> know what frequency a "normal" earth magnetic field would resonate,
2235 Hz give or take a few nano Tesla
Quoting from the Proton magnetometer Web
Pagehttp://hometown.aol.com/alka1/ProMag.html
"In the northern latitudes of the U.S. the total magnetic field strength is in the
order of 50,000 to 55,000 nanoTesla and varies from location to location. Short
period variations due to magnetic storms may reach several hundred nanoTesla.
Diurnal variations caused by solar induced ionospheric currents are in the order of
tens of nanoTesla. Presently, the long term trend of the total field is in the order
of minus 90 nanoTesla per year ( steadily decreasing).
The proton precession frequency detected by a suitable sensor in the geomagnetic
field of the earth will be at a frequency in the audio range:
Example: 42.58 mHz / Tesla x 52500 x 1E-9 Tesla= 2235 Hz
The"Larmor frequency" defines the angular momentum of protons precessing in the
presence of a magnetic field. There are currently quantum-mechanical views that
explain particle precession, but a classical explanation seems a bit easier to
follow.
A proton, a charged particle, may be thought of as having definite "spin" about an
"axis" and acts as a small magnet. An externally applied magnetic field does not
alter the spin rate, but causes the particle to wobble at a slower rate about an axis
of precession. This axis tends to align with an external magnetic field. However in
weak magnetic fields, any alignment tends toward randomness due to thermal effects
and other molecular interactions. "
Another comment ....
On the antennas are that any gain in voltage is due to the local storage of the
energy from cycle to cycle. The changing electromagnetic field is building up and
collapsing about the antenna structure. This being analogous to "q" in a resonant
coil.
Antennas have an aperture, effective height -area . The amount of energy a system
can absorb depends upon the cross sectional area the antenna and the wavelength of
the EMF. It cannot absorb any more energy then is available in the "near zone" of the
antenna structure. In the near zone the permeability and permittivity are not the
same as free space.
There is a difference between a resonant magnetic circuit and an antenna.
A resonant coil or magnetic circuit stores the electric and magnetic field from a
changing EMF.
An antenna will create EMF plain waves and the energy is radiated away.
In the near zone the antenna stores any absorbed energy.
The near zone or the inductive zone the electric and magnetic field can have phase
relationships other then 90 degrees as in electromagnetic waves. Phase velocities in
this close area can be superluminal and seemingly exceed the speed of light. This
does not violate any of the rules of relativity this just means the energy wave can
change its slope. The wave front does not travel at greater then the speed of light
no information is passing from point --a to point-- b faster then light.
Any radiation created an antenna is lost to free space and is not stored from cycle
to cycle of an oscillating EMF.
Any energy in the far zone does not interact with the antenna until it intersects
the antenna- Because of the phase retardation and the electromagnetic wave electric
and magnetic field have a 90 degree relationship. (The antenna cannot suck in energy
from
the far zone until the energy actually gets to the antenna.) Then the amount of
energy absorbed or radiated depends upon the physical dimensions and characteristics
dependent upon the wavelength of the EMF.
One could view the amount of energy an antenna can absorb as the same as the amount
of sunlight / energy that can pass through an open window. The amount of energy
absorbed in any one moment is limited to this effective height or area and the amount
of radiation passing through the opening.
If the antenna is part of a larger resonant cavity additional energy could be focused
to one area just as a magnifying glass can focus light.
Regards Scott Chesnick
Design Engineer
In Vivo Center for Nuclear magnetic Resonance Imaging
National Institutes of Health
Bethesda, Md
Science Hobbyist
Roy Lewallen <w7...@eznec.com> wrote:
> However, some components of the EM wave change and fade very rapidly
> with distance from the antenna, so components and characteristics
which
> are significant or even dominant when close to the antenna are for all
> practical purposes nonexistent at greater distances. This allows
> simplification of the equations governing EM waves in the far field.
The
> factors important in the near field still apply, but in the far field
> they're so small they can be ignored with no practical loss in
accuracy.
> So in this sense the behavior of the EM wave is different in the near
> and far fields as Beaty said.
Right. The nearfield contains static and quasi-static fields,
while the farfield contains only EM waves, yet all of it is
contained under Maxwell.
Part of the reason I'm going on and on about this subject
is that *I* want to achieve a better understanding of this
nearfield stuff. Maxwell's equations describe it all, but they
don't automatically produce visual and verbal models. If
Maxwell's equations are the "bricks," then I want to understand
"architecture." A pair of loop antennas is not the same as
a transformer, and I want a clear understanding of the
difference. Strange things seem to happen when we place a
tuning capacitor across a loop antenna, and I want the strangeness
to be replaced by understanding. Nearfield stuff is muddy for
me, and I want a much clearer visual picture of how RF energy
gets from the wires to the empty space.
Debates about "crossed-field antennas" forced me up against
these very concepts, which helped alot. "Energy-sucking
antennas" is doing the same. Those papers about atoms and
light exposed parts of antenna-physics which I was totally
clueless about. On looking around, I see that I'm not the
only one.
I think it was Richard Feynman who said "if you don't have
three or four different ways of explaining something, then you
don't really understand it." Textbook explanations give one
way, but if we take them as the holy words of Authority,
we'll never encounter all the other ways. Non-traditional
explanations could be dismissed as needless eccentricity. I
take the opposite stance: non-traditional explanations give
you an alternate set of mental tools, and they fill in the gaps
in traditional explanations. If the non-traditional
viewpoints haven't been explored to death, maybe there are
even some ideas for cool "toys" lurking unsuspected within
them.
"Genius in truth means little more than the faculty of
perceiving in an unhabitual way."
- William James
more quotes:
http://www.amasci.com/weird/skepquot.html
Science Hobbyist
Cortland Richmond <Cortland...@usa.alcatel.com> wrote:
> Ah yes, the Amateur Scientist. I remember they once had a series on
making
> your own hgh-quality vacuums. Started with refrigerator compressors
and went
> through mercury pumps for a hard vacuum.
>
> Interesting Web Page. Thanks!
I don't know if I mentioned this earlier. THE AMATEUR
SCIENTIST is going on sale. The whole thing is being
put onto cdrom by the SAS (Soc. for Am. Science) It's
not released as yet, but you can put in your order here:
TINKER'S GUILD: 70 years of "The Amateur Scientist"
http://www.tinkersguild.com
Science Hobbyist
"Scott Stephens" <Sco...@Mediaone.net> wrote:
>
> Science Hobbyist wrote in message <897h2d$ogr$1...@nnrp1.deja.com>...
> > Yep, it's weird and counterintuitive. But it's not nonlinear.
> > It's like the example I gave with the capacitor: if you
> > charge a capacitor at a 1mA rate, with 1 volt across the
> > capacitor,
>
> That would require a current source composed of a dynamic, nonlinear,
> resistance.
Not exactly. We were talking about a carbon sheet with a
power supply connected across two edges. If I place two
small electrodes at the center of the sheet, and then connect
a big capacitor to them, what will occur? At first the
capacitor will act like a dead short, since the voltage across
the capacitor starts out at zero during the first instant.
There will be a relatively constant capacitor current because
of the carbon resistor, and because the voltage of the capacitor
is so tiny compared to the power supply that drives the sheet.
No fancy constant-current supply is needed, we just need a
power supply and a resistor.
As the capacitor voltage rises, the current through it DOES
NOT fall much, since the voltage across the capacitor is still
so small. For small capacitor voltage, the energy flowing
into the capacitor is roughly proportional to voltage. It's
this way because the capacitor voltage is rising, but the
current through it is only falling a tiny bit. Under
these conditions, if we wanted to force the capacitor to
gather energy at a faster rate, we could goose up its
voltage artificially. Within limits, the higher the
capacitor voltage, the greater the energy flow going
into it.
> > then you're pumping in a millijoule of energy per
> > second into the capacitor.
>
> The current source to charge that capacitor might have used 1 volt,
but you
> failed to spec the capacitor which I must assume was constant, as
E=1/2
Yes, the C is constant.
> CV^2. Now if C is constant, and the voltage is constant, the energy is
> constant too.
Definitely not. When a capacitor is being charged with a
power supply and a resistor in series, the capacitor voltage is
not constant, yet the capacitor current is almost constant.
Energy flow into the capacitor starts at zero (because the
capacitor voltage starts at zero, and energy flow is V x I.)
Then the energy flow rate rises because the voltage rises MORE
than the current falls (look at P = V x I.) Then the energy
flow into the capacitor reaches a peak and starts
falling. Eventually it decreases to zero again because
the capacitor voltage has settled at a maximum value, and
the current is zero. If you don't believe this, plug it
into a spreadsheet or a CAD program. Calculate the V x I for
the capacitor, and you'll see the incoming power rise, peak,
and fall.
This is all an analogy for the "energy sucking antenna", but I
think it's a good one. Something similar should occur when
a lossless resonator is first illuminated with EM waves:
at first the energy flows in fast, then there is a peak in
the flow, then the flow tails off as the resonator settles down
to a constant high value of internal energy.
The important part is right at the beginning, because the amount
of energy flowing into the resonator depends on the intensity of
the resonator's fields. The stronger the fields, the greater
the intercepted power. It's analogous to the early stages of
the charging capacitor: the greater the voltage, the greater
the energy flowing in.
> > But if you let the voltage across
> > the capacitor rise to 2 volts, then you're pumping in 2mJ
> > per second.
>
> You must be talking about a capacitor that is dynamicaly changing
> capacitance,
Nope. ALL capacitors do this. (However, I certainly
never encountered this concept in engineering school. I never
sat down and plotted the energy flow of a charging capacitor.
Heh. Back then I wasn't totally away that "power" meant
"energy flow rate.")
> that is nonlinear, because you keep a constant voltage across a
> capacitor as you increase the stored energy at a linear rate.
When an "empty" capacitor is first connected to a supply with
a resistor in series, the voltage goes up but the current does
not go down in proportion, therefore the amount of energy per
second flowing into the capacitor goes up. Another way to say
it: the higher the voltage across the capacitor, the faster
the energy comes in. (This only holds true until the
capacitor voltage becomes significant relative to the power
supply voltage.)
>
> > In the case of small resonant
> > antennas, if we let the AC fields around the antenna build
> > up to a high level, then the antenna gathers energy at a higher
> > and higher rate, but only until the surrounding fields start
> > to affect the "power supply" and prevent further gains in
> > power reception.
>
> Now we're talking about a different situation, with an LC and
sinusoid.
Yes, different. The capacitor is only an analogy. But
not so different that the analogy evaporates.
The
> LC will 'ring up', initialy presenting a greater load to a source
delivering
> a constant voltage. Now I see what you mean, I think. You mean that
the
> power extracted from the incident field is dependant on the energy in
the LC
> tank.
Exactly. However, in the case of the antenna, we have some
three-dimensional field patterns, so it doesn't behave exactly
like a signal generator connected to a tank circuit through
a resistor. With direct wire connections, the ratio between
the voltage of the signal generator and the voltage of the
tank circuit is the determining factor. With an antenna, the
SHAPE of the fields (their broadside area, to be specific)
becomes important too.
> Considering a sinusoidal field potential, and a sinusoidal tank
> voltage of equal value, there be no energy or complete energy
extracted
> depending on relative phases, of 0 or 180 degrees respectively. OK.
It also depends on the amplitude of the current in the loop
antenna (or, if its a short dipole, it depends on the voltage
across it.) If the resonator hasn't "rung up" yet, then it is
not yet generating its own fields, therefor the incoming EM
waves are unaffected, and they pass right by it without
being absorbed. To be absorbed, they have to flow TOWARDS
the body of the resonator and not just flow along undeflected.
Only when the strong fields of the resonator are superimposed
with the fields of the incoming EM waves do we have energy
flowing INTO the tiny resonator.
Yes, all this is very weird. It's like putting a bucket out
in the rain, and discovering that a full bucket gathers more
rain than an empty one!
>
> This has nothing to do with "concentrating the Poynting vector
> flux..."sculpting" the e-fields and b-fields of the
> incoming EM waves in order to direct the flow of energy inwards
towards the
> antenna." Or, IMHO what goes on with atoms and photons. Your arguement
> involve changing the potential difference across circuit elements. I
think
> what happens with atoms and photons is a changing of the properties
of the
> vacuum, a warping of space-time for the EM poynting vector and
dynamic E and
> B fields.
If the e-fields and b-fields of the tiny resonant antenna are
the reason that EM waves flow into that antenna, then no
spacetime warping is needed. And, if no spacetime warping is
needed for small resonant antennas, it *MIGHT* be true
that individual atoms use similar physics.
> > This occurs naturally in a resonant
> > circuit, so we don't have to artifically drive a coil with a
> > power supply in order to see the "energy sucking" effect (but
> > we could do so if we wanted to.)
>
> I don't think so. If you don't criticaly damp, that is conjugate
match,
> absorb all the energy from the LC antenna, it
> will not cancel the field as you think.
You are right. The "lossless resonant antenna" requires a
load, otherwise it will become "full" and will stop absorbing
energy. However, the load resistor has unexpected effects.
Here's ANOTHER way to look at it. Suppose we have a simple
loop antenna (electrically small, not resonant.) Suppose
we illuminate it with EM waves. We can put a variable
resistor across it and adjust the resistor for maximum
received power. Matching the load impedance, obviously.
OK, now put a capacitor across that loop antenna and tune
it to resonance with the incoming waves. Finally, adjust
the load resistor to achive maximum power. You'll find
something very strange: the resistor value is very different
than with the non-resonant antenna (I mean WAY different), and
also the received power is much, much higher. This is not
just an example of impedance matching, since the resistor
in both cases was adjusted to match the antenna impedance.
Adding the capacitor did something odd. It increased the
antenna's coupling to space, as if the antenna had become
larger.
> If you let it ring up to the
> incident field potential and cease to absorb power. How do you get a
180
> degree phase shift field without constantly supplying the energy to
do it,
> and then radiating away that energy? It sounds like your talking about
> active signal cancellation. What wonderfull stealth that trick would
make!
Right! As far as I know, it really works this way: an array
of tiny antennas can act as an absorber-sheet, even though there
are huge empty spaces between the antennas. The stored energy
in the resonator makes the antenna behave like an actively-
driven device. (Unfortunately its a narrow-band phenomenon.)
>
> Consider an electron with its relatively powerfull magnetic and
electric
> potential, and its wavefunction. An incident photon impulse causes it
to
> ride the wave, and if the (DeBroglie?) wavelength is in phase, it
gets stuck
> in a new orbit, otherwise it falls. As the electron moves, it actively
> cancels the incident field with its powerfull potential, and stores
it in
> the potential energy of its orbit (or resonance).
Yep. The "resonant antenna" idea comes into play if we can
cause that electron to "slosh" much farther from the nucleus
than usual. When its close to the nucleus, its field is
partially canceled, but if we can give it some resonant
pumping, its field can expand out into space far from the atom,
and that means its field can interact better with EM waves.
That's the "energy sucking antenna" phenomenon in action.
Of course it would be best to just get rid of the positive
nucleus and let the waves hit the electron directly. An
antenna composed of uncancelled electrons would be REALLY
effective. But if the darned electrons insist on staying
near protons, then the next best thing we can do is to
get them "swinging", so they spend as much time as possible
lifted far outwards away from the protons, so the EM waves
can "see" them.
> > If this happens, it means that the fields must be intense enough
> > to make space go nonlinear. (Don't solitons only travel in
> > a nonlinear medium?)
>
> Yes, sort of. Nonlinear as in changing Mu0 or E0, as ferromagnetic and
> ferroelectric ceramics do near saturation, no. You would see lasers
> intermodulating and frequency dispersion and stuff. The nonlinearity
I'm
> talking about is like the nonlinearity of the Lorentz transform in
Special
> Relativity, where fields are bent and distorted, as energy (Poynting
vector)
> changes from dispersing as transverse waves in 3d space to higher
> dimensional longitudinal waves, which in turn can warp the transverse
waves.
> Energy knots can form. Fast rates of change are required, as we don't
see EM
> solitons short of Maser emissions (that I'm aware of).
Doesn't this require some modification to Maxwell's equations?
Nikola Tesla claimed to have achived a "bubble" effect which
could apply forces against solid matter. If he really did
this, then maybe the effect can be demonstrated with
desktop equipment, if we knew the right combinations of
coils, plates, and drive waveforms. Maybe there is a "standing
wave" version of your EM solitons. In particular, if one EM
soliton can reflect off of another, it might be possible to
generate a sphere-shaped structure made of soliton-stuff, where
the shell of the sphere keeps the solitons bouncing around
inside. If atoms are these, except with high frequency and
smaller size, then maybe it's possible to generate a stable
"VHF atom" which is many inches in diameter? Star Trek
technology, obviously!