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!
Science Hobbyist
"DrMilankov" <y...@eunet.yu> wrote:
>
> Hi there, I work on it!
Work on what? Do you work with resonant antennas?
> 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
--
Tom Bruhns
Science Hobbyist wrote:
>
> In article <38B58F6E...@agilent.com>,
> Tom Bruhns <tom_b...@agilent.com> wrote:
> > 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?
>
> Not at all.
...
Linearity, to me, means that the response of a system (the antenna) to
one input (signal) is independent of its response to any other signals.
That immediately tells me that the response to some signal we wish to
receive will not be changed by some other field around, or current in,
or voltage across the feedpoint of, our antenna.
Do I get to pick? If I do, I'll opt for linearity.
Cheers,
Tom
Bilge
>Linearity, to me, means that the response of a system (the antenna) to
>one input (signal) is independent of its response to any other signals.
>That immediately tells me that the response to some signal we wish to
>receive will not be changed by some other field around, or current in,
>or voltage across the feedpoint of, our antenna.
Linearity => An operation is linear if op(aX + bY) = a*op(X) + b*op(Y)
a,b complex, X,Y functions
multiplication by a scalar is linear, squaring is not, etc...
Boris Mohar
wrote:
>> 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.
So when after the five time constants the voltage is across the capacitor
is about 99 volts and the current has decayed to less than a milliamp the
"flow of energy" into the capacitor is higher then at time zero?
Regards,
Boris Mohar
Viatrack Printed Circuit Designs
Science Hobbyist
Tom Bruhns <tom_b...@agilent.com> wrote:
> > > Are you suggesting that such antennas are not linear systems?
> >
> > Not at all.
>
> ...
>
> Linearity, to me, means that the response of a system (the antenna) to
> one input (signal) is independent of its response to any other
signals.
OK, then suppose we illuminate an antenna with a CW EM wave, then
connect a receiver to detect it. Are you CERTAIN that no other
EM fields can possibly interfere with this process, yet do so
entirely by linear effects?
OK, what if I use a second distant transmitter with
identical frequency? I bet I can create an RF interference
pattern so that the above receiving antenna is in an antinode,
and the received power drops essentially to zero. I've done
it with wave-superposition, which obviously is totally linear.
This stuff with "energy sucking antennas" uses the same
process: it uses the superposition of fields of the SAME
FREQUENCY as the incoming waves. The waves and the antenna's
field are coherent. If you say that one AC field cannot alter
under any circumstances, then maybe you've never encountered
interference patterns.
Because the AC fields originated by the electrically-short
antennas have the same frequency as the incoming waves,
odd things occur which would not occur if the two
frequencies differed. In particular, if the short antenna
surrounds itself with a non-radiating local field which
partially CANCELS OUT the fields of an incoming EM wave,
then nothing nonlinear has occurred. Yet energy has gone
missing from space. The cancelled energy ends up within
the short antenna. Plots of the Poynting vector field show
that the cancellation process deflects the incoming waves so
that they flow into the tiny antenna. Their energy appears
in whatever load is connected.
I've said it several times now but it bears repeating:
"ENERGY SUCKING" ANTENNAS WORK BY TOTALLY CONVENTIONAL
PRINCIPLES. They're only "weird" because they aren't
commonly discussed or analyzed. And, since the same
basic principles apply to half-wave dipoles, the concept
is not weird in the least. It's just "different drummer"
thinking. We normally assume that a half-wave dipole is
purely an absorber, and we usually ignore the fact that all
antenns creates their own local field. It's this local
field which grabs the EM waves out of the air.
> That immediately tells me that the response to some signal we wish to
> receive will not be changed by some other field around, or current in,
> or voltage across the feedpoint of, our antenna.
If you are discussing DC fields, or fields which have
a different frequency than the incoming waves, then you are
right. But as soon as the "other field" has the same frequency
as the incoming waves, then that field gains the ability to
reinforce or to cancel those waves. Earlier I was talking
about synchronous motors as an analogy for "energy
sucking" antennas. I didn't think I had to point out
that synchronous PM motors are SYNCHRONOUS, and that their
rotor-magnets turn at the same frequency as the drive fields.
Science Hobbyist
Boris Mohar <bor...@interlog.com> wrote:
> On Sat, 26 Feb 2000 03:25:03 GMT, Science Hobbyist <bbe...@microscan.com>
> wrote:
> > 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.
>
> is about 99 volts and the current has decayed to less than a milliamp the
> "flow of energy" into the capacitor is higher then at time zero?
Try using a CAD program or a spreadsheet to plot the energy
flow into a capacitor versus time (when powered by a
100Vdc supply with a 100K resistor.)
The curve starts at zero, ramps up smoothly, comes to
a maximum, then falls back to zero as the current falls.
(The peak power is when the V/I of the capacitor is
100K ohms, which gives an impedance match for
an instant.)
When the Vc is much smaller than Vsupply, and if the
power supply has constant impedance, the energy
absorbed by the capacitor per second depends on the
voltage across the capacitor. If you wished to force the
capacitor to suddenly start absorbing more energy, you
could use another power supply to goose the Vc higher.
This is an analogy for the "energy-sucking antenna",
where a large e-field produced by the antenna can
cause it to receive more signal power from the incoming
EM waves. As with the capacitor, the LC resonant
antenna will create stronger local fields as its stored
energy ramps up, and this increases the absorbed
power, but since this is a 2-dimensional situation
(rather than the 1-D of the capacitor), I think
it means that the received power will rise exponentially
whenever an EM wavetrain first hits the tiny antenna-
resonator.
Boris Mohar
wrote:
>In article <f3u0cskfg9vj2tveq...@4ax.com>,
> Boris Mohar <bor...@interlog.com> wrote:
>> On Sat, 26 Feb 2000 03:25:03 GMT, Science Hobbyist <bbe...@microscan.com>
>> wrote:
>> > 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.
>>
>> So when after the five time constants the voltage is across the capacitor
>> is about 99 volts and the current has decayed to less than a milliamp the
>> "flow of energy" into the capacitor is higher then at time zero?
>
> Try using a CAD program or a spreadsheet to plot the energy
> flow into a capacitor versus time (when powered by a
> 100Vdc supply with a 100K resistor.)
>
> The curve starts at zero, ramps up smoothly, comes to
> a maximum, then falls back to zero as the current falls.
This is in contradiction with your statement about dozen lines up:
>> > the higher you let the capacitor voltage rise, the higher grows the energy
>> > flow into the capacitor.
> (The peak power is when the V/I of the capacitor is
> 100K ohms, which gives an impedance match for
> an instant.)
Impedance match? Of what to what?
> When the Vc is much smaller than Vsupply, and if the
> power supply has constant impedance, the energy
> absorbed by the capacitor per second depends on the
> voltage across the capacitor. If you wished to force the
> capacitor to suddenly start absorbing more energy, you
> could use another power supply to goose the Vc higher.
Now you are back on track
> This is an analogy for the "energy-sucking antenna",
> where a large e-field produced by the antenna can
> cause it to receive more signal power from the incoming
> EM waves. As with the capacitor, the LC resonant
> antenna will create stronger local fields as its stored
> energy ramps up, and this increases the absorbed
> power, but since this is a 2-dimensional situation
> (rather than the 1-D of the capacitor), I think
> it means that the received power will rise exponentially
> whenever an EM wavetrain first hits the tiny antenna-
> resonator.
I cannot see how you can compare the DC transient conditions of a simple RC
circuit with the AC dynamics of an resonant circuit. Antennas cannot store
energy.
Gary Coffman
>In article <38BF17FE...@agilent.com>,
> Tom Bruhns <tom_b...@agilent.com> wrote:
>
>> > > Are you suggesting that such antennas are not linear systems?
>> >
>> > Not at all.
>>
>>
>> one input (signal) is independent of its response to any other
>signals.
>
> OK, then suppose we illuminate an antenna with a CW EM wave, then
> connect a receiver to detect it. Are you CERTAIN that no other
> EM fields can possibly interfere with this process, yet do so
> entirely by linear effects?
I'm certain that fields (photons) can only be altered due to the
mediation of charged matter. Other fields alone cannot alter them.
> OK, what if I use a second distant transmitter with
> identical frequency? I bet I can create an RF interference
> pattern so that the above receiving antenna is in an antinode,
> and the received power drops essentially to zero. I've done
> it with wave-superposition, which obviously is totally linear.
> This stuff with "energy sucking antennas" uses the same
> process: it uses the superposition of fields of the SAME
> FREQUENCY as the incoming waves. The waves and the antenna's
> field are coherent. If you say that one AC field cannot alter
> under any circumstances, then maybe you've never encountered
> interference patterns.
Interference patterns are simple superposition. The Principle of
Superposition says that the components of a superposition are
*unaltered* by the superposition. Beyond the superposition zone
we still have the same two waves, still with the same directions
and the same energies as they had before the superposition
occurred.
> Because the AC fields originated by the electrically-short
> antennas have the same frequency as the incoming waves,
> odd things occur which would not occur if the two
> frequencies differed. In particular, if the short antenna
> surrounds itself with a non-radiating local field which
> partially CANCELS OUT the fields of an incoming EM wave,
> then nothing nonlinear has occurred. Yet energy has gone
> missing from space. The cancelled energy ends up within
> the short antenna. Plots of the Poynting vector field show
> that the cancellation process deflects the incoming waves so
> that they flow into the tiny antenna. Their energy appears
> in whatever load is connected.
The energy has *not* "gone missing". That is a misunderstanding
of what has happened. The E fields are vectors, and add vectrorially
at the point of superposition. So if their relative phase is 180 degrees
we have
(+E) + (-E) = 0
But that doesn't mean that energy has gone to zero. Energy
is proprortional to the *square* of E
(+E)^2 + (-E)^2
Squaring E (dot product) yields a positive scalar.
We can write this another way
|P| + |P| = 2P
That holds for any relative phase. Thus energy at the point of
interference is twice that of either component of the superposition
alone. This is always true. No energy goes missing, nor does energy
suddenly appear if the E field vectors happen to be in phase rather
than out of phase.
Diagramatically, if we have two beams of energy 1 that
cross, the situation looks like this
1 1
2
1 1
Now the E vectors may look like this if they're in phase opposition
1 -1
0
-1 1
or they might look like this if they are coincident in phase
1 1
2
1 1
But energy never goes missing. Energy is always a positive
scalar quantity, not a vector.
Gary
Gary Coffman KE4ZV | You make it |mail to ke...@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
Roy McCammon
> This is an analogy for the "energy-sucking antenna",
> where a large e-field produced by the antenna can
> cause it to receive more signal power from the incoming
> EM waves.
I've probably missed 95% of the postings on this thread.
If I take a transmitter far away and near by I have a
spherical volume and two cases:
1. the volume is empty
2. the volume contains a load and a dipole cut to
the frequency of the far away transmitter
I then compute the surface integral of the Poynting
vector over those spherical surfaces I will find
that in case 1, no power is absorbed and in case 2,
some power is absorbed. I will also find that
the em fields on those two surfaces are different
and I will find that the differences are entirely
attributable to the motions of charges in the load
and dipole. This is all true. A similar situation
exists regarding the secondary of an ordinary transformer.
Its the "more" in the quoted paragraph that I question.
Opinions expressed herein are my own and may not represent those of my employer.
Science Hobbyist
Boris Mohar <bor...@interlog.com> wrote:
> This is in contradiction with your statement about dozen lines up:
>
> >> > the higher you let the capacitor voltage rise, the higher grows
the energy
> >> > flow into the capacitor.
Have you tried plotting this curve? I ask because you
seem to be attacking what I say, and if you actually try
messing with a simulation of this triviall circuit ,
you'll instantly answer these questions.
It's not a contradiction: when the capacitor's voltage
is very small, the capacitor's incoming energy-flow
grows linearly, and also its voltage grows linearly. When
the voltage BECOMES LARGE RELATIVE TO THE POWER SUPPLY
VOLTAGE, this no longer holds true.
In the analogy with the electrically-short resonant
antenna, things work in similar fashion: the rising
antenna voltage can only act to "draw in" extra energy
when the field strength at a quarter-wavelength away
from the antenna is very small when compared to the
amplitude of the incoming EM waves. The incoming EM
waves are analogous to the power supply which drives
the capacitor above. When the voltage on the resonant
antenna grows very large, it stops "drawing in" extra
energy-flow in proportion to voltage.
> > (The peak power is when the V/I of the capacitor is
> > 100K ohms, which gives an impedance match for
> > an instant.)
>
> Impedance match? Of what to what?
Instantaneous impedance match, not just impedance match.
The instantaneous impedance match of the capacitor's V/I
at one instant, to the 100K resistor that's in series with
the power supply. In other words, as the V and I in the
capacitor are changing, at one instant the capacitor's V
divided by the I will be 100,000. That's also the instant
when the rate of energy flowing into the capacitor is
maximum. If we imagine a capacitor to be like a resistor
which changes its resistance over time, then when the
capacitor's "resistance" is 100K, the capacitor is absorbing
energy at a maximum rate.
> > This is an analogy for the "energy-sucking antenna",
> > where a large e-field produced by the antenna can
> > cause it to receive more signal power from the incoming
> > EM waves. As with the capacitor, the LC resonant
> > antenna will create stronger local fields as its stored
> > energy ramps up, and this increases the absorbed
> > power, but since this is a 2-dimensional situation
> > (rather than the 1-D of the capacitor), I think
> > it means that the received power will rise exponentially
> > whenever an EM wavetrain first hits the tiny antenna-
> > resonator.
>
> I cannot see how you can compare the DC transient conditions of a
simple RC
> circuit with the AC dynamics of an resonant circuit.
I was using this capacitor-analogy because an earlier posting
claimed (though not in these exact words) that there was no
situation where the fields associated with an electronic
component could affect the energy flowing into that component.
Capacitors do it. But this is only an analogy, not a proof
that resonant small antennas do the same. The whole point
of an analogy is an aid to understanding, and is not a proof.
How can I compare the two? BY ANALOGY! The capacitor is
sort of like a "low frequency case" of the way fields can
alter energy flow.
> Antennas cannot store
> energy.
ANTENNAS CANNOT STORE ENERGY????? Please recall that we
are discussing LC circuits which are being used as antennas.
That's what I mean when I say "small resonant antenna".
LC circuits don't store energy?
Science Hobbyist
rbmcc...@mmm.com (Roy McCammon) wrote:
> Science Hobbyist wrote:
>
> > This is an analogy for the "energy-sucking antenna",
> > where a large e-field produced by the antenna can
> > cause it to receive more signal power from the incoming
> > EM waves.
>
The critical part is that the antennas I'm discussing
are electrically short, and are connected to a tank
circuit which is tuned to resonance with the incoming
waves.
> If I take a transmitter far away and near by I have a
> spherical volume and two cases:
> 1. the volume is empty
> 2. the volume contains a load and a dipole cut to
> the frequency of the far away transmitter
>
> I then compute the surface integral of the Poynting
> vector over those spherical surfaces I will find
> that in case 1, no power is absorbed and in case 2,
> some power is absorbed. I will also find that
> the em fields on those two surfaces are different
> and I will find that the differences are entirely
> attributable to the motions of charges in the load
> and dipole. This is all true. A similar situation
> exists regarding the secondary of an ordinary transformer.
Agreed.
> Its the "more" in the quoted paragraph that I question.
Yes, that's the key question: does connecting a tank
circuit to a short dipole (or small loop) cause it to
absorb MORE energy from the incoming waves? More
specifically, if we connect just a resistive load to
a short dipole and adjust that resistor for maximum
received power, can we receive even MORE power if we
then connect a lossless tank circuit across that dipole,
then re-adjust that resistor value for maximum power?
These papers imply that the answer is yes:
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
These papers look at the absorbtion of em waves by
electrically small particles (both metal particles and
dielectric.) They show that whenever there is a resonator
onboard a particle, it creates a very strong local field,
and since this field is synchronized to the incoming em
waves, it distorts them in such a way as to make them deflect
towards the particle. The particle ends up absorbing more
energy than if the resonator was not present. In other words,
the "effective area" of a small particle becomes enlarged
when there is a resonator present.
Very strange, no? The upshot: a 1-angstrom atom can easily
absorb 6000-angstrom red light waves if that atom behaves
as an LC resonant antenna at that frequency. I had
previously imagined that tiny atoms absorb long light
waves because the light is "really" photons. This turns
out to be wrong. From a wave-oriented viewpoint, atoms
can absorb energy of huge wavelength because an atom is
like a tank circuit, and it can generate an intense AC
field in its nearfield region.
Also, it explains why the loopstick in an AM radio works
so well. That loopstick has a tuning capacitor, and if
this "energy sucking" effect is real, then the effective
area of the tiny loopstick antenna becomes much larger
when it's tuned to resonance.
I'd always assumed that the capacitor on an AM radio
loopstick was only there to form a bandpass circuit
which rejects off-freq stations. Imagine my suprise
when I read those two physics papers above. They
imply that AM loopstick antennas contain some very
interesting physics. Just imagine: we can vary the
electrical size of a small antenna by altering the
circuitry to which it connects. It's as if the tiny
antenna can throw up a "virtual lens" made out of vibrating
EM fields. Is any of this stuff useful? Who knows! At
least for me it's a new toy for my brain to futz with.
David M. Brodbeck
> 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).
--> Huh. Does this mean we can expect a magnetic field reversal in about
600 years?
---------------------------------------------------------------------------
David Brodbeck, N8SRE dmbr...@mtu.edu
finger gu...@cyberspace.org for my public key block.
"Infinite perversity and genius are often indistinguishable."
-- Thomas Scoville
Bilge
>On Sat, 04 Mar 2000 00:26:02 GMT, Science Hobbyist <bbe...@microscan.com> wrote:
>I'm certain that fields (photons) can only be altered due to the
>mediation of charged matter. Other fields alone cannot alter them.
Yes, but it seems the statement needs to be repeated, and often.
So continue to throw it in, prn.
>Interference patterns are simple superposition. The Principle of
>Superposition says that the components of a superposition are
>*unaltered* by the superposition. Beyond the superposition zone
>we still have the same two waves, still with the same directions
>and the same energies as they had before the superposition
>occurred.
>
Here is a source of some confusion. The individual fields are unaltered,
but you only measure them through the effect that the SUM has on your
instrument...
>
>(+E) + (-E) = 0
>
>But that doesn't mean that energy has gone to zero. Energy
>is proprortional to the *square* of E
>
> (+E)^2 + (-E)^2
>
You have to get the same result that you got by adding the fields
and then squaring the total. You get the result by remebering
that your square is an inner product. For a phase which isn't
constant in time, the inner product is 0.
Roy McCammon
> if we connect just a resistive load to
> a short dipole and adjust that resistor for maximum
> received power, can we receive even MORE power if we
> then connect a lossless tank circuit across that dipole,
> then re-adjust that resistor value for maximum power?
A short dipole presents a mainly capacitive (plus some
resistance) impedance to its load. So in case 1,
I get to optimize only the source resistance, and
in case 2 I get to optimize the source resistance
and throw in a parallel R and C?
It look like a no brainer. Case 2. If the
source is capacitive, let the load be inductive.
I'd look at it from a load matching point of view.
It might be easier to understand with a series L
rather than a shunt L. I think this is the same
concept as base loading the antenna.
Science Hobbyist
Gary Coffman <ke...@bellsouth.net> wrote:
> > OK, then suppose we illuminate an antenna with a CW EM wave, then
> > connect a receiver to detect it. Are you CERTAIN that no other
> > EM fields can possibly interfere with this process, yet do so
> > entirely by linear effects?
>
> I'm certain that fields (photons) can only be altered due to the
> mediation of charged matter. Other fields alone cannot alter them.
Then we're in agreement, I think. When a normal 1/2-wave
dipole antenna absorbs energy from incoming EM waves, it
is the charged matter within the metal which causes the
antenna to grab energy from the EM waves. However,
pointlike particles don't magically interact with EM
waves, instead it is their surrounding fields which
perform the trick. Regardless of the type of antenna,
it is the LOCAL FIELDS associated with the charges
which interact with the EM waves and cause the energy
to eventually wind up flowing along the antenna's
lead-in cable.
That's why I keep saying that the FIELDS of the electrically
short antenna are reaching out and grabbing EM waves. The
fields of the electrically short antennas are created by
the motions of charged matter within those antennas. By
superposing with the fields of the incoming EM waves,
the antenna's local fields cause enery to be diverted from
the wave. I certainly agree that fields alone
(meaning propagating EM waves far from any matter) cannot
affect other propagating waves in this fashion.
> Interference patterns are simple superposition. The Principle of
> Superposition says that the components of a superposition are
> *unaltered* by the superposition. Beyond the superposition zone
> we still have the same two waves, still with the same directions
> and the same energies as they had before the superposition
> occurred.
True for propagating waves, but not true for the fields in
the nearfield zone of a piece of charged matter such as an
antenna. When a half-wave dipole generates a local field,
the end result is that some of the energy in the incoming
EM waves is intercepted by the antenna. Superposition
still holds true, yet that half-wave dipole was able
to punch a hole in the wavetrain of EM waves passing by.
Do you object to this? If not, then why are electrically
small resonant antennas (with their huge local fields)
such a problem?
I think you might want to review your concepts, since
the idea that "fields allow antennas to intercept EM
waves" applies to all antennas, not just to these
weird resonant antennas.
And make no mistake, the charges are required as
well. You cannot create a dipole field without charges,
and it is the oscillating dipole field and its associated
charges in the conductors which performs the absorbtion
process in both a 1/2-wave dipole and in a tiny resonant
antenna.
> > In particular, if the short antenna
> > surrounds itself with a non-radiating local field which
> > partially CANCELS OUT the fields of an incoming EM wave,
> > then nothing nonlinear has occurred. Yet energy has gone
> > missing from space. The cancelled energy ends up within
> > the short antenna. Plots of the Poynting vector field show
> > that the cancellation process deflects the incoming waves so
> > that they flow into the tiny antenna. Their energy appears
> > in whatever load is connected.
>
> The energy has *not* "gone missing".
Gone missing FROM SPACE, from the travelling EM wave. The
energy is now inside the load resistor connected to the
antenna. This is true of a half-wave dipole, and just as
true of a tiny resonant antenna.
> That is a misunderstanding of what has happened.
I think not. I think I'm unable to get my ideas across
clearly. Also it might be because I'm coming from an
unconventional viewpoint; thinking in terms of the
local fields generated by an antenna rather than in terms
of current through it or voltage across it. I hadn't
realized this was unconventional, but people here are
attacking some concepts which I didn't think were
controversial or even open to debate.
If you are certain that a normal half-wave dipole can
intercept EM waves without the dipole generating fields
of its own, then we have a serious problem. If you
accept the existence of these local fields generated by
the antenna, but are certain that they play no role in
the interception of the energy from the EM waves, then we
have a serious problem. You're no longer arguing about
the tiny antennas, but instead have begun questioning
antenna-physics itself.
Roy McCammon
> Then we're in agreement, I think. When a normal 1/2-wave
> dipole antenna absorbs energy from incoming EM waves, it
> is the charged matter within the metal which causes the
> antenna to grab energy from the EM waves. However,
> pointlike particles don't magically interact with EM
> waves, instead it is their surrounding fields which
> perform the trick. Regardless of the type of antenna,
> it is the LOCAL FIELDS associated with the charges
> which interact with the EM waves and cause the energy
> to eventually wind up flowing along the antenna's
> lead-in cable.
As a matter of terminology, it is usually said
that there is one field, but if convenient, it
can be decomposed into terms attributed to charges
and currents at a far away source and other
terms that are attributed to charges and currents
in the nearby antenna. But I also use the short
hand terminology of talking about these separate
terms as separate fields.
Anyway, it is certain that the total field with the
antenna is different from the total field
without the antenna.
> That's why I keep saying that the FIELDS of the electrically
> short antenna are reaching out and grabbing EM waves.
I think I'd say that the currents and charge distributions
in the antenna distort the field from what it would be
if the antenna were not there.
> > Interference patterns are simple superposition. The Principle of
> > Superposition says that the components of a superposition are
> > *unaltered* by the superposition. Beyond the superposition zone
> > we still have the same two waves, still with the same directions
> > and the same energies as they had before the superposition
> > occurred.
>
> True for propagating waves, but not true for the fields in
> the nearfield zone of a piece of charged matter such as an
> antenna.
I'd say it was true for independent waves. But what is
different here is that the field component from the antenna
currents is dependent on the component from the far away
sources. Another way of looking at it is simply that
the field with the antenna is different from the field
without the antenna.
> When a half-wave dipole generates a local field,
> the end result is that some of the energy in the incoming
> EM waves is intercepted by the antenna. Superposition
> still holds true, yet that half-wave dipole was able
> to punch a hole in the wavetrain of EM waves passing by.
> Do you object to this?
My objection is one of emphasis. The way you have told it,
it sounds to me like you consider the source fields and the
antenna field to be two separate fields. I would say there
are two fields: one for the case with the antenna and one for
the case without (sounding now somewhat like a broken
record).
> If not, then why are electrically
> small resonant antennas (with their huge local fields)
> such a problem?
I missed something. What problem?
> I think not. I think I'm unable to get my ideas across
> clearly. Also it might be because I'm coming from an
> unconventional viewpoint; thinking in terms of the
> local fields generated by an antenna rather than in terms
> of current through it or voltage across it. I hadn't
> realized this was unconventional, but people here are
> attacking some concepts which I didn't think were
> controversial or even open to debate.
I think its just the way you tell it.
I think you could even apply your view to dc circuits.
The load allows currents to flow which change the fields
from what they would be if there were no currents. And if
there were no currents, Poynting's vector integrated over
the surface of the load would be zero.
Science Hobbyist
Roy McCammon <rbmcc...@ieee.org> wrote:
> Science Hobbyist wrote:
> As a matter of terminology, it is usually said
> that there is one field, but if convenient, it
> can be decomposed into terms attributed to charges
> and currents at a far away source and other
> terms that are attributed to charges and currents
> in the nearby antenna. But I also use the short
> hand terminology of talking about these separate
> terms as separate fields.
Sure. I see it in terms of mental models. Having a variety
of mental models gives us a "larger toolkit". If we see
the field as a single entity, some interesting ideas
unfortunately vanish. My hobby is to look for unorthodox
viewpoints in hopes of gaining insights I lacked before.
But since the ideas aren't in all the textbooks, I don't
trust them entirely, and I put them here so others might
find any obvious holes which I've missed.
With these antennas, I've been thinking in terms of three
viewpoints: incoming EM waves without the antenna fields,
antenna-generated fields without the incoming EM waves,
and also the superposition.
Which leads me to wonder: don't halfwave dipoles also
generate their own fields? If the field being generated
by a tiny resonant antenna is the reason that the antenna
can absorb EM waves, maybe the same idea applies to ALL
antennas.
> > That's why I keep saying that the FIELDS of the electrically
> > short antenna are reaching out and grabbing EM waves.
>
> I think I'd say that the currents and charge distributions
> in the antenna distort the field from what it would be
> if the antenna were not there.
OK, but it is not obvious that a current alone can "draw in"
the energy of an EM wave. Thinking in terms of the field
produced by that antenna current helps explain what's going
on. It takes some of the mystery out of the "nearfield"
stuff. The Bohren paper has a diagram where the dipolar
e-field of a tiny antenna is added to the e-field of
incoming plane EM waves, and when the Poynting vector is
plotted (it's perpendicular to the distorted field lines)
it proves to deflect inwards and dive into the tiny antenna.
Very weird.
> I'd say it was true for independent waves. But what is
> different here is that the field component from the antenna
> currents is dependent on the component from the far away
> sources.
Not totally true in the case of the resonant antenna. Yes,
the stored energy in the resonator did originally come from
the incoming EM waves. However, it built up over many
cycles. If the incoming wavetrain was to suddenly come
to an end, then the oscillating fields produced by the
small antenna's LC circuit would continue. (The antenna
is too small to radiate much energy.) The antenna's
fields are not created by the incoming EM waves, instant
by instant, and it is conceivable that they could be
created by a power supply with the goal of increasing the
antenna's effective size, as Sutton and Spaniol did in
their active ELF antenna (papers referenced at the end
of http://www.amasci.com/tesla/tesceive.html)
> My objection is one of emphasis. The way you have told it,
> it sounds to me like you consider the source fields and the
> antenna field to be two separate fields.
But they are, and in the same way that the fields of
two bar magnets are "separate" whether the bar magnets
are adjacent or very distant. It's also true that the
EM waves will permanently alter the fields of the small
antenna, but it takes many cycles for this to occur.
If we suddenly remove the incoming EM waves, yet the
antenna's fields persist, then I think I have reason to
assert that the antenna's fields are an independant entity
(which of course can superpose with any other field which
happens to appear.) And if we have two bar magnets, we
usually think in terms of two dipole fields which are
superposed, rather than thinking in terms of a single
more complicated field which cannot be decomposed into
something simpler.
> I would say there
> are two fields: one for the case with the antenna and one for
> the case without (sounding now somewhat like a broken
> record).
Heh. And a third: the case where there are no incoming
EM plane waves, but the LC circuit in the tiny antenna is
still oscillating and producing a local field surrounding
the antenna.
>
> > If not, then why are electrically
> > small resonant antennas (with their huge local fields)
> > such a problem?
>
> I missed something. What problem?
My previous reply was to Mr. Coffman, who insisted that
an AC EM field could not deflect the Pointing vector of an
EM wave (and therefore I am wrong about the ability of
these tiny antennas to deflect EM energy into themselves.)
>
> > I think not. I think I'm unable to get my ideas across
> > clearly. Also it might be because I'm coming from an
> > unconventional viewpoint; thinking in terms of the
> > local fields generated by an antenna rather than in terms
> > of current through it or voltage across it. I hadn't
> > realized this was unconventional, but people here are
> > attacking some concepts which I didn't think were
> > controversial or even open to debate.
>
> I think its just the way you tell it.
Right! I'm speaking in clear terms, yet they are
unconventional, so everyone seems to have objections.
Yet there is nothing wrong with my terminology, except
that it is non-traditional. My goal is to see if others
can find a hole in my arguments, and to make myself
think. Unfortunately, this tends to force others to
think as well, and I suspect that many people don't
enjoy that one bit! :) Of course I'm getting a bit
of an advantage, since I've been beating my head on these
ideas for awhile, rather than having them suddenly dumped
into my lap by some weirdo on the newsgroups.
> I think you could even apply your view to dc circuits.
> The load allows currents to flow which change the fields
> from what they would be if there were no currents. And if
> there were no currents, Poynting's vector integrated over
> the surface of the load would be zero.
Yeah! And circuits connect with antennas in the realm of
AC motors. A coil can drive a rotating permanent magnet.
If the magnet bearings have friction, the magnet is essentially
"sucking energy" from the drive coil, and integrating the
Poynting vector over a spherical surface surrounding only the
magnet would show energy flowing inwards. That same magnet
can be driven by radio waves (if the frequency is very low
or the RPM of the magnet is very high.) In that situation,
EM energy is absorbed by the rotating magnet and it ends up
as heat in the bearings. This is a very unorthodox
"radio antenna", no? If the magnet size is << wavelength,
then it is very similar to these electrically small
resonant antennas. If the magnet is made very strong, then
it couples more strongly to the incoming EM waves, and
can extract a larger energy flow. And if the EM field
generated by the resonator builds up to a high amplitude,
that antenna "acts larger" than it actually is.
Overall idea: take a standard receiving antenna, realize
that the antenna currents generate their own fields, then
conceptually shrink that antenna while adding some circuitry
which keeps its field pattern strong at a 1/4-wave distance.
You can shrink the antenna to any small size, yet if the
antenna-generated field remains large, the received power
will not decrease much. AM radio antennas the size of
large molecules become possible, at least in theory. A
desktop longwave antenna with the electrical size of a
broadcasting tower becomes possible (although
superconducting materials are probably required.)
Alan Boswell
> In article <38C4A0A7...@ieee.org>,
> Roy McCammon <rbmcc...@ieee.org> wrote:
> > Science Hobbyist wrote:
> > As a matter of terminology, it is usually said
> > that there is one field, but if convenient, it
> > > If not, then why are electrically
> > > small resonant antennas (with their huge local fields)
> > > such a problem?
>
>
> You can shrink the antenna to any small size, yet if the
> antenna-generated field remains large, the received power
> will not decrease much. AM radio antennas the size of
> large molecules become possible, at least in theory. A
> desktop longwave antenna with the electrical size of a
> broadcasting tower becomes possible (although
> superconducting materials are probably required.)
>
>
William - I have not followed this argument in detail, but you
might be interested in a fundamental theory which gives the
bandwidth of small antennas in terms of their size in wavelengths.
The theory, based on a transmitting antenna, establishes the stored
energy as a multiple of the radiated energy to derive a Q factor
which leads to an expression for the the bandwidth.
The paper, by Chu, is in J. Applied Physics, Dec. 1948, and the
theory gives an upper limit for bandwidth in terms of the radius of
the smallest sphere which can enclose the antenna, and it is
independent of the details of the particular antenna. A good
approximation from the theory, for a lossless antenna, is:
B/f0=250(r/lambda)^3
B is bandwidth, f0 is carrier frequency, r is the sphere radius
and lambda is the wavelength.
For a 150mm loopstick at 1MHz the bandwidth comes out at
0.004Hz from the formula BUT in practice there is sufficient
loss resistance present to raise the bandwidth to (say) 40kHz, a
factor of 10^7, whilst reducing the gain by 70dB. This is acceptable
because enough power is transmitted, and sufficient amplification is
present in the receivers, to make it acceptable. The theory might
provide guidance about the feasibility of atom-sized antennas.
Alan
Bilge
> Which leads me to wonder: don't halfwave dipoles also
> generate their own fields? If the field being generated
> by a tiny resonant antenna is the reason that the antenna
> can absorb EM waves, maybe the same idea applies to ALL
> antennas.
>
limit the usefulness of many possible geometries.
> Not totally true in the case of the resonant antenna. Yes,
> the stored energy in the resonator did originally come from
> the incoming EM waves. However, it built up over many
> cycles. If the incoming wavetrain was to suddenly come
This cannot be true. Many photons, yes, many cycles, no.
The energy cant be stored over a period greater than the
frequency of the wave, otherwise, the modulations would be
washed out. In an amplifier, you would call the lack of
ability to change at the signal rate a slewing limitation.
Bilge
>In article <2SLDOA06BxInEy...@4ax.com>,
>
> Then we're in agreement, I think. When a normal 1/2-wave
> dipole antenna absorbs energy from incoming EM waves, it
> is the charged matter within the metal which causes the
> antenna to grab energy from the EM waves. However,
> pointlike particles don't magically interact with EM
> waves, instead it is their surrounding fields which
No, the energy received by an antenna is exactly the interaction of
photon with a pointlike electron. The size of the antenna is what
determines how efficiently it provides electrons to cover the volume
of space in which that photon has a probability of being found.
A standard dipole just happens to meet this condition (along with
a couple of others). It doesnt have a monopoly on geometry. It just
happens to be particularly simple.
> That's why I keep saying that the FIELDS of the electrically
> short antenna are reaching out and grabbing EM waves. The
The fields cant do anything but move charges. If you can explain
it in that context, then you may be able to justify that statement,
but otherwise that statement is wrong.
> to punch a hole in the wavetrain of EM waves passing by.
> Do you object to this? If not, then why are electrically
> small resonant antennas (with their huge local fields)
> such a problem?
>
Because you are ignoring the antenna's and the rest of the system's
requirements for providing a signal from the currents produced by
radiation incident on the antenna.
> I think not. I think I'm unable to get my ideas across
> clearly. Also it might be because I'm coming from an
> unconventional viewpoint; thinking in terms of the
> local fields generated by an antenna rather than in terms
> of current through it or voltage across it. I hadn't
> realized this was unconventional, but people here are
> attacking some concepts which I didn't think were
> controversial or even open to debate.
>
In that case, try changing your viewpoint, because you aren't
making it clear that you are using the terminology in a way
that doesn't make your statements incompatible with the physics
you claim isnt in disagreement.
> If you are certain that a normal half-wave dipole can
> intercept EM waves without the dipole generating fields
> of its own, then we have a serious problem. If you
Of course there is a field. If there were not, no current
would flow, making it totally useless as an antenna. A charge
is accelerated by the incoming photon. Because it is displaced
from equilibrium, it produces forces on other charges and so
on. This is the definition of a current.
Science Hobbyist
dav...@david15.dallas.nationwide.net wrote:
> > Not totally true in the case of the resonant antenna. Yes,
> > the stored energy in the resonator did originally come from
> > the incoming EM waves. However, it built up over many
> > cycles. If the incoming wavetrain was to suddenly come
>
> The energy cant be stored over a period greater than the
> frequency of the wave, otherwise, the modulations would be
> washed out.
Right. If the energy is stored over many cycles, then fast
modulations will be washed out. That's what I'd expect.
The time constant for flourescent materials is long compared
to period of the waves involved. A resonant antenna would
act as if the incoming waves "pump it up" over time.
> In an amplifier, you would call the lack of
> ability to change at the signal rate a slewing limitation.
We're talking about the same thing, right? A high-Q tank
circuit connected to an electrically small antenna? We
shouldn't be suprised if it behaves differently than a simple
1/2-wave dipole. Because the tank circuit has high Q, won't
it respond slowly to changes? If the incoming wavetrain
begins abruptly, how could the high-Q tank circuit instantly
absorb enough energy to follow that leading edge of modulation?
And if the wavetrain suddenly ceases, why wouldn't the tank
circuit keep oscillating for many cycles? Because the tiny
antenna is weakly coupled to the incoming waves, won't the
AC voltage across the tank circuit change fairly slowly even
though the modulation is fast? (Hmmm. If the tank circuit had
infinite Q, maybe it would take infinite time for it to
aquire any energy from the EM waves.)
In the case of a real antenna like an AM radio loopstick,
it would make little difference if there was a significant
slewing limitation, since the audio bandwith is at least
50 times smaller than the carrier frequency. If it took
a 20-cycle time constant for the tank circuit to settle
to the instantaneous modulation envelope, the audio
fidelity wouldn't be changed much. Since the Q of a
realworld loopstick antenna isn't incredibly high, it
probably responds fairly quickly, rather than in hundreds
of cycles. It's a good point you've brought up though.
Raising the Q to enhance the "energy sucking" effect
might be good for S/N ratio, but bad for bandwidth and
audio fidelity of an AM signal.
Scott Stephens
Bilge wrote in message ...
> >mediation of charged matter. Other fields alone cannot alter them.
>
> So continue to throw it in, prn.
Did you know photons have a magnetic moment? That circular polarized laser
beams attract? ;-)
> >Interference patterns are simple superposition. The Principle of
> >Superposition says that the components of a superposition are
> >*unaltered* by the superposition. Beyond the superposition zone
> >we still have the same two waves, still with the same directions
> >and the same energies as they had before the superposition
> >occurred.
Solitons can do strange things, see http://www.sfu.ca/~renns/lbullets.html
Scott
Bilge
>In article <slrn8cau2...@radioactivex.lebesque-al.net>,
>
> Right. If the energy is stored over many cycles, then fast
> modulations will be washed out. That's what I'd expect.
> The time constant for flourescent materials is long compared
> to period of the waves involved. A resonant antenna would
> act as if the incoming waves "pump it up" over time.
>
state emitting the light are inhibited from decaying but
are not the states excited by the incident radiation. If they
were the same state, from considerations of time-reversal, you
coupldn't populate the state faster than it decays. It occurs
from transitions like:
excitation
--------
/ | fast transition to metastable state
/ --------
/ |
/ |
/ | slow transition
/ | inhibited by
------ -------- selection rules (J^pi, for example)
gs
There is no analogy in antenna. The resonance in an antenna means
X_C = C_L and the stored energy over a complete cycle is completely
determined by L and C.
>> In an amplifier, you would call the lack of
>> ability to change at the signal rate a slewing limitation.
>
> We're talking about the same thing, right? A high-Q tank
> circuit connected to an electrically small antenna? We
> shouldn't be suprised if it behaves differently than a simple
> 1/2-wave dipole. Because the tank circuit has high Q, won't
> it respond slowly to changes? If the incoming wavetrain
resistances of its elements is small. That doesn't allow it to
accumulate energy, since you have to connect to it to (1) attach
the antenna, (2) arrange for charge to go in and out if you want
to do anything. With nothing but the antenna attached, guess what
happens with the energy stored in the tank each cycle? Remember,
it's a reversible process.
> begins abruptly, how could the high-Q tank circuit instantly
> absorb enough energy to follow that leading edge of modulation?
By instantly, I assume you mean the velocity of the propagation
in the conductor, i.e., the frequency doesnt hit any anomalous
dispersion (this ought to be good to about 10^14 Hz). So, below
frequencies where speed of light violations would have to be
considered, it does happen "instantly" for all practical purposes.
Why is the peak large: Z = R, not jwl + 1/jwc + R, since wL = 1/wc
at resonance. Since V = iZ if you assume i is the same for any
frequency (in direct contrast to the "energy sucking" stuff),
you can only develop a potential difference as large as Z permits.
Plot Z vs w. At the resonance pt, w_0, tt will look real similar
to Q which is a plot of w_0 vs \delta w.
> AC voltage across the tank circuit change fairly slowly even
> though the modulation is fast? (Hmmm. If the tank circuit had
> infinite Q, maybe it would take infinite time for it to
> aquire any energy from the EM waves.)
>
I think you might be getting the idea except that instead of thinking
Q think "energy sucking idea". The process has to be totally
reversible.
> Raising the Q to enhance the "energy sucking" effect
> might be good for S/N ratio, but bad for bandwidth and
> audio fidelity of an AM signal.
That's another reason the "energy sucking" cant be right. Increasing
the signal to noise always increases the bandwidth provided the
encoding is optimal (an encoding which depends upon certain spectral
characteristics of the noise, may of course be worse off with a better
S/N that also changes those characteristics, but that's a pathological
case which resides with the coding scheme)
Scott Stephens
Science Hobbyist wrote in message <8a2ova$f7k$1...@nnrp1.deja.com>...
>In article <38C4A0A7...@ieee.org>,
> Roy McCammon <rbmcc...@ieee.org> wrote:
>> Science Hobbyist wrote:
>> > That's why I keep saying that the FIELDS of the electrically
>> > short antenna are reaching out and grabbing EM waves.
>>
>> I think I'd say that the currents and charge distributions
>> in the antenna distort the field from what it would be
>> if the antenna were not there.
>
> OK, but it is not obvious that a current alone can "draw in"
> the energy of an EM wave. Thinking in terms of the field
> produced by that antenna current helps explain what's going
> on. It takes some of the mystery out of the "nearfield"
> stuff. The Bohren paper has a diagram where the dipolar
> e-field of a tiny antenna is added to the e-field of
> incoming plane EM waves, and when the Poynting vector is
> plotted (it's perpendicular to the distorted field lines)
> it proves to deflect inwards and dive into the tiny antenna.
> Very weird.
Look at the ubiquitous roof-top log-periodic TV antenna, you notice (for a 3
element anyways) a short dipole called a director, the receiving dipole
that's 1/2 wave, and behind a long dipole called a reflector. The
electricaly short dipole is capacitively reactive at the receiving frequency
and bends radio waves into the receiving dipole. Behind the long reflector
dipole acts inductive, and reflects energy back into the receiving dipole,
which is purely resistive at the receiving frequency.
Nothing weird here. A constant phase shift occurs, reactance, when the
dipole is long or short compared to the wavelength. It 'bends' or 'reflects'
because the element is not loaded so it re-radiates energy. The
superposition of the incident and radiated energy is what refracts or
reflects. A field is required for this action.
But this is not the same as 'flux sucking'.
An atom has highly charged electrons or dipole moments. The electrons are
mobile. When a photon's EM field is present, the electron and its charge and
dipole moment move in the field to cancel it, and absorb the energy ending
the photon if the electron gets stuck in a higher orbit, or re-radiating
with a time delay when it falls to a lower orbit if the material is
transparent. In high permiability and permitivity ceramics, the dipole
moment of the molecules are physicaly stressed by ambient flux and cancel it
by displacing and concentrating the flux as stress in the ceramic.
An antenna is fixed and static. Currents only flow where conductors are. If
you had an antenna that had a high static charge and magnetic moment, and
was fluid, and virtualy massless, so it could re-configure itself in
response to changes in an incident field, you would have an interesting
antenna indeed.
Scott
Richard Herring
> Bilge wrote in message ...
> >
> > >On Sat, 04 Mar 2000 00:26:02 GMT, Science Hobbyist <bbe...@microscan.com>
> wrote:
> >
> > >I'm certain that fields (photons) can only be altered due to the
> > >mediation of charged matter. Other fields alone cannot alter them.
> >
> > Yes, but it seems the statement needs to be repeated, and often.
> > So continue to throw it in, prn.
> Did you know photons have a magnetic moment?
Really? What's its value? How did you measure it?
> That circular polarized laser beams attract? ;-)
Photon-photon interactions are a second-order effect in QED.
In the low-energy regime of this discussion, they can safely be
neglected.
> > >Interference patterns are simple superposition. The Principle of
> > >Superposition says that the components of a superposition are
> > >*unaltered* by the superposition. Beyond the superposition zone
> > >we still have the same two waves, still with the same directions
> > >and the same energies as they had before the superposition
> > >occurred.
> Solitons can do strange things, see http://www.sfu.ca/~renns/lbullets.html
In a nonlinear dispersive medium, certainly. But it's the
constitutive relation of the medium which produces the effect,
not any innate property of photons. In free space, superposition
still holds (apart from that 2nd-order QED caveat.)
--
Richard Herring | <richard...@gecm.com>
Roy McCammon
> Which leads me to wonder: don't halfwave dipoles also
> generate their own fields?
If there are currents in the dipole, then those currents
contribute to the (one) field.
> OK, but it is not obvious that a current alone can "draw in"
> the energy of an EM wave.
more oneness: currents and fields arise together.
> Thinking in terms of the field
> produced by that antenna current helps explain what's going
> on.
I have to agree with that.
> It takes some of the mystery out of the "nearfield"
> stuff. The Bohren paper has a diagram where the dipolar
> e-field of a tiny antenna is added to the e-field of
> incoming plane EM waves, and when the Poynting vector is
> plotted (it's perpendicular to the distorted field lines)
> it proves to deflect inwards and dive into the tiny antenna.
> Very weird.
Well, from the field theory point of view, it isn't
weird, it is necessary.
>
> > I'd say it was true for independent waves. But what is
> > different here is that the field component from the antenna
> > currents is dependent on the component from the far away
> > sources.
>
> Not totally true in the case of the resonant antenna. Yes,
> the stored energy in the resonator did originally come from
> the incoming EM waves. However, it built up over many
> cycles. If the incoming wavetrain was to suddenly come
> to an end, then the oscillating fields produced by the
> small antenna's LC circuit would continue. (The antenna
> is too small to radiate much energy.)
The concept of dependence is readily extended for this.
You simply note that a transmitter that is switched on
and later switched off does not produce a single frequency
but rather produces a band of frequencies. The transient
response of the LC circuit is accounted for by the relative
phase
of those constituent frequencies. It doesn't really matter
in this case, since we can confine the discussion to the
steady state.
> The antenna's
> fields are not created by the incoming EM waves, instant
> by instant,
it only takes a little Fourier math to put it into
that framework.
> My previous reply was to Mr. Coffman, who insisted that
> an AC EM field could not deflect the Pointing vector of an
> EM wave (and therefore I am wrong about the ability of
> these tiny antennas to deflect EM energy into themselves.)
Again, it is wording. One field doesn't deflect another.
There is only one field and it deflects.
> > I think its just the way you tell it.
>
> Right! I'm speaking in clear terms, yet they are
> unconventional, so everyone seems to have objections.
You can use the word "spoon" to talk about a fork,
and if you don't realize that your are using a different
definition and we don't realize it also, its likely
that we would disagree and how a spoon works.
> Yet there is nothing wrong with my terminology, except
> that it is non-traditional.
Except that you are talking to people who use traditional
terminology.
> Yeah! And circuits connect with antennas in the realm of
> AC motors. ...
yes, Poynting vector approach applies to all
> Overall idea: take a standard receiving antenna, realize
> that the antenna currents generate their own fields, then
> conceptually shrink that antenna while adding some circuitry
> which keeps its field pattern strong at a 1/4-wave distance.
> You can shrink the antenna to any small size, yet if the
> antenna-generated field remains large, the received power
> will not decrease much. AM radio antennas the size of
> large molecules become possible, at least in theory. A
> desktop longwave antenna with the electrical size of a
> broadcasting tower becomes possible (although
> superconducting materials are probably required.)
The reciprocal problem is easier to work. The mutual
inductance from a transmitter to a receiver is the same as
from the receiver to the transmitter. Let the
far away transmitter become a far away receiver. Let
the short dipole be a transmitter. It is trivial that if
the antenna is lossless and the matching components are
lossless that the antenna is 100% efficient, no matter
how small it is. Furthermore, the field from a dipole
of 0.01 wavelength is virtually the same as the field
from a 0.001 wavelength dipole. So, for the same power
in, I get the same signal at the far away receiver.
So, given lossless antenna materials and lossless
matching networks, all short dipoles are equal.
But to to consider some practical details, as our dipole
gets small, it gets thinner than skin depth. The resistance
at signal freq is the same as the dc resistance. As we
scale
the dipole down by a factor of 2, its length decreases by
two
and its cross section by 4 so that the dc resistance goes
up by 2. But, the radiation resistance goes down by a
factor
of four. At some point, it becomes very lossy.
Roy McCammon
> The antenna's
> fields are not created by the incoming EM waves, instant
> by instant, and it is conceivable that they could be
> created by a power supply with the goal of increasing the
> antenna's effective size, as Sutton and Spaniol did in
> their active ELF antenna (papers referenced at the end
> of http://www.amasci.com/tesla/tesceive.html)
I haven't read the paper, but I suspect that they put
more power into it than they pulled out of the incoming
wave.
>
> > My objection is one of emphasis. The way you have told it,
> > it sounds to me like you consider the source fields and the
> > antenna field to be two separate fields.
>
> But they are,
As I let the water out of my bath tub, I notice that there
there is a depression in the water level over the drain.
The
depression is really there and it is interesting and
deserves
some study, but I don't tend to think of that depression as
sucking water out of the tub and shoving it down the drain.
To me, your description of energy sucking sounds backward
in a similar sense.
But, consider this (I think you will like it).
If I wind a coil on a torroidal form and energize it
sinusoidal, and if I do an idea job, there is no
H or B field outside of the torroid. There is E, but no
H or B. I then run a wire down the middle and
connect the ends to a resister. I have made a
transformer. The resister absords power. But how can
the Poynting vector be non zero it there is no H or
B from the primary current? Easy, it comes from the
secondary current. So here is a case where the E
component of the field is attributed to source
currents and the H component is attributed to the
load current. And it works fine.
Why? Because there is only one field and Poynting
says P = E cross H. It doesn't say P = Esource cross
Hsource.
Scott Stephens
Richard Herring wrote in message <8a5do9$g5d$2...@miranda.gmrc.gecm.com>...
>In article <eAnx4.16603$84.505168@elnws01>, Scott Stephens
(Sco...@Mediaone.net) wrote:
>
>> Bilge wrote in message ...
>> >
>> > >On Sat, 04 Mar 2000 00:26:02 GMT, Science Hobbyist
<bbe...@microscan.com>
>> wrote:
>> >
>> > >I'm certain that fields (photons) can only be altered due to the
>> > >mediation of charged matter. Other fields alone cannot alter them.
>> >
>> > Yes, but it seems the statement needs to be repeated, and often.
>> > So continue to throw it in, prn.
>
>> Did you know photons have a magnetic moment?
>
>Really? What's its value? How did you measure it?
I'm sorry, I looked for the article but can't find it. I don't expect you to
take my word for it. Maybe a post to some physics newsgroup would get an
answer?
Scott
Science Hobbyist
"Scott Stephens" <Sco...@Mediaone.net> wrote:
> electricaly short dipole is capacitively reactive at the receiving
frequency
> and bends radio waves into the receiving dipole. Behind the long
reflector
> dipole acts inductive, and reflects energy back into the receiving
dipole,
> which is purely resistive at the receiving frequency.
>
> Nothing weird here.
If that's not weird, then "energy sucking" isn't so weird
either, in my opinion. If the induced V and I on the
director element causes energy to be "lensed" towards
the active element, and if the fields generated by the
director are the cause... then if this whole process
could be performed by a single object (being director
and receiver simultaneously), then we'd have an
"energy sucking" device.
Science Hobbyist
dav...@david15.dallas.nationwide.net wrote:
> > Right. If the energy is stored over many cycles, then fast
> > modulations will be washed out. That's what I'd expect.
> > The time constant for flourescent materials is long compared
> > to period of the waves involved. A resonant antenna would
> > act as if the incoming waves "pump it up" over time.
>
> Why? Flourescence occurs because the transitions from the
> state emitting the light are inhibited from decaying but
> are not the states excited by the incident radiation. If they
> were the same state, from considerations of time-reversal, you
> coupldn't populate the state faster than it decays. It occurs
> from transitions like:
I was under the impression that some fluorescence didn't
involve metastable states. I was thinking in terms of
an atom with a narrow absorbtion band having a small
probability of absorbing a photon (which would lead to
a long "pumping up" time) and a small probability of
emitting one (which would give a long decay time once
the incoming radiation ceased.) This would be analogous
to a resonator which takes many cycles to aquire energy
from a wavetrain, and many cycles to decay again.
> Because the tank has a large Q, it's losses through the internal
> resistances of its elements is small. That doesn't allow it to
> accumulate energy, since you have to connect to it to (1) attach
> the antenna, (2) arrange for charge to go in and out if you want
> to do anything. With nothing but the antenna attached, guess
what
> happens with the energy stored in the tank each cycle? Remember,
> it's a reversible process.
I understand what you're thinking (I think). If you're right,
then the short antenna would radiate energy as fast as it
absorbed it, and the presence of the resonant circuit would
not change this.
> I think you might be getting the idea except that instead of
thinking
> Q think "energy sucking idea". The process has to be totally
> reversible.
THERE'S a key point. If my understanding of the "energy
sucking" mechanism is correct, then because the process
involves interaction between the incoming EM waves and the
fields generated by the resonator, it is NOT reversible, and
the time constant for intercepting energy is shorter than
the time constant for losses by radiation from the antenna.
There would be an analog for Stimulated Emission: if the
phase of the incoming waves were to shift 180deg, then
any stored energy in the resonator would be "anti-sucked"
and would dump out faster than it would ordinarily
radiate.
> > Raising the Q to enhance the "energy sucking" effect
> > might be good for S/N ratio, but bad for bandwidth and
> > audio fidelity of an AM signal.
>
> That's another reason the "energy sucking" cant be right.
Slightly separate topic: does a resonant antenna
receive more energy than a non-resonant antenna of
similar geometery? Does the presence of a tank circuit
actually change the effective area of a loop antenna,
yes or no? In other words, is there evidence that SOMETHING
occurs, even if it might not be exactly what I am discussing?
If you insist that "energy sucking" cannot exist on
theoretical grounds, but if an ACTUAL ANTENNA does receive
significantly more energy when it's part of a resonant
circuit, then experiment beats theory.
I don't have reference books which discuss this, but
earlier messages have mentioned that the presence of
a tuned circuit DOES increase the effective area
significantly. If they had not, and if those two
physicist groups had not published papers about the
topic, then I would be far less confident about the
existence of the phenomenon.
Speaking of experiment. If I have time in the future, I'll
try measuring the attack time of a resonant loop antenna
receiving a carrier from a distant transmitter. If an AM
signal can create a couple of volts on it, then
a fast switch and a scope should let me watch as stored
energy ramps up. (Short the capacitor, then suddenly
remove the short and see if it ramps up over many cycles.)
Hey, I can even throw a capacitance across it afterwards,
to detune it so it ramps back down again.
Bilge
>>>In article <eAnx4.16603$84.505168@elnws01>, Scott Stephens
>Richard Herring wrote in message <8a5do9$g5d$2...@miranda.gmrc.gecm.com>...
>>In article <eAnx4.16603$84.505168@elnws01>, Scott Stephens
>>
>>> Did you know photons have a magnetic moment?
>>
>>Really? What's its value? How did you measure it?
>
>
>I'm sorry, I looked for the article but can't find it. I don't expect you to
>take my word for it. Maybe a post to some physics newsgroup would get an
>answer?
>
Good. I dont expect you to find it and this is as good a group as any
to post to for an answer, which is - photons do not have a maagnetic
moment. Mainly, because they aren't charged. They aren't charged, because
that would really screw up qed. If photons had magnetic moments, one could
observe effects of the usual m\cdot B, variety. They do have a spin
angular momentum, though and it happens to be 1. However, spin alone doth
not a magnetic moment generate. The true skeptic may wish perform an
experiment though. Take the plane polarized light from a laser and shine
it down a solenoid. Several days of sleep deprivation might convince one
that the plane of polarization rotated about the axis of the solenoid.
Another day or so awake, and a dubious non-zero result for the amount
of bend one gets from a magnet held next to a flashlight might emerge.
Finally, one may deduce a limit on the magnetic moment and the charge
(B\rho = p/q ; \rho = radius of curvature) and consider investing in a
Berlitz book of swedish phrases for the black-tie weekend ahead.
Bilge
>In article <slrn8cbkv...@radioactivex.lebesque-al.net>,
> I was under the impression that some fluorescence didn't
> involve metastable states. I was thinking in terms of
The process must be time reversal invariant. Excitation
directly to a state which may decay by the same process
must BE the same process. The only way to achieve a long lived
state is to poplulate a state in such a way that the decay
process is inhibited by selection rules. If you
> an atom with a narrow absorbtion band having a small
> probability of absorbing a photon (which would lead to
If you want to think of it in terms of a resonance widths,
you can do that. In fact, it's quite common to do so.
In terms of the reaction cross section, you get the
general Breut-Wigner form,
\sigma \propto [(E - Er) + {\Gamma^{2}\over 4}]^{-1}
for a lot of seemingly unrelated phenomena where E is the
Energy you have to use, Er is the energy required for the
reaction and \Gamma is 1/t, with t = lifetime of the state.
Notice at the energy where E = Er, the probability is a
maximum AND that it says nothing about whether that is
the probability of forming the state or decaying through the
same channel.
This should look uncannily like the impedance of an antenna
which will produce a current for any given potential difference
with some sort of dependence that goes as:
1/[(wL - 1/wc)^2 + R^{2})]
With the exact form being dependent upon all of the relevant
R,L,Cs, but the point being, at resonance, by definition,
the wL cancel the 1/wC. The basic differences between two
antennas that present comparable cross-sections is in the
exact form of the impedance. For comparable wavelengths, your
"energy sucking" is just the antenna presenting the best
current flow due to the impedance and potentials created by
the incoming photons. It's obviously highly frequency dependent.
> a long "pumping up" time) and a small probability of
> emitting one (which would give a long decay time once
> the incoming radiation ceased.)
This violates time reversal invariance.
> THERE'S a key point. If my understanding of the "energy
> sucking" mechanism is correct, then because the process
> involves interaction between the incoming EM waves and the
> fields generated by the resonator, it is NOT reversible, and
> the time constant for intercepting energy is shorter than
That involves two violations that no one plans on giving up
without quite a lot of wailing and gnashing of teeth.
QED and time reversal. If one E&M field can affect another
E&M directly, AT ALL, you have to ditch all of modern
physics. The only self-interacting field for which a theory
exists is QCD, and gluons have a range of quite a bit less
than infinity due to this. In fact, the range cant be greater
than a proton radius and it certainly is not going to have
a 1/r^2 dependence by any stretch of the imagination. As for
time reversal, since it is believed that EVERY physical
law is cpt-invariant, your antenna needs to violate cp
to violate t. Given that E&M is a vector interaction and
charge is a good symmetry, it'll be a hard sell. The weak
interaction can get away with this sort of thing since it's
vector - axial vector. E&M cant.
> Slightly separate topic: does a resonant antenna
> receive more energy than a non-resonant antenna of
> similar geometery?
No. It just doesn't lose energy due to the reactance.
> Does the presence of a tank circuit
> actually change the effective area of a loop antenna,
Only in the sense that from a calculational point of view
you may be able to find a particularly simple way to express
the losses that way, but not as the underlying fundamental
process. Recall that reaction cross sections are done analogously
and are expressed in termas of an area (barns, being the usual
units du jour) Certainly a target nucleus doesn't size from it's
point of view or the point of view of the labratory when the incident
beam enery changes.
> yes or no? In other words, is there evidence that SOMETHING
> occurs, even if it might not be exactly what I am discussing?
>
Take the "energy suck" factor, subtract it from the world
and call the result "power loss due to impedance". Mumble
something about gauge freedom and if it's useful to calculate
an answer, make the connection rigorous, but don't mistake
it for the underlyung physics.
> If you insist that "energy sucking" cannot exist on
> theoretical grounds, but if an ACTUAL ANTENNA does receive
> significantly more energy when it's part of a resonant
> circuit, then experiment beats theory.
>
Experimeents beat theory when they disagree on what the theory
claims the measurements should be and what the experiments say
they are. Your suggested experiment doesn't prove anything other
than the antenna receives more energy connected to a resonant
circuit. It's purely a phenomenological model that may be useful,
like the liquid drop model in nuclear physics, but it doesn't
address "why" at all. For that, you need to be able to predict
a result you can measure that cannot be compatible with any other
model. I don't see any incompatibility with your antenna and
classical E&M and right off hand, I have a hard time imagining
how you could find something that would provide an opportunity
to show a discrepancy.
> topic, then I would be far less confident about the
> existence of the phenomenon.
>
Look, it's possible to take anything and fit it to a particularly
convenient choice of parameters, especially if you have a lot of
parameters (I suggest a brief perusal of the nuclear optical
model which allows the fitting of scattering data to 11 parameters
- which are even physically reasonable after a looking closely).
Given a theory with enough parameters, I can explain the universe.
The hard part is reducing the set to the minimum, not conjuring up
new ones to replace looking deeper into the problem. Anyone
can do that.
> remove the short and see if it ramps up over many cycles.)
> Hey, I can even throw a capacitance across it afterwards,
> to detune it so it ramps back down again.
>
You realize that your Q is defined by the energy stored in a cycle
right? As the impedance has a direct bearing on this, you are
shooting yourself in the foot.
Bergervoet J.R.M.
>
>Photon-photon interactions are a second-order effect in QED.
>
interaction requires a fermion loop with 4 photons attached,
hence 4 vertices and the 4th power of the coupling constant, e.
>not any innate property of photons. In free space, superposition
>still holds (apart from that 2nd-order QED caveat.)
Breaking of superposition in free space not only comes from
photon-photon interaction, but also the vacuum polarization
(a kind of photon-vacuum interaction). It is important for
the hyperfine structure in every atom. It occurs at high
fieldstrengths (e.g. 10^21 V/m, or 10^12 Tesla).
And if you compute the fieldstrength at the outside of one
single proton (radius about 10^(-15) meter) you find ... !
-- Jos
Jos R Bergervoet
>
> Look at the ubiquitous roof-top log-periodic TV antenna, you notice
> (for a 3 element anyways) a short dipole called a director, the
> receiving dipole that's 1/2 wave, and behind a long dipole called a
That's not called a log-periodic antenna, but a Yagi-Uda antenna
because it was invented by Mr. Uda.
(Mr. Yagi presented it outside Japan and explicitely attributed it
to his colleague, but probably the attendants did not listen, or
could not understand his English).
-- Jos
Science Hobbyist
dav...@david15.dallas.nationwide.net wrote:
<massive snips>
> With the exact form being dependent upon all of the relevant
> R,L,Cs, but the point being, at resonance, by definition,
> the wL cancel the 1/wC. The basic differences between two
> antennas that present comparable cross-sections is in the
> exact form of the impedance. For comparable wavelengths, your
> "energy sucking" is just the antenna presenting the best
> current flow due to the impedance and potentials created by
> the incoming photons.
This argument is spreading all over the place. I want to
focus on one little part before going any further.
Please help me understand your position: are you saying
that, at resonance, if the short antenna's (real, lossy)
tank circuit appears as a nonreactive resistance, and
then if I replace the whole tank circuit with a carbon
resistor of the same value, the SAME energy will be received?
Just so there's no misunderstanding: place a load resistor
across a very short receiver-dipole and ADJUST THE
RESISTANCE for maximum received power. Measure the power
in the resistor somehow. No tank circuit. (Assume it
is receiving a CW radio signal.)
OK, now place a lossless LC circuit across the resistor on
the above dipole antenna, tune it to resonance, and
re-adjust the load resistor for maximum received power
(is this even necessary?) In both cases the short dipole
sees only a resistive load attached to it. In both cases
that load has been adjusted for maximum received power.
Will the received power being dissipated by the load
resistor be the same in both cases?
Bilge
>In article <slrn8cej5...@radioactivex.lebesque-al.net>,
> Please help me understand your position: are you saying
> that, at resonance, if the short antenna's (real, lossy)
My point is, antennas don't "suck", (well, some probably do, but not
in the context given here). I was attempting to use your descriptions
to point out what's happening, since you want to view it that way.
> tank circuit appears as a nonreactive resistance, and
> then if I replace the whole tank circuit with a carbon
> resistor of the same value, the SAME energy will be received?
>
Depend upon how you define "receive". As in you have an equal
opportunity to make use of it? None is re-radiated? what?
The same number of photons strike the antenna. Your ability
to make use of them varies.
> Just so there's no misunderstanding: place a load resistor
> across a very short receiver-dipole and ADJUST THE
> RESISTANCE for maximum received power. Measure the power
> in the resistor somehow. No tank circuit. (Assume it
> is receiving a CW radio signal.)
>
j
| wL
Impedance diagram: +------------> R
|
| 1/wc
Z = R + jwL - 1/jwC
> OK, now place a lossless LC circuit across the resistor on
> the above dipole antenna, tune it to resonance, and
> re-adjust the load resistor for maximum received power
> (is this even necessary?) In both cases the short dipole
> sees only a resistive load attached to it. In both cases
j
Impedance diagram: +------------> R
Z=R
That's not true. The dipole itself has some reactance, especially
a short one. Adding the tank circuit and tuning it for resonance
removes that reactance from the circuit. Tune your tank circuit
WITHOUT connecting it, then connect it and don't change the
resistor and see what happens.
> that load has been adjusted for maximum received power.
In one case yo have R + X_ant
in the other you have R since tuning the tank circuit
accomplishes X_tank - X_ant = 0 by definition of resonance.
Bilge
>photon-photon interaction, but also the vacuum polarization
>(a kind of photon-vacuum interaction). It is important for
>the hyperfine structure in every atom. It occurs at high
>fieldstrengths (e.g. 10^21 V/m, or 10^12 Tesla).
Uh-oh. I hope the words "acuumva olarizationpa" didn't attract
the keely carp to this neck of the woods. We'll have to offer
up AP as a sacrificial atom.
Scott Stephens
Science Hobbyist wrote in message <8a7565$m44$1...@nnrp1.deja.com>...
>In article <eAnx4.16604$84.505168@elnws01>,
> "Scott Stephens" <Sco...@Mediaone.net> wrote:
>
>> electricaly short dipole is capacitively reactive at the receiving
>frequency
>> and bends radio waves into the receiving dipole. Behind the long
>reflector
>> dipole acts inductive, and reflects energy back into the receiving
>dipole,
>> which is purely resistive at the receiving frequency.
>>
>> Nothing weird here.
I mean not weird in that linear superpostion of the vacuum is not affected.
> If that's not weird, then "energy sucking" isn't so weird
> either, in my opinion. If the induced V and I on the
> director element causes energy to be "lensed" towards
> the active element, and if the fields generated by the
> director are the cause...
> then if this whole process
> could be performed by a single object (being director
> and receiver simultaneously), then we'd have an
> "energy sucking" device.
True. What single device can simultaneously generate a complementary field
to an incident wave and absorb it too? It must occur with highly reactive
elements in a near-field, because it will radiate power (by definition) in
the far field.
Scott
Science Hobbyist
dav...@david15.dallas.nationwide.net wrote:
> > resistor of the same value, the SAME energy will be received?
> >
> Depend upon how you define "receive".
> As in you have an equal
> opportunity to make use of it? None is re-radiated? what?
Received power dissipated in the load resistor attached to
the antenna.
> The same number of photons strike the antenna. Your ability
> to make use of them varies.
If by "strike the antenna" you mean "come within a
quarter-wavelength distance", then we all agree. The
absorbtion occurs across the nearfield region. A small
resonant antenna absorbs a far larger number of photons
from its nearfield region, and a non-resonant antenna
absorbs far fewer. If the Poynting vector fields of a
resonant and non-resonant antenna are plotted, then in
the former case the vectors in the nearfield region curve
inwards to strike the tiny antenna, and in the latter case
they go straight by as if the tiny antenna was not there.
(This is not my stuff, this is straight from the two
physics papers.)
> > Just so there's no misunderstanding: place a load resistor
> > across a very short receiver-dipole and ADJUST THE
> > RESISTANCE for maximum received power. Measure the power
> > in the resistor somehow. No tank circuit. (Assume it
> > is receiving a CW radio signal.)
> >
> j
> | wL
> Impedance diagram: +------------> R
> |
> | 1/wc
>
> Z = R + jwL - 1/jwC
>
> > OK, now place a lossless LC circuit across the resistor on
> > the above dipole antenna, tune it to resonance, and
> > re-adjust the load resistor for maximum received power
> > (is this even necessary?) In both cases the short dipole
> > sees only a resistive load attached to it. In both cases
>
> j
>
> Impedance diagram: +------------> R
>
> Z=R
>
> That's not true. The dipole itself has some reactance, especially
> a short one. Adding the tank circuit and tuning it for resonance
> removes that reactance from the circuit.
BINGO! There it is. In your language, I should be saying
"cancelling the built-in reactance of a small antenna
causes the received power (in the load resistor!) to go up."
If you wish to call it "cancelling the reactance", while I
call it by a different name, then we're discussing the same
thing. ( If my EXPLANATION is wrong, that's different.)
If I insist that phenomenon involves the phase of the
time-domain changes in the shape of the fields
surrounding the antenna, and you insist that it involves
the antenna's reactance, then we are essentially talking
about the same thing, since the capacitance of a small
dipole (or the inductance of a small loop) as a concept
cannot be divorced from time domain and the shape of the
fields. Looking at measured capacitance and looking at
how geometry shapes the fields are two different ways
of looking at the same thing.
But rather than speaking in terms of reactance, I want
to analyze this circuit in terms of the current and voltage
of the antenna moment by moment, and the b and e-fields
which the current and voltage create. I want to ignore
the concepts "capacitance" and "inductance", and instead
watch the flux change over time, and look at the 3D
structure of the Poynting-vector field. Why?
As Feynman said (paraphrased), "unless you have four or
five ways of looking at something, you don't understand it."
Or Alfred Jarre' once said: "why, to be weird!"
But seriously, I see that observing the time-domain fields
gives insights that normally remain hidden within
"capacitance" and "inductance" concepts as applied to
antennas. The time-domain field changes give a viewpoint
that static reactance concepts do not.
Whether other parts of my aloud-thinking are flawed is
a separate issue (which I will continue to pursue.)
As for "sucking", I don't think there's any question that
the addition of a resonator bends the Poynting vector
energy flow inwards. If you think "sucking" is a bad
description for this, it has nothing to do with whether
cancelling the reactance causes the energy-flow to bend
inwards or not.
Science Hobbyist
> That's not true. The dipole itself has some reactance, especially
> a short one. Adding the tank circuit and tuning it for resonance
> removes that reactance from the circuit.
Also, please note that I described "energy sucking" in
these terms in the exchanges which started this entire
thread:
http://www.amasci.com/tesla/tesceive.html
Adding an inductor to a simple "capacitive antenna"
causes the AC voltage on the antenna and the received power
to both rise significantly. My example didn't involve
propagating waves though.
Bilge
>In article <slrn8cg4u...@radioactivex.lebesque-al.net>,
>
> Received power dissipated in the load resistor attached to
> the antenna.
called tuning.
>
>
>> The same number of photons strike the antenna. Your ability
>> to make use of them varies.
>
> If by "strike the antenna" you mean "come within a
> quarter-wavelength distance", then we all agree. The
> absorbtion occurs across the nearfield region. A small
A golf ball rolling over the hole falls in. One rolling around
the edge that doesnt fall in, still interacts with hole, the
hole doesnt conspire with the sandtrap to cause the ball to
miss the green (but since I dont do golf, ...)
>> That's not true. The dipole itself has some reactance, especially
>> a short one. Adding the tank circuit and tuning it for resonance
>> removes that reactance from the circuit.
>
> BINGO! There it is. In your language, I should be saying
> "cancelling the built-in reactance of a small antenna
> causes the received power (in the load resistor!) to go up."
>
>
This is hardly a novel concept. Any antenna has some reactance
associated with it. Take a piece of wire with a self-inductance
"L". Put it high enough above the ground and far enough away
from other conductors to neglect the capitance. You have an antenna
with a resistance R and inductive impedance jwL (taken to be in
parallel) for a net impedence of:
Z = [ 1/R + 1/jwL ]^{-1}
|Z| = wLR/[ R^2 + (wL)^2 ]^{1/2}
For a potential V that develops between the endpoints,
V
I = --- [ (wL)^2 + R^2 ]^{1/2}
wLR
Power dissapated in a resistive load (consider the R in the
antenna the load: For practical purposes, it is) :
P = IV cos(\phi) ; \phi = atan(-R/wL)
Note that (1) adding a capacitor changes I AND the power dissipation
on each cycle. At resonance, the current flow is simply
V/R and \phi = 0.
BUT wait... There is more. The atmosphere (or free space) has
a characterisic impedance, so you have the further constraint
that at the resonsnt frequency the impedance should match the
medium surrounding it. For the same reason you put terminators
on coax - impedance mathing.
> If you wish to call it "cancelling the reactance", while I
> call it by a different name, then we're discussing the same
> thing. ( If my EXPLANATION is wrong, that's different.)
Well, I hadn't considered reinvention of impedance matching to
be where you were trying to go here.
> If I insist that phenomenon involves the phase of the
> time-domain changes in the shape of the fields
> surrounding the antenna, and you insist that it involves
> the antenna's reactance, then we are essentially talking
> about the same thing, since the capacitance of a small
No. We aren't. Impedence matching occurs RIGHT at the BOUNDARY
and those BOUNDARY conditions are responsible for the fields.
Your viewpoint reverses cause and effect. Your boundary conditions
are fixed by the properties of the materials and the geometry
to produce fields consistent with those conditions -unless you
plan on allowing the antenna to move around on its own and
alter its atomic composition to "seek an optimal field shape".
> But rather than speaking in terms of reactance, I want
> to analyze this circuit in terms of the current and voltage
> of the antenna moment by moment, and the b and e-fields
> which the current and voltage create. I want to ignore
The fields don't determine the reactance. For example,
capacitance is a purely geometric property for a
given configuration of conductors. It matters none whatsoever
that you put 10 coulombs on two 1x1 plates psaced 1 in or
you put zero coulombs on them (apart from needing an army
of lou ferrignos to hold the plates in place). The capacitance
doesnt change.
It's not strictly true, because a high frequencies, the
effective geometry changes due to the skin effect and you
cant consider anything but the geometry of the surface
as you go up in f. (I cant see that it affects a capacitor
to any real extent, but an inductor, it will).
> the concepts "capacitance" and "inductance", and instead
> watch the flux change over time, and look at the 3D
> structure of the Poynting-vector field. Why?
>
Yes, why? The Fluxes are determined by those things:
\phi = LI, inductive
Q = CV ==> di/dt = C dV/dt + V dC/dt
/
[ N.B. the last term is called a microphone ]
> As Feynman said (paraphrased), "unless you have four or
> five ways of looking at something, you don't understand it."
>
Yes, that's always a good idea, but he probably didn't
mean "try and convince nature to adopt a new strategy"
> Or Alfred Jarre' once said: "why, to be weird!"
>
Gee. Has he posted here before... I think 99% of the world
following that advice (to greater or lesser extents) has
probaly logged a post in this group. Excluding, myself of
course.
>
>
> But seriously, I see that observing the time-domain fields
> gives insights that normally remain hidden within
> "capacitance" and "inductance" concepts as applied to
> antennas. The time-domain field changes give a viewpoint
> that static reactance concepts do not.
Yeah. Those would be what would be more natural to
consider in a quantum picture that treats photons
not waves, uncertainties in postion on the antenna
not wavelengths and boundary values. For that, draw a
box of size X x Y and calculate how it should be shaped
to cover the largest surfaace area under the constraint
that no part of it extend past the point that a photons
leaving the broadcast antenna that correspond to
the smallest time difference over which the signal
may change, not overlap due to the uncertainty in
their emission times. There's a standard dipole
in there.
> As for "sucking", I don't think there's any question that
> the addition of a resonator bends the Poynting vector
> energy flow inwards. If you think "sucking" is a bad
> description for this, it has nothing to do with whether
> cancelling the reactance causes the energy-flow to bend
> inwards or not.
>
Among other things, sucking tends to imply some action on the
part of the sucker to create the suck which sucks in the
suckee.
Jos Bergervoet
> Uh-oh. I hope the words "acuumva olarizationpa" didn't attract
> the keely carp to this neck of the woods. We'll have to offer
> up AP as a sacrificial atom.
Yes, the carp! He's always in for a short-time vialotion of
Egyrne Conservation. And he likes creation of tirvual tarpicles
from the cavuum, doesn't he?
-- Jos
Richard Herring
> In sci.physics.electromag, Richard Herring writes:
> >
> >Photon-photon interactions are a second-order effect in QED.
> >
> In QED this is called a 4th order effect. Photon-photon
> interaction requires a fermion loop with 4 photons attached,
> hence 4 vertices and the 4th power of the coupling constant, e.
I stand corrected. The point's the same, though. It's not significant
under the conditions discussed here.
--
Richard Herring | <richard...@gecm.com>
Scott Stephens
www.worldscientific.com/books/physics/2266.html
I found this during a google search. I read "indicates the presence in free
space of a novel, longitudinal, magnetic flux density" and after having read
something somewhere in the past about circularly polarized lasers being
attractive or repulsive, I ASSUMED the photon actualy has a magnetic moment.
Scott
"THE PHOTOMAGNETON AND QUANTUM FIELD THEORY
Volume 1 of Quantum Chemistry
by A A Hasanein (King Saud Univ. & Univ. Alexandria) & M W Evans (Univ.
North Carolina)
This first volume of this two-volume set deals with the important recent
discovery of the photomagneton of electromagnetic radiation, a discovery
which is fundamental in quantum field theory and in quantum mechanics in
matter. The photomagneton is the elementary quantum of magnetic flux density
carried by the individual photon in free space, and is generated directly by
the intrinsic angular momentum of the free photon. The volume develops the
theory of the photomagneton in a series of papers, which cover all the major
aspects of the theory, from classical electrodynamics to the relativistic
quantum field. Several suggestions are given for experimental tests, and the
available experimental evidence is discussed in detail. The overall
conclusion of the series of papers is that the photomagneton, which is
observable experimentally in magneto-optical phenomena, indicates the
presence in free space of a novel, longitudinal, magnetic flux density,
linked ineluctably to the usual transverse components. If the photomagneton
is not observed, then a paradox would have emerged at the most fundamental
electrodynamical level, necessitating a modification of the Maxwell
equations themselves. "
Gary Coffman
>In article <2SLDOA06BxInEy...@4ax.com>,
> Gary Coffman <ke...@bellsouth.net> wrote:
>> I'm certain that fields (photons) can only be altered due to the
>> mediation of charged matter. Other fields alone cannot alter them.
>
> dipole antenna absorbs energy from incoming EM waves, it
> is the charged matter within the metal which causes the
> antenna to grab energy from the EM waves. However,
> pointlike particles don't magically interact with EM
> waves, instead it is their surrounding fields which
> it is the LOCAL FIELDS associated with the charges
> which interact with the EM waves and cause the energy
> to eventually wind up flowing along the antenna's
> lead-in cable.
What *local* electromagnetic field would that be? And how does
it "grab" another field? What is the source of its energy?
IMHO there's only one electromagnetic field, the one generated
by the emitter. All of the EM effects we are discussing are a result
of this single field. The energy for this field comes from the emission
source. There is no other energy source to produce other fields.
> That's why I keep saying that the FIELDS of the electrically
> short antenna are reaching out and grabbing EM waves. The
> fields of the electrically short antennas are created by
> the motions of charged matter within those antennas. By
> superposing with the fields of the incoming EM waves,
> the antenna's local fields cause enery to be diverted from
> the wave. I certainly agree that fields alone
> (meaning propagating EM waves far from any matter) cannot
> affect other propagating waves in this fashion.
What is the net electromagnetic field of a length of copper wire
which is not being excited by an energy source? And please, if
you agree that independent EM fields in free space cannot affect
each other, what are the changes at short distances which you
claim permit them to do so?
>> Interference patterns are simple superposition. The Principle of
>> Superposition says that the components of a superposition are
>> *unaltered* by the superposition. Beyond the superposition zone
>> we still have the same two waves, still with the same directions
>> and the same energies as they had before the superposition
>> occurred.
>
> True for propagating waves, but not true for the fields in
> the nearfield zone of a piece of charged matter such as an
> antenna. When a half-wave dipole generates a local field,
> the end result is that some of the energy in the incoming
> EM waves is intercepted by the antenna. Superposition
> still holds true, yet that half-wave dipole was able
> to punch a hole in the wavetrain of EM waves passing by.
> Do you object to this? If not, then why are electrically
> small resonant antennas (with their huge local fields)
> such a problem?
Yes, I object to that. You're creating out of whole cloth
some mysterious unpowered EM field that doesn't exist,
which you say "grabs" other EM fields when they superpose
(at some distances but not at others). That simply sounds
like nonsense.
> I think you might want to review your concepts, since
> the idea that "fields allow antennas to intercept EM
> waves" applies to all antennas, not just to these
> weird resonant antennas.
Fields are what receiving antennas intercept. Those
fields are generated by other antennas being driven
by energy sources.
>> The energy has *not* "gone missing".
[due to superposition of fields]
>
> Gone missing FROM SPACE, from the travelling EM wave. The
> energy is now inside the load resistor connected to the
> antenna. This is true of a half-wave dipole, and just as
> true of a tiny resonant antenna.
No, that's not the context. Two EM waves crossing in space do not
lose any of their energy, either to each other or in any other fashion,
due to superposition. Superposition never alters the components
of the superposition in any manner. This is the fundamental principle
upon which all superposition is based. If you reject this idea, then
you are rejecting the entire basis of (classical) wave mechanics.
(When a charge is accelerated or decelerated, and only
then, is electromagnetic energy produced or absorbed.
There are no other methods.)
>> That is a misunderstanding of what has happened.
>
> I think not. I think I'm unable to get my ideas across
> clearly. Also it might be because I'm coming from an
> unconventional viewpoint; thinking in terms of the
> local fields generated by an antenna rather than in terms
> of current through it or voltage across it. I hadn't
> realized this was unconventional, but people here are
> attacking some concepts which I didn't think were
> controversial or even open to debate.
The concepts are totally bizarre, and have no physical
basis. There is no "local field" unless you have a transmitter
hooked to the receiving antenna (in which case that simply
overloads the receiver and you extract no useful signal at
all from the distant source). There is only the field from
the distant transmitting antenna, which is arriving at the
receiving antenna where it accelerates charges on that
antenna. That acceleration of charge is an AC current,
which can then be modeled by normal circuit theory.
> If you are certain that a normal half-wave dipole can
> intercept EM waves without the dipole generating fields
> of its own, then we have a serious problem. If you
> accept the existence of these local fields generated by
> the antenna, but are certain that they play no role in
> the interception of the energy from the EM waves, then we
> have a serious problem. You're no longer arguing about
> the tiny antennas, but instead have begun questioning
> antenna-physics itself.
I'm certainly questioning your notion of antenna physics.
It is true that any receiving antenna will reradiate a portion
of the energy it receives from an EM wave that it intercepts.
But reradiation is an EFFECT, and not a CAUSE. You're
putting the cart before the horse.
There is no local EM field until the antenna is excited by the distant
EM field. That's because there's no energy source to accelerate
charge until energy has been obtained from the distant field.
This reradiation is what happens to some of the energy coming
from the distant source *after* it encounters the antenna. It is not
there a priori to "grab" that incoming wave. It doesn't hang around
to grab later waves either. It simply radiates off into space, never
to be seen again.
Look, we can simplify this situation to its fundamentals and
derive any other more complicated case by use of superposition.
The fundamental case is to have two point charges separated in
space. One over here, another over there. If you wiggle the one over
there, the one over here wiggles in sympathy. Action at a distance.
Momentum has been transferred across empty space. We need some
mechanism by which momentum could be transferred from over there
to over here. Experiment showed that there was a lag between wiggling
the charge over there and when the charge over here started to wiggle.
That lag was proportional to 1/c. Momentum transfer and finite velocity
of transfer hint at the presence of a particle, which we call a photon.
Now the photon has no rest mass, but it does have size of a sort. Its size is
inversely proportional to the energy one quantum (photon) carries (E=hv).
As frequency v increases, the "size" of the photon decreases. (This explains
several things about antenna behavior at different frequencies.) Due to wave
particle duality, this size is what we can call the wavelength of the photon.
(We can map this extended particle out as a field, but that is only a mapping.
I'll stick to picturing particles of differing sizes here.)
A quantum is indivisible. Either all of its energy is transferred, or none of
it is. When any part of a photon intercepts a charged particle, all of its
energy is transferred to that particle, or none of it is. No fractions allowed.
(This is fundamental, and fundamentally different from the classical view.)
Small antenna or large, it doesn't matter. As long as it intercepts any
part of the photon, it intercepts all of it. No local "sucking" fields are
required to explain why a small antenna (in terms of wavelength) can
receive nearly as much energy as a large one. (What the antenna can
usefully do with that energy is another matter, involving circuit theory.
Since the small antenna will be highly reactive, efficiently extracting
the energy it has intercepted to do useful work will be difficult.)
We can explain this another way. We can say that the presence of
the receiving antenna alters the permeability and permitivity of the
space in which it resides. The field mapping of the signal originating
from the distant source changes from what it would be in flat empty
space, and the field lines concentrate around the antenna. The result
is the same, just the point of view (wave or particle) is altered. In no
case do we need "sucking" fields to exist. (Good thing too, since
there is no such thing.)
The key concepts are that a quantum is all or nothing, and a quantum
has an effective size inversely proportional to its energy (and frequency).
If any part of it brushes a charged particle, all or none of its energy will be
transferred to the charged particle. It takes direct interaction with charged
matter to alter a photon.
Gary
Gary Coffman KE4ZV | You make it |mail to ke...@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
Bilge
>From:
>www.worldscientific.com/books/physics/2266.html
>
>I found this during a google search. I read "indicates the presence in free
>space of a novel, longitudinal, magnetic flux density" and after having read
>something somewhere in the past about circularly polarized lasers being
>attractive or repulsive, I ASSUMED the photon actualy has a magnetic moment.
>
From what I can tell, that isn't the implication, The field from
something with a magnetic moment is carried by a photon. This field
is carried by a particle designated B(3). Also, one should view with
caution anything that mentions ghost-fields. Do you have any other
references that have some better info? It's kind of interesting.
Scott Stephens
http://sciserv.ub.uni-bielefeld.de/elsevier/03784371/sz954371/
"The photomagneton and photon helicity" by Evans, Physica A, Vol: 214,
Issue: 4, April 1, 1995
Too bad I don't have an account.
And try this ftp for some exchages about that B(3) stuff. I'll have to read
up and see what its about.
http://www.navi.net/~rsc/physics/B3/evans/
And these from LLNL (no doubt your Greek is better than mine so you can tell
me what it all means ;-)
9609144 17 Sep Essay on the Non-Maxwellian Theories Electromagnetism
physics/ 9707014 16 Jul 1997 The Weinberg Formalism and a New Look at the
Electromagnetic
Theory
9802039 Historical Note on Relativistic Theories of Electromagnetism
If you don't like the longitudinal B(3) field stuff:
9801024 v2 20 Jan 1998 Comment on 'Comment on the Longitudinal Magnetic
Field of
Circularly Polarized Electromagnetic Waves' by E. Comay
I'm slowly crawling my way through this one now:
9711002 14 Nov 1997 INTRODUCTION to EXTENDED ELECTRODYNAMICS Stoil Donev
Scott
Bilge
>up and see what its about.
>http://www.navi.net/~rsc/physics/B3/evans/
>
Don't bother. From what I can tell, it's about being mistaken.
Science Hobbyist
dav...@david15.dallas.nationwide.net wrote:
>
> >> The same number of photons strike the antenna. Your ability
> >> to make use of them varies.
Ah. This is wrong. I hadn't noticed it earlier.
> >
> > If by "strike the antenna" you mean "come within a
> > quarter-wavelength distance", then we all agree. The
> > absorbtion occurs across the nearfield region. A small
>
> Forget the 1/4 wave bit for the moment. Just think of putting.
The 1/4-wave bit is the key concept.
>
> A golf ball rolling over the hole falls in. One rolling around
> the edge that doesnt fall in, still interacts with hole, the
> hole doesnt conspire with the sandtrap to cause the ball to
> miss the green (but since I dont do golf, ...)
Uh. Are you imagining that the effective area of an antenna
is the physical cross-section of the wire, viewed broadside?
I mean, do you imagine that RF photons come flying in on
straight trajectories, and if they miss the wire by a tiny
bit, they go right on by? That's what you seem to be saying
with your golfcourse hole analogy. If so, then you are flat
out wrong. The whole point of the Bohren paper is to explain
how a resonating particle can absorb TOO MUCH energy. Somehow
it's able to grab EM energy which was flowing by at many
particle-diameters distance. In your analogy, if the particle
is a hole in a golfcourse, then something mysterious is
occurring, because that tiny hole is intercepting golf
balls which never even rolled onto the green.
Without resonance, Bohren's particles behave as your
"golfcourse hole" analogy. If resonance plays a part,
suddenly the size of the "hole" is greatly increased,
and increased to far larger size than the physical
particle diameter. How can this occur?
If I double the diameter of the wire in a conventional
1/2-wave dipole, would you predict that the received
power must double? That's what your "golfcourse hole"
analogy implies.
> > BINGO! There it is. In your language, I should be saying
> > "cancelling the built-in reactance of a small antenna
> > causes the received power (in the load resistor!) to go up."
> >
> >
>
> This is hardly a novel concept. Any antenna has some reactance
> associated with it.
Then why are physicists writing papers about it? The whole
point of those papers is to explain how small particles
are able to absorb EM energy as if their diameters were
far greater than their physical diameters.
"How can a particle absorb more than the radiation
incident upon it?" If the particle is like a hole in
a golf course, then how can it grab any more than the
photons which actually hit the "hole"? But they do! I
think you don't understand the reason for those papers.
It's to explain known experimental results.
Do you have an explanation for how a tiny metal particle
can intercept EM radiation which is a large number of
particle-diameters away from its surface? The phenomenon
only occurs at resonant frequencies. How do you imagine
the particles are able to do this? Why does it only
occur at resonance?
> > As for "sucking", I don't think there's any question that
> > the addition of a resonator bends the Poynting vector
> > energy flow inwards. If you think "sucking" is a bad
> > description for this, it has nothing to do with whether
> > cancelling the reactance causes the energy-flow to bend
> > inwards or not.
> >
>
> Among other things, sucking tends to imply some action on the
> part of the sucker to create the suck which sucks in the
> suckee.
Add a resonator, increase the effective area of an
antenna. Increase it so much that the effective area
has a diameter MANY TIMES greater than the length of
the antenna. The antenna is interacting with photons
which SHOULD BE COMPLETELY MISSING IT. This sounds like
"sucking" to me. Or "lensing". Or "poynting-vector
deflecting." Or whatever you want to call it.
Perhaps you are imagining that the resonator only lets
the antenna absorb a bit more of the energy that passes
within one antenna-length distance. If that's all that
it did, I wouldn't be the least bit excited, and those
physics papers would never have been written. The resonator
lets the antenna absorb energy which can miss it by
thousands of antenna-lengths (in the case when the
physical antenna is thousands of times smaller than
1/4 wavelength.)
Science Hobbyist
"Scott Stephens" <Sco...@Mediaone.net> wrote:
Yep. It only works for short antennas. And how can it
simultaneously absorb and generate a complementary field?
Not be being reactive per se, but by having a memory.
By storing energy from previous cycles, then using that
energy to drive an oscillator connected to the same
antenna, which absorbs MORE energy for future cycles.
Which is what a tuned circuit does naturally. It can only
work if the phase of the incoming signal is not varying
all over the place. Which is the same as saying that
it works best for single-frequency waves and high-Q
resonators.
Science Hobbyist
rbmcc...@mmm.com (Roy McCammon) wrote:
> A short dipole presents a mainly capacitive (plus some
> resistance) impedance to its load. So in case 1,
> I get to optimize only the source resistance, and
> in case 2 I get to optimize the source resistance
> and throw in a parallel R and C?
>
> It look like a no brainer. Case 2. If the
> source is capacitive, let the load be inductive.
>
> I'd look at it from a load matching point of view.
Thats what it SEEMS like, until you find out that the
antenna is absorbing energy which would otherwise pass
by at a large distance. "Load matching" implies that
we're letting the antenna grab energy which was already
there. The suprise: "already there" includes
the whole nearfield, and if frequency is low and the
nearfield region is huge, then the antenna acts like
it is "reaching out" across a non-trivial area.
Call it "load matching" to hide the details, or "energy
sucking" if you like controversy! :)
>
> It might be easier to understand with a series L
> rather than a shunt L. I think this is the same
> concept as base loading the antenna.
Could be. Is a base-loaded antenna only effective over
a certain frequency range? I thought that base-loading
was some sort of impedance matching, but if it forms
a low-Q resonator, then it might be analogous to putting
a capacitor across the loopstick in an AM receiver. For
longwave using electrically short whips, it's gotta be
a good thing.
Science Hobbyist
rbmcc...@mmm.com (Roy McCammon) wrote:
> > antenna's effective size, as Sutton and Spaniol did in
> > their active ELF antenna (papers referenced at the end
> > of http://www.amasci.com/tesla/tesceive.html)
>
> I haven't read the paper, but I suspect that they put
> more power into it than they pulled out of the incoming
> wave.
Yep. Active drive can't grab any more energy than a
passive resonator, and it dissipates energy in the
load resistance. It just allowed them to make the
"energy-enhancement effect" be broadband, since they
weren't relying on a resonator to supply the "drive field."
In the frequencies they were messing with, it let them see
fast-changing signals which otherwise could only be
detected with long integration times, which normally
blocks observations of fast-changing signals.
> > > My objection is one of emphasis. The way you have told it,
> > > it sounds to me like you consider the source fields and the
> > > antenna field to be two separate fields.
> >
> > But they are,
>
> As I let the water out of my bath tub, I notice that there
> there is a depression in the water level over the drain.
> The
> depression is really there and it is interesting and
> deserves
I wonder if "energy sucking" applies to acoustics? If I
connect a resonant chamber to an orfice where the orfice
diameter is far smaller than the wavelength, will extra
energy pass through that orfice?
> some study, but I don't tend to think of that depression as
> sucking water out of the tub and shoving it down the drain.
Say I have one electron. It is surrounded by a
radial e-field. A distant proton is surrounded by a
similar field. Hold them close, and the "two fields"
superpose to create "one field" with a dipole pattern.
The radial fields have apparently vanished into the
dipole field. However, if I move the electron around
without moving the proton, the result will be as if I
had moved the electron's underlying e-field, as if the
"two fields" were still there inside the "one field."
*OR* I could imagine that the charge on the moved
electron had merely distorted the "one field." Which
viewpoint is right?
Does the current in the antenna simply distort the one
EM field? Or does the independant field generated by
the antenna-current superpose with the UN-distorted
EM waves in such a way as to deflect their trajectory?
Either the charges cause the EM waves to deflect inwards,
or the "antenna's local field" does the job. It's
two ways of looking at the same situation.
In years of arguing with people, I find a spectrum of
philosophies with two opposite ends: on one end are
people who know the world is REAL, and therefore there
must be ONE explanation for a phenomenon. Any other
explanations are therefore distortions, or perhaps
blasphemy, but in any case it must be stamped out or
at least prevented from contaminating the One True
Explanation. At the other end of the spectrum are people
like Feynman, who realize that we can only see the world
through our mental models, but never perceive it directly.
There is not one "right answer", there are a variety.
The more mental models one has in the "toolkit", the
better one understands reality.
> To me, your description of energy sucking sounds backward
> in a similar sense.
>
> But, consider this (I think you will like it).
>
> If I wind a coil on a torroidal form and energize it
> sinusoidal, and if I do an idea job, there is no
> H or B field outside of the torroid. There is E, but no
> H or B. I then run a wire down the middle and
> connect the ends to a resister. I have made a
> transformer. The resister absords power. But how can
> the Poynting vector be non zero it there is no H or
> B from the primary current? Easy, it comes from the
> secondary current. So here is a case where the E
> component of the field is attributed to source
> currents and the H component is attributed to the
> load current. And it works fine.
Yes. My version from long ago: drive your
electrically-small toroid with RF, but it cannot
radiate since it's too small and it lacks an external
b-field. Now thread the toroid with a straight rod
which is 1/2-wavelength long. The metal rod has "let
out radio waves!" They were blocked by the lack of a
b-field. If we were dealing with megawatts of UHF
with superconducting coils, it could be dangerous to
poke a metal rod into an apparantly-intert tiny ring.
Suddenly your corneas would fry and your fillings would
melt.
Scott Stephens
Science Hobbyist wrote in message <8acrfb$q39$1...@nnrp1.deja.com>...
> I wonder if "energy sucking" applies to acoustics? If I
> connect a resonant chamber to an orfice where the orfice
> diameter is far smaller than the wavelength, will extra
> energy pass through that orfice?
If you literaly suck with a Hoover, sound will be refracted into the orifice
:-)
You can put disk resonators in an array to form an acoustic antenna (looks
like a lens), but its not too efficient
Reflectors work better.
> Say I have one electron. It is surrounded by a
> radial e-field. A distant proton is surrounded by a
> similar field. Hold them close, and the "two fields"
> superpose to create "one field" with a dipole pattern.
> The radial fields have apparently vanished into the
> dipole field. However, if I move the electron around
> without moving the proton, the result will be as if I
> had moved the electron's underlying e-field, as if the
> "two fields" were still there inside the "one field."
> *OR* I could imagine that the charge on the moved
> electron had merely distorted the "one field." Which
> viewpoint is right?
I prefer to condsider the space occupied by the particles is capable of
being polarized, or polarizing virtual transient electron/positron pairs, or
affecting potentials, or whatever, due to the character of the particle
occupying the space.
> Does the current in the antenna simply distort the one
> EM field?
> Or does the independant field generated by
> the antenna-current superpose with the UN-distorted
> EM waves in such a way as to deflect their trajectory?
I'll reiterate again, An incident wave's field induces currents and voltages
in the antenna, which (antenna resistive loss notwithstanding) the antenna
then re-radiates. If the antenna isn't resonant, there will be a phase
shift, which can be called reactance, that will then bend or refract the
waves. Any old additional signal on the antenna will just superposition. The
wave in question is bent, because it is synchronized with itself.
One mental hangup I, and others I've seen have had, is thinking of space as
a place where seperate, individual waves are traveling in all different
directions. Space can be thought of as a crystal lattice, where the elements
of the crystal at any instant are the sum of the myriad of waves. Actualy
space is like a boiling foam, at a small enough level.
> In years of arguing with people, I find a spectrum of
> philosophies with two opposite ends: on one end are
> people who know the world is REAL, and therefore there
> must be ONE explanation for a phenomenon. Any other
> explanations are therefore distortions, or perhaps
> blasphemy, but in any case it must be stamped out or
> at least prevented from contaminating the One True
> Explanation.
Have a look at this :-) http://www.navi.net/~rsc/physics/wallace/farce.txt
> At the other end of the spectrum are people
> like Feynman, who realize that we can only see the world
> through our mental models, but never perceive it directly.
> There is not one "right answer", there are a variety.
> The more mental models one has in the "toolkit", the
> better one understands reality.
And when our mental models are schizophrenic double speak about
particle-wave collapse double-speak, how can we have the congnitive tools to
think clearly?
A quote from a very good (partial) online textbook at
http://www.dse.nl/motionmountain/C-5-QEDB.pdf (page 18)
"In summary, there is no irrationality in quantum theory. Whoever uses
quantum theory
as argument for irrational behaviour, for ideologies, or for superstitions
is guilty of disinfor-mation.
A famous example is the following quote.
"Nobody understands quantum mechanics.
Richard Feynman"
Scott Stephens
Bilge wrote in message ...
Wish I could understand it better. Where's the mistakes?
Scott
Scott Stephens
Richard Herring wrote in message <8aavdc$9is$1...@miranda.gmrc.gecm.com>...
What? 4th order? fermion loop with 4 photons???
Bilge
>In article <slrn8ch49...@radioactivex.lebesque-al.net>,
>
>
> Uh. Are you imagining that the effective area of an antenna
> is the physical cross-section of the wire, viewed broadside?
If P watts are radiated into 4-pi and you cover all 4-pi with n antennas,
then what is the average power absorbed by each if all n antennas are
equivalent, 100% efficient and lie a distance r from a source which
radiates isotropically? If you have an answer different from P/n, stop
reading and subscribe Astrology Today, since you've violated conservation
of energy. Now assume they are 10% efficient rather than 100%, but all of
them have a 10% efficiency and nothing else is different. If you didn't
get 0.1 P/n for each, you'll have to come up with some excuse to arrive
at an asymmetric answer to a completely symmetric problem. I'll get to
the case of identical gaps in a moment, but first, nobody seems to have
a problem with this concept when applied to gamma rays and scintillators,
why should it differ for an antenna? photons are photons. Just because
certain phenomena produce high energy photons (like the peaks in 60Co)
and some produce lower energy photons (like a radio), why should there
be a difference in the way they behave other than using a detector that
takes advantage of phenomena of the appropriate energy scale? (you wont
see any scintillation in a NaI(Tl) crystal from channel 4, for example).
> I mean, do you imagine that RF photons come flying in on
> straight trajectories, and if they miss the wire by a tiny
> bit, they go right on by? That's what you seem to be saying
Go draw a probability distribution about some point P(r,\theta, \phi)
in space for a photon emitted in the interval of ime t + \delta t
from a source at the origin (or the equivalent -- calculating the
probability distribution for it being anywhere else) Now trace the
center of the probability distribution over the length (or surface
area if you don't have approximately a line of some sort for an antenna).
Now figure in the phase space factor (the probability of absorption
vs some other process, like elastic scattering, inelastic scattering,
multiple scattering, etc., due to kinematics). By the way, this same
excercise tells can be used to descibe skin depth. The attenuation
is nothing more than what you get when considering the penetration
of a potential step by a particle wit wavefunction \psi. It just
may not be easy to come up with a height, V_o, for the step from
first principles.
>
> If I double the diameter of the wire in a conventional
> 1/2-wave dipole, would you predict that the received
> power must double? That's what your "golfcourse hole"
> analogy implies.
>
Do you really want me to finish this? I can, but I imagine it's
getting tedious to read as well as try to find the clearest way
to get the point across. However, I will if there is any point
to doing so and I'm not just wasting my time by providing an
infinite number of possibilities to digress and avoid just having
to deal giving up on the "energy sucking" tack. I'm not about
to deal with an endless series of irrelavent tangents.
As a starting point, you might consider thinking of the antenna
as a large collection of point-like receptors of a phased array
that add up at the point the signal is injected or detected with
the relative phases determined by the distance from that point
and the frequency of the carrier. You'll see that it's not as
obvious that twice as physically large corresponds to twice the
collection efficiency since you are also constrained in time by
the requirement that later signals arriving nearer the collection
point cant overlap earlier ones from further away.
>> This is hardly a novel concept. Any antenna has some reactance
>> associated with it.
>
> Then why are physicists writing papers about it? The whole
Don't say physicists. Say: A. Uthor, Journal of Stuff,
No. N pp# (yyyy)
I cant comment on what is even being claimed without seeing the paper
for the simple reason that if I think you've misinterpereted some
genuine scientific research, I'm not any more likely to think it backs
up your claim. On general principles, (which, if need explaining, means
don't bother to do so) and just the basic waste of time, be sensible
about A. Uthor and Jounral of Stuff. I consider Astrology and the usual
keelynet fare to be equally wasteful examples of points which the
divergence of information is always negative -- no matter what
information goes in all that emerges is the ascii version of blackbody
radiation. Someday, a credible theory of something may ooze out, but
that day isnt today.
>
> "How can a particle absorb more than the radiation
> incident upon it?" If the particle is like a hole in
> a golf course, then how can it grab any more than the
> photons which actually hit the "hole"? But they do! I
> think you don't understand the reason for those papers.
Before you ask me to finish the above, do you understand the
concept of probability distributions as opposed to a deterministic
case? Do you understand why quantum mechanics allows tunneling
through a barrier while classically tunneling cant occur? If
not, this wont make sense either.
> It's to explain known experimental results.
>
As I said before, with an infinite number of parameters to cover
every phenomenon, the "I have a new theory of everything" or the
"Let me speculate without considering the implications" , approach
anyone can explain the universe and by increasing the jargon can
bullshit people lacking a big enough shovel. Providing the minimal
description of nature in a consistent way is the hard part.
> Do you have an explanation for how a tiny metal particle
> can intercept EM radiation which is a large number of
> particle-diameters away from its surface? The phenomenon
It doesnt. It's your notion of "a distance away" that's the problem.
Photons are not classical objects. You cant treat them that way.
You can only treat their probability density that way.
> Perhaps you are imagining that the resonator only lets
> the antenna absorb a bit more of the energy that passes
> within one antenna-length distance. If that's all that
> it did, I wouldn't be the least bit excited, and those
Then dont. Fix your conception of electrically small.
Hard to calculate doesnt mean "new theory required"
or hard to understand conceptually.
> physics papers would never have been written. The resonator
> lets the antenna absorb energy which can miss it by
> thousands of antenna-lengths (in the case when the
> physical antenna is thousands of times smaller than
> 1/4 wavelength.)
I'd be willing to bet that your notion of electrically small is
incorrect. Look at an archimedean spiral. How big should an
antenna be from consideration of the unccertaint principle?
In that case, is a straight line required? What changes if
you consider 2 dimensional areas or 3 dimensional volumes?
Would a 3-d volume of metal be an improvement over a hollow
cube (it's bigger; has more metal). The last example just
shows even a simple-minded picture cant be applied ind-
iscriminately. So far, either you have tried to do exactly
that with whatever I've provided or you really just cant
tear loose of the classical picture.
Jos Bergervoet
> Richard Herring wrote in message <8aavdc$9is$1...@miranda.gmrc.gecm.com>...
>>
>>I stand corrected. The point's the same, though. It's not significant
>>under the conditions discussed here.
>
> What? 4th order? fermion loop with 4 photons???
Yes. Not significant, as Richard said.
-- Jos
Gary Coffman
> Yes, that's the key question: does connecting a tank
> circuit to a short dipole (or small loop) cause it to
> absorb MORE energy from the incoming waves?
And the key answer is NO. Resonance has nothing
to do with the amount of energy intercepted by the
antenna.
>More
> specifically, if we connect just a resistive load to
> a short dipole and adjust that resistor for maximum
> received power, can we receive even MORE power if we
> then connect a lossless tank circuit across that dipole,
> then re-adjust that resistor value for maximum power?
> These papers imply that the answer is yes:
My answer is also yes, but not because the antenna
intercepts more power. It is because the circuit is made
non-reactive by being resonated, allowing more power
to flow into the load instead of being re-radiated. In other
words, it is a circuit matching issue.
P = E * I * cos(theta)
When theta is 0, power out of the circuit is maximized.
Theta is only 0 when the circuit is non-reactive, and we
can make it non-reactive by resonating it.
Science Hobbyist
Gary Coffman <ke...@bellsouth.net> wrote:
> On Mon, 06 Mar 2000 19:42:09 GMT, Science Hobbyist <bbe...@microscan.com> wrote:
> > Yes, that's the key question: does connecting a tank
> > circuit to a short dipole (or small loop) cause it to
> > absorb MORE energy from the incoming waves?
>
> And the key answer is NO. Resonance has nothing
> to do with the amount of energy intercepted by the
> antenna.
But because of resonance, the circuit stores energy from
previous cycles. That is critically important, and that's
why "impedance matching" is too limited to truely describe
what is happening. Also, if the wavelength is long, the
resonant antenna can absorb energy which would other
wise miss it by a large number of antenna-lengths. That
is part of impedance-matching too, but it is hidden because
"impedance matching" in this situation is only one
viewpoint, and it has serious limitations if expanded insight
into the physics is the goal.
>
> >More
> > specifically, if we connect just a resistive load to
> > a short dipole and adjust that resistor for maximum
> > received power, can we receive even MORE power if we
> > then connect a lossless tank circuit across that dipole,
> > then re-adjust that resistor value for maximum power?
> > These papers imply that the answer is yes:
>
> My answer is also yes, but not because the antenna
> intercepts more power. It is because the circuit is made
> non-reactive by being resonated, allowing more power
> to flow into the load instead of being re-radiated. In other
> words, it is a circuit matching issue.
I see the difficulty. You seem to be arguing that BECAUSE
it is an impedance matching issue, it IS NOT a matter of
resonance. As if there was one right answer, and we must
get rid of any other viewpoints. This is improper, in my
opinion, because in order to understand anything completely,
you have to look at it from all possible viewpoints. I realize
that I violate some particular belief when I say such a thing,
and it causes people to raise objections and become
argumentative.. If we're SUPPOSED to view it only
as circuit matching, and never in any other way, then what
say is sort of like blasphemy. It is an alternate "religious
position" which, because it is ALTERNATE, is perceived
as being incompatible. No. It is only alternate. But if you
believe that there is "one right answer", then the
existence of alternate viewpoints must be "wrong"
somehow. (And from my viewpoint, if there are several
ways to view a phenomenon, and they give differing
insights, then the focusing on "one right answer", and
the attacks on other viewpoints, THAT is the
blasphemy.)
>
> P = E * I * cos(theta)
>
> When theta is 0, power out of the circuit is maximized.
Right. Heh. AT RESONANCE, power out of the circuit is
maximized, and if the freq of the incoming wave should
change, it's no longer at resonance, so the effect doesn't
work. To make it work, sweep the frequency of the
transmitter around until resonance is achieved in the
receiver.
Johnathan Swift had things to say about big-endian versus
little-endian warfare in GULLIVER'S TRAVELS. It is
particularly appropriate in any physics debate, since often
the fight is over the One True Way to "crack" a
complicated "egg."
Roy McCammon
> Thats what it SEEMS like, until you find out that the
> antenna is absorbing energy which would otherwise pass
> by at a large distance.
You may be holding an unwarranted assumption about
where energy is when it is in transit. There is no
classical physics requirement that the energy be in
any particular place when it is not interacting
with matter. It is conventional to say that energy
density is proportional to the square of the field
strength, but it is not necessary.
Feynman had something say about this. I'll
see if I can find the section and give you
a reference.
> "Load matching" implies that
> we're letting the antenna grab energy which was already
> there. The suprise: "already there" includes
> the whole nearfield, and if frequency is low and the
> nearfield region is huge, then the antenna acts like
> it is "reaching out" across a non-trivial area.
> Call it "load matching" to hide the details, or "energy
> sucking" if you like controversy! :)
Consider this. The distant transmitter has two antennas
which create an interference pattern. The location
in space where the pattern shows complete cancellation
has zero thickness. If a dipole was there, it would receive
no signal. But move your dipole to where the signal
is strong and let the near field build up. Now move
it to a null in the pattern before the near field
dies out. Since the true null is near zero thickness,
the near field ought to stretch beyond that and continue
to pull in energy from the field.
But it doesn't.
Opinions expressed herein are my own and may not represent those of my employer.
Roy McCammon
> Say I have one electron. It is surrounded by a
> radial e-field. A distant proton is surrounded by a
> similar field. Hold them close, and the "two fields"
> superpose to create "one field" with a dipole pattern.
> The radial fields have apparently vanished into the
> dipole field. However, if I move the electron around
> without moving the proton, the result will be as if I
> had moved the electron's underlying e-field, as if the
> "two fields" were still there inside the "one field."
> *OR* I could imagine that the charge on the moved
> electron had merely distorted the "one field." Which
> viewpoint is right?
The "one field" view will serve you better as you
study more advanced physics.
> In years of arguing with people, I find a spectrum of
> philosophies with two opposite ends: on one end are
> people who know the world is REAL, and therefore there
> must be ONE explanation for a phenomenon.
Measurements are real. Theories are judged on their
usefulness.
> Any other
> explanations are therefore distortions, or perhaps
> blasphemy, but in any case it must be stamped out or
> at least prevented from contaminating the One True
> Explanation.
Well, I sort of follow the teachers equivalent
of the Hippocratic oath "do no harm". Which means
I am reluctant to support "alternate" explanations
when I suspect that they will cause confusion
later in the educational process. It is my value
judgment that most people are better served by
teaching "the standard" explanation. If the
"standard" explanation has short comings, that
needs to be admitted. Alternate explanations
are ok, but need to be clearly labeled as such.
Throw in "as if" every so often.
> Yes. My version from long ago: drive your
> electrically-small toroid with RF, but it cannot
> radiate since it's too small and it lacks an external
> b-field. Now thread the toroid with a straight rod
> which is 1/2-wavelength long. The metal rod has "let
> out radio waves!"
I would say that the rod has changed the boundary
conditions.
Bilge
>In article <=bvKOFgE21xD4p...@4ax.com>,
>
> But because of resonance, the circuit stores energy from
> previous cycles. That is critically important, and that's
> why "impedance matching" is too limited to truely describe
on this description. Then look at the Q for a resonant circuits
with both large and small Q, i.e., { f \over\Delta f }. The
result of storing energy means your bandwidth goes DOWN.
Why? Because the signal cant change faster than you remove
the energy and remain distinguishable from the that coming
in on the next cycle. By making the antenna small and resonant,
you lose bandwidth. Since you are storing energy longer, at
least in principle, you can make up for the small size by
sacrificing bandwidth.
> what is happening. Also, if the wavelength is long, the
> resonant antenna can absorb energy which would other
> wise miss it by a large number of antenna-lengths. That
> is part of impedance-matching too, but it is hidden because
> "impedance matching" in this situation is only one
> viewpoint, and it has serious limitations if expanded insight
> into the physics is the goal.
>
No. The insight is when you realize just how interrelated all
of this and how the puzzle pieces fall into place so that you
don't need to invent new ways to explain ordinary events.
> I see the difficulty. You seem to be arguing that BECAUSE
> it is an impedance matching issue, it IS NOT a matter of
> resonance. As if there was one right answer, and we must
Resonance IS an impedance issue. By definition, resonance occurs
when Z = 0. Impedance matching is obviously an impedance issue.
It may or may not be as obvious, but the boundary conditions at
the dielectric interface of the antenna and the media surrounding
it, completely determines the impedannce mathching.
> say is sort of like blasphemy. It is an alternate "religious
> position" which, because it is ALTERNATE, is perceived
Don't start with the all viewpoints are equal bit. That may
fly for religion, but here you need to provide some evidence
of this "energy sucking". According to your assertion of a
"grab" over 1000 wavelengths away, I should be able to
set up one of these and a measure a drop in field stregth
several counties away. That is, of course, unless it also
creates a replacement so you cant tell but do violate
conservation of energy.
> as being incompatible. No. It is only alternate. But if you
Telling people that gravity occasionally makes things fall "up"
doesnt make it an alternate approach merely because one doesnt
understand the way a volcaano erupts. You cant just lump effects
you don't understand in with what you think would be a cool cause.
> believe that there is "one right answer", then the
> existence of alternate viewpoints must be "wrong"
In this case, it is wrong, regardless of whether it's blasphemey.
There may be better theories of everything, but you should cut
your lossage on this one.
> somehow. (And from my viewpoint, if there are several
> ways to view a phenomenon, and they give differing
> insights, then the focusing on "one right answer", and
> the attacks on other viewpoints, THAT is the
> blasphemy.)
>
It's usually best if whatever approach one takes remains compatible
with observed phenomena. Fields reaching out of the deep and grabbing
energy (stealling joulery, perhaps?) is not consistent with anything
that has been reported.
Gary Coffman
>In article <=bvKOFgE21xD4p...@4ax.com>,
> Gary Coffman <ke...@bellsouth.net> wrote:
>> On Mon, 06 Mar 2000 19:42:09 GMT, Science Hobbyist <bbe...@microscan.com> wrote:
>> > Yes, that's the key question: does connecting a tank
>> > circuit to a short dipole (or small loop) cause it to
>> > absorb MORE energy from the incoming waves?
>>
>> And the key answer is NO. Resonance has nothing
>> to do with the amount of energy intercepted by the
>> antenna.
>
> previous cycles.
That's your assertion, but saying it doesn't necessarily make it
so. A *high Q* circuit stores energy, but there is no requirement
that a resonant circuit be high Q, nor is there a requirement that
a high Q circuit be resonant. All that is required to have a high Q
circuit is for the ratio of reactance to resistance to be large. That's
very different than the criteria for resonance, where inductive and
capacitive reactance have to be equal. Both could be negligible
compared to resistance, and the circuit would still be resonant,
but Q would be very low.
Now a very short antenna (in terms of wavelength) is extremely
capacitively reactive. It also has an extremely low radiation
resistance. So a short (unloaded) antenna *is* high Q, but that
is regardless of whether it is resonant or not. Resonance has
nothing to do with the amount of energy storage a very short
antenna has. Nor does resonance have anything to do with
whether the antenna intercepts energy or not (for a different
reason).
Note that I said that a short *unloaded* antenna has a very high
Q. The moment you load it, in order to extract energy from it,
the Q drops sharply. So if you are trying to pull energy from this
circuit, it isn't an extremely high Q circuit anymore. And if you
don't pull the energy from the antenna, it will be re-radiated
and lost forever. Catch 22.
>That is critically important, and that's
> why "impedance matching" is too limited to truely describe
> what is happening. Also, if the wavelength is long, the
> resonant antenna can absorb energy which would other
> wise miss it by a large number of antenna-lengths. That
> is part of impedance-matching too, but it is hidden because
> "impedance matching" in this situation is only one
> viewpoint, and it has serious limitations if expanded insight
> into the physics is the goal.
Again, that is just your assertion. As I mentioned in a previous
post, there is no localization of energy until the quantum probability
wave function collapses. If any part of a photon encounters a charged
particle in the antenna, the wave function collapses and *all* of the
photon's energy is transferred to the charged particle (usually an
electron).
The photon energy is E=hv, where v is frequency and h is Planck's
constant. The "size" of the photon is inversely proportional to its energy.
Low energy, and consequently low frequency, photons are very large.
Or said another way, they have a large wavelength. But the energy of
the photon is not localized until the wave function is collapsed. You
can't say that some of it misses a nonresonant antenna while a
resonant antenna "sucks" it in. That's not correct. The quantum
is all or nothing. It is the smallest unit of radiant energy that can
exist at that frequency. If the antenna receives any of its energy,
it receives *all* of its energy. That's true regardless of whether
the antenna is resonant or not.
Now I put "size" in quotes in the previous paragraph because the
size is not a classical size. What is meant is the probability density
function has a large non-zero area. We can't localize the photon,
or its energy, until that wave function collapses. The presence of
charged matter in that area of non-zero probability can collapse
the wave function, localizing the photon and its energy at the
position of the charged particle. There really isn't a classical
equivalent of this, but the classical explanation that the presence
of charged matter distorts the permeability and permitivity of the
space in its vicinity so that the field lines converge on it says a
similar thing, though it is physically inaccurate. (The math works,
but the physics doesn't. We thought it did at one time, but we have
a better understanding now, and know that it does not.)
>> >More
>> > specifically, if we connect just a resistive load to
>> > a short dipole and adjust that resistor for maximum
>> > received power, can we receive even MORE power if we
>> > then connect a lossless tank circuit across that dipole,
>> > then re-adjust that resistor value for maximum power?
>> > These papers imply that the answer is yes:
>>
>> My answer is also yes, but not because the antenna
>> intercepts more power. It is because the circuit is made
>> non-reactive by being resonated, allowing more power
>> to flow into the load instead of being re-radiated. In other
>> words, it is a circuit matching issue.
>
> I see the difficulty. You seem to be arguing that BECAUSE
> it is an impedance matching issue, it IS NOT a matter of
> resonance. As if there was one right answer, and we must
> get rid of any other viewpoints. This is improper, in my
> opinion, because in order to understand anything completely,
> you have to look at it from all possible viewpoints. I realize
> that I violate some particular belief when I say such a thing,
> and it causes people to raise objections and become
> argumentative.. If we're SUPPOSED to view it only
> as circuit matching, and never in any other way, then what
> say is sort of like blasphemy. It is an alternate "religious
> position" which, because it is ALTERNATE, is perceived
> as being incompatible. No. It is only alternate. But if you
> believe that there is "one right answer", then the
> existence of alternate viewpoints must be "wrong"
> somehow. (And from my viewpoint, if there are several
> ways to view a phenomenon, and they give differing
> insights, then the focusing on "one right answer", and
> the attacks on other viewpoints, THAT is the
> blasphemy.)
You seem to think this is a religious argument. It isn't.
Nature either works a certain way, or it doesn't. As we
increase our understanding of the way Nature works,
we may at rare intervals have to accept a paradigm
shift, and view Nature in a different way. In other words,
our previous understanding was *wrong* in some way,
and we have to adopt a new view which is not wrong
in that way, but our new view still has to be right in all
the ways the old view was right.
We still probably don't have the whole story, but we
now know that any explanation that is wrong in that
old way is still wrong, and any explanation that violates
things that we now know are right, is also wrong. Your
hypothesis falls in that category.
Now sometimes we can have several alternative
explanations, and none of them seem to violate
anything that we know is right, or fail to denounce
anything that we know is wrong. In such cases,
we apply Ockam's Razor and choose the simplest
explanation that adequately explains all observations.
As another poster said, we can explain anything if
we throw in enough hidden variables. But Ockam
says that the explanation with the fewest such
hidden variables is the one we should embrace.
Einstein put it this way, "An explanation should
be as simple as possible, but no simpler."
>> P = E * I * cos(theta)
>>
>> When theta is 0, power out of the circuit is maximized.
>
> Right. Heh. AT RESONANCE, power out of the circuit is
> maximized, and if the freq of the incoming wave should
> change, it's no longer at resonance, so the effect doesn't
> work. To make it work, sweep the frequency of the
> transmitter around until resonance is achieved in the
> receiver.
This equation describes the transfer of energy from the
antenna to the load. It has nothing to say about transferring
energy from photons to the antenna.
> Johnathan Swift had things to say about big-endian versus
> little-endian warfare in GULLIVER'S TRAVELS. It is
> particularly appropriate in any physics debate, since often
> the fight is over the One True Way to "crack" a
> complicated "egg."
Well, not if one of the ways works the way we understand
the laws of Nature say it must work, and the other way
requires us to discard fairly fundamental and well tested
laws of Nature in order to embrace it. If we were to embrace
your hypothesis, we'd have to revise most of QED. Now
QED works very well, we don't know of anything that it fails
to properly explain (within its scope), so we're very loath
to have to discard it just so you can have your energy sucking
resonant antennas.
Mike Lucas W5CHR
Bilge wrote in message ...
>
> with observed phenomena. Fields reaching out of the deep and grabbing
> energy (stealling joulery, perhaps?) is not consistent with anything
> that has been reported.
>
on the internet!
Mike Lucas W5CHR
Memphis, Tenn.
Jos Bergervoet
> Bilge wrote in message ...
>> energy (stealling joulery, perhaps?) is not consistent with anything
> You are hereby placed on report for perhaps the SECOND worst pun I've seen
> on the internet!
What was the worst? If Bilge has failed to deserve that honor, then so
be it (although it's a sad message for us at s.p.em). But then at least
we want to know by whom, and how, this defeat was caused.
Sir, I demand more information!
-- Jos
Bilge
Me, too. I was going for the gold. I demand a recount.
--