Re: teeny atoms absorb huge EM waves

[William Beaty <billb@ESKIMO.COM>]

On Mon, 2 Aug 1999, William Beaty wrote:

> I've been told that common AM radios use antenna-tuning.  This
> clears up a question I've always had about AM radios: how can they get
> away with such a small antenna?  Do they simply have immense front-end
> gains?  Maybe not.  If their ferrite loop antenna is tuned to the received
> frequency, then it will create its own EM field, and take advantage of the
> same "energy sucking" effect that atoms use to grab light waves.  A
> portable AM radio is like a "giant atom".

Here's a possible experiment.  If an AM radio acts like a "giant atom" and
sucks RF energy from around itself, then one radio would tend to shield
another another one tuned to the same station.  The automatic gain control
would normally nullify any changes in loudness, but for weak stations, the
circuit noise might vary.  If we tune one radio to a very weak,
hiss-filled signal, then we tune a nearby radio to the same frequency, the
noise heard from the first radio might increase.

If the circuit noise is a small component of the sound from the
loudspeaker, this wouldn't work because the AGC circuit would just crank
up the loudness.  The received noise would stay the same.  To make the
shielding effect obvious, we might need to break into the radio and
disable the AGC.  Also, if the tuned antenna did not actually draw much
energy from surrounding space (if its resistive load wasn't matched to the
antenna's impedance), then one radio might not perceptably shield another.

Weird thought: a small antenna, if it's within 1/4-wavelength of an AM
broadcast tower, should be able to suck significant energy from the AM
transmitter.  To do this, there needs to be a high-voltage wave on the
small antenna.  The "anti-radio" signal, if the voltage is high enough,
would cancel the output of the big transmitter and absorb it's energy.
Maybe such an antenna could run a motor or light up an incandescent bulb!

VERY weird thought.  Pure speculation! If a plasma is resonant at tens of
kilohertz, and if a thunderstorm should "broadcast" a significant e-field
signal at such a frequency, then the "resonant absorbtion" phenomenon
could explain Ball Lightning.  One contemporary Ball-lightning explanation
is the Thunderstorm Maser theory, where thunderstorms supposedly emit
microwaves, and small regions of plasma can absorb the energy and stay
"lit."  If a hi-Q plasma-resonance was at "longwave" frequencies rather
than at microwave frequencies, then even a Ball Lightning that is far
smaller than this wavelength could absorb significant energy.  Being a
near-field effect, this might involve only electrostatic signals, not
conventional EM waves.  A radio receiver might not pick up a
high-frequency e-field if lacked the normal b-field of a propagating EM
wave.


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William J. Beaty                                  SCIENCE HOBBYIST website
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