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Re: Tesla's Wireless Power Transmission ==> was Re: Non-tech Qu
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> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Tesla's Wireless Power Transmission ==> was Re: Non-tech Qu
> Date: Sunday, May 21, 2000 1:17 AM
>
> Original Poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>
>
> Tesla List wrote:
>
> > Original Poster: "Jim Lux" <jimlux-at-earthlink-dot-net>
>
> > Actually, the signal is easily detectable. Omega signals are in the 10
kHz
> > area and detecting both short and long path is possible without too
much
> > trouble with inexpensive equipment. These signals propagate in a mode
that
> > is essentially a waveguide between surface and ionosphere.
>
> Ok, but the transmitter power is in the kW (MW?) range, and the received
> signal is useless as energy source.
Indeed.. actually, the radiated power (not the transmitter power) isn't all
that high (same for the ELF comm systems). The path losses are quite low
(compared to skywave, for instance). The real problem is that the antenna
efficiency is terrible. I seem to recall that for the ELF systems they put
in several MW to get a radiated power of 5 watts. The radiation resistance
of a physically short radiator is pretty low (milliohms, at best).
Omega transmitters have large antennas (so big that Tesla would only dream
of them). A top load several km long on a vertical of 1000+ meters. They
do stuff like string the top load across a valley, with the transmitter at
the bottom of the canyon or fiord). Fairly high transmitter powers, but
not MW, as I recall
>
> Looking at the autobiography that Fr. McGahee mentioned, apparently
> what Tesla had in mind was to use the currents injected in the Earth
> by the ground connection of a big coil as the signal source. But (much
> as you say below) these currents return to the other end of the coil,
> where a big distributed capacitor is, through the displacement currents
> in the dielectric of this same capacitor, the air around the coil.
> This is a very local effect, and if something is transmitted, is just
> a regular TEM wave irradiating in all directions around the coil, that
> acts just as a short vertical antenna with a large top load. I don't
> know why Tesla didn't see this, even in 1919, where these issues were
> already sufficiently known. His affirmations of lossless transmission
> using this system, if this was the system, are unrealistic.
>
> > A more
> > significant problem with this around the world thing is that the earth
is
> > NOT a sphere, particularly not at RF. If you were to pick an arbitrary
> > direction, the propagation path would neither be straight, nor uniform
> > speed, nor match the path in another starting direction.
>
> A serious problem, but I thing that the worst problem of the idea is
> that the walls of the "waveguide" are far from lossless, and absorbe
> a lot of energy.
At low frequencies (<100 kHz) the waveguide losses aren't all that high.
The ionosphere and ocean are both very good conductors. A big factor is
absorption going across the poles.
>
> > There is a worldwide lightning detection network that relies on the
fact
> > that the RF energy from lightning everywhere in the world propagates
> > worldwide. In fact, this is a big constituent of the background noise
in
> > the LF, MF, and HF radio bands.
>
> But not the main constituent, or radio would not work better at night.
I think it is actually the main constituent. Receiver thermal noise is
insignificant below 30 MHz. 1/f noise would be insignificant above 100 kHz.
All that's there is atmospheric and environmental noise. Atmospheric
noise is almost entirely lightning in origin. Radio appears to work better
(in terms of SNR) at night because of the change in frequency selective
nature of propagation. The propagation for the desired signals gets better
(for some) and the interfering signals gets worse. Of course, if you have
big thunderstorms over the transmitter site, then your kind of out of luck.
For LF and MF broadcasts, the atmospheric noise level during the day is
high, so the receiver AGC reduces the receiver gain. At night, the noise
level drops, so the receiver gain rises, making the desired signal seem
louder.
>
> > You actually don't need a return path, per se, any more than a standard
> > radio receiving antenna has a path to the radio transmitter. Think of
an
> > antenna as a "energy scoop".
>
> Ok, but you can't pick much energy in this way.
Indeed... it's all aperture.. how many watts/square meter
> > Out of curiosity, how low... I'll bet it is <1.. The multiple paths and
> > high loss make it more of a group of noncoherent time delays that
happens
> > to clump around 1/7 second.
>
> I don't know. This was certainly measured. Can someone provide the
> answer?
I think you could do a quick model assuming an ellipsoidal earth.. An
interesting problem for a Sunday morning and a spreadsheet...
>
> A test if this works is simple. Set a Tesla coil to cause a single
> powerful
> arc to a grounded object. This will inject a strong current pulse in the
> Earth, right?
> Set a vertical antenna close to the coil and look at the sharp voltage
> decrease when the arc hits. Look for an echo 133 ms later.
You're going to need to integrate a LOT of pulses to see it over the
noise...
However, if you use a loop antenna and detect the omega signals, you can do
it with a sound card in a computer. You can get very narrow band (2 Hz BW)
filters for omega frequencies to improve the SNR. Measure the signals over
a day, and you can see both short and long path signals, manifested as a
change in the phase of the combined signal as the relative attenuation of
the two paths change.
Of course, since GPS came on the scene, I understand they are
decommissioning Omega.