
Tesla: Art of Transmitting Electrical Energy through the Natural Mediums (1900) - hownottowrite
https://patents.google.com/patent/US787412A/en?before=priority:19030101&after=priority:18900101
======
Bud
Wouldn't it be better to post a link to the full patent here, since the OCR
quality is so bad that it's almost unreadable on Google's site?

Here's that patent on the USPTO site:

[http://pdfpiw.uspto.gov/.piw?docid=00787412&PageNum=1&IDKey=...](http://pdfpiw.uspto.gov/.piw?docid=00787412&PageNum=1&IDKey=C89A7D242A7E&HomeUrl=http://patft.uspto.gov/netacgi/nph-
Parser?Sect1=PTO1%2526Sect2=HITOFF%2526d=PALL%2526p=1%2526u=%25252Fnetahtml%25252FPTO%25252Fsrchnum.htm%2526r=1%2526f=G%2526l=50%2526s1=0787412.PN.%2526OS=PN/0787412%2526RS=PN/0787412)

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Bromskloss
Why do they publish each page in a separate file? Here are all pages joined
together:
[https://a.pomf.space/sgpnalxtzbae.pdf](https://a.pomf.space/sgpnalxtzbae.pdf)

~~~
panopticon
If you click the "Full Document" button on the left, it provides a single PDF.

Why that's not the default behavior though...

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leggomylibro
I started reading some of Tesla's speeches recently, and one thing that struck
me was how he happily talks about enormous flaws in the implementations of his
designs, but still went on to prove that they were POSSIBLE even if the
practical design might have to wait.

His idea for ultra-efficient high-voltage, high-frequency AC power lines is a
good example. It would probably work, but his proposed system required liquid
insulation on the wires; it would be important to keep gases out of the
medium, and the slightest break in a solid insulation like rubber or silicone
(or gutta-percha) could basically turn the wire into the business end of a
tesla coil.

So...I don't understand enough about the subject to say for sure, but we
probably landed on 50-60Hz for a reason. I wonder why this one didn't wind up
working out, but I'll bet it's described somewhere in the application which
I've only skimmed.

Also, for anyone else trying to dive into it, 'condenser' = 'capacitor' in
olde-speak.

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PoachedSausage
The choice of 50/60Hz is an engineering trade off. Engines, Turbines and
alternators are happiest spinning in 100s to 1000s of revolutions per minute
range. At that RPM range, alternators with 2, 4, 6 etc magnetic poles
translate to AC line frequencies in the 10's of Hz range. AC power on aircraft
is usually at 400Hz because it makes equipment lighter.

It is similar with the choice of 3 phases for electrical power distribution,
you can add more phases but it just adds to the cost with little benefit.

~~~
m4x
Another relevant trade off is transformer size vs. efficiency.

AC is used because it's very simple to step up to very high voltage for
efficient long distance transmission and then back down to safer low voltages
for use, while doing the same with DC requires significantly more complex
electronics.

However, at very low frequencies you need to use very large transformers which
cost a lot and look ugly, and at higher frequencies you lose efficiency due to
skin effect [1].

50 Hz is a good compromise - transformers are of a practical size and skin
depth is about 9 mm, which is larger than most conductors and therefore
doesn't add much loss.

If you increase the frequency to just 10 kHz (which is still considered very
low) the skin depth decreases to only 0.6 mm, and you would have significant
loss on even moderate sized conductors.

[1]
[https://en.m.wikipedia.org/wiki/Skin_effect](https://en.m.wikipedia.org/wiki/Skin_effect)

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JoeAltmaier
Most remarkable are the number of very modern patents that cite this one! How
surgical instruments benefit from earth-transmission technology is beyond my
understanding.

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bhousel
The patent helps sensitive equipment work (think like an EKG monitor) during a
lightning storm.

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pjc50
So this seems to be
[https://en.wikipedia.org/wiki/Extremely_low_frequency](https://en.wikipedia.org/wiki/Extremely_low_frequency)

Including "The attenuation of ELF waves is so low that they can travel
completely around the Earth several times before decaying to negligible
amplitude, and thus waves radiated from a source in opposite directions
circumnavigating the Earth on a great circle path interfere with each
other.[20] At certain frequencies these oppositely directed waves are in phase
and add (reinforce), causing standing waves. In other words, the closed
spherical Earth-ionosphere cavity acts as a huge cavity resonator, enhancing
ELF radiation at its resonant frequencies."

Does anyone have a technical explainer of Tesla in modern terminology?

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m4x
Which of those terms do you not consider modern? As far as I know all those
terms are still in cirulation

Edit: sorry, I see you probably mean the content of the patent rather than the
passage you quoted

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coldcode
Fascinating to read the text and know this was done nearly 120 years ago. Such
an amazing genius.

~~~
Johnythree
Actually, it wasn't done. Every one of his Earth Conduction attempts ended up
a spectacular failure.

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romdev
The wording reminds me of this whimsical story that I read several years ago
(before Tesla motors), about the electric car that he powered with vacuum
tubes and an antenna:
[http://keelynet.com/energy/teslcar.htm](http://keelynet.com/energy/teslcar.htm)

Come to your own conclusions, but there's evidence that it was a hoax:
[https://en.wikipedia.org/wiki/Nikola_Tesla_electric_car_hoax](https://en.wikipedia.org/wiki/Nikola_Tesla_electric_car_hoax)

~~~
13of40
Something I've always wondered about is whether the electrical charge of the
earth is uniform across the entire surface, or of you could harvest electrical
power by just running a (presumably really long) wire between two grounded
spots. I guess if they don't do it the answer is probably "no", "not enough to
pay for the wire", or "Where do you put the meter?"

~~~
Johnythree
It is common knowledge that a pair Earth stakes will pick up a small amount of
current.

Hobbyists have been using the idea for years to run small radios.

Likewise that same ground current will screw up Telegraphs (etc) which try to
use an earth-return path.

The problem for large scale energy harvesting is that the Earth is conductive,
so any voltage differences are shorted out by the Earth itself and dissipated
as heat.

To put it another way, the Earth is a lossy medium, so any signals are heavily
attenuated by distance.

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DaniFong
This is amazing

