# Re: C of Earth...

```Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Jim,

At 01:30 PM 5/7/2001 -0700, you wrote:
snip...
>however, looking at the AGU chart you linked, it looks like the conductivity
>of the ionosphere is comparable to that of the earth (sigmaE shown, looks
>like 1E-3 (ohm meter)^-1) Typical ground conducitivities are something like
>5 millisiemens, from what I recall.
>
>Anyway, using that 1E-3 number, a stripe that is, say 100 km long (i.e. 1E5
>m), 10 km wide (1E4 m), and 1 km thick (1000 m), would have a resistance of
>1E3 ohm meter * 1E5m/(1E4m * 1E3m) = about 10 ohms.
>

Assuming a "resistivity" of 1000 ohms per meter, with 112 meter diameter
electrodes (10000m^2 cross section), and 100kM distance.  Assuming the
resistors is a cylinder from the transmitter to the receiver electrode.  I
"think":

R = rho x length / area
= 1000 x 100000 / 10000 = 100000 ohms

It is one of those obnoxious 3-D boundary problems so the real resistance
is still less.  but this would be around say ~~50k ohms instead of 10 ohms
for our little Tesla system.  Does this sound right or did I mess up?
~~50k ohms is still "ok", but our electrodes would need to be terribly high
and the full Earth sphere conductivity would be "messy".

It is also interesting to note that 7Hz is probably "out" since the ground
based AC transformers and generators would be very iron heavy operating at
only 7Hz.  Tesla's patent (645576) suggested 925Hz which would be far more
practical.  Tesla could easily make the high powered generators needed to
power the system at this frequency.  The Schumann resonances would probably
not matter much since the system's Q would be low due to the "city" load at

That "load" of the city on the other side of the system is a real
"problem".  It lowers the voltage, Q, and thus efficiency of the system
terribly...  Probably the next "terrible" problem.  Loosely couple
transformers may loose their high-voltage advantage over tightly coupled
devices if the Q is going to be bad...

Also, I am very concerned that getting 112 meter conductive balloons up
80km with a tether that can withstand lightning, wind, and such
(remembering STS-75's problems)...  If the tether has to be insulated to
20MV (I think the shuttle's tether insulation is what failed) we are
doomed...  Assuming the mechanical engineers can get the darn things up
there, the electrical problems would only be just beginning...  We could
"try" to capacitively couple to the ionosphere but that is very "messy" too...

I can feel J.P. Morgan's check writing hand quivering a bit...

Cheers,

Terry

```