Re: Tesla Coil RF Transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Ed Phillips <evp@xxxxxxxxxxx>

See comments interspersed below.

"As noted by James Corum, et al in the paper "Concerning Cavity Q,"
PROCEEDINGS OF THE 1988 INTERNATIONAL TESLA SYMPOSIUM, and others,
the earth possesses a naturally existing negative charge with respect
to the conducting region of the atmosphere beginning at an elevation
of about 50 Km.  The potential difference between the earth and this
region is on the order of 400,000 volts.  Near the earth's surface
there is a ubiquitous downward directed E-field of about 100
V/m.  This is what I'm referring to when I use the phrase "earth's
charge."

	There are various values quoted for the field and I'll take the
following slightly different values from Stong's Scientific American
book "The Amateur Scientist".

	Average height of the ionosphere - ~ 60 miles  (insulated body)
	Average voltage - ~ 360,000
	Capacitance to earth - ~ 0.25 FARAD
	Average discharge current due to lightning - ~ 1800 amperes
	Approximate equivalent resistance - ~ 200 ohms

This represents, of course, a more or less static field and perturbing
it with RF won't have any consequences as far as power transmission is
concerned.  The approximate power (due to thunderstorms and ultimately
derived from solar heating) is 360,000 x 1800 = 648,000,000,000 watts or
648 megawatts.  This sounds like a lot but it's actually only 1/10 of
the power of Grand Coulee Dam, which has a total installed generating
capacity of 6480 megawatts.  So much for "harnessing the power of
lightning" for limitless "free energy".

"    A point of great importance would be first to know what is the
capacity of the earth? and what charge does it contain if
electrified?  Though we have no positive evidence of a charged body
existing in space without other oppositely electrified bodies being
near, there is a fair probability that the earth is such a body, for
by whatever process it was separated from other bodies-and this is
the accepted view of its origin-it must have retained a charge, as
occurs in all processes of mechanical separation.  If it be a charged
body insulated in space its capacity should be extremely small, less
than one-thousandth of a farad.  But the upper strata of the air are
conducting, and so, perhaps, is the medium in free space beyond the
atmosphere, and these may contain an opposite charge.  Then the
capacity might be incomparably greater."

	Not incomparably; the capacitance of an isolated sphere such as the
earth is approximately 1.11 x R pf, where R is the radius in cm.  If the
earth's radius is the commonly-used value of 6370 km, this works out to
a capacitance of about 707 ufd.  If we add  100 km to the radius to
approximate the outer diameter of the ionosphere this increases the
capacitance to about 718 ufd.

"    In any case it is of the greatest importance to get an idea of
what quantity of electricity the earth contains.  It is difficult to
say whether we shall ever acquire this necessary knowledge, but there
is hope that we may, and that is, by means of electrical
resonance.  If ever we can ascertain at what period the earth's
charge, when disturbed, oscillates with respect to an oppositely
electrified system or known circuit, we shall know a fact possibly of
the greatest importance to the welfare of the human race. I propose
to seek for the period by means of an electrical oscillator, or a
source of alternating electric currents.  One of the terminals of the
source would be connected to earth as, for instance, to the city
water mains, the other to an insulated body of large surface."

	The earth doesn't contain electricity per se; the charge is on the
outer surface.  If by the earth's charge we keep your original
definition then this charge is already disturbed, of the order of 100
times per second, by lightning discharges.  The resonances of which you
speak are the Schumann resonances, whose frequency AND BANDWIDTH are
readily observed.

"    It is possible that the outer conducting air strata, or free
space, contain an opposite charge and that, together with the earth,
they form a condenser of very large capacity.  In such case the
period of vibration may be very low and an alternating dynamo machine
might serve for the purpose of the experiment.  I would then
transform the current to a potential as high as it would be found
possible and connect the ends of the high tension secondary to the
ground and to the insulated body."

	As noted above, the properties of this "condenser", as well as its
charge, have become known since Tesla's time.  We can calculate the
reactance of same at the lowest resonant frequency of about 7.8 Hz; it's
about 0.08 ohms.  If Tesla's "alternating dynamo machine" were to charge
this to a million volts, far lower than the values he discussed, the
current flowing would thus be 12,500,000 amperes and the associated
reactive power would be 12,500,000 MEGAWATTS.  He didn't mention that,
but in his patents refers to maintaining this voltage with "a few
horsepower". It all goes downhill from there.

Ed