(2016-09-10) Tesla Coil
High-voltage low-current generator.
Below is the schematic of a simple commercial low-current adjustable high-voltage DC generator
(5 kV to 100 kV)
using a Tesla coil transformer (labeled TRANS1)
driven by a thyristor
(BT151 scr) circuit with a 470 k potentiometer.
The output voltage is crudely limited by the distance between two facing needles connected to the
output electrodes (rightmost).
The breakdown spark discharge in air being typically about 1.2 kV/mm,
a maximum output voltage of about 100 kV is achieved when the points are
90 mm apart (per manufacturer's specifications).
Continuous operation is limited to 15 minutes.
A double-pole double-throw switch (SW-DPDT) allows the polarity of the
output to be reversed without rewiring the external load
(that switch isn't meant to be operated when the unit is powered up).
(2008-05-17) Schumann's Cavity
Between the Eartn and the ionosphere is a cavity resonating at 8 Hz.
Schumann resonance modes are observed as peaks in the spectrum
of the natural electromagnetic background noise at extremely low frequencies
They are excited by lightning strikes all around the globe.
The fundamental mode is around 7.83 Hz
and the following harmonics are about 6.5 Hz apart.
The First Schumann Resonances (in Hz)
Those are named after the German physicist
Otto Schumann (1888-1974)
who computed the relevant spectrum of the spherical waveguide formed by the Earth and
the conductive layers of the ionosphere.