Tesla Experiments


Sounds impressive? I assure you it is not! I have been wanting 
to transcribe some of my lab notes concerning a series of
experiments that I happened into quite accidentally in the fall
of 1992 while working with a four inch coil system. Before I jump 
into the simple equipment and instructions required to duplicate
these very educational experiments, I want to give a brief
history of how I happened onto this line of investigation with
Tesla Coil systems. But even before that: The disclaimer!

This short paper was written for those interested in Tesla
systems who already have a small working coil or two. These
experiments, like any high-voltage or Tesla experiments, can be
dangerous. In addition, several setups detailed below can produce
excessive radio frequency interference (RFI - EMI). It is under-
stood among ALL coilers that any adjustments, tuning, or changing
of connections in a coil system are done with the power off and
with the primary capacitors discharged. It is also understood
that setups which may produce excessive RFI - EMI are properly
shielded (as in a grounded Faraday cage). A REAL Tesla ground is
REQUIRED for some of these experiments. You don't want to set up
the transmitter configuration detailed below under "Optional
Experiments" and ground it to your house wiring!

I was back-tracking down in size from 6 - 8 eight inch coils
prior to the construction of a new 10" coil system. I was con-
cerned about the expense in time and materials for the new large
primary coil that I was beginning to envision. I wanted to have a
work table or platform where I could wind and test fire simple
primary coil designs. I was looking to resonate several Tesla
secondary coils in the 4 - 5 inch diameter range with a variety
of temporary "lashed up" primary coil shapes and sizes. Due to
space constraints I wanted a rolling platform with a lower shelf
where my homemade capacitor tanks could rest, a side shelf for
the placement of spark gaps, and some method of making a simple
low impedance connection to my heavy, dedicated, RF ground. I
went ahead and built a rolling platform from scratch wood.

The grounding system on my rolling platform is what led to the
following series of experiments with electrical counterpoises and
RF grounding. The top of the rolling platform had a hole drilled
into the center for a ground wire to come through. For a ground-
ing point directly below the secondary coil, a wire is led
through the hole and it clamps to a rather solid brass block that
was screwed into the underside of the tabletop (junk box find).
The brass block has four #6 multi-strand wires soldered to it
(scrap wire box, the sections were too short for anything else,
so I used all of them). Each wire is insulated with heavy vinyl
tubing as it runs down the four legs of the platform (insulation
was required here because of the close proximity to the capacitor
terminals and the tank circuit wiring). 

I looked around for some method of tying the four #6 ground
cables together at the base of the platform, and settled on what
turned out to be an aluminum traffic sign which came out of a
sheet aluminum scrap bin. It fit precisely under the base of the
platform, and I bolted the four cables to the conductive plate. 
A heavy ground strap could be brought in from any direction, the
conductive plate pried gently with a screwdriver, and a large
surface area temporary connection could be made by inserting the
ground strap between the conductive plate and the wooden bottom
of the platform....   Now I will move on with this paper.


A well tuned Tesla coil with a 4 - 6 inch ( 10 - 15 cm ) diameter

Some one inch (2.5 cm) high plastic medicine cups, or some pieces
of plastic scrap about inch high that can be used for simple
light-weight standoff insulators. 

A section (any shape) of flat sheet metal of at least 2.25 square
feet, but not much over 4 square feet (.7 to 1.2 square meters).
The exact size to get the best experimental results will depend
on the size and efficiency of the coil system you are using.
Since this component need have no special characteristics, and
any flat conductive material may be used, you might want to get a
selection of pieces of various sizes.

A low pressure gas tube (neon, florescent)

Some sections of braided ground strapping or other flexible
conductor with a large surface area.

Some simple clamps (clothes pins, large paper clips, etc.)

Some thick plastic sheeting may be required in places for

A dedicated RF ground for ground pathing and for grounding HV
xfmr cores and Tesla resonators.


Toroid or sphere discharge terminals of various sizes. These
additional dischargers are highly recommended for any degree of 
experimentation with resonating coils.

A separate Tesla secondary just a bit larger than the secondary
used in the operating system. The optional experiments do not
require a second coil SYSTEM with tank circuit, etc.. Just a bare
secondary coil that resonates at a slightly higher frequency than
the system used to power these experiments.

Set four or more of the plastic standoff insulators on a
concrete, dirt, or metal floor. A wooden floor will not be
satisfactory, and may well become a fire hazard during the course
of experimentation. A concrete basement or garage floor is ideal.

Place the flat sheet of metal on top of the plastic insulators so
that the conductor is electrically isolated 1 inch (2.5 cm) above
the floor. This forms an insulated capacitance or "counterpoise".
Use a clothespin or other small clamp and connect one end of a
section of ground strap (or other flexible low impedance
conductor) to the piece of sheet conductor. Connect the other end
of the ground strap to the base wire of a Tesla secondary coil in
a system that has been previously tuned until it will produce at
least 6 inches (15 cm) of spark. The secondary coil should NOT be
connected to any other ground while experimenting with the
counterpoise. Fire the coil using a variac voltage controller on
the primary of the step up xfmr, bringing the coil slowly up and
down in power levels.
1) Observe the performance of the coil at various power levels.
How does spark from the coil when connected to the counterpoise
compare to spark from the coil when it is grounded to a low
impedance RF ground? Switch the ground connection back and forth
between your counterpoise and your low impedance RF ground.

2) Observe the space between the counterpoise and the floor when
the coil is in operation at various power levels.

a) My lab notes indicate that at low power the Tesla secondary
operated normally without a ground connection. The counterpoise
alone is all that is required to achieve efficient resonance
during low power operation. However, as power levels grew, spark
lengths failed to increase, despite significant increases of
input power.

b) The point at which the coil "stalled" (where additional power
into the system caused no increase in spark length) was also the
point at which a visible electrical disturbance began in the
space between the counterpoise plate and the floor. This
disturbance was marked by bright corona and sparking between the
counterpoise and the floor. This disturbance increased with the
amount of power input into the system, though there was little or
no improvement in the output of spark from the top of the coil.

c) If you were not able to overwhelm the counterpoise during the
experiment to produce any noticeable effect, your counterpoise
was too large, or your coil was not processing enough energy. Try
a smaller section of flat sheet conductor and re-run the
experiment until you are getting visible effects beneath the

1) With the coil ground wire connected to the counterpoise fire
the coil system at various power levels while holding a low
pressure tube near the counterpoise plate. Observe the tube

2) Repeat experiment #1 above with the coil well grounded to a
dedicated low impedance RF ground. Hold the low pressure tube
near the ground strap.

a) My lab notes state that when the coil is working off the
counterpoise, a low pressure tube indicates significant standing
voltage and current. Since the counterpoise is insulated from the
floor, leakage and radiation of energy must be unloading the
counterpoise. When the counterpoise is overwhelmed, this leakage
is quite visible with the naked eye, and appears in the form of
corona and sparks to the floor. This indicates a situation where
large amounts of RF interference (RFI) is leaving the system.

b) When the coil is grounded to a low impedance RF ground there
is only a faint glow from the low pressure tube when it is held
near the ground strap. The tube does brighten when one terminal
is in direct contact to the ground strap, which shows the ground
is energized. This indicates that the RF voltage and current is
no longer trapped and radiating, but is going to ground. 

1) Connect the base of the secondary coil to the counterpoise.
Place the low pressure tube in series between the counterpoise
and the RF ground. Fire the coil at various power levels and
observe the tube.

a) This experiment clearly shows the need of a dedicated RF
grounding system on Tesla resonating systems. At very low power
the tube glows brightly, at higher power the tube begins to heat
from the RF current through the low pressure gas.



Load the Tesla coil system with a toroid or other discharger that
is large enough to prevent spark from breaking out, then retune
the system with the new discharger. (hint: without spark,
retuning may be done by the glow of a low pressure tube {brighter
= closer in tune} or by drawing off spark with a grounded probe)

           Repeat the experiment series above.

a) The first thing that will be noted is that ground current has
increased dramatically when spark is no longer allowed to break
out of the discharge terminal. The counterpoise is overwhelmed
immediately, even at very low power. The energy forced into the
secondary is trapped. Due the damped nature of the secondary
oscillations, radiation is inefficient. The trapped energy is
TRANSMISSION IDEA. This may now be called a transmitting coil, or
transmitting system.

Take a second Tesla resonator (just a bare coil, no primary or
tank circuit) of slightly higher frequency than the transmitting
system used to power these experiments. Load discharger onto the
bare secondary until the coil is tuned to match the frequency of
the "driver" system. This simple uncoupled tuned coil will now be
referred to as the "free" coil. 

1) Connect the transmitting Tesla coil system {set up and tuned
as detailed under [OPTIONAL EXPERIMENTS]} to the counterpoise.
Note: the counterpoise is overwhelmed almost the instant the
transmitter coil is energized. Connect the base wire of the
"free" coil to the counterpoise, then energize the transmitter

2) Connect the transmitting Tesla coil system to the dedicated RF
ground. Run a ground strap or other flexible low impedance
conductor from the dedicated ground to the base of the "free"

a) The "free" coil is retrieving the RF current from the
counterpoise and resonates to spark despite lack of inductive or
electrostatic coupling. This coil may be placed quite some
distance, even off axis, from the transmitting coil and will
still spark well.

b) The "free" coil still resonates to spark despite the fact that
the transmitter coil is driving into a dedicated low impedance
RF ground. This shows the ability of even a small coil system,
properly set up and tuned, to "power up" a low impedance RF
ground to the point where usable energy may be drawn off. 

These experiments clearly show the importance and function of RF
grounds for the efficient operation of Tesla resonators. The more
advanced "Optional Experiments" show the basis of Tesla's
wireless power transmission through earth resonate ground

Richard Quick

... If all else fails... Throw another megavolt across it!