Nikola Tesla was a man who thought outside of the box.  One of his far reaching determinations was the fractionalization of electricity into it's electrostatic and magnetic components through the use of his magnifying transmitter.  What we know as a Tesla Coil.  Knowing Nikola Tesla is to know his competitors; Thomas Edison, C.P. Steinmetz and J.P. Morgan.  Tesla was aligned with George Westinghouse in the battle of the currents versus Thomas Edison and financier J.P. Morgan.  Steinmetz was employed by J. P. Morgan to understand the inventions of Nikola Tesla.  Tesla's tale is a fascinating mix of business intrigue and scientific discovery that inspires people to this day.  


Nikola Tesla George Westinghouse
Nikola   GeorgeWestinghouse



Thomas Edison J. P. Morgan C.P. Stenmetz
ThomasEdison  220px JohnPierpontMorgan   Charles Proteus Steinmetz


In the end George Westinghouse won the bid to build the first power generation plant at Niagra Falls with Nikola Tesla's Alternating Current (AC) system.  Not to be outdone, J.P. Morgan, who was the most powerful financier of his time took Westinghouse to court and ultimately brought all the patents to General Electric.  To survive, George Westinghouse asked Tesla to relieve him of his patent royalties and that is what Tesla did in a very magnanomous gesture in which George was forever indebted.

Charles Proteus Steinmetz was born with dwarfism and a curved spine.   He overcame all this to become a person of great personal fame in his time and was known as the Wizard of Schenectady, which at the time was the headquarters for General Electric.  As an electrical engineer I had never heard of him through all of my schooling.   Only later in life were his achievements apparent to me.  His research into magnetism allowed for the modern industrial age that we know.  Understanding magnetic hysteresis allowed for the development of transformers that supported the A.C. system.  He was a professor at Union College for many years and a great friend and colleague of Thomas Edison.  While Edison was the astute pragmatist and consummate experimenter Steinmetz was the theoretical mind that could put mathematics to theory.  His lectures on Electric Discharges, Waves and Impulses is a  work worth reviewing. He had the respect of many peers including this guy.  

einstein and steinmetz


   Albert Einstein in a visit to RCA in 1922 meeting with Steinmetz.















So what is a magnifying transmitter?

The basis for all of Tesla's work on this subject culminated in a series of experiments conducted in Colorado Springs, Colorado in 1899.  This is the subject of the so-called Colorado Springs Notes. Very technical, but the best we have to understand what he was researching.

At that time electricity as a technology was in it's infancy.  Tesla used a distinct naming convention for electrical components.and terminalogy.  Some examples are:

  • Condensor = Capacitor
  • Coherer = Diode
  • Pressure = Voltage


They ( Tesla and Steinmetz) had a different view of the force fields around a wire.  In their day they viewed the electrostatic and magnetic fields as components of the "Electric field".  The circles being the magnetic field and the lines eminating from the wire the electrostatic.   Both of these components were taken into account to explain the arcing and sparking as they struggled to control electricity.  Today the emphasis is on the magnetic fields created by the flow of electrons through the wire.

When Steinmetz studied Tesla's patents he noted that the electrostatic effects were only pronounced above 2000 volts.  So neglecting the electrostatic component below that was a reasonable assumption.

What Tesla was researching after his A.C. system inventions was to determine a means to amplify the electrostatic (dielectric) component of electricity.  This was brought about by the use of inductors of various parameters with what he termed a circuit controller.  This circuit controller or "break" would disrupt a current flow through an inductor abruptly.

When a current is interrupted through an inductor a large voltage spike is induced as the magnetic field collapses which eventually dissipates.  What is typically a nuisance when controlling solenoids is exploited in his magnifying transmitter.



The Tesla magnifying transmitter circuit controller

 Tesla spent a great deal of time designing his circuit controller to increase the BPS ( Breaks per Second ) that they could achieve.  Early on he experimented with various configurations of a spark gap that would achieve the intense break in current he was after.  It's important to realize that he was working with thousands of volts and hundreds of amps in Colorado Springs.  The power levels he was working with had set the central dynamo in Colorado Springs afire which Tesla repaired at his cost to keep his experiments going. 

SparkGap TeslaA major way to extinguish the spark in a gap was through the use of magnets.   He employed this with great effect at his Houston Street lab in New York City.  The spark gap was made of brass which held in its cups graphite balls.  This proved easier to arc than metals.  On either side was magnet covered by mica to prevent arcing to the magnet.




As time progressed Tesla improved on this configuration and came up with many different configurations of circuit controller that enabled him to achieve as much as 100 thousand BPS.  Many were based on multiple tooth wheels and some used mercury streams as the conductor instead of an ionized gas.  Additionally he used ammonia as a way of suppressing any atmospheric arcs.



 RotaryBreaks CircuitCntl 

The Magnifying Transmitter

J. P. Morgan backed Tesla's Wardenclyffe installation on the idea that he would achieve transatlantic radio transmission.  That was the understanding but what Tesla had his sights on was to transmit power through the whole of the earth.   Once JP learned of this and realized there would be no way to put a meter on it he pulled the plug on Wardenclyffe and it fell into disrepair.  The building still exists on Long Island and there are some efforts to have it preserved as a museum.

This illustration below best shows the main theory on it's operation.  It assumes that the earth can be a lumped conductor by which to conduct electrical power.  In my research the farthest Tesla was able to transmit power was about 60 miles from his Long Island, New York plant.





How to design a Tesla Coil

200px EricDollard

 Although the Colorado Springs Notes are a wealth of information one of the best resources to engineer a Tesla coil is  E.P, Dollard.  He has inspired a lot of people to understand this technology and made many demonstrations about the curious effects that Tesla coils can achieve.  He recently gave a presentation demonstrating a 20:1 Tesla Scale model and sells the plans to build such a device.

Here are the main design parameters thet Eric has layed out for optimizing a Tesla Coil.

  • Magnifying transmitter is electrostatic in nature.
  • It's the break in current that yields the effect.
  • Electron flow was blocked - use of carbon in sparkgap and nitrogen. Carbon acts as semiconductor at high frequencies.
  • This was called "fractionalization" of electricity.
  • Pulses < than 100 microsecs are not felt.
  • Mass of primary = Mass of secondary.
  • Secondary needs high capacitance - bifilar wound.
  • Secondary coil to physically have hieght = 20% of width.
  • Extra coil needs to physically have width = height.
  • Extra coil very low capacitance.
  • Coil spacing needs to be 60% of wire diameter.
  • Ground plane must be robust.

An assumption is made for the length of each coil made on the length of the wave form.

  • Primary = wave length / 2n; where n is chosen to be an odd harmonic (1.3 5....)
  • Secondary = wave length / 4
  • Extra coil = wave length / 4


 The Crystal Set Initiative.

This is link to some engineering concepts for a Tesla coil that can be used to receive AM radio through the ground.  It gives mechanical design parameters and equations for designing the coil and is doable with little money.  Best of luck and I hope you have enjoyed this inaugural blog post.


About the author

Mark is an engineer in multiple disciplines.  An avid music lover and gardener.

He also likes to keep the 'ol truck running in his spare time.

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