Various Tesla book cover images

Nikola Tesla Books

Books written by or about Nikola Tesla

Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 198

September 28-29, 1899

up to a point on the structure and connected to same or else brought into proximity, as for instance when a spark is used. This point should now be so located that there is at the same moment, say, a position maximum on top and a negative on the bottom or ground, that is the top and bottom should be one half of the wave apart or a multiple thereof.

When secondary is grounded as usual it will probably be advantageous to make the wave length in both systems so that they work in unison on the ground.

Colorado Springs

Sept. 29, 1899

Various advantageous arrangements of oscillating circuits for producing disturbances in the natural media.

The object of these arrangements is to produce especially in conjunction with an “extra coil”, as before explained, disturbances in the most effective and economical manner. In such a coil the e.m.f. is raised to an extremely high value by the “magnifying ratio”. The arrangements furthermore contemplate doing away with the spark which consumes energy, although in many respects it possesses advantages giving, in particular, a very high rate of energy delivery. In the diagrams three such arrangements which have been experimented with are illustrated.

In Fig. 1. the form of connection is shown most frequently experimented with here. The primary energizes secondary s shunted by condenser c, the secondary exciting extra coils e e with their capacities C C1 at the free terminals, one of which, C1, is at some distance from the ground or groundplate E forming a condenser with same. All the three systems, primary, secondary and extra coil have the same period of vibration. Fig. 2. illustrates a simplified way; in this instance the extra coils are partially influenced by induction from the primary p. In Fig. 3. again the extra coil e may be only electrically or also inductively excited. The upper terminal is here a very large capacity as the roof of a building and the terminal of high potential is C1.

This seems to be very effective.


September 28

The circuit diagrams are of great interest because they illustrate a new approach to feeding the antenna (now known as shunt feed(73) which obviates the problem of insulating the aerial pole. Unfortunately the explanations Tesla gives are too cryptic to be fully comprehensible. The figures do not clearly show whether the lower terminal of the antenna is grounded or insulated. Tesla’s conclusions that a standing wave is set up along the antenna and that the distance between points of equal potential is half a wavelength are correct.

The frequencies he was using were not high enough for his antennas to work in the manner shown by the figures (in which case they would be much more efficient radiators than he usually had), so that this contribution to the theory of wire antennas was never properly formulated.

September 28

Tesla displays new ideas about aerial excitation. The shown schemes are very interesting because they show a new approach to the problem of feeding the aerial (it is known today as shunt feed) by which the problem of the aerial support insulation is eliminated. Tesla's idea was that by such aerial feeding he would avoid discharge when supplying energy to the aerial. Unfortunately, the given explanations are not suficient in order to provide a clear understanding. On the figures it is not clearly designated whether the lower aerial terminal is grounded or isolated. The conclusions that the standing wave is created along the aerial and that location of the same potentials are at the distance of half a wavelength are correct. It appears that Tesla did not take into account the aerial reduction due to final capacitance when considering the events on the aerial. Remarks could be made on the chosen aerial length as well as the voltage distribution (or current?) along the aerial. Unfortunately Tesla did not apply high enough frequencies in order to get the aerials to operate under conditions as shown on the indicated figures, and so this contribution in an area of wire remains unfinished.

September 29

Tesla says that he experimented with the antennas shown in the drawings, but he does not compare them with a grounded antenna.

The shortness of the antennas relative to the wavelength made them inefficient radiators. The configuration shown in Fig. 3 was best probably because it had the greatest terminal capacity, providing the most favourable current distribution on the antenna. Lack of coil and ball dimensions makes it impossible to go into any more detailed analysis of these antennas.

September 29

Three wiring schematics are shown with final capacitances connected to isolated secondary terminals C and C1. Tesla said that he experimented with such aerials but he did not compare them with a grounded aerial. Due to their small aerial length in comparison with the wavelength, all these structures are now efficient radiators. The combination given in Fig. 3 is the best, probably because it has the largest final capacitance which provides the best current distribution along the aerial. For more detailed analysis of these aerials the data on the coils and sphere dimensions are missing.


Lowercase tau - an irrational constant defined as the ratio of the circumference of a circle to its radius, equal to the radian measure of a full turn; approximately 6.283185307 (equal to 2π, or twice the value of π).
A natural rubber material obtained from Palaquium trees, native to South-east Asia. Gutta-percha made possible practical submarine telegraph cables because it was both waterproof and resistant to seawater as well as being thermoplastic. Gutta-percha's use as an electrical insulator was first suggested by Michael Faraday.
The Habirshaw Electric Cable Company, founded in 1886 by William M. Habirshaw in New York City, New York.
The Brown & Sharpe (B & S) Gauge, also known as the American Wire Gauge (AWG), is the American standard for making/ordering metal sheet and wire sizes.
A traditional general-purpose dry cell battery. Invented by the French engineer Georges Leclanché in 1866.
Refers to Manitou Springs, a small town just six miles west of Colorado Springs, and during Tesla's time there, producer of world-renown bottled water from its natural springs.
A French mineral water bottler.
Lowercase delta letter - used to denote: A change in the value of a variable in calculus. A functional derivative in functional calculus. An auxiliary function in calculus, used to rigorously define the limit or continuity of a given function.
America's oldest existing independent manufacturer of wire and cable, founded in 1878.
Lowercase lambda letter which, in physics and engineering, normally represents wavelength.
The lowercase omega letter, which represents angular velocity in physics.