Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 404

June 25

The device shown in the drawing was intended to amplify the vibrations, in the following way: some of the power driving cylinder A is converted by friction of brush b against A into vibrations of b. Since the friction is a function of the current in the electromagnet, the vibrations of b have a time variation similar to the time variations of the current. If the circuit of the electromagnet includes a microphone and a battery, then the device should amplify the speech signal, brush b vibrating in synchronization with the speech pressure but with much more energy. This amplified signal could be used in a modulator (see June 13th and 14th). The drawing shown on p. 405 (from Tesla's slide in Nikola Tesla Museum, Belgrade) illustrates how Tesla thought of implementing some of these ideas*.

June 26

The principle of this device using high voltages to separate gases would be that the molecules (in fact ions) of the different gases would behave differently because of their different mass: charge ratios. It is not known whether Tesla tried to verify this idea experimentally. In a later article⁽²⁸⁾ on electrical oscillators he mentions among the possible applications “formation of chemical compounds through fusion and combination; synthesis of gases; manufacture of ozone ...” but does not mention separation of gases, so that it may be he never went any further than the initial idea.

June 27

The transmitter (Figs. 1 and 2) and receiver (Fig. 3) having several tuned circuits, the transmitter generating several signals at different frequencies and the receiver responding only when all these signals act at the same time, were the subject of two patent applications filed 16 July 1900 (subsequently granted)⁽³⁸⁾.

This method allows much more selective reception than a single-frequency channel, and is much less sensitive to interference, and the signal can only be decoded by a special receiver. In his patent applications Tesla likens it to a lock which can only be opened when one knows the combination.

The entry of June 27th was subsequently brought in evidence in a dispute before the U.S. Patent Office about priority to the idea of a multi-frequency system⁽⁶⁸⁾. The back of the page bears the stamp “U.S. Patent Office, Nov. 1902".

June 28

Tesla considered that the self-capacity of the secondary winding was proportional to the number of turns and inversely proportional to the spacing between turns, so that the ratio of the distributed capacities of the new and the old coil is N₁d/N d₁ (N - number of turns, d - spacing between turns).

The ratio of the inductance of the secondaries with different numbers of turns he finds from the relation

$! {{\left({N_{1} \over N}\right)^{2}} = {{\left({N_{1} \over N}\right)^{2}}{Nd \over Nd_{1}}} = {N_{1} d \over Nd_{1}}} $!