Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 214

The total length of wire in the extra coil circuit was: the extra coil itself 889 meters, namely 149 turns each of diameter of 1.9 meters plus special coil inserted in series: 307 meters, namely 160 turns each of diam. of 0.61 meter.

This special coil was used when the ball on top was not employed as capacity and the coil was so adjusted that the vibration was the same without the ball as with the ball and without the special coil; it being understood that the ball was at its highest position in such case. The total length of wire was therefore:

  secondary + special coil + extra coil = 803 + 307 + 899 = 1999 metersone system           one system

with all connections the length was increased to 2030 meters (17 meters rubber wire on top; 13 meters lower connecting wire).

Now capacity in primary was 4 tanks = 4 x 0.03816. = 0.15264 mfd.

Total self-ind. in primary circuit was approximately

89,000 cm   }    56,400 cm one primary turn
  6600 cm approx. - all connections in primary circuit
26,000 cm self-induct. coil

As the self-ind. of the regulating coil was rather a little larger we may take total self-induction as 90,000 cm, or $! {9 \over 10^{5}} $! H. This would give

$! {T = {{2 \pi \over 10^{3}} \sqrt{0.15264 \times {9 \over 10^{3}}}} = {{2 \pi \over 10^{5}} \sqrt{0.137376}} = {{6.28 \times 0.37} \over 10^{5}} = {2.3236 \over 10^{5}}} $! and n = 43,000.

This would give a wave length approx. $! {186 \over 43} $! = 4.33 miles or $! {λ \over 4} $! = 1.08 miles = 5700 feet while there is a little more wire. Probably self-induction and capacity or either of them in the primary have been slightly underrated or else the wire is not quite as long as calculated before.

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