I know many others, far latter, have proposed running coils at say
7.1Hz. However, all of "Tesla's" systems were designed to run at far
far higher frequencies. I have never seen anything suggesting that
Tesla was trying to run his coils at say less than 40kHz. He
thought it would work fine at the higher frequencies...
Once the Schumann resonances become understood, everyone jumped on
those as being what Tesla was trying to do. Perhaps a way to
finally "repair" Tesla's idea. But "Tesla" never tried to run into
those resonances at all and he thought the earths resonances were at
far higher frequencies dictated by two concentric spheres...
http://teslamania.delete.org/frames/Non-Herzian_Waves.html
I forget this moment if Tesla quoted the operating frequency of the
Wardenclyffe coil...
Cheers,
Terry