Hello all
I have been reading this site for some time and thought I would post this link for all to read http://www.scribd.com/doc/3876818/Denicolai-Tesla-Transformer-for-Experimentation-and-Research-96pp2001 (http://www.scribd.com/doc/3876818/Denicolai-Tesla-Transformer-for-Experimentation-and-Research-96pp2001)
There is some information contained in the above document that can be applied to the "joule thief" thread as well as others. I would also like to point out that the "near-field" portion of EM radiation is defined as equal to wavelength/2pi, which for the radius of the Earth works out to be about 7.5 Hertz. So, IMO,Tesla was working with "near-field" EM radiation in his experiments.
:)
Perhaps there's something garbled here.
"Near-field" refers to a distance. The formula definition you give, wavelength/2pi, is indeed a distance.
But then you say, "7.5 Hz" which is not a distance, it's a frequency.
The near field distance for 7.5 Hz EM radiation is pretty large. So your conclusion is correct: when Tesla was working with these frequencies in his laboratory, he was in the "near field". But it is incorrect to say that "7.5 Hz is near-field."
That frequency is directly related to distance (just like Earth's pulse is directly related to it's diameter).