Re: Fwd: That secondary harmonic voltage distribution stuff...
Terry Fritz wrote:
> I just took the measurements on my coil without top load. Here
Nice measurements. I made similar experiments some time ago, but
didn't try to actually measure the fields. Note that the presence
of even small objects close to the coil (as a probe) can shift
the patterns substantially. Only the nodes can be accurately
observed. In my measurements, I produced repetitive beat waveforms
exciting a closed primary circuit with a high-impedance square wave
current source and made all the monitoring at the low-impedance
primary. The system is resonant when the beats appear, and it is
possible to map the field by just sliding a finger along the
secondary coil, observing at what distance the finger is from the
coil for a degree of changes in the beat waveform. Low power
measurement, of course.
The method is extremely sensitive, and I could observe as many
modes as my primary allowed (more than 10 modes). I have to make
this experiment again, and annotate the measurements...
I have scanned a picture from Fleming's book, showing three
different modes (the last with the top of the coil grounded,
not clear how):
The book lists the references (and a few others):
G. Seibt, "Elektrische Drahtwellen", Elecktrotechnische Zeitschrift,
April 10, 17, 24, May 1, 8, 1892, vol. xxiii.
J. A. Fleming, "On the propagation of electric waves along
spiral wires", Phil. Mag., Oct. 1904, ser. 6, vol. 8, p. 417.
Antonio Carlos M. de Queiroz