Re: measuring the resonant frequency of the secondary

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq-at-uol-dot-com.br> 

Tesla list wrote:
 >
 > Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com>
 >
 >  >You have to use a signal generator with very low output impedance to
 >  >see the peaks cleary.
 >
 > To check the tuning of a complete TC (primary and secondary together) I like
 > to use a ferrite transformer to couple the output of the sig gen to the
 > primary. I connect the sig gen to a 30 turn winding on a ferrite ring, and
 > drive the TC tank circuit from a single turn secondary (an alligator clip
 > lead passed once through the ferrite ring, and hooked across the TC spark
 > gap)
 >
 > This works great with an old HP 200 style tube oscillator- these have a
 > generous output of ~40V into 600 ohms. It actually excites the TC enough
 > that I can pick up the secondary output from a scope probe held in mid-air
 > about 2ft away, and see the resonant frequencies that way. I can also see
 > the oscillator's output voltage being loaded down at the resonances.
 >
 > To test the secondary alone, you can base drive it directly from the
 > oscillator (connect one lug of the oscillator output to the secondary base,
 > and the other to a groundplane, or the AC line ground.)

This would probably work well also with my suggested square wave
excitation.
Something to try. Instead of a buffer after the oscillator, I have tried
too to just shunt the output of a 50 Ohms, 10 V generator with an 1 Ohm
resistor. But this reduces the driving voltage to 196 mV. A transformer
with 7:1 turns ratio would also reduce 50 Ohms to 1 Ohm, but with an
output of 1.43 V.

Antonio Carlos M. de Queiroz