otmaskin5@xxxxxxx wrote:
I have been trying to use a signal generator and scope to tune my coil more scientifically than the old fashioned trial-and-error method.? I believe I pegged the?secondary frequency at 127.24 kHz.? This is pretty close to the freq I got from JAVATC which was 125.21 kHz.? However, in trying to tune the primary, I'm coming up with a tap point 13 5/8 turns which is significantly different from that the JAVATC indicated 16.2 turns.? This makes me think I might be doing something wrong.?A couple of questions: 1.? Should you tune the primary coil while it is still hooked up to the NST & Terry filter?? Or do you need to disconnect everything & totally isolate the primary coil and tank cap? 2.? Would someone out there be able to point me to a source showing how to properly hook-up the scope & signal generator for both the primary & secondary?? Just want to confirm I got the circuits right.
I always use this method: http://www.coe.ufrj.br/~acmq/tesla/tuner.gifYou can use a signal generator, but you have to lower its output impedance to a very low level. A simple way is to connect a 1 Ohm resistor across the output. You will operate with small signals, but the oscilloscope will observe them without trouble. Just set the generator to produce a low-frequency square wave (~1 kHz) with high amplitude and connect it across the spark gap. You can leave all the elements of the coil in place, of course not powered. Observe the voltage over the primary coil at each transition of the square wave. With the coil properly tuned, you will observe a series of complete beats. The frequency of the oscillations within the beats is the resonance frequency of the primary and secondary circuits. The number of cycles in each beat depends on the coupling coefficient, and can be used to determine it. If you want to take into account streamer loading, connect a piece of wire with the expected streamer length and position to the terminal.
Antonio Carlos M. de Queiroz _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla