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Re: Why does running an NST on an async gap kill it?
Original poster: "Dr. Resonance by way of Terry Fritz <teslalist-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>
When the sparkgap fires the stored energy in the cap will take the path of
least resistance, ie, into the primary coil.
While the energy is swapping back and forth some of the energy tries to get
back to the xmfr. The 1K resistors offer a high impedance path so most all
of the energy goes into the inductor and not into the NST. In effect, you
create a Q spoiler circuit that dampens any residual oscillations.
I've run NST's on asynch gaps many times --- the secret is to set the gap
spacing so it will definitely fire. I've read of experimenters setting
their main gap to 0.3 or 0.4 inches. This is bad --- keep it down to around
0.180 - 0.240 range and you won't have the NST deaths.
Also, it is very cricital that you do the coeff. of coupling experiments ---
you want to be sure as much energy goes into the sec. coil and doesn't stay
in the primary where it can form standing waves and large potential spikes.
Many experimenters skip this step --- and their NST xmfrs die.
PT's and pole xmfrs can withstand more abuse but they should also be
protected at least with an air core coil and some inductance. We use a 4"
dia. tube wound with 50-100 turns of #12 AWG with PVC insulation on the xmfr