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RE: Gap turn off at zero current and TVI

Thanks for trying the cap in parallel with the primary.  Beyond the Fres,
was there any difference in performance that may indicate different
quenching?  I'm sure this had some effect upon the parasitic primary
oscillations, but perhaps the better question is whether these primary
parasitics are what's actually responsible for TVI.  Upon further
reflection, it may well be that the TVI is caused by VHF action on the part
of the streamers themselves, just like lightning.  No zero-current-crossing
action there.  Clouds are simple DC capacitors that discharge towards the
earth, but the lightning arcs themselves have all sorts of interesting VHF
dynamics that cause TVI.  I think Terry published streamer current waveforms
measured with his excellent fiber-optic VI probe, and it was rich in high
frequency action unrelated to primary or gap activities.  If it's the
streamers generating the TVI, all you can do is run it in a cage.

Regards, Gary Lau
Waltham, MA USA

>Original Poster: "R.E.Burnett" <R.E.Burnett-at-newcastle.ac.uk> 
>Connecting a snubber across the gap or the primary winding (maybe both)
>is an interesting idea.  I have quite a few poly caps and bits from
>MMC's around but need to get some good HV resistors.  I tried
>connecting various caps across the gap or across the primary coil but
>they did not seem to make much difference.  (The resonant frequency did
>drop slightly when connected across the coil.)  This should have a
>similar sort of effect as using a ribbon primary,  Gary ?
>I was dissapointed that I could not "shift" the VHF bursts to a less
>anoying frequency by adding capacitance.  I must try adding some
>resistance to make an RC network as this should actually absorb some of
>the energy better.  Some PSpice sims make this look very promising.  It
>may indeed give better quenching !
>					- Richie
>					- In sunny Newcastle
>					(except when Alan's in town :-)