Gap Sounds

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

Original poster: "Matt S. by way of Terry Fritz <twftesla-at-uswest-dot-net>" <matt777777-at-hotmail-dot-com>

Hi,
I am finally to the point where I have fired my gap for the first time on my 
soon to be completed coil and I have a few questions.
I have a multi-segment gap composed of 9 sections (8 gaps) of 1" cu pipe 
laid out horizontally on a slab of G-10 (fan and enclosure to come later).

1. I have a 12kv/60ma NST and for now I have the total spacing somewhere 
around 0.200" (no, not to three significant digits, .. I'm lucky if it's +/- 
30% .. setting the spacing with my feeler gage was much harder than I 
anticipated for some reason).... anyway, as I ramp up the voltage, it seems 
to hum in a really constant way....    but when I dial it down, it has more 
of a raspy (but for some reason more appealing) sound to it.  I was 
wondering if I need to have my gap spacing set to a minimum in order to tune 
my coil, and/or is 0.2" appropriate. ... and is the sound of it any 
indication (of anything)?

2. As I dial up the voltage, before the gap fires, I hear the usual 60hz (B 
flat) hum, but I also hear another (higher) audible frequency superimposed 
that increases in pitch as the voltage increases and 'flattens out' (ie. 
pitch doesn't change any more) a little below the voltage that the gap fires 
at.
I'm guessing that this is not really related to the gap at all, and is 
probably a H.V./corona related thing, .. but I am curious about it and am 
trying to figure out what the sound actually is and was wondering if someone 
could comment in it.

Thanks a lot,
Matt.
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