# Re: [TCML] John Freau's streamer length equation

```At the risk of raining on the parade, I'm frankly puzzled that there could
be such a simple relationship between power and arc length.  Never having
ventured into the pig-powered coil world, I've always been power-limited to
one 15/60 NST and milked that for all I could (66 inches -
http://www.laushaus.com/tesla/sparks.htm ) .  My sparks have always been
longer than what others report, but also not remotely as bright. With the
singular goal of maximum spark length, I ended up with a sync 120BPS RSG
and a very large top load.  I wish it were easy to just spin a dial and
trade off long wispy point-to-point sparks for shorter,
brighter, frantically writhing sparks.  But to achieve that, I'd need
higher BPS gap, smaller Cp, smaller primary, smaller topload, etc -  a
completely different coil.  And with no way to quantify the result, there
goes the bragging rights ;-)

Gary Lau
MA, USA

On Mon, Apr 13, 2020 at 11:05 AM Steve White <steve.white1@xxxxxxxxx> wrote:

> I was wondering if John Freau's empirical streamer length equation applies
> equally well to both SGTCs and DRSSTCs? It seems to me that it would since
> both SGTCs and DRSSTCs both operate on the principal of feeding a rapidly
> repeating stream of CW pulses into the primary coil.
>
> A related question involves how to measure the streamer length as
> predicted by the John Freau equation. Do you mentally straighten out the
> streamer removing all the bends and curves or do you just measure the
> straight-line length from start to finish with a straight line cutting
> through the bends and curves? My thinking is that you mentally straighten
> out the bends and curves into a straight line before making the measurement.
>
> Here is John Freau's equation for spark gap coils for reference:
>
> Length = 1.7 sqrt(input power)
>
> where Length is in inches and input power is in watts.
>
> Steve White
> Cedar Rapids, Iowa
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