Re: R-C-R restrictor, uh... filter

Hi Ross,

At 04:01 AM 09/13/1999 -0700, you wrote:
>(Alternate subject: Remover your RCR filter and I'm calling the police!)
>I performed the most beneficial experiment in the history of my coil
>I have been using the "Fritz" R-C-R filter between my spark gap and NST bank
>since I began coiling about a year ago.  I am running a 6"x25" secondary, RQ
>gap (.180-.210"), and currently .045uF of capacitance and a NST bank that
>measures 12KV open and 150ma shorted.
>I placed 2 toroids on my coil, retuned, and began testing for maximum arc
>length.  I managed to just barely squeeze out 48 inches to the ground rod.
>I never got a good power arc, just little spindly, barely visible arcs (I
>was also fighting a mild crosswind).
>Now for the scary part - Risking a hundred plus pounds of NSTs, I removed
>the RCR filter and jumpered the wires that used to route through the filter.
>I stepped back and hit the dead man switch on the controller.  WOW!  A
>white-hot arc the diameter of a pencil attached itself between my corona
>point and the top of the ground rod!  It arched up from the heat and
>immediately reattached to the rod.  The sound and intensity of the arc made
>me take a step back - my coil was acting like an entirely different machine!
>It looked much more like a PT powered coil than NST coil.
>I managed to get a solid 66" arc point-to-point with the new configuration.
>Not only did I get another foot and a half of arc, the arc is entirely
>different in it's color, sound, and movement.

At 120mA, the 20k ohms of resistance in my filter was chewing up about 450
watts which is 1/4 of your system's 1800 available watts!  The filter I
presented was meant to only be used with one NST.  With higher currents,
the loss would increase as a squared function of the current which could
become too overwhelming for the system.  I would leave out the two
resistors between the NSTs and the filter caps and change the remaining two
to 1K ohm resistors.  The remaining 2K of resistance will drop about 45
watts which will be much more in line...  A bit of risk there, but the
"real" point at which filters should be designed is not known...  I would
be interested in see if the great performance remains but the protection is

>The new sound seemed to impress others too - a patrol car came by at 8:37PM
>and put the spot light on the coil.  It was a really funny conversation, the
>policeman kept asking me what it was and I kept telling him "tesla coil,  t
>e s l a  c o i l", then he would just ask again, must have asked 4 times,
>hehehe.  Then it was the typical "what's it do and what's it for" game.
>Anyway, he was cool and told me that he "didn't think it was a crime, but I
>should shut it down for the night".  I reassured him that it was not a
>crime, but I could see the "we need some sort of law to stop this unruly
>behavior" look on his face.  I digress... back to the filter circuit...

Tell the cops it just landed in your yard a while ago.  If they are "real
quiet", the little people may come out and sing the ET song again.  Then,
get them to hide with you behind the bushes and hum the ET song and watch
for an hour or so.  That will send any jury into hysterics and the case is
won...  Or...  Tell them you just bought it at Toys-R-Us and there were
only 50 left.  It is THE BIG Christmas toy this year that all the "Kewl"
kids will have...  If they hurry right over, they still may be able to get
one for their kids too...

See, now ya even got ME started :-))

Actually, tell the cops...  You apologize for working the coil so late....
Maybe your were keeping little kids awake and stuff...  Then tell them it
IS a Tesla coil and SHOW them what it does (that will quite them down).
Then explain to them "exactly" how it works.  When you get to the point of
explaining the "simplified" forth order differential equation model of it's
operation, there will be some mysterious "situation" at the donut shop that
they have to immediately investigate and they will go away.  Then find the
neighbor that turn your rear in (they will be the ones next door that hate
you anyway...)  Go over an profusely apologize.  Offer to take care of
their house, lawn, watering... when they go on that loooooong vacation they
have always dreamed of.  Best to fight this battle with "love" rather than
fire....  Perhaps the old guy would be interested in making a coil of his
own :-))

>I figure that I was losing (.150^2*5000) = 112.5 watts on each of the
>resistors.  That means that I was turning about 450W into heat all in the
>name of making life easier on the NSTs.  That 450W sure did make a huge
>difference when I put it to good use.  Furthermore, nothing died (yet)!
>Hmmm, I still have more caps and more NSTs...

Since all the emphasis on filters and safety gaps has come up, there have
been far far fewer blown NSTs.  We must try to find that magic point
between performance and safety.  Right now, the window is very wide.  We
can run without any protection and get away with it for awhile.  Or, run
with big filters that will protect the NST against anything and they will
last forever, but performance will suffer.  We have both extremes but we
can hit any point we want.  However, the "best" point is unknown...

Thanks for bring up this subject I knew would hit eventually...



BTW - the filter in question is at:


The latest and greatest filter I use on my LTR coil is at:


>Wishing I still lived back in the woods,
>Ross Overstreet
>Huntington Beach, CA