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Re: More facts: Coil size to faraday cage size ratio

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

I also second the use of big ferrite cores liberally placed around the primary and especially at the spark gap.

Right before the spark gap fires, there is a lot of energy stored as capacitance between the gap electrodes. When the electrodes fire, that energy is shorted out without much R and L in the way which causes giant RFI.

All my spark gap coils have ferrites but I never think about them much since they are passive things. Note my big gap that has ferrites directly on the electrodes:

http://hot-streamer.com/TeslaCoils/MyCoils/BigCoil/Rgap.jpg

I can't really quantify how much they help, but they do reduce RFI "a bunch".

DigiKey sells them from very small to pretty big:

http://dkc3.digikey.com/PDF/T043/0793.pdf

Maybe you just need to cage the spark gap.

Also, streamer just to air will have far less RFI than streamers striking to ground.

Hope this helps!

Cheers,

        Terry


At 11:53 AM 11/23/2004, you wrote: 
Since the signals of concern are fairly HF (i.e. >30 MHz), it would be
interesting to find out where they are coming from.  Is it high order
harmonics from the LC ringdown (unlikely... we're talking VHF frequencies
here, and 100 MHz would be 1000th harmonics of the 100kHz fundamental).
Probably more likely radiation from primary circuits (as Terry had noted
some years back) or from the streamers themselves.

So, maybe something to kill the HF content in the primary circuit (ferrite
cores on the wires to/from the sparkgap?  Have to choose an appropriate
material, so they don't absorb too much energy at the fundamental and
overheat.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, November 23, 2004 9:00 AM
Subject: Re: More facts: Coil size to faraday cage size ratio


> Original poster: "Bob (R.A.) Jones" <a1accounting@xxxxxxxxxxxxx>
>
> Hi Fin
>
> Its probably cheaper and less demanding on the each cage to have a double
> one.
> Two poor performance cages can be more effective than one good one and
> possibly two are essential if the inner is going to be in the discharge
> path