Here's some notes on RFI and tesla coils for the FAQ

Terms to know:
RF:radio frequency.
white noise: basically like the static you hear on a radio.
AM:  amplitude modulation.
harmonic: a frequency that is a multiple of the carrier.
fundamental: the carrier frequency.

Tesla Coils generate white noise
The interference is generally only heard on AM bands.  This is because
there is no frequency modulation happening(well, not much).  AM, though
will make a pop or click everytime a harmonic of  your coil gets through(
or even the fundamental in some cases).
If your coil generates to much, and someone complains, the FCC(U.S.)
might track you down and take all your high voltage stuff for good.  For
someone to complain about RFI with a 150 watt coil they could be maybe
two houses down and for 2kw, they could be within a radius of maybe two
city blocks.  

Most of the noise I believe is generated by the spark gaps, as this is
how Marconi's original transmitter's worked(actually Marconi used Tesla's
patents as we all know)

If your tesla coil does start really messing up FM, then your in trouble.
 There are alot more bands on FM that can get your coil confiscated. 
Police and airtraffic are the biggies.

So this is what it means: if you leave your coil on for to long, don't be
surprised if you wake up at 2am, your HV stuff is in a large unmarked
truck, there is a equivalent of a SWAT team in your room and one of them
has a gun in your face and reading you your rights.  Actually that
probably won't happen, you might get a warning that you should stop your
wideband jamming.  At least that is how it works for pirate radio in the

What you can do about it : to get rid of most of the noise, you can
probably get away with putting your spark gaps in a box covered with
aluminum foil that is grounded.  If you want to be able to see your gaps,
 the holes in the screen must be smaller than the size of the 1/4
wavelength  of the frequency you are worried about.  For AM, any thing
will work.  I would recommend chicken wire as this should get everything
but the higher end of the microwave band which your coil can probably not
emit(this being greater than about 5ghz!!!).  If you think it is worth
your time and effort, you can cover your ceiling, floor and walls with
chicken wire(actually, you don't need to do the floor) or aluminum foil.

Wait a minute.  I think that actually you will have to cover your garage
with chicken wire.  Wasn't Tesla's original idea for the TC to transmit
power. ;)

Bryan S.
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