>    From: Esondrmn-at-aol-dot-com 
 > Subject: Tesla Coil RFI

 > I am now designing a new Tesla coil and need help in a couple  
 > of areas: First, how do I avoid FCC problems?  How much RFI    
 > will be produced?  

Assuming you are building for spark output your main RFI problem
is going to come from the secondary base wire. The base wire is a
low voltage, high current output that will energize or "power up"
the local ground. If you ground to your 60 cycle breaker box you
are turning the neutral wire into a radiating antenna for a
tremendious amount of RFI hash. My experiments verify this
conclusion. I advocate the use of a low impedance, dedicated, RF
ground system for Tesla work. It works for me.

The output energy from the top of the secondary coil is mostly
consumed in light, heat, and ozone production if the coil is
efficient and tuned for spark. This output does not compare to an
improperly grounded base wire as a source of interference.

After the base wire, the next sore spot is the spark gaps. The
arc does produce some RFI. Fortunately the gaps are easily
sheilded if RFI is a problem.

Some experiments may require the use of a Faraday cage to trap
and suppress RFI, but my experience is that a properly grounded
coil in these power ranges does not affect RF sensitive equipment 
much beyond 50 feet.

 > I am planning to use a 15,000v 60ma transformer for the
 > primary (900watts). Second, how do you select the operating    
 > frequency? According to my calculations an ideal frequency     
 > would be around 300khz. This keeps the capacitor as well as    
 > the secondary coil a reasonable size. 

I like a nice tight wound magnet wire secondary with about a five
inch diameter and a resonate frequency of 400 - 450 kHz. I bring
the coil down in frequency by using a 12 inch diameter toroid

Richard Quick

... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12