Re: TESLA COIL RFI
Subject: Re: TESLA COIL RFI
Date: Tue, 17 Jan 1995 13:30:51 -0500
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> From: Richard Quick
> Subject: Tesla Coil RFI
>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.
I plan to build and operate the Tesla Coil in my basement. I have a 1.5 inch
copper pipe that goes through the cement and runs underground (5 to 6 feet
deep) about 80 feet out to my well. This should provide a good, non
>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.
I plan to build a rotary spark gap. It should be relatively easy to build a
Faraday cage around it.
>I like a nice tight wound magnet wire secondary
I have read many books on Tesla coils, but not nearly enough. I thought the
reccomendation was to space the secondary windings somewhat apart - like
winding a string along with the wire then remove the string. This makes
sense as it would reduce the secondary capacitance and increase the Q. Is
this not the case?
Several books reccomend a L/D ratio of 2.5 : 1 or 3.0 : 1. This means a
shorter coil with a large diameter, of say 10.0 to 14.0 inches - like the
coils that Tesla built and we see in all the old pictures. Do you find that
this is not necessary? You mentioned 5.0 inch diameter - which must be about
3.0 feet high?
Thanks, Ed Sonderman