Re: ElectroMagnetic Compatibility and Tesla coils (fwd)

---------- Forwarded message ----------
Date: Fri, 24 Apr 1998 19:21:21 EDT
From: SBJohnston <SBJohnston-at-aol-dot-com>
To: tesla-at-pupman-dot-com
Subject: Re:  ElectroMagnetic Compatibility and Tesla coils

JIM LUX wrote:

>Here is my concern: Virtually all modern electronic equipment
>(particularly PC's) has to meet fairly stringent EMC 
>requirements, both to keep interference inside, but also to 
>insure that it's behavior isn't corrupted by outside signals
>(e.g. a TC output). At the simplest level this is accomplished
> by putting it in a metal box, although in practice, this
>doesn't even get close to meeting the fairly stringent CE and 
>FCC requirements.

>I can see an electronic device being affected, operationally, 
>by the RF from TC, but as for actual damage, I find it more 
>unlikely. Modern Electrostatic Discharge (ESD) precautions on 
>equipment make it pretty immune to fairly high voltage 
>(although low energy) zaps.

My experience has been quite the opposite.  Considering both professional and
consumer equipment, in my home ham radio/tesla coil environment and my
professional radio station environments, I find the majority of modern
electronic equipment has little if any effective RF and electro-static
suppression - either going in or out.  Just turn on a RF field strength meter
near a PC and measure those signals coming out!

After a *nearby* lightning strike, (not direct), over $50K worth of computer,
phone, and studio equipment were damaged at my radio station offices.  And
damage was probably minimized by our excellent wiring and grounding practices.
It was amazing how many devices were smoked.

Phones and their accessories are notorious for interference and damage
problems from both RF and static discharge.    Computers are often susceptible
thru their I/O connections, particularly network card ports.  

At some of our stations around the country we've found it difficult to install
computer gear at medium- and high-power transmitter sites due to interference
and, yes, damage.  Nasty, smoking damage.   An engineer representing one of
the big-time network card manufacturers I talked to about damage from nearby
RF sources expressed surprise - he said the MOV across the network port should
have stopped it.   Sigh...

The radiation from a TC seems to be quite high when coil is not discharging
into a target or the atmostphere.  Before breakout I detect much higher levels
of RF.   Plus the low frequency of operation of Tesla Coils may be a factor in
the damage and interference levels reported -- the RF may be it may be
"sneaking under" conventional filters and bypassing. 

Steve Johnston