Re: faraday cages (II)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ray von Postel by way of Terry Fritz <twftesla-at-uswest-dot-net>" <vonpostel-at-prodigy-dot-net>

Bill:

Glad you joined this thread. You are preceded by your reputation.

>From what I can find out, there is little SPECIFIC information available
relating
to the output of a Tesla coil.  I hope you can point me
to a source.  There is an old saying: "You don't really know until you
can write an equation."  (that should produce a flame).  The equations are
there for the design of the coil itself, but almost everything else seems to be
anecdotal.

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<wysock-at-ttr-dot-com>
>
> To Ray, et. al.
>
> (Terry, my apologies for not "snipping" this thread, but I felt
> it was a necessary addendum to this discussion).
>
> All good shielding techniques aside, the *real* problem has
> been (and continues to be), at least in my experience, how to
> attenuate the *very broad-band* RFI emitted by the SPARK
> DISCHARGE ITSELF, from a medium to high powered
> Tesla Coil.  It turns out, that the R.F. spectrum from the
> spark discharge (itself), can (and will be), the *main* culpret
> in mitigating RFI issues of any given installation.

You speak of attenuation of  a "very broad band" of RFI.
RFI to me means an annoyance rather than a real problem. Stopping
it is usually as much public relations as technical skill.  It is often messy,
tedious and time consuming and can involve such little things as
a ground wire touching a rusty tomato can. What I  am
concerned about is sufficient electrical energy at what ever power and
at what ever frequency and wave shape sufficient to cause physical
damage such as burning out transistors.

When I spoke of the "output" spectrum of a Tesla coil, it was not my intent to
limit
the problem to the SPARK DISCHARGE ITSELF.  By that I assuming
you mean the fixed or rotary gap.  I take it as a given that every Tesla coil
system
 is a very dirty r.f. source.  However, I don't know if anyone has taken the
time to measure it in terms of frequency and amplitude.   i.e. How many
microvolts
per
meter, at what frequencies,  at some specified distance from the coil and
how many
decibels above or below
some recognized standard power.  Developing a field pattern for  the radiation
from a Tesla
coil would at best be difficult because of the almost infinite number of
frequencies.  Not
only that, but such a pattern would be unique to that particular
installation just
as it
is for radio transmitters in general.  You can engineer a radio
installation and
hope
you get the coverage you want, but the result still has to be proven
experimentally.
If EMP is generated, how much?    What, if any thing is the problem?
Have you or do you know of any one who has attempted these measurements on
a Tesla
coil?

>
>
> Unfortunately, manufacturer's components (and systems), that
> are most affected by this type of interferance, are not covered
> by any of the existing standards governing the sale and
> distrubution of these types of components.  It remains an
> on-going problem, on a case-by-case situation.

As you say, it is an on-going problem.
The lack of design and construction standards for consumer goods has been
with us
since the
first use of radio.  It is not so long ago that every ham held their breath
when
their neighbor bought a TV.  The difference is that transistors, working at low
voltages and currents are much more vulnerable.   Cases in point:

Lightning hit a neighbors tree.  I lost the mother board in my computer.

Lightning hit the tower at a broadcast station and produced a fire ball inside
the transmitter.  Loss one mica capacitor.  Transmitter down for 25 minutes.
This was before transistors.


>
> Best regards,
> Bill Wysock.

Perhaps my interest in this is related to the fact that I would rather design
something
on paper first, then build and test it, with some assurance that  what I am
working on
has a reasonable chance of doing what I want it to.  But then, as Dr.
Terman was
quoted
as saying:  "You can design something, but in the end, you often find yourself
tinkering."
Tinkering is fun but it is cheaper to waste paper.


Thanks for your input.  It is valuable because you are well know  and respected
for your
experience with and knowledge of Tesla coils.

Ray von Postel