Re: faraday cages (II)

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>

Computations in progress on just this issue...

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, February 24, 2001 11:47 AM
Subject: Re: faraday cages (II)


> Original poster: "Ray von Postel by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <vonpostel-at-prodigy-dot-net>
>
> Dave:
>
> I agree with every comment you made, but there still remains the need to
> determine the extent of the problem in terms
> of the amplituede and frequencies of the energy output by the typical
Tesla
> coil.
>
> > > Perhaps some one on the list has the information on the r.f. spectrum
> > > generated by Tesla coils and will share it with us.
> >
> >         Varies with the coil.  Gnerally under 1MHz, usually under
> >         200 KHz.  Harmonics above, of course, these usually drop
> >         rapidly in power.
>
> I assume you are talking about the "fundamental" frequency of the coil
> recognizing that the output occupies a fairly broad band.  What IS the
power
> of the 10th harmonic at a distance of 20 feet from a coil running 10 KW
input?
> That rehtorical question is asked to emphasise the point I am trying to
> make that there is room for a lot of productive experimentation and study.

It's not going to be a harmonic issue, really, but more of a peak power
thing, since what destroys things is the peak power, not the average power
(at least for the "zap the junction" type damage.. )

>
> Considering that you can have excellent electrostiic shielding with very
> poor electromagnetic shielding. is it axiomatic that Electro Magnetic
Pulse
> precautions are always effective for electrostatic shielding?  If so, then
> might it be well to concentrate on the EMP side of things?

One could have good magnetic shielding or a scheme that clips pulses, but
lets through fairly high levels of average power.  It depends on whether you
are worried about RF noise (say, if you had a receiver you're
trying to adjust), or if you are worried about damage (in which case the
peak clipping is just what you need).

On the whole, I bet that nobody is going to worry too much about RF
interference from a TC. The frequency is so low, and the coil is such a
terrible antenna, that radiated noise is a non-issue when you get a few
meters away. This is borne out by "AM radio tests" that have been reported
and the following anecdote: My office mate (an experienced transmitter and
interference hunter)  tried to find the SoCal Teslathon last year by using a
directional antenna and a radio, and drove around for 40 minutes without
finding us..  We were running many kVA of TCs at the time.  He knew where it
was within a few miles (remembered the town, but left the map and address at
home), and still couldn't locate it.

>