Re: Don't throw out the oven!

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

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

> Yes but if memory serves a Faraday cage is good from it's design freq on
> down (not up). Since Microwaves work at very high freqs (GHz I think) then
> the KHz range of a coil would be just fine for it.
>
> Now, if you build a tiny coil and put it inside the box, it may not work
> since the tiny coil may have a freq higher than the cage can hold. The
upper
> freq limit is set my the largest opening of the box, and it's relationship
> to the wavelength. Basicly it's like you can't fit something with a 2"
> wavelength through a 1" hole or something like that. One of the RF guru's
> (like Jim :) ) understand thes things far better than I do, but I *think*
> that's how it works.

Basic rule of thumb... perimeter of hole must be less than a wavelength... a
slot 1/2 wavelength long (and very narrow) will be a fine antenna.


> Please correct me if I'm wrong, I'd like to know for sure the reasons WHY
a
> faraday cage works.

There's both a DC/electrostatic issue (Gauss's law) and an RF shielding, as
well as a magnetic field issue They're all different.